This section primarily covers the early hours of Apollo 15's twelfth day in space, 6 August 1971.
This is perhaps the quietest day of the mission. The main objective, i.e. exploration of the Hadley/Apennine region of the Moon, has been achieved as well as a huge clutch of secondary aims and there is little remaining to do except to ensure they return safely in a healthy and well-aimed spacecraft. Al Worden will continue to make navigation sightings of Earth and Moon against the stars. This is in case communication with Earth is lost, a situation that would force him to manually navigate Endeavour home. In the interests of science the crew of Al, Dave Scott and Jim Irwin will continue to operate the SIM bay, take photographs of the approaching Earth and conduct another experiment to help characterise the light flash phenomenon experienced by many other crews.
In the middle of the day, the crew will witness a lunar eclipse from a unique vantage point, and they will answer questions from the press. This will be covered in the next chapter of the flight journal.
This is Apollo Control at 253 hours, 30 minutes. It appears at this time that the crew is either asleep or beginning to drop off to sleep. Jim Worden on whom we have - or Jim Irwin rather, on whom we have biomedical data this evening, has been asleep for about the past 30 minutes. We plan to take the air-to-ground lines down now leaving the recorders up to record any conversations for playback. And we are going to replay the videotape in the News Center from today's EVA. Apollo 15 at the present time is 149,755 nautical miles [277,346 km] from Earth, travelling at a speed 3,536 feet per second [1,078 m/s]. All of the systems on the spacecraft are continuing to operate satisfactorily. The Scientific Instrument Module experiments have been operating since departure from lunar orbit and good data is being obtained. The camera cassettes, of course, from the Pan and Mapping cameras were recei - retrieved today by Al Worden during the extravehicular activity. The Apollo Lunar Science Experiment Package, left at the Hadley Base site, is also functioning well, power from the radioisotope source, the thermoelectric generator, is remaining at a constant 74.1 watts. And we're monitoring the temperature on the Central Station electronics at 112.8 degrees [F, 44.9°C]. The Passive Seismic Experiment continues to record the venting of the Lunar Module descent stage. We're also noticing the characteristic wobbling that is apparent as the instrument settle - settles out. These disturbances are gradually decreasing in amplitude. And analysis of experiment data indicated that the Apollo 15 station recorded a seismic signal, probably a meteorite impact, beginning at 21:25 Greenwich Mean Time on August the 2nd. The Lunar Surface Magnetometer experiment is also operating normally. Continues to measure magnetic fields as the Moon passes in and out of the tail of the magnetopause. We're also getting normal operation from the Sol - Solar Wind Spectrometer Experiment. And the Heat Flow Experiment appears to be performing normally, with all of the temperature sensors returning data. The thermocouple temperatures indicate a lunar surface temperature of about 192 degrees Fahrenheit [88.9°C]. At this time we will take the live air-to-ground line down and we'll be feeding the audio from the - along with the video from the television of the EVA today. At 253 hours, 34 minutes; this is Apollo Control, Houston."
This is Apollo Control at 254 hours, 29 minutes. The crew has now been asleep for about an hour and a half. We have about 7 hours remaining in their sleep period. And just a few minutes ago, Flight Director Glynn Lunney checked with his flight control team on the status. The reports from around the room are generally about the same. All is quiet and everything is looking good. Apollo 15 at the present time is 147,745 nautical miles [273,623 kilometres] from the Earth, and the spacecraft is traveling at a speed of 3,591 feet per second [1,094 m/s]. We'll continue to provide status reports hourly. The air-to-ground lines are down but we do have the tape recorders running, and should we get any unexpected calls from the crew, we'll play those back for you shortly afterward. At 254 hours, 30 minutes; this is Apollo Control."
This is Apollo Control; 256 hours, 34 minutes Ground Elapsed Time in the mission of Apollo 15. Heading homeward at 3,714 feet per second [1,132 m/s]. Still 143,341 nautical miles [265,468 km] out from Earth. Splashdown is in the North Central Pacific; 38 hours, 36 minutes away. Crew is still asleep at this time. No recent communications. They have 4 hours and 54 minutes of their scheduled sleep period remaining. Milton Windler's Maroon Team has taken over for the graveyard shift here in the Control Center. The spacecraft slowly rotating in the Passive Thermal Control mode; which for the people here in the Control Center, is rather like watching the grass grow. At 256 hours, 35 minutes Ground Elapsed Time; this is Apollo Control."
This is Apollo Control at 258 hours, 26 minutes. Some other times; 3 hours and 3 minutes remaining in the Apollo 15 crew rest period. Splashdown some 36 hours, 45 minutes away. Apollo 15 spacecraft Endeavour now 139,283 nautical miles [257,952 km] out from Earth. Velocity building up very gradually, now 3,831 feet per second [1,168 m/s]. Current vector shows the Ground Elapsed Time of Entry Interface, Saturday, of 294:58:06; velocity at the Entry Interface would be 36,097 feet per second [11,002 m/s]. All these numbers concerned with entry and splashdown will change back and forth over the next day and a half. Crew apparently in fairly deep sleep at the present time according to the Flight Surgeon. Spacecraft rotating about the longitudinal axis in the barbecue roll, or Passive Thermal Control mode. All spacecraft systems are in excellent shape, operating nominally. No problems with spacecraft or crew. At 258 hours, 28 minutes; this is Apollo Control.
This is Apollo Control; 261 hours, 29 minutes Ground Elapsed Time. Should be coming up on crew wakening here momentarily. Spacecraft communicator Joe Allen will be giving the crew a call followed by some wake-up music. The spacecraft, meanwhile, is 132,367 nautical miles [245,144 km] out from Earth. Velocity: 4,038 feet per second [1,231 m/s]. Spacecraft communicator is checking the weather room display for a forecast for the landing area which calls for scattered clouds and good visibility. And looks like he's getting all set to wake the crew up.
261:30:07 [Music - "Anchors Aweigh"]
261:31:20 Allen: Good morning, Endeavour. This is Houston. [Long pause.]
The choice of music to awaken the crew is somewhat tongue in cheek. 'Anchors Aweigh' is a song that had been unofficially adopted by the US Navy. The Apollo 15 crew, however, are all US Air Force. The naval theme will be continued later by the mention of sea shanties and by pointing out that their spacecraft, Endeavour, was named after a ship, HMS Endeavour.
261:31:34 Worden: Hello, you guys.
261:31:35 Scott: Good morning.
261:31:37 Allen: Good morning, Dave. A little something special for your LMP from your lunar lift-off Flight Director with young Ed Fendell on the cymbal.
261:31:50 Worden: Oh, man; he's standing at attention right now. [Pause.]
261:32:00 Allen: Roger. We copy that. [Long pause.]
261:33:00 Allen: Endeavour, this is Houston, with our first request of the day. We'd like the X-ray Spectrometer, On, please.
The early morning tasks for the crew include going through the post-sleep checklist, stopping the PTC rotation and aiming the SIM bay so that the X-ray Spectrometer can get a look at another astronomical target. The Flight Plan omitted to include the instruction to switch the instrument on so Allen is prompting them. Since the spacecraft will be at a stable attitude, Mission Control will advise the crew of what angle they can set the steerable High Gain Antenna to, thereby maintaining a high quality link to Earth.
261:33:08 Scott: Rog. Coming on.
261:33:12 Allen: Okay, Dave. And I've got High Gain Antenna angles for you when you exit PTC. [Pause.]
261:33:25 Worden: Okay. Stand by one, Joe. [Long pause.]
261:34:25 Scott: Okay. Go with your High Gain angles.
261:34:31 Allen: Roger. High Gain pitch, plus 24; yaw, 264. And, Dave, I've got CSM consumables if you're interested in copying those. [Pause.]
261:34:53 Scott: Okay. Go, Joe.
261:34:55 Allen: Roger. GET 261 plus 00. RCS total, 38. Quad A, 42; 39, 32, 38. H2 tank: 34, 32, 33. O2 tank: 49, 50, 40. And there's a note on that which reads, "Fat City." Over. [Pause.]
With only one day left in the mission, they have over a third of their original consumables load remaining. Thus the comment "Fat City". However, the reader ought not to think that the mission planners miscalculated their load. Given any one of a vast number of entirely conceivable scenarios and their apparently generous margin would be quickly used up. For example, a rescue rendezvous on a stricken Lunar Module in the wrong orbit around the Moon would have cut deeply into their RCS margin. American spacecraft were designed with acceptable leak rates from their cabins and it is entirely possible that Endeavour's hull could have developed a greater leak rate than it did, increasing the flow of oxygen from the tanks. Power and cooling requirements could have changed, affecting usage of their hydrogen and oxygen stocks. It is a measure of the mission's highly nominal nature and the careful husbanding by the crew and ground controllers of the spacecraft's systems that they have these excellent reserves at this stage of the flight.
261:35:45 Allen: Yes, sir. [Pause.] And, Dave, a comment...
261:35:52 Scott: What a machine.
261:35:54 Allen: Roger. A comment: you're being served now by the MOCR shift that witnessed a new endurance record for Apollo flights, being set during the night. [Pause.]
Joe Allen is careful to qualify this endurance record by applying it to Apollo. Other American and Soviet flights have been in space longer. For example, the Gemini VII flight of Frank Borman and Jim Lovell stayed up for 14 days and the ill-fated visit of Soyuz 11 to the Salyut 1 space station lasted nearly a month.
261:36:32 Allen: And, Endeavour, I'll be standing by for when you're ready to copy down the few changes in your Flight Plan for today. I can bring you up to date over the next 7 hours or so and get all that out of the way. I'm also curious to know if you've had time to listen to any sea shanties from the HMS Endeavour up there. Over. [Pause.]
261:37:02 Scott: No. We haven't had a chance to, Joe. Stand by and I'll get my trusty pen out, after we get through with this - coming out of PTC, and we'll do the Flight Plan.
261:37:13 Allen: Okay, fine. You should ask your trusty record librarian, Al, where the sea shanties are, if you have time today.
261:37:25 Scott: Okay. We were talking about that last night, and came to the realization that we brought all these neat things along, and we hadn't had time to listen to a single one of them.
261:37:35 Allen: Not at all surprised to hear it.
261:37:41 Scott: I'll tell you, yesterday, we finally got to catch our breath. [Pause.]
261:37:53 Allen: You always said the hours are long. [Pause.]
261:38:01 Scott: Rog. [Long pause.]
261:38:16 Scott: The hours are long but the accommodations are palatial.
261:38:23 Allen: Was that the way it went, Dave? [Pause.]
261:38:33 Scott: Sounds like you've recovered from all that - the other - couple of last few days, too.
261:38:40 Allen: Very nearly.
Very long comm break.
Within the next minute, the X-ray Spectrometer will begin a 55-minute period of data collection while pointed at the galactic south pole. This is a point in the celestial sphere which is between the constellations of Cetus and Sculptor and is chosen to exclude as much galactic-sourced x-ray flux as possible, essentially providing a control measurement with which to compare other readings.
261:49:00 Irwin: Houston, this is 15. Standing by to copy Flight Plan update.
261:49:06 Allen: Roger, Jim. Good morning. The first...
261:49:10 Irwin: Good morning, Joe.
261:49:11 Allen: ...entry should be at 261:42. [Pause.] And it is a - a change in the first register of the DAP load - the time column. We want that to read, 11101. Over. [Pause.]
The five digits read to Jim set the status of a register in the computer which controls how the Digital Auto Pilot operates. In this case, the fourth digit is being changed from a "1" to a "0" which narrows the deadband from ±5.0° to ±0.5°. The attitude of the spacecraft will therefore be maintained within this tolerance. These tighter limits require more use of the RCS thrusters to maintain. However, at this late stage of the mission, they have generous reserves and little reason not to use them.
261:49:44 Irwin: Give me the time again on that, Joe.
261:49:49 Allen: Roger. 261 plus 42. [Long pause.]
261:50:04 Irwin: Okay. At 261:42, I don't see any DAP information. I see one on 261:35.
261:50:15 Allen: I may have done it again, Jim. Let me see. [Long pause.]
The version of the Flight Plan used in the compilation of this Journal does indeed have this DAP load at 261:44.
261:50:29 Allen: Stand by on that. Let's - let's continue on with some of the easier steps. At 262...
261:50:36 Irwin: Roger. [Laughter.]
261:50:37 Allen: ...plus 05, it should - that - that - that's 262 plus 05 add "Gamma-ray Gain Step, two steps." [Long pause.]
261:51:08 Irwin: Understand. At 262:05, Gamma-ray, two steps.
261:51:13 Allen: Roger. And at 263:55, under the line "Noun 70," et cetera, add "X-ray to Standby." And at 263:59 delete the Verb 48 line and the DAP load over in the time column. [Long pause.]
261:51:55 Irwin: Okay; at 263:55, we'll add a step there after the Noun 70, X-ray to Standby; and then, at 263:59, we'll delete the Verb 48 and also delete the DAP load that's in the time column.
261:52:18 Allen: Roger. Turning the page to 264:02, the DAP [pause] load in the time column should read, 11101. And at 265...
261:52:44 Irwin: Okay; understand.
261:52:45 Allen: ...the DAP load status in the notes column should read, 11101, X1111, and this continues through for 2 hours. Over. [Long pause.]
261:53:16 Irwin: Okay. Understand that 264:00, in time column, changed the DAP load there from all ones to 11101; and then, at 265, the DAP load will be changed the same way to continue for 2 hours. [Pause.]
261:53:43 Allen: That's correct, Jim. And moving on to 266:30, delete the "Gamma-ray Gain Step to Shield, On" line. [Pause.]
261:54:02 Irwin: Okay. 266:30, to - eliminate the Gamma-ray Gain Step.
261:54:10 Allen: Roger. Moving to 267 plus 20, add the two steps: "Gamma-ray boom, Retract, talkback barber pole for about 2½ minutes, then gray, and then Off." And the second step, "Gamma-ray Gain Step to Shield, On." [Long pause.]
261:55:01 Irwin: Okay. Understand, there are two steps there. The first one is Gamma-ray Retract, barber pole for about 2½ minutes, then gray, and then turn it Off. Second one is Gamma-ray Gain Step to Shield, On.
261:55:17 Allen: That's correct. Moving to 267 plus 42, change the DAP load in the time column to read 11101, X1111. Over.
261:55:38 Irwin: Understand, from all ones to 11101.
261:55:43 Allen: That's correct. Turning the page to 268:02, the DAP load in the time column, the same change. [Pause.]
261:56:02 Irwin: Okay. I copy. [Long pause.]
261:56:15 Allen: Okay. On the same page, 268:30, Gamma-ray Gain Step, five steps. [Long pause.]
261:56:35 Irwin: Understand, Gamma-ray Gain Step to five steps. [Pause.]
261:56:46 Allen: That's correct, Jim. Now looking at page 3-378, the "UV photos - Trans-Earth Coast," A couple of changes there. About halfway down the page where it reads "two frames, filter 2, exposure time 20 seconds,". [Pause.] Delete that line, and add the line - the two lines, "one frame, filter 2, exposure time 20 seconds; one frame, filter 2, exposure time 2 seconds." [Pause.]
261:57:45 Irwin: Okay. I have that. Joe. It's kind of our standard change in the UV procedures.
261:57:49 Allen: That's correct, Jim. And the mag Metro under the "configure camera" section should be changed to read mag Papa. [Pause.]
261:58:13 Irwin: Okay. Understand mag Papa.
261:58:18 Allen: Okay, Jim. And the last one for you, a biggie, turning over four pages to the "Sextant Photo Test", strike the line "PCM Cable". [Pause.]
261:58:39 Irwin: Okay. Eliminate PCM cable on - on the Sextant Photo Test.
261:58:43 Allen: Roger. [Pause.]
261:58:52 Irwin: Can we go back now to the very first one? [Pause.]
261:58:58 Allen: Jim, I knew you were going to ask that. The first one, I guess, was a small typographical error, and there's no change required there. And, please don't tell Dave about it. He's keeping score against me.
261:59:17 Irwin: Okay [chuckle].
Long comm break.
Of course, Dave can hear everything that's being said.
The PCM cable was found to be missing early in the mission. It was intended to electronically indicate to Mission Control when a camera was being operated for the purposes of accurate data collection. Joe is referring to procedures detailed on page 3-382 of the Flight Plan for the Sextant Photography Test
262:05:21 Allen: Endeavour, this is Houston with a forecast weather report for your landing area. They're calling for a high scattered - 2,000 [feet altitude] scattered, 10 miles vis[ibility], winds about 15 knots out of the east-northeast, waves going to 4 feet, and we're predicting no midcourse 6 correction for trajectory reasons. From the weather report none is required for weather reasons. Over.
Had the weather at the planned landing site been unsuitable, the trajectory of the spacecraft could be altered within limits to move splashdown to a more suitable site. The near limit is set by the ability of the spacecraft and crew to withstand a steeper, hotter, higher-g re-entry. The far limit is constrained by the fact that if the spacecraft enters at too shallow an angle, it will not lose enough velocity before flying out of the atmosphere again, only to re-enter a second time, long after the Command Module's limited reserves have run out.
262:06:04 Scott: Gee, that sounds pretty good, Joe. Except we saw a movie about that weather stuff once. [Long pause.]
262:06:22 Allen: Rog. We copy that. And, Dave, we do have one question. Is it true that nothing can stop the Army Air Corps? [Pause.]
262:06:41 Allen: I'm beginning to believe it. [Pause.]
262:06:49 Scott: Well, that means you're just about qualified. [Pause.]
262:06:58 Allen: I'm glad you still have reservations, though. Your Gamma, by the way, is right on 6.5 as close we can tell right now. [Pause.]
Based on their current trajectory, Mission Control expect the spacecraft to intercept the atmosphere at an angle of 6.5° to Earth's local horizontal. This is in the middle of the prescribed range of angles and indicates that their navigation is spot on.
262:07:12 Scott: Well, that's pretty good. Must be compensating errors along the way somewhere.
262:09:41 Scott: We reviewed our entry stowage last night. We're going to do the stowing this morning. And in the process, why, we came up with one extra little bag up here, which we're labeling LM return items, which is essentially the same thing as 14 brought back. And I wonder if you might check with our good FIDO and see if he wants the details of that, or whether maybe Ed Mitchell can give you the general kind of items, and that would be acceptable. But we have one - one bag, which I'm sure you're aware of, and we'll stow it and tell him exactly where we stowed it. And if he wants the details, well, we'll give it to him.
262:10:22 Allen: Okay, fine, Dave. We copy that, and pass that information along. I have the morning news report if you're interested in listening.
262:10:33 Scott: Rog. Everybody's hooked up and listening. Go.
262:10:38 Allen: Roger. This is the news for 6 August, 1971. In the first round in the American Classic at Firestone Country Club, Akron, Ohio, the leaders are Jerry Heard and Mike Hill, both with 3 under par 67s. Arnie Palmer shot a 70 and Nicklaus a 73. The U.S. built its gold medal total to 50 in the Pan Am Games, and they're entering their second week now. Cuba is a distant second with 17 gold medals, but a Cuban set a world record yesterday in the hop, skip, and jump. The record was 57 feet, 1 inch. We're coming up on the first full weekend of national football exhibition games, and New Orleans Saints play the Buffalo Bills; Dallas Cowboys play the L.A. Rams. And these two games are the beginning of an 11-game weekend. I've got the baseball scores. American League East: Yankee's beat Baltimore, 5 to 0; Boston over Detroit, 5 to 4, American League West: Kansas City over Minnesota, 7 to 4; and Oakland edged out Milwaukee, 2 to 1. The National League: Chicago over San Diego, 3 to 0; Pittsburgh beat Montréal, 7 to 2; and Houston 0, the Dodgers 3. The government reports today the latest figures in the nation's unemployment problem, and one private economist predicts the jobless rate probably will show still another rise. Five days after the steel industry and Union agreed on a new contract without a strike, tens of thousands of steel workers have been laid off, and the hearths are cold as users consume steel-strike-preparedness stockpiles. William Martin, Jr., who reorganized the New York Stock Exchange 33 years ago, proposes an overhaul of the entire securities industry. [Pause.]
262:13:00 Allen: We want to interrupt here. If we could have Accept, please, we'll provide you with a new state vector.
Placing the Up Telemetry switch to Accept allows the computer to accept information radioed digitally from Earth, in this case to upload revised numbers that define their best estimate of the spacecraft's position and velocity in three dimensions.
Allen (continuing with the news): The Senate shelves, until September 13, that compromise draft-extension bill, which Nix - President Nixon wants now, and when it comes up, it will, quite possibly, face a filibuster. [Pause.] The U.S./Middle East expert Joseph Sisco concludes "practical and concrete," and those are in quotes, talks in Israel. He says no decisive breakthrough was achieved, and he didn't expect any. The Middle East cease-fire, which went into effect last August 7, hasn't ushered in peace, but it has suspended Israeli-Arab fighting. The last 12 months have been the best year for Israel since 1967 and the euphoria induced by results of the Six-day War. A government study says Americans will spend more than 105 billion for medical care in 1974, and even the most ambitious Federal health insurance proposal would add less than 12 billion to the tab. [Pause.] Congress is set to embark on a month-long summer vacation after the Senate completes action on a measure keeping Federal agencies in business until October 15. That's good news. And - a - an added word which could be a science update; you may have heard yesterday, but let me repeat it anyway. We've had very clean laser returns off the LR cubed, which is located at Hadley Base; In fact, very good and immediate returns from that. Also, as you know, we have a good subsatellite orbiting the Moon, and are getting data from all the experiments onboard that. Over.
262:15:06 Scott: Oh, that's very good news, Joe. Thank you. We hadn't heard about the LR cubed, but we were hoping it was super-clean. [Pause.]
The LR cubed, or LR3 or LRRR is the Laser Ranging Retro-Reflector. It is an array of glass cube-corners which have the property of reflecting a light beam back in the same direction from whence it came, similar to reflectors placed on bicycles to improve their visibility in car headlights. Dave and Jim placed the third LR3 on the Moon (see the Apollo 15 Lunar Surface Journal starting at 124:19:13), forming a network with reflectors set up by the Apollo 11 and 14 crews. By sending laser pulses from Earth to these reflectors and timing how long it takes for a return reflection, it is possible to measure the intervening distance to great accuracy and to monitor changes in that distance over time. During training and while actually deploying it, it had been made clear to Dave and Jim that it ought to be kept "super-clean", something that could be very difficult to achieve in the dusty, low-g environment of the Moon.
262:15:19 Allen: Roger; and it's your computer.
262:15:25 Scott: Rog.
262:15:27 Allen: And, an added a note for Al. Alfredo, I'm not sure if you got a report on your bistatic radar experiment. Taylor Howard got very, very clean echoes on both the S-band and the VHF frequencies, and he's busy analysing that data right now.
During some near-side passes of the Moon, the spacecraft's antennae were aimed at the lunar surface for the Bistatic Radar Experiment. The echoes received by antenna on Earth yield information about the electrical properties of the surface and can reveal some structure in the subsurface.
262:15:51 Worden: Very good, Joe. [Long pause.]
262:16:48 Allen: Endeavour, this is Houston with a final update concerning the trusty LCRU on the lunar surface. We turned it on yesterday, and it worked beautifully for about 13 minutes. We w - we were panning around, zooming in and out, got a few more good pictures of the - the surrounding mountains, and suddenly we lost the TM [telemetry] downlink. In fact, we lost everything in a very short time, about 1/60th of a second, almost as though someone had turned it off. We tried - we waited awhile and tried to reactivate it, and did such things as send signals back to it to pan around, while we looked carefully on the passive seismometer for evidence of motion. Apparently it was not responding to the signals. The temperatures were completely normal right before it went off the air. We're not exactly sure what happened. Over. [Pause.]
The LCRU (Lunar Communications Relay Unit) is a suitcase-sized box mounted on the Rover which integrated all the communications requirements of the crew on the surface into one package, being an interface between their VHF communications and the S-band links to Earth. It also handled the remote control function for the Rover's TV camera.
262:17:59 Scott: Gee, that's interesting, Joe. It's - you sh - I guess it completely went off, and just didn't get hung up somewhere.
262:18:06 Allen: That's right, Dave. It wasn't a mechanical problem. We most likely popped a circuit breaker or something like that. It's a little difficult to sort out.
262:18:18 Scott: Would you like us to go back up and check it for you?
262:18:23 Allen: Knew you were going to ask. Stand - stand by. [Long pause.]
262:18:51 Scott: Joe, I'm - I'm in - I'm interested in hearing you say that the temperatures were normal. One of the things that - Of course, we'll debrief them on when we get back, but Jim and I both noticed that each successive day was warmer than the preceding day. And, on the last day, if you left your hand or something in one position for any period of time, it would really - the suit would really heat up on that particular surface. And I'm surprised that the system ran this long with that temperature up there, because I suspect it really got pretty hot. [Pause.]
262:19:30 Allen: Dave, that's interesting comment. By normal, I guess I mean within limits. It apparently was about 90 degrees [Fahrenheit, 32°C] on the LCRU and about 90 de - 92 degrees [F, 33°C] on the camera when it gave up the ghost. However, that's well within its limits, and we don't think that circuit breakers, or whatever, let go because of the temperature. The one thing we did not have sensored, as I understand it, were the - the batt[ery] temperatures of the Rover that was - that was feeding the power into the TV, however. [Pause.]
262:20:11 Scott: Gee, 92 sounds pretty cool to us. I - I would have guessed much - much hotter than that. That's a pretty good thermal system on it, if it kept the temperatures down that low.
Thermal blankets, solar radiators and the melt-freeze cycle of a number of wax packages on top of the LCRU were designed to keep the internal temperature stabilised.
262:20:23 Allen: That's correct. [Pause.]
262:20:27 Scott: Or maybe [laughter] Jim mentioned maybe that's centigrade, huh? [Pause.]
262:20:36 Allen: Negative on the centigrade, Dave. However, when we turned the camera off at the end of EVA 3, the temperature was up around 122 degrees [F, 50°C]. [Pause.]
262:20:52 Scott: Yeah, I'd believe that, easily.
Long comm break.
As with all anomalies during a mission, the loss of the radio link with the Rover was extensively researched to try and determine its cause. The main clue to the problem was the rate of decay of the signal received on Earth from the LCRU as it died. While the crew was on the surface, the unit was powered from its own batteries. Before they left the Rover for the last time, the power was switched to the Rover's batteries via a capacitor so the lift-off could be watched from Earth and the progress of the lunar day and the changes in lighting could be monitored. In tests with a duplicate unit, the observed rate of decay could only be duplicated by disconnecting this external power supply.
Despite Allen's comment, suspicion does eventually fall on a 7.5-amp circuit breaker which, in tests, did open at high temperature when the heatsink effect of its connecting wire altered it characteristics. In subsequent missions a 10-amp breaker was substituted.
262:26:02 Allen: Endeavour, this is Houston. The Surgeon reports that we have good respiratory data from your biomed volunteer, but we have evidence that one of the three EKG leads is open-circuited, either not attached or broken somewhere. And, sometime over the next few hours, we'd like - we'd like you to troubleshoot this for us, please; and, if need be, there is an extra biomed harness in the medicine kit. Over.
262:26:37 Scott: Roger. Okay. We'll check into that.
Very long comm break.
As the crew finish their breakfast, the current period of X-ray data collection comes to an end. Al has a few tasks before the PTC roll is re-established and he proceeds with a realignment of the spacecraft's IMU (Inertial Measurement Unit) platform using program 52. For this realignment, Al sights on the stars Menkent (computer code 30) and Alphecca (code 43) to derive the torquing angles for the platform. As the spacecraft is stable and the HGA (High Gain Antenna) is in use, Mission Control can directly view these angles as Al brings them up on the DSKY. The platform is being realigned to the PTC REFSMMAT, an orientation that makes it easier for Al to set up the PTC roll.
Meanwhile, to keep the cabin atmosphere cleansed of exhaled carbon dioxide, the crew change a lithium hydroxide canister, number 20 in receptacle A, for a fresh one, number 22.
263:08:27 Irwin: Okay, Joe, I have the crew status. We all got 8 hours sleep. PRD readings were: Al was 25031, and mine was 08042. Consumables at 261:00; RCS total, 38. Quads: 42, 32, 39 and 38. H2: 34, 32 and 33. O2: 49, 50 and 40. Over.
263:09:07 Allen: Okay, Jim. Thank you.
Very long comm break.
As Jim will report the next day, at 287:56:16, Dave's PRD is out of business.
This is Apollo Control at 263 hours, 25 minutes Ground Elapsed Time. Shift change underway here in the Control Center. Spacecraft now 127,788 nautical miles [236,663 km] inbound toward Earth at a velocity of 4,181 feet per second [1,274 metres per second].
Al's next task is to prepare the optical system for another set of cislunar navigation sightings as part of the their backup ability to navigate themselves to a successful splashdown in the Pacific Ocean tomorrow. Once the optics have been calibrated and the spacecraft maneuvered to the required attitude for the exercise, Al measures angles between three stars and Earth's horizon on the opposite side of Earth from the star using P23 in the computer. The three stars are Zeta Tauri, Alpha Tauri (Aldebaran) and Alpha Aurigae (Capella). The positional information derived from this fix combined with the time of the measurement and a knowledge of where their current state vector ought to place them allows the computer to update the state vector as required and thus allow the entry angle, or gamma, to be calculated.
263:25:58 Worden: Houston, 15.
263:26:04 Henize: Go ahead, 15.
263:26:09 Worden: Roger. I've resensored the EKG and appreciate a checkout from the docs down there.
263:26:16 Henize: Roger. Stand by.
263:26:22 Worden: Good morning, Karl.
263:26:24 Henize: Good morning, Al. How are you doing?
263:26:29 Worden: Just fine.
263:26:32 Henize: Says the EKG looks good down here. Hold one.
263:29:27 Henize: Al, your new CapCom is just coming up to speed this morning. I understand that there has been a problem with the biomed harness, and they want to know if the one you have on right now is the one that gave trouble shortly before.
263:29:41 Worden: That's affirmative. And I did find the loose one.
263:29:47 Henize: Okay; we're getting a good signal on you, and I guess that information makes everybody happy down here. Thank you.
263:29:55 Worden: Okay.
Very long comm break.
Worden, from the 1971 Technical debrief: [To Scott.] "I think both you and I got a reaction from the paste or whatever was used on the disk on the biomed sensors. Now, I've still got some welts, some lesions, that I got off those biomed sensors."
Scott, from the 1971 Technical debrief: "I'm not sure it was the paste or just the pressure of the sensor being on that same spot on my skin."
Worden, from the 1971 Technical debrief: "Well, that could be. I'm just wondering if maybe there isn't something that could be looked into to see if there's a different kind of adhesive or something that would alleviate that problem."
Slayton, from the 1971 Technical debrief: "Did they test you for allergy to that paste preflight as they are supposed to?"
Scott, from the 1971 Technical debrief: "Yes."
Worden, from the 1971 Technical debrief: "Yes."
Scott, from the 1971 Technical debrief: "We wore it all preflight."
Worden, from the 1971 Technical debrief: "Maybe you're right, Dave."
Scott, from the 1971 Technical debrief: "We tried to put them exactly in the same spot on launch morning. Dr. Teegan painted a circle on us where they had put those things. I redrew mine every once in a while, and it was very helpful. You just stuck them right where the mark was. And it was real easy to locate them there. But I think that doing it over and over sort of made you a little sensitive in that area. Al and I both have little rings there where the thing sort of cut in. But it was far better than wearing them all the time. I know that we could hardly wait to get ours off after we came up off the surface, because it was really getting irritable. I think it was very beneficial to be able to take those things off and let your skin dry out."
Woods, from 2004 mission review: "After you've come back up from the surface, and they've asked Jim to wear his biomeds again and again, and you're wanting to give Jim a bit of a break because you don't realise there's a problem with Jim's heart rhythm. You talk about how they are really quite sore things to wear."
Scott, from 2004 mission review: "Yeah, quite sore. That goes back to just having [them on] a long, long time. We got ready to go on 15 before the flight and we knew it was a twelve-day flight. We said, 'Can't wear sensors the whole time.' And the doctors said, 'Well, you have to because there's nobody up there to put them on.' We said, 'We can put them on.' They said, 'No you can't.' 'Yes, we can put them on.' They said, 'Well, it won't be in the right place.' We said, 'Oh, it'll be in the right place.' The doctors said, 'No, we're going to have to tattoo you to make sure you put them in the right place.' We said, 'No, you're not going to tattoo us. We'll put them in the right place. Just show us how to do it.' And they finally condescended and putting the sensors on was really no big deal. But some of the other guys came back. I remember, I think 12 came back and they had some real sores. Those things - just - I don't think it's because necessarily what's under them, it's just you cover up the skin, put a plaster on your hand, you cover up the skin for that long and it gets itchy and sore. So we said let's rotate and take them off. So that's what we did."
This is Apollo Control at 263 hours, 52 minutes. The crew is performing a series of cislunar navigation star sightings and Apollo 15 is 126,706 nautical miles [234,659 km] from Earth. Velocity: 4,215 feet per second [1,285 metres per second].
263:58:43 Henize: 15, this is Houston. We still have a concern about your OPS pressure and would appreciate it, if it's at all accessible, to have a reading at the present time. [Pause.]
The OPS (Oxygen Purge System) package that Dave and Jim brought up from the lunar surface, and which Al used during his EVA as an emergency backup, contains a highly pressurised tank which Mission Control want to bleed into the cabin before re-entry.
263:59:01 Scott: Okay; it's - it's pretty well buried right now, Karl. What's your concern on it?
263:59:07 Henize: Well, first of all, they're anxious that the OPS pressure be down close to zero at - at entry, and they'd like to figure out how much they're going to use tonight and how much tomorrow night in order to bring that down. I guess we don't have it tomorrow night. They're - they're anxious to know whether or not it's - we're going to be able to bring down it's pressure in using it tonight. [Pause.]
263:59:34 Scott: Okay. I guess it came down to 800 [psi, 5,500 kPa] from 2,000 [psi, 13,800 kPa] last night, but probably came back up. As soon as we get a chance to do some shuffling around here, why, we'll check it and give you a call.
263:59:46 Henize: Good enough. Thank you.
263:59:51 Scott: Rog. It's sort of down in the bottom of the pile right now; and we're getting ready to start reentry stowage, so we'll be able to - to get to it in a little while.
264:02:48 Henize: Al, the way people talk down here, they're going to give you a medal for good sightings up - up there. They say that the - the gamma [this is the re-entry angle] from this last series of sightings was 6.55 [degrees], whereas the value we have down here is 6.50.
264:03:09 Worden: Roger, Karl.
Comm break.
Now that all the tasks requiring a stable spacecraft orientation are out of the way, Al can get the PTC roll going again. The first part of this is to maneuver the spacecraft to the PTC attitude, essentially broadside on to the Sun. To do this, he enters the three angles for required attitude, with respect the current platform orientation, into the three registers required for Verb 49, collectively called Noun 22. The first angle, for roll, is not defined so the current roll angle, called up by Noun 20, is used instead. The pitch and yaw angles are 90° and 0°, as defined in the Flight Plan. At this point, Al hits a problem.
264:04:33 Scott: Houston, 15. You may have seen an - an excursion there as we started the Verb 49 maneuver to PTC, and we're trying to figure it out, too.
The spacecraft has begun to pitch down unexpectedly.
264:04:43 Henize: We copy.
264:04:46 Voice in Mission Control: What was that?
Comm break.
264:05:49 Henize: 15, Houston. We didn't see any obvious glitches down here, but we're going to go back and look at the data.
264:05:58 Scott: Okay. What happened was, we were loading Noun 22 to the Verb 49; and, apparently on the - the last entry, on the third register, we got about a 1-degree-per-second pitchdown pitch rate, and went to SCS, and then back to ch - to CMC, and tried it again, and it worked just fine.
264:06:25 Henize: Roger. [Long pause.]
264:07:03 Scott: Houston, it looks like we might have got that old 22 degree glitch in the CDU. [Pause.]
264:07:16 Henize: We copy. [Long pause.]
264:08:15 Scott: And, Houston, right now, we're reading about: 93, 93 and 334 on the ball. [Long pause.]
264:08:38 Henize: Roger. [Long pause.]
264:09:27 Henize: 15, this is Houston. We feel that we can get rid of that discrepancy if you'll do a Verb 40, Noun 20.
264:09:36 Scott: Okay, we'll do one of those. [Long pause.]
Verb 40, Noun 20 translates as "Zero ICDU" and "Present ICDU angles"; essentially zeroing out any confusion in the ICDU.
The CDU (Coupling Data Unit) is an electronics box in the lower equipment bay, right next to the CMC. There are two parts to it: The ICDU (Inertial CDU) and the OCDU (Optics CDU), The ICDU and OCDU seem to be quite independent systems, but share a common box simply because of their similar tasks. The inputs to the CDUs come from the "resolvers", devices fitted to pivots that produce pulses when these pivots are turned. There are resolvers on the gimbal pivots on the IMU (for the ICDU) and also on the shaft and trunnion axes of the optics systems (for the OCDU). One positive pulse from a resolver, and the CDU adds one increment to the angle number; one negative pulse, it subtracts one increment from the angle number. It is possible that these "pulses" are a nasty source of error if, for whatever reason, they get out of sync. We speculate that's what has happened, and why the CDUs had to be zeroed out. The system will reset itself after the zeroing is completed.
Now, we might think that zeroing the CDUs would be done only in unusual cases. Interestingly, the "Zero Optics" switch on the sextant/telescope panel not only moves the optics to the zero shaft/trunnion position, it also sends a "zero OCDU" command to make sure that the OCDU angle number is truly reset.
264:10:13 Scott: Yep. Looks like that's what it was.
Comm break.
264:11:18 Henize: Dave, we suspect the cause of that glitch back there was possibly due to the fact that you might have loaded a Noun 20 instead of a Noun 22. Is that possible? [Pause.]
One possibility is that since Noun 20 forms part of Noun 22, the two have been mixed up in some way.
264:11:35 Scott: We're thinking. Stand by. [Long pause.]
264:12:17 Scott: Karl, I guess it's a possibility, but we were both looking at it, and I guess we don't think so, but that's a distinct possibility. [Long pause.]
264:12:52 Henize: 15, Houston. About all we can say is that everything's looking fine at the moment, and we'll go back and look over the data. We haven't had a chance to do that yet.
264:13:01 Scott: Okay. Yes. Roger. Understand. It - it looks fine up here and that - that could have been the problem.
Comm break.
Once the spacecraft has been properly maneuvered, Al can continue with the PTC roll which requires him to use P20, the tracking program.
264:14:49 Scott: Houston, 15. Talking it over, I guess that must have been a - a Noun 20 load because, I guess as I remember it, the CDU glitches occur in increments of 11. And 11 plus 11 doesn't equal 26, I don't think.
264:15:06 Henize: Okay; we copy.
Comm break.
264:16:11 Scott: And, Houston, in our present attitude, a yaw CDU change would be converted to a pitch rate, so that sort of all adds up.
264:18:04 Henize: 15, Houston. When you have some time to listen, I have a couple of sentences of comments on the procedure for the - the light flash experiment.
The crew's third light flash experiment continues their probing into the properties of the visual flashes seen by many crewmembers. These flashes are thought to be due to high energy cosmic rays interacting with their visual system.
264:18:17 Scott: Okay. Why don't you stand by 'til we get our trusty crew all lined up and ready to go.
264:18:23 Henize: Very good. [Long pause.]
264:18:44 Henize: Incidentally, Dave, as we line them up, one of the changes is that we'd like to keep the cabin lights bright this time.
264:18:53 Scott: Oh, you like the lights bright? Okay.
Comm break.
During the first light flash experiment, it seems the cabin lights were dimmed though the crew wore eyeshades to help them become dark-adapted. This change to the procedure is intended to check whether dark-adaptation affects the visibility of the flashes, perhaps indicating whether they are caused by stimulus of the retina or of the brain's visual cortex. As Karl Henize is about to explain, one of the crew will expose their eyes to the cabin lights for one minute in the middle of the test to see if the count is affected.
264:21:04 Henize: 15, Houston. We see indications that the optics aren't zeroed, and we'd recommend that you zero them, with the reminder, of course, to bring the angles down to 10 degrees - less than 10 degrees before you zero them.
On the third day of the flight, ground controllers noticed that when the optics were motor driven to their zero position, a slight bias was being introduced into their reading. The message went up for the crew to bring the trunnion angle (similar to the tilt axis of a camera tripod) to less than 10° prior to zeroing them.
264:21:18 Scott: Okay; that's - that's standard procedure. We'll get it. Thank you. [Pause.] It's even been written up on the panel for about 8 days now, or so.
264:26:11 Scott: Okay, Houston. Go ahead with your procedures on the light flash.
264:26:15 Henize:Roger. We'd like to have you put the window shades on, as usual, but to leave the cabin lights bright. And what we're going to do is to sort of calibrate one crewman in terms of the degree of a dark adaption required to see the flashes. That would be interesting to know. After you don the eyeshades and give us a mark and go ahead and count things, after a while, you - one of you - and we prefer you, Dave, just to be specific - can expect for us to call up to you to take off the eyeshade for 1 minute. And after a minute we'll do the timing for you, if you like. We'll tell you to put it back on and, in this minute time look around at the lights, get back to sort of - your eyes normally adjusted, then put on the eyeshade again, and - and give us marks as you start seeing things. And that's - that's the only difference from the normal procedure. We would - we would prefer to have all - all the data on the voice downlink, if possible. [Pause.]
264:27:25 Scott: Okay. Understand the - open the eyes, and - Stand by one. [Pause.]
264:27:40 Scott: And, Houston, we talked over the - the downlink bit, and it's just impractical if we're all going to try and keep up with the comments on where and what we see. It would just be too confusing for you. And I think - if - if you cannot get your data from the tape, we'll do that; but, I think it is much more practical to go ahead and put it on the tape and just inform you of when we get the marks.
264:28:05 Henize: Okay, we've had - we've had - we've had some trouble with the tape in the last couple of times around, is the reason the people are sort of saying "Hey, if we could possibly get it down in real time we'd feel happier." [Pause.]
264:28:24 Scott: Oh, you - you mean you - you cannot get the data off the tape, huh? [Long pause.]
264:28:43 Henize: I guess we've been having trouble with the voice quality on the DSE [Data Storage Equipment], and Gerry just now says, "Hey, let's check it right now. See how it's doing." And we'll let you know in the next few minutes as to what's pref - preferable.
264:28:58 Scott: Okay. That's a good idea. [Long pause.]
264:29:57 Henize: 15, this is Houston. It looks as though the DSE voice downlink is acceptable, now; and we'll do it your way. [Pause.]
264:30:11 Scott: Okay. Let us get squared away here and make sure we get all the shades up and all. [Long pause.]
264:30:42 Henize: 15, one more comment on that DSE voice problem. This is, to some extent, dependent on how well your mikes are adjusted. So make sure that they're in a good position.
264:30:54 Scott: Rog. I guess a downlink would probably be the same problem. We'll get them all squared away.
Comm break.
Similar to a simple tape recorder, the DSE stores data and voice on narrow parallel tracks without using the helical scan techniques seen in later tape machines. The machine on board Endeavour has a much higher data packing density than the models used on previous missions, to cope with the upgraded J-mission spacecraft and the data coming from the SIM bay, and it has to work for longer. Over the past day, Mission Control have been having some problems with its first few feet of tape which have been contaminated with flaking silver oxide from the leader tape. Tiny scratches on the recording heads, much higher data densities and a longer mission duration are taking their toll on the recorder's efficiency. This problem, though, might not be directly linked with the quality of the voice track.
264:32:19 Scott: Houston, 15.
264:32:21 Henize: Go ahead, 15.
264:32:25 Scott: How do the rates look for PTC now?
264:32:28 Henize: Just got the word that they look good for spin-up.
264:32:33 Scott: Okay.
264:32:37 Henize: I think that's another great example of ESP at work.
Comm break.
The previous Apollo mission, Apollo 14, gained notoriety in the news media when it was revealed that Ed Mitchell, the Lunar Module Pilot, had independently carried out experiments in ESP (Extra Sensory Perception) during the flight. Though a deeply serious and intellectual man, Mitchell's foray into the fringes of accepted science seemed out of place in the hard science and engineering realm of America's most prestigious agency and, to some extent, was a source of some mirth among his colleagues, therefore the humour from Henize. Joe Allen made a couple of similar quips while Dave and Jim were on the Moon.
This is Apollo Control at 264 hours, 34 minutes. Apollo 15 now establishing a 3/10th's per second rotation, 3/10ths of a degree per second rotation, for Passive Thermal Control. Shortly, the crew will begin the light flash experiments again. The marks on this experiment will be put on the onboard tape recorder. It will not be on the air to ground.
The crew are somewhat surprised to find that they are not seeing any flashes and discuss their attitude relative to possible sources, especially the Sun.
Distance is 124,934 nautical miles [231,377 km]. Velocity; 4,272 feet per second [1,302 metres/second].
264:37:17 Worden (onboard): It's a quiet morning.
264:37:19 Scott (onboard): Say again?
264:37:20 Worden (onboard): It's a quiet morning.
264:37:21 Scott (onboard): Yes.
264:38:47 Worden (onboard): Maybe that means that they come from the Sun. Huh?
264:38:51 Scott (onboard): Hmm.
264:38:57 Worden (onboard): Very interesting. Or that the window shield's cutting them off.
264:39:02 Scott (onboard): No, we had the window shields up before.
264:39:04 Worden (onboard): Did we?
264:39:05 Scott (onboard): Yes.
264:39:06 Worden (onboard): Um hum.
264:39:07 Scott (onboard): Because we had them - the cockpit all dark.
264:39:08 Worden (onboard): Be dark. Yes.
264:39:09 Scott (onboard): Yes, that's right. We did. The only difference now is that the Sun's behind...
264:39:13 Worden (onboard): We're not - we're not pointed at the Sun - Yes. And the Moon's behind us. Some place behind the Sun. Isn't it?
264:39:23 Scott (onboard): No. No, nobody's behind the Sun to us.
264:39:27 Worden (onboard): Hey, we - You know, we're not shielded - we're not - Gee, I don't know.
264:39:44 Worden (onboard): We may not be in orientation in PTC to be looking at the Sun either. Well, that shouldn't make any difference yet. Were we in PTC when we did it before?
264:39:59 Scott (onboard): [Garble].
264:40:00 Worden (onboard): Huh?
264:40:02 Scott (onboard): I think so. Because I remember thinking, "How are they going to figure the attitude?" They'd have to get it off the - the data.
264:40:11 Worden (onboard): Yes.
264:40:19 Scott (onboard): Yes, I see. The - the Sun - will soon be behind the Earth, right?
264:40:25 Worden (onboard): Yes, should be.
264:40:27 Scott (onboard): So, if the Sun is close to being behind the Earth right now, maybe the Earth will shield it.
264:40:32 Worden (onboard): Oh, you mean warpage in the pausal tail?
264:40:37 Scott (onboard): Yes.
264:40:38 Worden (onboard): That could be. It comes out in a - in a pinwheel fashion.
264:40:56 Worden (onboard): Although I saw some last night when I went to sleep.
264:41:00 Scott (onboard): Yes, I did, too.
264:41:01 Irwin (onboard): Yes.
264:41:09 Scott (onboard): That's good, Jim. Is that an hour? [Laughter.]
264:41:14 Worden (onboard): [Laughter.] Change the sheet.
264:41:15 Scott (onboard): Wake up, Jim [laughter].
264:41:16 Worden (onboard): [Laughter.] [Garble] Houston [laughter]. You're [garble]...
264:41:22 Scott (onboard): ...[garble].
264:41:23 Worden (onboard): ...for minutes.
264:41:24 Scott (onboard): All you got to do is repeat that 10 times now, Jim.
264:41:36 Irwin (onboard): Boy, that was fast.
264:46:04 Scott (onboard): Maybe we've been desensitized to them.
265:01:34 Irwin (onboard): Flash at 8 o'clock on the periphery; intensity 2.
265:04:02 Scott: Mark CDR. [Long pause.]
265:04:01 Scott (onboard): It was in the left eye at 6 o'clock at about a third of the way from the center out; intensity 3; point source of light.
265:04:23 Worden (onboard): You two guys must be shielding me.
265:04:27 Scott: Mark CDR.
Comm break.
Al is beginning to wonder whether the other two are shielding him from whatever is producing the flashes and starts some gentle banter with Dave by suggesting that his Commander is making up the results.
265:04:28 Scott (onboard): It was in the left eye about 2 o'clock; a quarter of the way in; intensity 1; point source. Yes, we're taking it all for you, Al.
265:04:41 Worden (onboard): You must be.
265:04:42 Irwin (onboard): I think Dave's imagining all these.
265:04:45 Scott (onboard): Got to do something for the [garble].
265:04:46 Worden (onboard): [Garble] he's gotten to the point where he's conjuring them up on me.
265:04:51 Scott (onboard): Dedicating my imagination to science.
265:04:53 Worden (onboard): Right. Protecting all those who go after you.
265:04:59 Scott (onboard): Wait until you see how many I'm going to see in the last minute [laughter].
265:05:04 Worden (onboard): Confound that curve.
Then, after half an hour, Al sees what he has been waiting for.
265:05:49 Worden: Mark CMP.
Comm break.
265:05:47 Worden (onboard): Mark CMP.
265:05:48 Scott (onboard): Yay!
265:05:49 Worden (onboard): Left eye; dead center; intensity 2; point source. Only ones I can see are the ones that hit me right between the eyes like a ...
265:08:03 Worden (onboard): Right eye; about 1 o'clock; 2/3rds of the way out; intensity 2; and a little streaking - some towards the center of the eye - about another third of the way down.
265:09:03 Irwin (onboard): Do you have your eyelids closed?
265:09:06 Worden: Mark CMP.
Comm break.
265:09:07 Worden (onboard): Two flashes: one at 9 o'clock in the left eye and one at 6 o'clock in the left eye; both intensity 3. Yes, my eyes are closed, Jim.
265:09:17 Irwin (onboard): Your eyelids are closed.
265:09:18 Scott (onboard): Yes. Me, too.
265:09:24 Worden (onboard): Your eyelids aren't going to stop anything.
265:09:27 Irwin (onboard): Don't think so. Just want to get consistent data.
This is Apollo Control at 265 hours, 10 minutes. The Apollo 15 crew has about another 10 minutes left in the light-flash experiment. They're recording this data on the onboard tape recorder. Although obviously every once in a while the Command Module Pilot keys the air to ground when he takes a mark; you can hear that. Apollo 15 now 123,490 nautical miles [228,703 km] from Earth. Velocity: 4,320 feet per second [1,317 m/s]. We're 30 hours away from landing.
In fact, the crew are keying their mike on every count, then allowing their description of it to be recorded on the DSE. On the next mark, Jim keeps his mike keyed.
265:10:34 Irwin: Mark LMP. Flash. One at 4 o'clock, halfway out. Another one at 2 o'clock on the periphery. Intensity 3. [Long pause.]
265:11:18 Worden: Mark CMP. [Long pause.]
265:11:19 Worden (onboard): Two o'clock; almost on the periphery; and intensity between 3 and 4. Bright one.
265:11:53 Worden: Mark CMP.
Comm break.
265:11:54 Worden (onboard): Two o'clock; streak from right to left; centered about the 2 o'clock radial; about halfway out; intensity 2.
265:28:51 Irwin (onboard): Flash; position 2 on the periphery; right eye; intensity 2.
265:29:00 Irwin: Mark LMP. [Long pause.]
265:29:01 Irwin (onboard): Same position; intensity 4; flash.
At this point the recording on the DSE stops.
265:29:54 Henize: 15, Houston. Be advised the DSE just ran out tape. If there's anything significant to be said from here on in, say it on the air to ground, please.
265:30:04 Scott: Okay. Will do.
Comm break.
265:31:19 Irwin: Mark LMP. Flash. Four o'clock, about a quarter of the way out. Intensity 3. [Long pause.]
265:31:48 Scott: Mark CDR. Right eye; a streak about 3 o'clock to 6 o'clock. Intensity 2. [Long pause.]
265:32:31 Scott: Mark CDR. Point source; right eye, 12 o'clock, halfway out. Intensity 2. [Long pause.]
265:33:31 Scott: Mark CDR. Right eye; point source; 7 o'clock about half way out; intensity 2.
Comm break.
One hour assigned to the experiment passes at 265:35:28. Readers might note that one of the crew does not appear to have exposed their eyes to the cabin lighting in the middle of the experiment as was requested at the start of the experiment.
265:36:48 Henize: 15, this is Houston. We find an hour's passed now, and we thank you very much for the data, and there's a general question. Since the counting rate was less than previously, is there - is there any impression that you have that the intensity may have been less than previously. Also, the intensity of the individual flashes. [Pause.]
265:37:13 Scott: Rog. I think that'd be a general comment that all three of us experienced. [Long pause.]
265:37:35 Scott: And, Houston, also, you might note that we all saw flashes last night when we went to sleep - just before we went to sleep, and I guess - we feel like there's a surprising decrease in numbers and intensity today.
265:37:53 Henize: Roger. We copy that you feel today's frequency is less than last night's and also that the intensity is less today. [Pause.]
265:38:09 Scott: Rog. That's correct. [Pause.]
265:38:17 Henize: Thank you very much for the free information. [Pause.]
265:38:24 Scott: Okay.
Comm break.
The crew is scheduled to begin a 1-hour exercise period followed by a 1-hour mealbreak.
265:40:53 Irwin: Looking back at 264:16, there's a callout there to close the Mapping Camera cover. We did not do that because [of] the extension of the Mapping Camera. [Pause.]
265:41:16 Henize: Roger. We concur with you that that was the right action; the one that you took. [Pause.]
265:55:36 Henize: 15, this is Houston. We'd like to set your mind at ease about that attitude glitch [at 264:04:33]. It was indeed due to loading a Noun 20 in place of a Noun 22.
265:55:48 Scott: Okay. Thank you.
Long comm break.
This is Apollo Control at 265 hours, 57 minutes. Apollo 15 now 121,548 nautical miles [225,106 km] from Earth. Velocity has increased to 4,385 feet per second [1,337 m/s].
266:04:13 Scott: Houston, Apollo 15. The OPS pressure is 1,000 [psi, 6,900 kPa].
266:04:18 Henize: Roger, 15. We copy 1,000 on the OPS pressure. And we have a suggestion down here that may make the OPS - simpler to handle. We'd like to put the hose over its connector there and simply turn the OPS on to bleed down gradually and simply replenish the cabin pressure and then you don't have to bother with you - operating it tonight.
266:04:48 Scott: Rog. That's sounds like a pretty good idea. Okay; we'll do that.
266:04:51 Henize: Rog. And then everybody will be completely satisfied that it's bled out by the time you reenter.
This is Apollo Control at 266 hours, 17 minutes. And at 28 hours, 54 minutes away from landing, Apollo 15 is 119,694 nautical miles [221,673 km] from Earth. Velocity: 4,413 feet per second [1,345 m/s].
This is Apollo Control at 266 hours, 23 minutes. A briefing on the subsatellite in lunar orbit is scheduled for the MSC News Center Briefing Room at 11 am today Central Daylight Time. This briefing will not be carried on the PAO release line.
This is Apollo Control at 266 hours, 50 minutes. Apollo 15 will reach the halfway point, in distance, from the Moon to the Earth at 271 hours, 30 minutes, 34 seconds Elapsed Time. At that time the distance will be 106,662.7 nautical miles [197,538.9 km]. Earth-referenced velocity will be 4,920 feet per second [1,500 m/s]. The Moon reference to velocity: 4,077 feet per second [1,243 m/s]. At this time, Apollo 15 is 119,243 nautical miles [220,838 km] from Earth, and the velocity is 4,462 feet per second [1,360 m/s].
267:08:33 Henize: 15, this is Houston with a couple of comments about the SIM bay experiments, if you're willing to listen. [Pause.]
267:08:46 Scott: Rog, Houston. Go ahead.
267:08:50 Henize: First of all, on the Gamma-ray experiment, Dr. Arnold reports that Al Worden probably performed the first recorded repair of a scientific instrument in space, because earlier in that day he'd began to experience some problem with excess noise in the Gamma-ray experiment. And when Al went out in the EVA - we don't know what happened there - but at the end of the EVA, the Gamma-ray cleared up and has been doing beautifully ever since. You must have given it a pretty good kick there, Al.
267:09:29 Scott: Well, not - not only is he a plumber, he's an electrician as well.
267:09:32 Henize: Roger. On the X-ray Spectrometer, the work you've been doing on the galactic sources of X-radiation has - is already showing considerable interest. And, in particular, the Scorpius X-ray 1 data gives us a longer continuous observation of this source than we've ever had before and shows a fairly long period variation, whi - which - I with - I should put in a word of caution - which still might be instrumental, but looks real, and was previously unrecorded and has the - has Dr. Adler rather excited. And I'm sure the other as - astronomers will be much interested also. Indeed, we may go back to that source later today, although I don't think that's clearly decided yet. [Pause.]
The Apollo 15 Preliminary Science Report reveals that these variations in the X-ray measurements from Scorpius X-1 might be due to wobbles in the spacecraft's attitude. As has been regularly discussed in this journal, the spacecraft can never adopt a precise attitude. Rather, it constantly tends to drift, being brought back within an acceptable range of attitude limits called the deadband. Outside of this deadband, the computer takes active measures using the RCS jets to bring the attitude back in.
Even though the deadband was 1° wide (±0.5°) during the measurement, this amount of variation in the pointing accuracy of the X-ray Spectrometer is enough to cause variations of up to 1.5 per cent. However, superimposed on this were larger, long-term variations in the X-ray flux from Scorpius X-1 which were believed, at the time to be statistically significant.
267:10:32 Scott: Rog. That sounds interesting.
267:10:34 Henize: And otherwise, I guess - that - that's about the most exciting news from the SIM bay.
267:10:46 Scott: Okay. Very good. We're ready to talk about entry stowage, if you'll get out your - your map and your little legend there...
267:10:55 Henize: Okay.
267:10:56 Scott: ...on where things go and we'll run down the line here.
267:10:59 Henize: Okay. We've - incidentally - one more comment, the Mass Spectrometer, on the retraction sequence yesterday, showed us no increase in contamination, which was something of a surprise. And it's probable that we might try that once more today to make sure that that wasn't some sort of instrumental difficulty there. Maybe we just have a cleaner spacecraft atmosphere than we thought, though.
267:11:25 Scott: Yes, from what Al said when he was looking around out there, it sounded to me like things were pretty clean.
267:11:30 Henize: Roger. [Long pause.]
This conversation refers to an experiment carried out yesterday which tested the degree of gaseous contamination around the spacecraft. The Mass Spectrometer was operated on its boom at varying distances from the spacecraft and the science team hoped to characterise the gases at different distances from the hull. These contaminants could include oxygen leakage from the cabin, water and urine dumps, RCS propellant, water from the cooling evaporators.
267:11:51 Henize: Okay, 15. If you will turn off your squelch it will help, because we may occasionally have periods in - when comm is rather weak. And, otherwise, go ahead.
267:12:04 Scott: Okay. What - what we use as a reference is the Entry Stowage Map, spacecraft 112, 26 July 1971, which is in the front of our Flight Plan. And, if you have that in front of you, why, I'll just go through that and give you the additions, deletions, and changes, of which there are very few. [Pause.]
Endeavour is returning a substantial amount of cargo to Earth including 76.8 kilograms of rock. The placement of all this material within the cabin cannot be left to whim. Rather, it is important that the spacecraft's centre of mass, and therefore the distribution of mass inside, be carefully controlled for its flying characteristics depend on it. Since the centre of mass is displaced away from the physical centre, the spacecraft's shape provides it with a small, but important degree of lift as it re-enters the atmosphere. This will be used to fly the spacecraft to the landing site in the Pacific Ocean. Ground controllers will check the placing of items in the cabin to keep the position of the centre of mass within limits.
267:12:30 Henize: Okay. We're [pause] - Stand by one moment.
267:12:40 Scott: Okay. [Long pause.]
267:13:16 Henize: Okay. Go ahead. [Pause.]
267:13:23 Scott: Okay. A-1 is stowed as prescribed there. Top of A-1 has a bag - a decontam bag in which we have sample container number 2, for 23 pounds, and the LM return items. [Pause.]
267:13:50 Henize: Roger.
267:13:53 Scott: A-2 is as you have listed. [Long pause.]
267:14:10 Henize: Roger.
267:14:13 Scott: And, on top of A-2, we have the ISA decontam bag, for 64 pounds.
267:14:22 Henize: We copy.
267:14:27 Scott: Okay. A-3, A-4, A-5 and A-6 are as you have on your list right now.
267:14:33 Henize: We copy.
267:14:37 Scott: A-7 is as you have on your list, with the addition of the LM DAC and the LM - 70 millimeter camera that failed on the surface, which we thought you might like to take a look at.
While at Hadley, the crew had two failures with their cameras. By returning both, engineers can determine the cause of the problems and rectify them before the next flight.
The DAC (Data Acquisition Camera) is a small 16-mm movie camera, one of which was taken to the lunar surface. Five of the eight magazines taken with it jammed in use. Post-flight analysis found that the problems were due to procedural errors and training was improved for subsequent flights.
Jim's 70-mm Hasselblad stills camera failed during their second and third lunar EVA, only to resume functioning once returned to the spacecraft. It was used successfully on the trip home. Post-flight analysis found that two set screws on the motor drive spindle were slipping and steps were taken to prevent this on subsequent cameras.
267:14:51 Henize: Right. Both of those are - are added items, I take it.
267:14:56 Scott: That's correct. [Pause.]
267:15:04 Henize: We copy.
267:15:08 Scott: Side of A-7 is the EVA umbilical and bag, as per - prescribed.
267:15:13 Henize: Rog.
267:15:16 Scott: Top of A-7 is a sample collection bag - Oh, stand by. [Long pause.]
267:15:39 Scott: Okay. Let me - let me go back and make a correction here, Karl. Look over in the left-hand column where it says top of A-1, and scratch "Sample collection bag number 2."
267:15:53 Henize: Okay.
267:15:56 Scott: And then go back to your right-hand column there. On top of A-7, we have a decontam bag with sample collection bag number 2 and the BSLSS bag, for a total of 48 pounds. [Pause.]
267:16:16 Henize: We copy. [Pause.]
267:16:21 Scott: Okay.
267:16:19 Scott (onboard): The 35-millimeter bracket in the bag, we're going to put that in the...
267:16:24 Henize: Could I clarify that - both of those bags together were 48 pounds, or do I also put over the 20 - the 23 pounds we had on A-1?
267:16:26 Irwin (onboard): That's going to go in there.
267:16:35 Scott: No, the total of collection bag number 2 plus the BSLSS is 48 pounds.
267:16:40 Henize: I understand.
267:16:45 Scott: And you can scratch the collection bag number 2 for 23 off of A-1.
267:16:49 Henize: Roger. [Pause.]
267:16:58 Scott: Okay. And then in A-8, it's stowed as prescribed [radio noise] with the exception of one less lightweight headset, which is some - somewhere on the Moon.
267:17:18 Henize: Roger. [Pause.]
267:17:24 Scott: Okay. On the side of the next page in the left column, on the side of A-8 in the bag, as you have there, with the addition of the core tube pole. [Pause.]
267:17:43 Henize: Say again.
267:17:48 Scott: Okay. I - I figured that would be a strange one. On the side of A-8 in bag, there are four items there, and one additional item has been added. The drill core-stem, which we just labelled as a core tube pole, because it looks like a pole.
267:18:05 Henize: Roger. That's the three-foot core stem.
267:18:09 Scott: That's correct. [Pause.]
267:18:15 Henize: Okay.
267:18:18 Scott: And A-9 is collection bag number 3, for 30 pounds.
267:18:27 Henize: We copy.
267:18:31 Scott: B-1, B-2 and B-3 are as you have them listed.
267:18:38 Henize: Okay.
267:18:41 Scott: B-5 is rock box number 1, for 36 pounds; and B-6 is rock box number 2, for 40 pounds.
267:18:51 Henize: Okay. We copy.
267:18:57 Scott: And then B-5 and 6, B-8, L-2 and L-3 are as you have them listed.
267:19:06 Henize: Okay.
267:19:11 Scott: And R-1 is the Flight Data File and the LM PPK. [Pause.]
267:19:21 Henize: We copy.
267:19:26 Scott: And then, on the next column, they're all as you have listed. From the top; R-2, R-3, and in R-3 we have the entire LM data file. And we've taken R-12 out of R-3 and put it in another spot.
267:19:47 Henize: Okay.
267:19:51 Scott: R - far - R-4 is as you have it, as is R-5, R-6, R-8, R-11, R-13.
267:20:02 Henize: We copy.
267:20:06 Scott: Okay. U-1 will only have one temporary stowage bag in it.
267:20:12 Henize: We copy.
267:20:16 Scott: U-2 will have the items listed, plus the accessory bag, in which we have - the contaminated gloves. And I'll read you a list of those items, if you're ready to copy.
267:20:29 Henize: Okay. Go ahead.
267:20:33 Scott: Have one set of EV gloves and one set of IV gloves, the tethers - the - the waist tethers, paper towels. And I guess that's about it.
267:20:47 Henize: Roger.
267:20:51 Scott: U-3 is as you have prescribed there.
267:20:56 Henize: Roger. [Pause.]
267:21:02 Scott: Stand by one, Karl. [Long pause.]
267:21:46 Scott: Okay, Houston. Ready to go with the right-hand column. U-4 is as prescribed, and R-2 is as prescribed.
267:21:54 Henize: Roger.
267:21:59 Scott: Okay. The PGA bag is as prescribed with the following additions. First we have - in - in the bag where we'll put the lunar sample - we'll have R-12, with the CSM Malfunction Procedures and Systems Book. [Pause.]
267:22:26 Henize: We copy.
267:22:29 Scott: And the lunar sample is bag number 7, for 24 pounds. [Pause.]
267:22:40 Henize: Roger.
267:22:47 Scott: Okay. And then, everything else is as prescribed. And the CMP PGA will be in the sleep restraint under the right-hand couch with two TSBs, which are now acting as waste containers. [Pause.]
267:23:10 Henize: Roger. And that - that location was where again?
267:23:17 Scott: Underneath the right-hand couch, strapped down as - as it's prescribed. We just wanted to note that, within that sleep restraint with the PGA, will also be two TSBs.
267:23:29 Henize: Roger. We copy.
267:23:34 Scott: And that's just light waste material in those TSBs. And I guess that pretty much takes care of it, unless you have any questions. [Long pause.]
267:23:54 Henize: Thank you, Dave. We copy all of that.
267:23:59 Scott: Okay. And, as you go through it and look it over, if you have any questions or anything you would like us to shuffle around, why, let us know.
267:24:09 Henize: Okay. We sure will. Thanks.
Very long comm break.
267:25:44 Irwin (onboard): ...to have some wet packs. I think I'll finish what I have, and then I still - Yes, I'll hit the wet packs.
267:25:59 Worden (onboard): That's enough to keep us alive.
267:26:01 Scott (onboard): Oh, yes.
267:26:02 Worden (onboard): Do we have - How many deals do we have to mark? Two?
267:26:05 Scott (onboard): Just two. Let me stick that in there, too.
267:26:08 Worden (onboard): Great. I think, Just to clean this place out a little bit, I'm going to take some of these bacon squares and throw them.
267:26:23 Scott (onboard): Yes [laughter]. It's probably a good idea.
267:26:46 Worden (onboard): As a matter of fact, we could consolidate a lot of this stuff.
267:26:48 Scott (onboard): Yes.
267:26:50 Worden (onboard): We could use these bags for garbage bags.
267:26:53 Scott (onboard): Yes.
267:27:00 Irwin (onboard): You dropped yours.
267:27:06 Scott (onboard): God damn! Dropped it on the floor. Lord a'mighty.
267:27:32 Scott (onboard): Get what you want?
267:27:35 Worden (onboard): Yes.
267:27:41 Irwin (onboard): Oh, a little spaghetti. I had some for breakfast; it wasn't bad. A vast spectrum.
267:27:54 Scott (onboard): Two meals tomorrow, breakfast, and two more meals today...
267:28:05 Irwin (onboard): One - two - Uh-oh, we'll have to eat - to eat fast, to eat it all up.
267:28:13 Worden (onboard): No, I don't think so [laughter]. I think we're going to be there.
267:28:17 Scott (onboard): Do you guys think...
267:28:18 Worden (onboard): We've got 10 wet packs.
267:28:19 Scott (onboard): Ten wet packs, huh?
267:28:22 Worden (onboard): Yes, one for lunch, one for dinner, and - one for tomorrow.
267:28:50 Scott (onboard): Want a wet pack, Jimmy?
267:28:52 Irwin (onboard): Yes, I'll probably take one as long as you got them out.
267:28:54 Scott (onboard): Anybody tried the beef stew?
267:28:55 Irwin (onboard): Yes, I have a beef stew here.
267:28:57 Scott (onboard): Mine was pretty good.
267:28:58 Scott (onboard): I'll try one.
267:28:59 Scott (onboard): You want to try one?
267:29:00 Worden (onboard): Yes.
267:29:03 Scott (onboard): Pretty interesting.
267:29:06 Worden (onboard): Have a wet pack.
267:29:10 Scott (onboard): Okay.
267:29:14 Worden (onboard): [Garble] get the drinks out here.
267:29:18 Scott (onboard): And right now you got a P52.
267:29:21 Worden (onboard): Oh, really.
267:29:22 Scott (onboard): Just to stir you up a little bit.
267:29:25 Worden (onboard): Okay. Here's the beverage.
267:29:27 Irwin (onboard): Okay. What kind of beverage do you want here, Dave?
267:29:33 Scott (onboard): I can't take anything but water, grape, and cocoa. I'm through with that other stuff. Somebody ought to...
267:29:37 Irwin (onboard): There's one grape left.
267:29:38 Scott (onboard): Well, you can have it.
267:29:39 Irwin (onboard): Getting lucky.
267:29:40 Scott (onboard): I don't care. I'll just drink water.
267:29:41 Irwin (onboard): Oh, I - I'd like the grape, too.
267:29:43 Scott (onboard): I can't take anymore. I've had 21 days of those juices, and that's all I can handle.
267:29:51 Irwin (onboard): Yes. I'm with you, pal. I feel that way about a lot of this stuff. Well, what do you want to drink, Al? Did you get your drink?
267:29:59 Worden (onboard): No, not yet.
267:30:00 Irwin (onboard): Do you want an orange?
267:30:02 Worden (onboard): Yes, I don't guess there's any pineapple left, is there?
267:30:05 Irwin (onboard): There's a pineapple-orange.
267:30:07 Scott (onboard): Is there a pineapple-orange in there?
267:30:08 Irwin (onboard): Yes.
267:30:09 Worden (onboard): Yes, that's what I'd like.
267:30:17 Irwin (onboard): No, I take that back. There's an orange-grapefruit. There's no - no pineapple. What's your choice?
267:30:24 Worden (onboard): Oh, I'll have an orange.
267:30:25 Irwin (onboard): Okay.
267:30:48 Scott (onboard): Is that P52 due now?
267:30:50 Worden (onboard): Yes.
267:30:51 Scott (onboard): Okay. Jim, put these back.
This is Apollo Control at 267 hours, 35 minutes. Apollo 15 is 117,343 nautical miles [217,319 km] from Earth. Velocity: 4,528 feet per second [1,380 m/s]. All systems performing normally, and the back up Command Module Pilot Vance Brand has joined CapCom Karl Henize.
267:35:44 Henize: 15, we have your torquing angles. [Pause.]
267:35:54 Scott: Ro - Roger.
Very long comm break.
Prior to making another set of P23 navigation sightings, Al realigns the IMU to the PTC REFSMMAT using P52. For this he sights on Polaris (code 05 in the computer), also known as the North Star and as Alpha Ursae Minoris, and Aldebaran (code 11) or Alpha Tauri. As the spacecraft's systems' are being relayed to Earth by the High Gain Antenna (HGA), Mission Control note the three platform torquing angles as Al brings them up on the DSKY. These are -0.005° in X, -0.006° in Y and +0.019° in Z. On this occasion, the star difference angle is zero. This means that the measured angle and known angle between these two stars is the same. Al's sighting accuracy is excellent.
Having completed the P52, Al stops the PTC rotation and maneuvers Endeavour to an attitude, given in the Flight Plan, from which he can calibrate the spacecraft's optics prior to another period of cislunar navigation. This is the first in a series of tasks, including photography of Earth and of an upcoming lunar eclipse, which will have the spacecraft being maneuvered to various attitudes. For the P23 sightings, angles are given in the Flight Plan to point the HGA at Earth.
Al's three sightings for the cislunar navigation are to measure the angles between the following: Elnath (Beta Tauri) and Earth's horizon furthest from the star, Capella (Alpha Aurigae) and Earth's horizon furthest from the star, Alphard (Alpha Hydrae) and Earth's horizon nearest the star. Note that at this point of the flight, Endeavour is poised almost equidistant from the Moon and Earth while, in a couple of hours, Earth's shadow will sweep over the Moon.
Diagram showing the current geometry of the spacecraft with respect to Earth and Moon, prior to the eclipse.
This diagram, though simplified and not to scale, shows the current geometry of the spacecraft with respect to Earth and Moon. The two planets are almost in line with the Sun, but by virtue of the motion of Moon in its orbit (upwards on the diagram) and the direction of Endeavour's initial motion away from the Moon at Trans-Earth Injection (downwards on the diagram), the crew are well to one side of the Earth/Moon line and see Earth as a thin crescent.
Crescent Earth displayed along with the nearly full Moon, as would be seen from the spacecraft.
These two images are reproduced from the Flight Plan at around this time (page 3-377 and 3-379). The crescent Earth is displayed along with the nearly full Moon. Al must take his P23 marks on the outside edge of Earth's crescent, finding the point within it's hazy atmosphere where he believes the solid edge of the planet begins, a skill he has practised in a simulator at MIT and during the early stages of the flight.
267:53:48 Henize: 15, this is Houston. The next several attitudes are going to require us to use Omni Delta, and we suggest that you go Manual and Wide and stow the High Gain Antenna.
267:54:03 Irwin: Okay. We'll do that and go to Omni Delta.
Once the P23s are out of the way, the UV photos of Earth are their next task. The procedures detailed on page 3-378 of the Flight Plan call for omni-directional antenna D for this. The instructions for subsequent tasks do give HGA angles relevant to the attitudes used for those tasks so it is unclear at the time of writing why the HGA is being folded away.
This is Apollo Contral at 268 hours, 20 minutes. Apollo 15 is 115,361 nautical miles [213,648 km] from Earth. Velocity: 4,598 feet per second [1,401 m/s]. We're 26 hours, 50 minutes from landing.
268:20:04 Irwin (onboard): I guess we're going to dim the lights and do all this on time. Rather sit for - we can get a flashlight out.
268:20:14 Scott (onboard): [Garble].
268:20:18 Irwin (onboard): Well, we'll see. One minute. Let's see. I don't know why - cabin lights are not going to affect it anyway with that cover over it.
268:20:28 Scott (onboard): [Garble].
268:20:40 Irwin (onboard): Says we're supposed to use the PCM cable. How can we shoot - that PCM cable for the 250? The EL? It won't reach this window, will it? And we'll have the Nikon in the other window.
268:20:55 Scott (onboard): Didn't we have that this morning?
268:20:57 Irwin (onboard): Well, it's ruined the other things, Dave. That's for the sextant photos.
268:21:22 SC (onboard): (Sneeze)
268:21:36 Irwin (onboard): Solid 24 minutes of activity, isn't it?
268:21:59 Irwin (onboard): We got MAG N on there. And I still have a MAG way back here with a - color - Q. They suggested T, but...
268:22:24 SC (onboard): (Yawn)
268:22:26 Scott (onboard): [Garble] Q [garble].
268:22:28 Irwin (onboard): Might as well.
268:22:56 Scott (onboard): [Garble].
268:23:04 Irwin (onboard): I'll look in this TSB over here.
268:23:06 Worden (onboard): Look in - in U-1 back there.
268:23:58 Irwin (onboard): [Garble].
268:24:00 Worden (onboard): Roger. You messed up 190 [garble]...
This is the time reference used to start the Mission Timer from which subsequent photographic events are coordinated.
268:24:53 Irwin (onboard): Yes, my camera's still up here, Dave.
268:24:55 Scott (onboard): Okay, good.
268:25:00 Worden (onboard): Hey, we're going to have to rush.
268:25:01 Scott (onboard): Huh? I know it. Why - logical.
268:25:04 Worden (onboard): Okay, 59, 47, [garble].
268:25:07 Scott (onboard): How long is that from now?
268:25:10 Worden (onboard): Three minutes.
268:25:11 Irwin (onboard): Well, why don't we go ahead to U - Why don't you go...
268:25:13 Henize: Al, we had a question on the Mass Spectrometer and it may be too late. Was it possible to confirm by visual look through the window that it was retracted? [Pause.]
268:25:27 Worden: Negative, Karl. You can't determine that it's retracted. All you can determine is that it's full out.
Al discovered during his solo mission that he could just make out the boom-mounted instruments from window 5, the right-hand window, by peering through it obliquely, but only when the boom was fully extended. Therefore, he can inform them that it is no longer fully extended but cannot tell by how far it has come in.
268:25:33 Henize: Rog. Well, when it was retracted, you wouldn't be able to see it. That's what I'm asking. Is it possible for you to take a look now and see if it slowly comes into view. [Pause.]
268:25:44 Worden (onboard): You want...
268:25:45 Scott (onboard): Okay, he wants you to watch and see if it does come full out.
268:25:50 Worden: Roger. In other words, you're asking to a confirm that it does come full out.
268:25:54 Scott (onboard): All right,...
268:25:54 Henize: That's correct.
268:25:56 Scott (onboard): ...look down...
268:25:57 Worden: Okay.
Comm break.
268:25:58 Scott (onboard): ...and if you can't see it, it was retracted. If you can see - You can't see it then.
268:26:02 Irwin (onboard): Yes.
268:26:06 Scott (onboard): [Garble].
268:26:08 Worden (onboard): Sure I can. Okay, Jim, I'll go ahead maneuver you. You're the act again.
268:26:17 Irwin (onboard): Okay.
268:26:19 Scott (onboard): Let's see a Flight Plan.
268:26:53 Irwin (onboard): Well, if we can't find that other mag, Al, we might have to use this one. Got the one MAG here of black and white from the LM. It has got to be...
268:27:02 Henize: Just to clarify...
268:27:03 Irwin (onboard): ...very high speed.
268:27:04 Henize: ...our question, Al, the main question was just to confirm whether or not it did go out of your field of view. Did it actually move from the full - from the full-extended position? Since we saw no change in the data when we retracted it during the test yesterday, there is a suspicion that, even though you actuated the switch, that for some reason it didn't retract.
268:27:26 Worden: Understand. [Pause.]
268:27:26 Irwin (onboard): I see - there's one boom extended.
268:27:31 Worden: Okay. It's fully extended now, Karl. But it may be too late. It may have already been out by the time we looked.
268:27:43 Henize: Roger.
Long comm break.
268:27:44 Worden (onboard): Is that talkback barber pole or gray?
268:27:46 Irwin (onboard): Gray.
268:27:46 Worden (onboard): Yes.
Al's sighting of the Mass Spectrometer here doesn't help answer the question from the back room. To prove that the instrument is indeed being retracted, they need Al to confirm it has left his field on view.
268:27:50 Scott (onboard): It kind of oscillates back and forth, doesn't it?
268:28:08 Worden (onboard): Karl doesn't realize we don't want to get too much UV. He must think we watch out that window every time we extend and retract it.
268:36:53 Henize: 15, this is Houston. We have a rather extensive update to the Flight Plan. And also, a change to the procedure for the contamination photos, which we can read up to you at your convenience. [Pause.]
268:37:09 Scott: Okay. Does it involve the things going on here in the next couple of hours?
268:37:17 Henize: It's pertinent beginning at 271. [Pause.] We probably ought to get it in before the press conference at 270.
268:37:35 Scott: Okay. Stand by one. [Long pause.]
268:37:56 Scott: Okay. Go ahead, Karl
268:38:02 Henize: Okay. If you've got the Flight Plan out, we go over to 271 hours. And at 271:20, just under S-Band Aux TV Science, we add Verb 49, maneuver to contamination photo attitude. [Pause.] The attitude is 014, 195, 016; High Gain [Antenna]; pitch, minus 23; yaw, 252. [Pause.]
268:38:53 Scott: Okay. At 171:20 [means 271:20] just after S-band Aux TV Science, Verb 49 to 014, 195, 016; High Gain; pitch, minus 25 - 23; and the yaw, 252.
268:39:09 Henize: Roger. Just after that, we delete "Mass Spectrometer, Ion Source, Off", and in the space there, add "Configure for urine dump." [Pause.]
268:39:25 Scott: Rog. Delete the Mass Spec. and Ion Source, Off, and configure for urine dump. Go.
268:39:32 Henize: Okay. Delete the next one, two, three, four lines, but we - and that brings us to Gamma - Gamma-ray Gain Step, Shield, Off, which we leave in.
268:39:44 Scott: Rog. Delete four and leave in the Gamma-ray Gain Step, Shield, Off. Go.
268:39:48 Henize: Delete all of the rest of that page. And add at 271:40, Verb 48, 11101, 01111, and P52, option 3. [Pause.]
268:40:22 Scott: Okay. 271:40, Verb 48, 11101, 01111, and a P52, option 3.
268:40:32 Henize: Roger. And at 271:45, we add Gamma-ray Boom Deploy, 41 seconds, then Off. Gamma-ray Gain Step, Center, and start contamination photos. [Long pause.]
268:41:16 Scott: Okay. 271:45, Gamma-ray Boom Deploy, 41 seconds, then Off. Gamma-ray Gain Step to Center. Start the contamination photos.
268:41:26 Henize: And there's a note on the photos that you begin to dump according to the photo procedures, which are - I have an update to that I'll give you later. And that we dump the water to 40 percent, in order to have the right weight at entry. [Pause.] Roger. It's important that we don't go below 40 percent on the water dump. [Pause.]
268:42:01 Scott: Okay. Understand. Dump according to photo procedures and the water dump to no less than 40 percent for entry.
268:42:08 Henize: That's affirmative. On the next page, 272 hours and zero minutes, we - I - I presume you know that we're not doing the midcourse correction 6. We cancelled the P52 there. And we keep the H2 purge line heater on, but we cancel the P30 external Delta-V. We cancel the Verb 49 maneuver, we cancel the next one, two, three, four, five, all the way down to the H2 and O2 fuel cell purge, which we keep.
268:42:48 Scott: Okay. Understand. Keep the H2 purge line heater, cancel the P52, and the set of lines below H2 line heater on, and keep the H2/O2 fuel cell purge.
268:43:03 Henize: Roger. And at 272:28, a note that you should be ending the contamination photos at that point.
268:43:13 Scott: Say again.
268:43:14 Henize: 2 - 272:38. [Long pause.]
268:43:31 Scott: Okay. 272:38, end contamination photos. Go ahead.
268:43:35 Henize: Right. At 42 we cancel - we delete the waste water dump, since we've already done it. And at 42 we add: "Start the Mass Spec. boom test." and the procedures are to be read up in real time. At 58 we cancel the midcourse 6. [Long pause.]
268:44:09 Henize: At 273:01 we...
268:44:11 Worden: Okay. At 272:47, that's the - hold on. Let me read it back. 272:42 the Mass Spec. boom test procedures in real time, and cancel MCC-6. Go ahead.
268:44:25 Henize: Roger. At 273:01, we cancel the burn status report and we add: "X-ray experiment, On. Alpha/X-ray Covers, Open, and record the GET." [Long pause.]
268:44:58 Worden: Okay. 273:01, X-ray experiment, On, Alpha/X-ray Covers, Open, and record the GET. Go ahead.
268:45:05 Henize: Roger. At 03, we delete the Gamma-ray, X-ray, alpha particle, MSO, On. And down at 273:47, we add Gamma-ray Boom, Deploy. [Long pause.]
268:45:34 Worden: Okay. A deletion at 273:00 - or 03, the four items there and then Gamma-ray Boom, Deploy, at 273:47. Go ahead.
268:45:47 Henize: Roger. And one final item on 274:05, in the Mass Spectrometer instructions there, the discriminator should be Low instead of High. [Pause.]
268:46:03 Worden: Okay. 274:04 Mass Spec. discriminator, Low vice High.
268:46:09 Henize: Roger. And if you have the time, I can give you the update on the contamination photography, which is on photo 25 and 26 in the back of volume 1 of the Flight Plan.
268:46:21 Worden: Stand by one, please. [Long pause.]
268:46:54 Worden: Okay, Houston. Let's hold off on the updates of those other photos, so we can get squared away for the eclipse photos.
268:47:00 Henize: Roger.
Very long comm break.
As detailed in page 3-378 of the Flight Plan, the crew are busy taking photographs of Earth using film and equipment which can work in ultraviolet light. Then at the top of the hour, they will continue with photography of the lunar eclipse, procedures for which are detailed in page 3-380.
Worden, from the 1971 Technical debrief: "Most of the UV photography was done when all three of us were on board. Jim handled all of that. I read the checklist, and it worked very well."
Worden (continued): "Window number 5 was covered with a Lexan shield, which acted as an ultraviolet filter for those portions of the flight when we weren't taking ultraviolet pictures out that window. Because of the distortion and the poor optical quality of the Lexan, pictures would have been greatly degraded if they had been taken through the Lexan shield. There were some portions in the Flight Plan where it called for the Lexan shield to be removed for visual or for orbital-science photography, which was not ultraviolet photography. At some portions in the Flight Plan, where some of that photography was being done, the Lexan shield was left off the window for periods greater than the time prescribed in the Flight Plan. I observed no effects from any ultraviolet radiation. I don't believe there's anything that was observed after flight either."
The spacecraft is maneuvered to face window 5 towards Earth. This window has panes made from quartz rather than glass because of this material's transparency to UV light. A Hasselblad camera is fitted with a specialised 105-mm UV capable lens and magazine N, which is loaded with IIa-o UV sensitive film. The RCS is configured in an minimum impulse mode where single jets rather than pairs of jets are used to control the spacecraft's attitude. The motion rates of the spacecraft are allowed to settle down until they are less than 0.2°/sec in all axes. This is to minimise smearing of the images due to the long exposure times (up to 20 seconds) called for.
Eight images, AS15-99-13483 to 13490 are planned in this sequence; two each through four filters. In the pair taken through filter 2, the crescent Earth is virtually invisible. Other images in the sequence do show Earth better but a streak of flare, probably caused by the Sun reflecting off wipe marks on the window, runs across the images. With Earth presenting such a thin crescent, the Sun is very near the camera's field of view and causes a lot of light spill. An additional colour frame on magazine Q is taken for comparison. By measurement of the size of Earth's image on the film, the spacecraft's distance is calculated to be about 112,000 nautical miles (207,500 km).
AS15-99-13483 - Ultraviolet photograph of Earth taken through filter 1. Image is contrast stretched. Image without contrast stretching - Image by NASA/JSC/Arizona State University.
AS15-99-13484 - Ultraviolet photograph of Earth taken through filter 1. Image is contrast stretched. Image without contrast stretching - Image by NASA/JSC/Arizona State University.
AS15-99-13485 - Ultraviolet photograph of Earth taken through filter 2. Image is contrast stretched. Image without contrast stretching - Image by NASA/JSC/Arizona State University.
AS15-99-13486 - Ultraviolet photograph of Earth taken through filter 2. Image is contrast stretched. Image without contrast stretching - Image by NASA/JSC/Arizona State University.
AS15-99-13487 - Ultraviolet photograph of Earth taken through filter 3. Image is contrast stretched. Image without contrast stretching - Image by NASA/JSC/Arizona State University.
AS15-99-13488 - Ultraviolet photograph of Earth taken through filter 3. Image is contrast stretched. Image without contrast stretching - Image by NASA/JSC/Arizona State University.
AS15-99-13489 - Ultraviolet photograph of Earth taken through filter 4. Image is contrast stretched. Image without contrast stretching - Image by NASA/JSC/Arizona State University.
AS15-99-13490 - Ultraviolet photograph of Earth taken through filter 4. Image is contrast stretched. Image without contrast stretching - Image by NASA/JSC/Arizona State University.
Next, by the Flight Plan, the magazine on the back of the Hasselblad camera body is changed to colour film and a reference shot taken through the same camera/lens combination. An earlier change in the Flight Plan asked for magazine P to be used instead of M. However, this magazine was finished three orbits before Endeavour left the Moon. Magazine Q is substituted.
AS15-96-13104 - Comparison image of Earth on colour film - Image by NASA/Johnson Space Center.
With the UV photography out of the way, the crew prepare to photograph a lunar eclipse.
