Apollo 15

This chapter covers the final period of lunar orbit science before the crew of Apollo 15 begin their preparations to return to Earth. Date: 4 August 1971.

Endeavour is about to complete rev 71, having just passed out of sight of Earth. The crew's main task during this far-side pass is to get in some exercise and have their lunch. Most photography will be by the Mapping and Panoramic cameras in the SIM bay. Rev 72 will comment in about 20 minutes time and the crew's conversation has been caught on the voice track of the Data Storage Equipment.

FCS refers to the Fecal Containment System.

The DSE onboard recording ceases for about twenty minutes. Meanwhile, Endeavour's seventy second orbit of the Moon commences at about 217:55 GET.

Flight Plan page 3-330.

The Mapping Camera begins operation for the coming daylit pass at 218:17 GET and at about the same time, the Gamma-ray Spectrometer is retracted in preparation for a later test. The images for this Mapping Camera pass run from AS15-M-2624 to 2752. At image 2744, the camera is stopped for a while then restarted after the spacecraft has travelled a further 15 degrees in its orbit. 2744 is double exposed. Beginning with AS15-M-2625, every tenth image in this sequence will be presented here along with 2743, the last good frame before the stoppage, and 2751, the last frame in the sequence that isn't dominated by the landscape beyond the terminator.

As the Mapping Camera is coming on, a sequence of terminator photos is being taken on magazine R of the inner ring of Milne, the southeast rim of Scaliger and the crater Bowditch. These are AS15-98-13387 to 13393.

The final image in this sequence, AS15-98-13393, is marked in the Apollo 15 photo index as being blank. With contrast stretching however, detail can be seen and its position has been located for the journal.

Sklodowska is a Polish name. It is the maiden name of the Polish-French physicist Marie Curie.

Note that there is no record of these photos having been taken in the Apollo 15 Index of 70-mm Photographs.

Very long comm break.

REFSMMATs (reference to a stable member matrix) are used to define a set of orientation vectors to be used by the inertial measurement unit to define, essentially, "which way is up". In theory, any set of coordinates could be used, but those that represent well defined and easily measured references are best. Several are rather obvious; the launch pad at the Kennedy Space Center, the landing site of the LM, and the lift-off site of the LM. What is apparent here is that on a rotating body such as the Moon, Falcon's site on the Moon at lift-off has moved quite a bit since the landing.

Al will soon do a double P52 platform realignment and two REFSMMATs are important for this. The "lift-off" REFSMMAT, which has been used since Falcon's return to orbit, will be used for the first P52 realignment to check on the platform's drift since it was last realigned. The "TEI" REFSMMAT, which will define the orientation needed for the burn to return to Earth, will be employed for the second P52.

Joe Allen is referring to the TEI REFSMMAT that is being uplinked to the spacecraft about 20 minutes earlier than planned.

Some time during the Trans-Earth Coast, the Gamma-ray boom will be partially extended. The way they plan to do this is to time how long a full extension takes. Then, later, they will be able to give a time for extension which will give a proportionate distance from the spacecraft.

Very long comm break.

At 218:52:55, the Panoramic Camera is operated for the penultimate time and will run until they reach the terminator. Of the 207 images from this pass, all but the last 15 were taken with the camera operating in stereo mode. This is where the camera nods back and forth between frames so that a forward-looking image will be matched by a rearward-looking image five frames later. A selection from these images is presented here at the approximate time of taking.

Flight Plan page 3-331.

Joe Allen was mistaken. It was battery A that was charging.

Long comm break.

At around 219:07, the Mapping Camera is stopped. Joe Allen will ask for it to be restarted after about 5 minutes. One image, AS15-M-2744, is double exposed due to this stoppage.

Long comm break.

As a result of the Mapping Camera not being extended on its track, part of its cover is visible on the right of the subsequent pictures

The next selected image from the current panoramic sequence shows a change in exposure part way through the process of taking the image. This would have been due to the size of the shutter slit varying as the exposure was being made.

As Endeavour approaches the sunrise terminator, four photographs are taken on the high-speed magazine R of unremarkable areas of Oceanus Procellarum. The extremely low-angle lighting makes these normally smooth-looking surfaces appear very rough. The first two of these are marked in the Apollo 15 photo index as being unidentified, but their positions have been located for the journal.

Mission Control want to verify the items on the cue cards in light of the short circuit discovered in the SPS on the second day of the mission. Dealing with the fault, which is in the primary control circuit, requires that they use the secondary, or "B" circuit to start and stop the engine, bringing the A circuit in manually in the middle of the burn.

Comm break.

Long comm break.

Having reached the terminator, they are busy getting the cameras in the SIM bay configured off and someone is timing the deployment of the Gamma-ray boom.

Right now, Al is busy in the Lower Equipment Bay performing two realignments of the guidance platform using the stars Acamar (in the constellation Eridanus - the River) and Fomalhaut (in the constellation Piscis Austrinus - the Southern Fish). The first reorientation will be to the landing site REFSMMAT. Once a good alignment is achieved, Mission Control will know by how much the platform has drifted since the previous realignment. Then the platform will be realigned to the TEI orientation, using the REFSMMAT sent to the spacecraft earlier and the same stars, Acamar and Fomalhaut.

Comm break.

Long comm break.

Prior to Al carrying out the P52 realignments, the spacecraft's attitude control is taken away from P20 so it is no longer in its orb-rate motion. With the realignments completed, control is given back to P20.

Very long comm break.