Skylab, combining the unique features of an orbiting spacecraft with the convenience of a roomy, well-equipped laboratory, offers an unprecedented opportunity for research in a number of scientific and technical areas. Almost 300 separate investigations, taking advantage of this opportunity, will advance knowledge in four major areas: science, Earth observations, zero-gravity technology, and the reaction of man to the environment of space.
In the space science area, major emphasis rests on solar observations, most of them with the instruments mounted on the Apollo Telescope Mount. The ATM will observe the Sun with eight instruments: the white light coronograph, two X-ray telescopes, three ultraviolet spectrographs, and two heliographs imaging the Sun in the red light of the H-alpha line. (The H-alpha line is the red line in the Balmer series of the hydrogen spectrum, 656.28 nanometers or 6562.8 Angstrom units) 1 An ultraviolet and X-ray spectrograph will observe the Sun through a scientific airlock in the wall of the Orbital Workshop.
Several instruments will record the ultraviolet and X-ray emissions of stellar objects within our Milky Way galaxy.
Cosmic ray particles will be recorded, and the minute impact craters of micrometeoroids on polished metal plates will be studied after the exposed plates have been brought back to Earth.
Medical doctors and biophysicists will utilize the state of weightlessness on board Skylab for scientific investigations. The effects of complete absence of gravitational forces upon metabolism, growth, and division of cells, upon tissues and organs, upon development cycles, and upon the wake-and-sleep rhythms of animals, will be studied in several experiments.
Observations of the Earth's surface from orbit, one of the major objectives of Skylab, will be carried out by the EREP assembly (Earth Resources Experiment Package). It contains six different instruments which will view targets on Earth in visible light, in infrared, and with microwaves. These observations will cover large areas of the Earth in a very short time under identical lighting conditions; they will provide information on such large-scale variables as cloud cover, snow and water conditions, ocean state, crop conditions, vegetation growth, development of urban and rural areas water pollution, land use, and other factors which are of vital importance in the interaction of man with his environment.
The effects of gravity, ever-present on Earth, are not observable in the environment of an orbiting spacecraft. Processes such as convection, mixing of dissimilar components, diffusion in fluids, heat conduction, flow patterns,  liquid surface forming, crystal growing, casting of composites, welding, and flame propagation, which are influenced by gravitational forces on Earth, will be different in space. Some of the familiar methods of manufacturing and assembly will require new techniques under space conditions; on the other hand, some processes which cannot be achieved on Earth, such as the alloying of metals with greatly different densities or the formation of certain glasses, may become easy under weightlessness. A series of experiments to study such processes will be carried out on Skylab.
For the first time in the space program, Skylab will offer an opportunity to systematically study the problems of life and work of man under prolonged exposure to space conditions. Numerous experiments were prepared to observe physical and mental functions of the astronauts, environmental conditions inside and outside the spacecraft, habitability features of the Workshop, the utility of tools, interfaces between astronauts and instrumentation, and the functioning of auxiliary systems. Many of these experiments are biomedical in character; their results will help us understand how man will adapt to the unique environment of a laboratory in space and how future space stations and deep space probes should be equipped to assure a comfortable and productive existence for astronauts. At the same time, experiments in this program will teach us how to build and equip spacecraft of the future in such a way that they offer optimum technical conditions for scientific research, for Earth observations, for zero-gravity technology, and as a habitat for the astronauts.
Experiments on Skylab will be described m four groups according to their objectives: science, Earth observations, life sciences, and space technology. Sections on the Skylab student project and on the postflight evaluation of Skylab data will follow.
The numbers listed with each experiment are the official designations for the Experiment Program; see also Chapter VIII, Listing of Skylab Experiments.
1. SPACE SCIENCE PROJECTS
As an observing station in orbit, Skylab has attracted the interest of astronomers, physicists and biologists from the time it was first conceived. In fact, a number of crucial observations in these three areas of scientific endeavor are planned, with the expectation that results will greatly advance our knowledge and will lay the groundwork for further research. The most prominent package of scientific instruments on Skylab, the Apollo Telescope Mount, will permit a study of the Sun. Some observations are planned of stellar objects, and some studies will be made of phenomena near the Earth which are difficult or impossible to observe from the ground. Biological studies on the effects of weightlessness will be described under Life Science Projects, Chapter V-3.
a. Solar Studies
Skylab's total man-attended time of 140 days, spread out over a period of eight months, will provide a unique opportunity to observe the Sun and its many surface phenomena in wavelength regions which are not accessible  from Earth. Fig. 132 shows a portion of the Sun as viewed from Earth in the red light of hydrogen. Skylab instruments will be able to view such active areas also in ultraviolet and X-ray light. In orbit, seeing conditions are always flawless; the image quality depends only on the resolving power of the optical system, the pointing stability of the instrument, and the capability of the sensor.
Eight different telescopes on ATM will observe details of the Sun in various wavelength regions, as indicated in Fig. 133 which shows the spectral coverage of the instruments and also the transmissivity of the Earth's atmosphere as a function of wavelength. ATM will attack a wide variety of problems in solar physics (Fig. 134) through coordinated observations with such instruments as a white light coronagraph which will photograph the corona out to about six solar radii, a spectrograph for the 97 to 394 mm range, a spectrometer-spectroheliometer for the 30 to 140 nm range, a spectroheliograph for the 15 to 62.5 nm range, two X-ray telescopes covering the 0.2 to 6 nm range, and two H-alpha cameras (656.3 nm) which will provide images of the Sun's disc in the red light emitted by excited hydrogen atoms (Fig. 135). All of these instruments are rigidly mounted on the spar inside the ATM canister (see Chapter IV-I-e). The canister can be fine-pointed within pitch and yaw movements of ± 2° relative to the rest of the Skylab. These movements will permit the exact orientation of the telescopes to any point on the Sun; the solar disc subtends an angle of 0.5° when seen from points on or near the Earth.
A single control and display console in the Multiple Docking Adapter adjacent to the ATM will permit manual operation and visual monitoring of all the experiments on ATM through selector switches, pointing controls, TV monitors, and a variety of indicators of experiment status, film usage, solar conditions, and other parameters (Fig. 99).
The role of the scientist astronaut on board Skylab will be to recognize and to point at targets of opportunity which promise a particularly high yield of scientific information; to survey, diagnose, report on, and possibly modify instrument performance; and to retrieve photographic film by extravehicular activities ( EVA ) for transport back to Earth.
Observing programs that will be carried out during the Skylab operation do not emphasize individual experiments, but broad problems in solar physics which will be attacked simultaneously by all investigators. Among these observing programs are the following (Fig. 136):
- Chromospheric network and supergranulation.
- Active regions; their morphology and development.
- Solar flares.
- Prominences and filaments.
- Center-to-limb studies of the quiet Sun.
- Observations of slowly varying phenomena over periods of days and weeks.
Solar studies on Skylab will be complemented by a coordinated program of numerous ground-based observations, sounding rocket launches, and observations from other spacecraft.
During the Skylab mission, several sounding rockets will be used to launch subscale models of the ATM experiments S082 and S055 (ultraviolet spectrographs) for calibration purposes. The sounding rocket instruments will acquire data of a quiet solar region nearly simultaneously with the corresponding Skylab instruments. Since the rocket-launched payloads can be calibrated immediately before and after Right, the data obtained with these instruments will serve as reference for the near-simultaneous data acquired by the Skylab instruments. Resulting calibration factors will then be used in post-mission analysis of all Skylab data. Two calibration flights are scheduled for each of the two experiments during the Skylab flight; one during the first, and one during the second manned mission. If the first rocket flight should fail, a calibration flight will be scheduled during the third manned mission.
It is expected that the Skylab program of solar studies will bring a decisive increase in our knowledge of the Sun by extending our observing capability toward shorter wavelengths, toward higher resolution, and toward greater sensitivity. The fact that the same phenomena on the Sun will be observed...
....simultaneously by several different instruments on Skylab and from the Earth will greatly enhance the gain of scientific knowledge and under. standing.
Observations of the Sun from Earth reveal three distinct outer layers on the Sun (Fig. 137). These are the very bright and almost opaque photosphere (about 5700° K temperature) with granules and sunspots; the more tenuous chromosphere (as low as 4000° K) with supergranules, plage areas, occasional violent outbursts in the form of solar flares, and other transient features such as vertical plasma jets called spicules; and the very tenuous corona which extends from the chromosphere (about 14,000 km-9,000 miles above the photosphere) to a distance exceeding that of the Earth's orbit. Prominences, consisting of huge plasma clouds, represent extensions of the chromosphere far out into the corona. The inner corona has a temperature up to several million degrees K. The chromosphere is the region where the continuous spectrum radiated by the photosphere becomes the absorption spectrum with the black Fraunhofer lines.
Problem areas in solar physics which Skylab will attack and hopefully help clarify include such processes as the transport of energy from the photosphere through the chromosphere and into the super-hot corona; the origin, ....
....development, and energy-producing mechanism of solar flares; and the processes which produce the solar wind. Better knowledge of these solar processes will improve our understanding of the Sun's influence on our Earth environment, particularly on weather and climate. It will also expand our knowledge of plasma physics, a relatively young branch of science which will probably play a major role in future science and technology.
One of the solar instruments on Skylab (S020) is located in the Orbital Workshop; all the others are mounted on the central spar of the ATM canister. These experiments are described in the following sections.
S020, Ultraviolet and X-ray Solar Photography (Fig. 138) 2
Record on photographic film a spectrum of the X-ray and ultraviolet radiation from the Sun in the one to 20 nanometer ( 10 to 200 Angstrom) region, with modest angular resolution. Radiations in this spectral range are emitted by highly ionized atoms in the solar chromosphere and corona. They are indicative of high-temperature atomic and plasma processes which are extremely difficult to duplicate on Earth.
Sunlight will enter a narrow slit and impinge upon a grating under a very small angle of incidence. Under conditions of grazing incidence, gratings reflect sufficient energy even in the one to 10 nm wavelength region (soft X-ray region) to make film recordings feasible when long-time exposure can be made. Thin metallic films in front of the slit will block out undesired ultraviolet and visible light.
The instrument is mounted in the solar airlock of the Orbital Workshop facing the Sun. A finder telescope will enable the crew member to place the solar image on the slit of the spectrograph. Exposures will last up t. one hour.
S052, White Light Coronagraph (Figs. 139, 140)
Obtain high resolution, high sensitivity photographs of the solar corona; from 1.5 to 6 solar radii (300,000 km or 186,000 statute miles to almost three million km or 1.86 million statute miles above the solar surface) Study brightness, form, size, composition, polarization, and movements o the corona. Correlate the observations with solar surface events and with solar wind effects.
Coronagraphs are designed to block out the image of the Sun's disc and to take pictures of the faint corona which extends from the Sun far into space. Light scattering by optical elements and by structural surfaces must be carefully avoided. This instrument containts four coaxial occulting discs and photodetectors for alignment corrections. Pictures will be recorded on 35 mm film; they are taken either in unpolarized light or in one of three possible orientations of plane polarized light. Also, the instrument can operate in the "video mode" which will permit display for the astronauts or TV transmission to the ground.
Operation in four photographic modes is possible. In each mode, the shutter of the camera makes three exposures of 0.5, 1.5, and 4.5 seconds duration. In the first mode, this triple exposure is made at each of the four different positions of the polarization filter wheel. In the second mode, this same sequence of 12 exposures is repeated continuously for 16 minutes. In the third mode, the triple exposures repeat in fast sequence for 16 minutes, with the filter wheel in the "clear" position. The fourth mode will be the same as mode three, except that a shutter opening will occur every 32 seconds only; this mode will continue until manually stopped.
S054, X-ray Spectrographic Telescope (Figs. 141, 142)
Obtain X-ray images of the Sun over a wavelength range from 0.2 to 6 nm (2 to 60 Angstrom). Record X-ray emissions of flares with a spatial resolution of two arc sec. Use selective filters and a transmission gratin' to obtain spectral information. Follow the evolution of active areas ant correlate X-ray emissions with solar events observed in ultraviolet and visible light.
Solar X-rays are emitted from flares and also from other regions o activity, such as plage areas, prominences, and the corona. Two basic....
....processes of the Sun seem to be responsible for most of the X-ray emission, the heating of plasmas, and the sudden acceleration or deceleration of electrons.
X-ray sources can be imaged with mirror optics utilizing very flat angles of incidence below about 0.5 degrees (Fig. 143). This experiment uses two cylindrical, coaxial mirrors of this kind with diameters of 31 and 23 cm (12.3 in and 9.2 in), with a total collecting area (two concentric rings) of 42 cm2 (6.7 in2), and with a focal length of 213 cm (85 in). The transmission grating is mounted behind the rear end of the cylindrical mirrors; it will produce spectra on both sides of the zero-order image of a source (Fig. 144). A filter wheel mechanism will permit the insertion of selective filters into the path of the X-rays, thus providing broad-band; spectral filtering of the flux. X-ray images will be recorded on 70 mm film.
A 7.6 cm (3 in) diameter, coaxial X-ray mirror will produce an X-ray . image of the Sun on a scintillator crystal where it will be sensed by the....
....photocathode of an image dissector tube. The output of this tube will be used for a visual display on the ATM console.
A photomultiplier tube, oriented toward the Sun, will measure the total solar X-ray flux; when a preset level is exceeded, an alarm for the astronauts will be given. The signal from this tube will also serve as a reference for the exposure setting of the film camera on the main telescope.
S055, Ultraviolet Scanning Polychromator/Spectroheliometer (Figs. 145, 146)
Obtain photometric data of six spectral lines (O IV, Mg X, C III, O VI, H I, C II) 3 and the Lyman continuum 4 in the wavelength region from....
....30 to 140 nm (300 to 1400 Angstrom) from 5 arc sec by 5 arc surface elements of the Sun. Also, obtain a spectral scan of the 30 to 140 nm region by tilting the grating.
Raster scanning of 5 arc min by 5 arc min areas will be achieved by rocking the primary mirror around two axes.
Radiations in this part of the spectrum are emitted by hot chromo-sphere and corona regions. The study of relative spectral line intensities will provide information about plasma composition, temperatures, and energy transfer processes in quiet and active solar phenomena.
An off-axis paraboloidal primary mirror will form a solar image on a 56 micron by 56 micron entrance slit of the spectrometer, corresponding to a 5 arc sec by 5 arc sec area on the Sun. Diffraction by a concave grating, ruled in gold with 1800 grooves per mm, will produce a spectrum on the Rowland circle 5 where seven photomultiplier detectors (Channeltrons) in fixed positions will simultaneously record the intensities of the six lines and the Lyman continuum. Bi-axial motion of the primary mirror will generate the desired raster scanning pattern (polychromator mode).
In the grating scan mode, the primary mirror will remain fixed while the grating is tilted to scan the entire operating spectrum past one or more of the photomultiplier detectors. The signals from the detectors will be transmitted to the ground by telemetry.
S056, X-ray Telescope (Figs. 147, 148)
Photograph the solar disc in X-ray light (0.6 to 3.3 nm or 6 to 33 Angstrom) with high resolution in space and time, and modest spectral resolution. Attempt to obtain pictures during quiet and active periods.; Monitor the total solar X-ray flux with proportional counters in the 0.2 to 0.8 nm (2 to 8 Angstrom) and the 0.8 to 2.0 nm (8 to 20 Angstrom) regions. Correlate the X-ray pictures with measurements of ultraviolet, visible, and microwave radiations from the Sun.
Observation of X-ray fluxes from the Sun will provide information on high-temperature regions and on interactions between hot plasmas and magnetic fields. Details of mass and energy transfer mechanisms and of the development of flares and prominences can be studied from X-ray measurements.
A cylindrical X-ray mirror with paraboloid-hyperboloid surface and grazing incidence, built of quartz, will form an image of the Sun on photographic film. Broad spectral discrimination will be achieved with five filters of beryllium, titanium, and aluminum, mounted on a filter wheel. Filters will be selected by astronaut decision.
Two proportional counters with mechanical collimators to improve the signal-to-noise ratio will continuously record the total X-ray intensity from the Sun in two wavelength regions. Their pulses will be pulse-height-analyzed and recorded on tape.
S082A, Extreme Ultraviolet (XUV) Spectroheliograph (Figs. 149, 150)
Record monochromatic images of the entire Sun in the emission lines of a spectral range from 15 to 62.5 nanometers (150 to 625 Angstrom). Obtain information about composition, temperature, energy conversion and transfer, and plasma processes within the chromosphere and lower corona. Correlate these data with results from simultaneous observations in the other wavelength regions. Among the most intense lines in this extreme ultraviolet region are those of helium, oxygen, neon, magnesium, and iron.
Imaging of the Sun and generation of the spectrum will be achieved by a single concave mirror of 2 m (80 in) focal length, ruled in gold with 3600 lines per mm. Monochromatic, overlapping solar images of 18.6 mm (0.75 in) diameter will be formed on a film strip. Two spectral ranges of 15 to 35.5 nm and 32.1 to 62.5 nm (150 to 335 Å and 321 to 625 Å) will be photographed separately, with two angular positions of the grating. The unused part of the solar spectrum will be reflected out into space in order to avoid unnecessary heating of the instrument. A thin aluminum filter in front of the film will keep stray light out. Four film cameras, each loaded with 200 film strips, will be used; a crew member will exchange cameras by extravehicular activity (EVA).
S082B, Ultraviolet Spectrograph (Figs. 151, 152)
Obtain UV spectra (97 to 394 nm or 970 to 3940 Angstrom) of small portions of the solar surface with high spatial and spectral resolution. Photograph spectra at various locations on and off the disc and across the limb, from 12 arc sec below to 20 arc sec above the limb. Try to obtain spectra of flares and other active areas on the Sun.
Information on the change of the solar energy transportation mode from convection to plasma-dynamic shock waves will be derived from these observations. Also, details of structure, density, and temperature of the chromosphere and the lower corona will be studied
Attached to this instrument will be the Extreme UV Monitor, providing a video image of the full solar disc in a broad spectral band (17 to 55 nm or 170 to 550Å), for coarse pointing and reference purposes.
An off-axis paraboloidal mirror will generate a solar image in the plane of the entrance slit of the spectrograph; the image on the reflecting slit jaws 6 will be viewed by a white-light TV system for pointing, selection, and verification by the astronauts.
For reasons of stray light elimination, a predisperser grating assembly with two gratings will generate a light beam containing only the desired wavelength regions. The main grating, a concave mirror ruled at 600 grooves per mm, will produce a spectrum on photographic film with a resolution of 0.004 nm (0.04 Angstrom) in the 97 to 197 nm (970 to 1970 Å) range and a resolution of 0.008 mm (0.08 Angstrom) in the 194 to 394 nm ( 1940 to 3940 Å) range. The entrance slit will admit light from a 2 arc sec by 60 arc sec area on the Sun.
Several operational modes can be selected by the crew members, such as the boresight mode which will permit an astronaut to point at a specific area on the solar disc, the limb scanning mode which will produce a sequence of exposures across the limb by stepwise angular motion of the primary mirror, and the flare mode in which the instrument will take a preprogrammed series of exposures of flares or other active areas when commanded by a crew member. Pointing of the instrument to a desired area will be accomplished by moving the experiment canister with the hand controller on the ATM Control Console. Using the solar limb as a reference, the movable crosshair in one of the hydrogen-alpha telescopes will be adjusted so that its position coincides with the limb at the same time that the limb falls on the spectrometer slit, as viewed on the slit jaw image7 with the white light TV system. After adjustment, the crosshair in the hydrogen-alpha telescope will always mark that point on the image of the solar disc which falls in the middle of the spectrograph slit.
Hydrogen-Alpha Telescopes (Figs. 153, 154)
Two telescopes imaging the Sun in the red light of the hydrogen-alpha line (Balmer series) will provide a visual aid to the astronauts and a photographic record of solar conditions during ATM observing periods. Each of the telescopes has a mechanically movable crosshair; that of Telescope I will be aligned with the boresight of Experiment S055, that of Telescope II with the boresight of Experiment S082B. Alignment will be accomplished by crew members, using the solar limb in two right-angled directions as reference system.
Hydrogen-alpha images of the solar disc will help crew members locate areas of solar activity and to recognize early stages of flare developments. Aiming the telescope and their crosshairs at such targets will automatically point those instruments which are aligned with the crosshairs to the same targets.
Hydrogen-alpha Telescope I will provide simultaneous photographic an TV pictures; its resolution is one arc sec at a field of view of 4.5 arc minutes. Telescope II will operate only in the TV mode, with a resolution of  about 3 arc sec. Each telescope has a zoom capability, varying the field of view between 4.5 and 15.8 arc min for telescope I and between 7.0 and 35 arc min for telescope II. Selection of the desired spectral line (656.28 nm or 6562.8 Angstrom) is accomplished with a Fabry-Perot filter which contains a solid glass flat with coated surfaces as interference gap. Band pass is 0.07 nm (0.7 Å) for both telescopes. Polarizing elements in the optical path will permit polarization studies with both telescopes.
b. Studies in Stellar Astronomy
Although the total program in stellar astronomy on Skylab is modest, experiments in this program will pursue very interesting objectives. Two experiments will study ultraviolet low-dispersion spectra of star fields, nebulae, interstellar dust, and galaxies. Each photographic picture will contain the spectral images of numerous objects, permitting statistical evaluation of star populations. A third experiment, recording celestial X-rays with a large field-of-view instrument, will provide information on number and location of X-ray sources in various parts of the sky.
These experiments will provide important new data, leading toward astronomical observations with larger and more sophisticated telescopes on future space missions.
S019, UV Stellar Astronomy (Fig. 155)
Obtain ultraviolet spectra from stars, using a reflecting telescope and an objective prism in front of a 35 mm camera. The image of each star will be drawn out into a small spectrum. Evalute large numbers of spectra for spectral classes, temperatures, and compositions of stars. Obtain spectra of nebulae, interstellar dust, and stellar gas shells.
Mounted in the anti-solar airlock of the Orbital Workshop, the telescope will look at different portions of the sky by means of a movable flat mirror. Photographs will be taken only while Skylab is on the dark side of its orbit. The field of view of the system is so large that a number of star spectra are photographed with each exposure. Films will be developed and evaluated on the ground.
The telescope has a 15 cm (6 in) mirror, and a field of view of 4° by 5°. Several different prisms can be inserted in front of the telescope, depending on the desired spectral resolution and sensitivity. The instrument is sensitive in the spectral region from 300 to 140 mm (3000 to 1400 A). Details can be resolved to about 20 arc seconds.
S150, Galactic X-ray Mapping (Fig. 156)
Survey selected portions of the sky for X-ray sources in the range from 0.2 keV (6 nm or 60 Å) to 10 keV (0.12 mm or 1.2 Å), and determine the location of sources with an accuracy of 20 arc minutes
This experiment will provide knowledge of the existence and variability of celestial X-ray sources, and of mechanisms of the generation and absorption of X-rays in space.
The instrument package consists of nine gas-filled proportional counters, surrounded by 13 additional proportional counters operating as an active anti-coincidence shield. Mechanical collimators above the counters, admitting X-rays only within narrow angles, will determine the directions from which X-rays arrive. As the cluster changes its attitude, the instrument receives radiations from different areas of the celestial sphere. Star sensors will provide directional information, which is recorded on tape together with the X-ray data, and transmitted to Earth for analysis.
S183, Ultraviolet Panorama Telescope (Fig. 157)
Obtain UV photographs with spectral information of selected stars, star fields, stellar clouds, and galaxies. This experiment will furnish a large amount of data not available from Earth. Star fields in two W bands (150 to 210 nm and 270 to 330 nm or 1500 to 2100 Angstrom and 2700 to 3300 Angstrom) will show the distribution of stars and of other celestial objects with strong ultraviolet emission. Color indices of these objects will be calculated from the photographs, and interstellar reddening will be determined from the color indices for about 1000 stars. Color indices will also be determined for star clusters, unresolved areas of the Milky Way, and selected galactic nuclei; statistical interpretation of large stellar populations will thus be possible.
The UV Panorama Telescope will be mounted in the antisolar scientific airlock for operation, similar to Experiment S019. Scanning of the sky will be achieved with the articulated mirror used for S019.
Spectral photometry of star fields requires the combination of a wide angle imaging system with a spectrum-producing element. The UV Panorama Telescope uses reflecting mirrors and a plane grating. In order to make the System insensitive against angular drifting of the pointing direction, z mosaic of small lenses is placed in the focal plane of the telescope. A photographic plate in the focal plane of these small lenses will record minute images of the entrance pupil of the telescope. Only those of the small lenses which receive a star image in the focal plane of the telescope will produce bright pupil images on the plate.
As shown in Fig. 158, the grating will disperse the beam of light in such a way that the spherical mirror receives a spectrum. Two rectangular openings in a diaphragm in front of this mirror will admit only the two desired wavelength regions, with the result that each star produces two images, one for each wavelength region.
c. Space Physics Studies
Several physical phenomena in near-Earth space will be studied by Skylab experiments which will profit from the relatively long stay-time in orbit, the large weight-carrying capability of the spacecraft, and the presence of astronauts.
Cosmic ray particles, for which the atmosphere represents an almost impenetrable barrier, are numerous in empty space. Layers of photographic emulsion on Skylab, exposed to cosmic radiation, will trap such particles. Their tracks in the emulsion can be made visible by photographic development.
Faint luminosities in interplanetary space, caused by the scattering of sunlight from finely dispersed dust grains, have been observed from Earth. However, light from the Sun and other celestial objects, and also light from Earthbound sources, is scattered by the atmosphere to form a background of sky...
 ....brightness even at night which makes the observation of faint luminosities almost impossible. Observations from Skylab will avoid these difficulties.
Most of the meteoroids entering the Earth's atmosphere burn up before they reach the surface. However, in free space even small meteoroidal particles present a potential hazard to spacecraft because they can inflict damage to surfaces and container walls. Skylab will carry an experiment that will record impacts of micrometeoroids. It is expected that exposure times offered by Skylab will be long enough to permit statistical evaluations of abundance and mass of at least small micrometeoroids in the submicrogram category.
S009, Nuclear Emulsion Package (Fig. 159)
Record the tracks of cosmic ray particles as the particles penetrate a stack of photographic emulsion layers consisting of gelatin and silver bromide. Study the relative abundance of particles as a function of their masses.
Cosmic ray particles are fast moving nuclei of chemical elements, probably originating in thermonuclear reactions of certain stars. Of particular interest will be the tracks of heavy nuclei. Such particles do not normally penetrate the Earth's atmosphere because they quickly lose their energy in ionization and in strong interactions with other nuclei.
Two stacks of emulsion layers are arranged like the two sides of an open book. After arrival in orbit, one of the astronauts will open the "book" and deploy it inside the Multiple Docking Adapter, pointing toward outer space. While Skylab is moving through areas of high background radiation, the "book" will be closed The emulsion layers will be exposed for about 240 hours during the first manned period and returned to Earth with the first crew.
Upon photographic development, the tracks of particles in the emulsion turn black because nuclear particles activate silver bromide crystals in their paths, similar to the way light activates an ordinary photographic emulsion. The thickness of a nuclear track corresponds to the ionization rate of the particle, which in turn is a function of its charge-to-mass ratio and of its energy.
S063, Ultraviolet Airglow Horizon Photography (Fig. 160)
Photograph the Earth's ozone layers and the horizon airglow in visible and ultraviolet light. Take pictures in reflected sunlight and at night
These observations will provide information on oxygen, nitrogen, and ozone layers in the Earth's atmosphere, and on their variations during night-and-day cycles.
Pictures will be taken with 35 mm cameras from three positions within the Orbital Workshop, the solar scientific airlock, the anti-solar scientific airlock, and the wardroom window. Ultraviolet pictures and visible light pictures will be taken simultaneously and, after return to Earth, correlated for detailed evaluation.
S073, Gegenschein and Zodiacal Light (Fig. 161)
Measure the brightness and the polarization of the night glow of the sky over a large portion of the celestial sphere in visible light. Determine the extent and the nature of the spacecraft's corona daring daylight.
The night glow of the sky is caused by sunlight reflected from interplanetary dust which accumulates preferably in the plane of the ecliptic (Zodiacal Light). Opposite the Sun, this band of light widens into an elliptical spot about 10 degrees in diameter (Gegenschein). Ground observations of the night glow are severely hindered by the airglow layer in the atmosphere at an altitude of about 90 km (56 statute miles or 43....
 ....nautical miles). Any halo around the spacecraft will curtail astronomical observations while Skylab is exposed to sunlight
These observations will be made with the photometer built for the Contamination Measuring System T027 (Fig. 209). The photographic camera of T027 will provide star pictures for sky region identification. Observations will be made through both the solar and the anti-solar scientific airlocks.
S149, Micrometeoroid Particle Collection (Fig. 162)
Collect micrometeoroid particles on exposed surfaces and determine their abundance, mass distribution, composition, morphology, and erosive effects.
Four polished metal, glass, and plastic collector plates, each measuring 0.15 by 0.15 meters (6 inches by 6 inches) and mounted on a box-like support unit, will be exposed after deployment through one of the scientific airlocks on the universal extension mechanism of Experiment T027. Observations will be made on all three missions. After exposure times of few days up to two months, the plates will be retracted and sealed in containers for protection. Analysis of the collected particles and of the effects will be performed on Earth after return of the plates in the Command Module.
 S228, Trans-Uranic Cosmic Rays
Record the tracks of heavy cosmic rays from iron (atomic number Z=26 to trans-uranic nuclei (atomic numbers Z<92) in layers of plastic material. (Lexan). Determine the relative abundance of nuclei with atomic numbers above 26. Determine the energy spectrum of cosmic ray particle with atomic numbers from Z=26 to Z-numbers as high as possible. Particle energies from about 150 MeV 8 to more than 1500 MeV per nucleon are expected.
Cosmic ray particles with atomic numbers representing the heavy elements are extremely rare. However, measurement of their abundance an energy spectra will provide very valuable information about the synthesis of heavy elements in stars. Also, results of these measurements will be useful in the design 0f detectors for ultra-heavy cosmic rays proposed for future space projects.
Tracks of very heavy cosmic ray particles have been found in meteorites. Observations with high-altitude rockets have also provided some data on cosmic ray particles with high atomic numbers. The atmosphere prevents such particles from reaching the Earth's surface.
The heavy cosmic ray particle detectors are completely passive. The consist of stacks of identical layers of Lexan plastic sheets, mounted inside the thin walls of the Orbital Workshop. After returning to Earth, the Lexan sheets will be chemical etched. Etch pits develop at the top an. bottom surfaces of each sheet where cosmic ray particles have entered an. left the plastic layer. The length of a pit is proportional to the square c the ionization rate of the particle. By observing the track of a particle through many layers of a stack, atomic number and energy of the particle can be derived. The two stacks of Lexan sheets have a mass of 30 kg (6 Ibs).
S230, Magnetospheric Particle Composition
Collections of helium, neon, and argon by exposing metal foils to the particle fluxes encountered by Skylab while traveling through the magnetosphere. In this sphere, which extends from about 160 km (100 statute miles or 90 nautical miles) to several Earth radii, the Earth's magnetic field strongly influences the trajectories of charged particles. The sources of charged particles to be collected by Skylab sensors include the Van Allen Belt radiation, possibly the solar wind, and the interstellar gas. Charged particles, particularly ions of atmospheric gases, may even reach orbital altitudes from the upper layers of the atmosphere.
Exposed foils will be returned to Earth after the second and the third Skylab missions. Implanted particles will be released by heating and analyzed with mass spectrometers. Particle energies can be estimated by employing layered foils, and by determining the depth of particle penetration by separate analysis of the different layers.
It is known that isotope ratios of noble gases in the Earth's atmosphere are very different from the ratios in the solar wind and probably in interstellar gas clouds. By determining isotope ratios in the collecting foils, particle fluxes of terrestrial, solar, and interstellar origin can be distinguished. Instruments:
Charged particles of the solar wind have been successfully captured by metal foils in several Apollo experiments on the surface of the Moon and in rocket probe experiments. The experiment on Skylab will consist of sheets of collecting foils mounted on flexible plastic substrates. Collectors of aluminum, aluminum oxide, and platinum will be used. They will be mounted in the form of two "double cuffs" on a truss of the ATM supporting frame before launch. Each of the six collectors has a size of 0.35 by 0.48 m ( 14 by 19 inches).
After return to Earth, parts of each foil strip will be heated and finally melted in ultra-high vacuum systems, and the evolving gases will be analyzed in mass spectrometers.
Except for EVA retrieval, this experiment is entirely passive.
2. EARTH RESOURCES EXPERIMENT PROGRAM
Skylab offers an opportunity to expand remote sensing investigations of the Earth from orbit by utilizing relatively large aperture, flexible, high performance sensors, and crew members to operate the sensors. The Earth Resources Experiment Package (EREP) represents an experimental facility dedicated to that purpose.
Photography from spacecraft in Earth orbit in the visible and near-infrared wavelengths has proven valuable for mapping geographic and weather features over large areas of the Earth. Systematic application of remote sensing techniques using additional wavelengths may extend the usefulness of this capability to mapping of Earth resources and land uses. Resources subject to this type of study include crop and forestry cover, health of vegetation, types of soil, water storage in snow pack, surface or near-surface mineral deposits, sea surface temperature, the location of likely feeding areas for fish, etc. (Fig. 163).
In July 1972, the first Earth Resources Technology Satellite (ERTS-1) was launched into an approximately circular 1,000 km ( 600 mi. ) polar orbit. ERTS 1 is providing, routinely, images of the U.S. and selected foreign areas in several bands encompassing the visible and infrared portions of the electromagnetic spectrum.
The Skylab Earth Resources Experiment Package is the next step in this important effort. EREP will use visible light and infrared photography. In addition, it will include imaging devices, electronic infrared spectography, and microwave radiometry surveys. EREP film and onboard storage techniques will permit large quantities of remotely sensed data to be gathered, and it will establish the feasibility and usefulness of Earth-survey techniques. The planned investigations will assess sensor types, designs, and capabilities needed to identify specific Earth resources and features. Requirements of future systems for specific applications can then be more firmly established. Methods for processing and interpreting data and the effects of atmospheric scattering and attenuation will also be defined.
Proposals to use EREP data have been submitted by university, government, and industry groups both within the U.S. and from abroad. From the more than 300 proposals which were submitted, 146 investigations were selected to comprise the EREP data-user program. These investigations have been subdivided into 170 individual tasks representing studies in 32 applications areas.
The EREP facility includes six sensors together with their associated support equipment. The support equipment includes the electronics to  handle data from each sensor, a control and display panel, and primary and spare tape recorders.
EREP photography will greatly improve resolution of Earth resources phenomena by virtue of simultaneous exposures using six matched cameras, and by precise photometry that can provide more accurate knowledge of light intensity levels of various bandwidths in each survey photograph. The infrared spectroscopic survey will operate in wavelengths not recordable on photographic film and will provide data from which recognizable spectral signatures of the observed phenomena can be plotted. By simultaneously operating in frequencies transmitted by the atmosphere and in those attenuated by atmospheric moisture, atmospheric moisture density profiles can be generated.
The microwave radiometry equipment, because of its low sensitivity to atmospheric moisture, will provide an all-weather source of information on surface moisture and temperature and on vegetation distribution. Microwave radiometry over the oceans will provide information on wind and sea conditions.
Two crewmen are required to operate the sensors. The control and display panel contains individual switches which activate and select the operating modes for five of the EREP sensors. Also included are master power switches and the controls for the tape recorder. The assigned crewman will be responsible for operating each of the sensors from the control and display panel during its functional period. Other functions of the crew involve positioning the S19OA boresighted camera array over the photographic viewing window, changing film/filter combinations, and changing lens dessicants and f-stops as required. Supply and return of film cassettes for the S19OA array and the 16 mm camera, used with the S191 Infrared Spectrometer, will also be required. A crewman will operate slewing control of the tracking telescope to bring targets into the field of view of the S191 Spectrometer. The S19OB Earth Terrain Camera will be deployed by the third crewman to view through the scientific airlock Opposite the Sun in the Workshop. Film supply and retrieval to and from this instrument will also be accomplished by this crewman.
Another major function of the crew will involve coordination with ground based activities and Mission Control to update EREP operations. Real time decisions will be required because of local weather and cloud cover conditions. This important astronaut function will optimize the utilization of the EREP and, therefore, maximize Skylab's contribution of useful data to the Principal Investigators. An artist's conception of the ground coverage of the EREP is shown on Fig. 164.
The six sensors comprising the EREP package can be categorized under the headings of photography, infrared observations, and microwave studies. A description of each sensor follows.
S190A Multispectral Photographic Cameras (Figs. 165, 166)
Objective and Instrumentation:
Obtain precision multispectral photography by selecting various 70 mm film/filter combinations for a wide range of Earth science studies. Detail not apparent in ordinary photography can be studied. Ground resolution will be 30 meters (100 ft); ground area coverage will be 161 km (100 statute miles) on a side. Observable features include water pollution, geological features, development of metropolitan and urban areas and others. Six high-precision cameras with matched distortion and...
....focal lengths are mounted together and bore-sighted. Wavelength-film combinations are:
500 to 600
0.5 to 0.6
Pan X black and white.
600 to 700
0.6 to 0.7
Pan X black and white.
700 to 800
0.7 to 0.8
Infrared black and white.
800 to 900
0.8 to 0.9
Infrared black and white.
500 to 800
0.5 to 0.8
400 to 700
0.4 to 0.7
High resolution color.
S190B Earth Terrain Camera (Fig. 167)
Objective and instrumentation:
Obtain high-resolution data of small areas within the fields of view of the Earth Resources Experiment Package sensors to aid in interpretation of data gathered by these sensors (Fig. 168). The camera will offer the first opportunity to obtain high-resolution Earth photography from a manned spacecraft. Ground resolution is expected to be 11 meters (35 ft.); ground area coverage will be 109 km (68 statute miles) on a side. The anticipated resolution will be a marked improvement over prior photography obtained on manned flights to date or the photography of the S19OA camera.
One crewman will be required to unstow the camera, install it in the Scientific Airlock, operate the controls, and restow the camera. Film has to be loaded in the camera magazine and unloaded after exposure for return to Earth in the Command Module.
 b. Infrared Observations
S191 infrared Spectrometer (Fig. 169)
Objective and /Instrumentation:
Provide data for evaluation of Earth resources sensors for specific regions of the visible and infrared spectra, and for quantitative evaluation of the effects of atmospheric attenuation. These data will enable scientists in various disciplines to evaluate the utility of remote spectrometer sensing from space. Using a filter wheel spectrometer, measurements will be made in the 0.4 to 2.4 and 6.2 to 15.5 micrometer regions (400 to 2400 and 6200 to 15,500 nm). The spectrometer has pointing and tracking capabili-...
 ...-ties 45° forward, 10° aft, and 20° to either side, and a field of view of 0.46 km (one-quarter statute mile) in diameter. The astronaut will use a viewfinder and tracking telescope with zoom capability to find interesting ground sites at nadir that usually will be in his field of view for less than a minute.
S192 Multispectral Scanner (Fig. 170)
Objective and instrumentation:
Provide, and record on tape, sensor signals representing line-scan images of selected test sites. Sensors will respond to 13 bands of reflected and emitted radiations in the visible, near-infrared, and thermal infrared regions of the spectrum (0.4 to 12.5 micrometers). Investigators can then evaluate the usefulness of spacecraft multispectral data for crop identification, vegetation mapping, soil moisture measurements, identification of contaminated areas in large bodies of water, and surface temperature mapping. A dichroic beam splitter is used to separate the incoming radiation into visible to near-IR and thermal IR components. A triple prism spectrometer will disperse the incident radiation in the visible to near-IR region. The instrument has a field of view of approximately 11 degrees and will survey ground swaths 74 km (46 statute miles) wide with a resolution of approximately 79 meters (260 feet).
 c. Microwave Studies
S193 Microwave Radiometer/Scatterometer and Altimeter (Fig. 171)
Objective and instrumentation:
Provide simultaneous measurements of reflected radar signals (differential backscattering cross-section) and emitted microwave radiation (brightness....
 ....temperature) of land and ocean areas, obtain altimetry data relating sensor response to actual oceanic state. Data will provide information relative to seasonal changes in snow cover and the border between frozen and unfrozen ground, gross vegetation regions and their seasonal changes flooding, feasibility of measuring soil types and texture, heat output of metropolitan areas, regions of lake and sea ice, and ocean surface characteristics. The transmitter for the radar signals and the receiver for reflected radar signals and emitted microwave radiation will operate at a frequency of 13.9 GHz. Brightness temperature and backscattering will be measured as functions of incidence angle. The instrument will operate in several modes; the maximum forward pointing is 48°, and the maximum side pointing is 48° to either side. The ground area coverage at nadir is 11.1 km (6.9 statute miles) in diameter. The pulse radar altimeter, which shares the antenna assembly with the microwave experiment, will record normal return radar pulses. Their evaluation will provide information about ocean state effects on pulse characteristics. The altimeter has a nadir alignment capability which will give the altimeter a more accurate alignment with the vertical than the vehicle could provide.
S194 L-Band Radiometer (Fig. 172)
Objective and instrumentation:
Measure and map brightness temperatures of terrestrial surfaces to a high degree of accuracy with a passive radiometer operating at a frequency of...
 ....143 GHz. Measurements of the brightness temperature of the Earth's surface will supplement the S193 experiment. Effects of cloud cover on radiometric measurements can be determined by comparing measurements at both S193 and S194 frequencies (13.9 GHz and 1.43 GHz). The instrument will survey ground swaths 111 km (69 statute miles) wide.
3. LIFE SCIENCES PROJECTS
From the beginning of manned space flight, there has been concern about the ability of man to survive a flight through space and to perform satisfactorily in the space environment. Specific concern has centered around the exposure of the human body to launch accelerations, its adaptation to weightlessness, its ability to withstand reentry loads, and its readaptation to full gravity following the return to Earth.
The first decade of manned space flight was devoted to the preparation of man for the Apollo Program and to his qualification for lunar landing missions. During the Gemini III mission, limited medical experiments were conducted to study man's physiological reactions during a two-week mission. The other Gemini and Apollo flights were used for studies of physiological effects on man through pre- and postflight medical experiments.
Before long-duration programs of explorations and operations in space can be undertaken, man's viability and usefulness under space conditions must be further assured. This can only be accomplished through careful quantitative studies of man's physiological, psychological, and social adjustments as they occur during flight. Limiting influences exercised by the space environment on the capabilities of crew members must be studied, and proper levels of performance for any given time during a flight must be established. Those studies will result in time profiles of the adaptation of men to space conditions, and they will show whether long-term adjustments eventually lead to new stable levels, or whether the need for continual adjustments threatens to exceed man's reserve capacity for meeting stress. Even if the crew members do successfully adapt to space conditions, the return to Earth involves an additional adaptive change about which more must be learned.
The Skylab Program offers the first opportunity to study these questions in depth The 28- and 56-day missions are long enough for a study of acute effects which could threaten man's safety, and also for the observation of slower biological processes. The biomedical experiments on Skylab have been designed to study the suspected changes and to investigate the basic mechanisms involved in these changes. The experimental investigations are much more comprehensive than previous investigations which served only medical safety monitoring purposes. Medical safety monitoring will be performed operationally on Skylab by known and fully tried bioinstrumentation, medical techniques and procedures.
The Skylab medical program represents an intensive study of normal, healthy men and their reactions to the stresses of space flight. Seldom has such a comprehensive examination been performed in ground-based studies and never under the unusual stresses of prolonged space flight. As an additional benefit, preparing and conducting these multi-man extended missions  will lead to advances in Earth-based medicine in such areas as non-invasive biosensors (medical probes which do not have to be inserted into the body) and biotelemetry where significant contributions to medical diagnosis and treatment are expected.
A basic set of biomedical data has been collected as a safety monitoring procedure on all manned flights of the Mercury, Gemini and Apollo pro grams. Heart and respiration rates, and at times body temperature and blood pressure were recorded. These data were supplemented by a variety of pre- and postflight measurements of such factors as exercise capability, cardiovascular stress response, hematological-biochemical changes, immunology studies, and microbiological evaluations. In the Gemini program, medical experiments of limited scope were conducted in flight to investigate the time course of the changes which had been noticed before and after previous missions.
The following physiological effects of space flight on man have been observed:
A consistent loss of body weight; a small and inconsistent loss of bone calcium and muscle mass; and generally after return to Earth, a reduction in the ability of blood vessels to actively distribute blood to those parts of the body that need it (orthostatic intolerance).
These effects completely reversed themselves within a few days after return to Earth. So far, they have shown no consistent relation to flight duration (up to 14 days). However, some concern remains that continued exposure to flight conditions on extended missions could significantly reduce man's effectiveness in space and increase the difficulty of re-adapting to the gravity conditions on Earth or on another celestial body.
Each manned mission in the U.S. space program was built upon the cumulative experience of preceding flights. Skylab will expose more men, in a larger spacecraft, with more varied activities, and for longer times to the weightlessness of orbital flight than any previous space project. It will allow more thorough evaluation of biomedical observations under extended periods of zero gravity, and it will use more rigorous evaluation techniques, than has previously been possible (Fig. 173).
 The Skylab biomedical program will cover four areas:
The knowledge and experience gained from all four parts of the program will help establish criteria for incremental increases in the duration of future manned missions after the 28- and 56-day Skylab flights.
Two animal experiments on Skylab (S071, S072) will help determine whether the force of gravity may have an influence on the regulators of some of the fundamental rhythms in living organisms. A small colony of mice and a sampling of pupae of the vinegar gnat will be flown on Skylab and observed for changes in specific life cycles under the zero-gravity condition of space.
M071, Mineral Balance
Collect data for a predictive understanding of the effects of space flight on the muscle and skeletal system by measuring the day-to-day gains or losses of pertinent biochemical constituents.
The following data are to be collected: daily body weight; accurate food intake (quantity and composition); accurate fluid intake; volume of a 24-hour urine output; samples of pooled 24-hour urine output; and preflight, inflight and postflight blood samples taken for analysis. Also, all feces and all vomitus (if any) will be collected, weighed, processed, and stored for return and postflight analysis.
 Urine will be analyzed for calcium, phosphorus, magnesium, sodium, potassium, chlorine, nitrogen, urea, hydroxyproline, and creatinine. Feces will be analyzed for calcium, sodium, phosphorus, magnesium, potassium, and nitrogen. Blood will be analyzed for calcium, phosphorus, magnesium, alkaline phosphotase, sodium, potassium, total protein, glucose and hydroxproline, creatinine, chloride, and electrophoretic pattern.
All instruments used in this experiment are parts of other systems. They will be described in the appropriate sections. These instruments include the following:
Urine Measurement and Collection System (a part of the Habitability Support System).
Fecal Collection System (a part of the Habitability Support System). Specimen Mars Measurement Device (a part of M074).
Body Mass Measurement Device (a part of M172).
Inflight blood collection equipment.
M073, Bioassay of Body Fluids (Fig. 174)
Assess the effect of space flight on endocrine-metabolic functions including fluid and electrolyte control mechanisms. Collect the following data: daily body weight; accurate food intake (quantity and composition);...
 ...accurate fluid intake; volume of a 24-hour urine output; samples of pooled 24-hour urine output (collected and processed inflight for return and postflight analysis); and preflight, inflight, and postflight blood samples taken for analysis.
Urine will be analyzed for sodium, potassium, aldosterone, epinephrine, norepinephrine, antidiuretic hormones (ADH), urine osmolality, hydrocortisone, total body water, and total and fractional ketosteroids. Blood will be analyzed for renin, sodium, potassium, chloride, plasma osmolality, extracellular fluid volume (ECF), parathyroid hormone, thyrocalcitonin, thyroxine, adrenocorticotropic hormone (ACTH), hydrocortisone, and total body water.
All instruments used in this experiment are parts of other systems; they include the following:
Urine Measurement and Collection System (a part of the Habitability Support System).
Specimen Mass Measurement (a part of M074).
Body Mass Measurement ( a part of M 172 ) .
M074, Specimen Mass Measurement (Fig. 175)
Demonstrate the capability of accurately determining masses from 50 to 1000 grams in a zero-gravity environment. Determine the masses of feces , vomitus, and food residue generated in flight.
Data to be collected include the following: preflight calibration of the Specimen Mass Measurement Device (SMMD), measurement of known masses three times during each Skylab mission, and Skylab environmental temperature. The SMMD will also be used to determine the masses of feces, vomitus, and food residue.
The SMMD utilizes the inertial property of mass instead of the gravitational force to determine mass. Basically, the SMMD consists of spring-mounted tray. The oscillatory period of the spring is a function of the amount of mass on the tray. The spring's period is measured electro-optically, and this measurement is electronically converted to: direct mass read-out.
M078, Bone Mineral Measurement
Assess the effects of the spaceflight environment on the occurrence and degree of bone mineral changes in the left heel and forearm (radius) by measuring bone masses before and after Skylab flights. These measurements will indicate the degree of calcium deposition (calcification) in the bones. Normal chemical activity in bones is stimulated by the pulling force of attached muscles and by gravitational forces acting upon the body. Both forces are altered during weightless flight.
Measurements of bone masses will be taken only on the ground, before and after flight. A scanning probe, using the soft gamma radiation of the radioactive isotope iodine-125, a gamma ray detector, and a multichannel analyzer will take radiograms of the bones; by comparing postflight with  preflight pictures, the changes can be determined. Calibration will be achieved by comparing the bone absorption, mostly due to calcium, with the absorption in test layers of known thickness and composition Measurements will be taken of ail crew members and of control group members.
M092, Lower Body Negative Pressure (Figs. 176, 177, 178, 179)
Determine the degree and the time course of cardiovascular adaptation under zero-gravity conditions. Provide data on cardiovascular changes...
...for correlation with preflight and postflight measurements. Collect inflight data for predicting the impairment of physical capacity and the degree of orthostatic intolerance to be expected upon return to Earth (orthostatic intolerance is the inability of the organism to distribute the blood properly, and under the proper pressures among the different organs and places in the body when the body assumes an erect position in a gravitational field). Data to be collected are blood pressure, heart rate, body temperature, vectorcardiogram, lower body negative pressure, leg volume changes, and body mass.
 The Lower Body Negative Pressure (LBN) experiment imposes a slight reduction of external pressure to the lower half of the body. This "negative" pressure (negative with respect to the environment of the upper half of the body) will have a blood pooling effect in the lower part of the body, similar to the effects of the normal hydrostatic pressure of the blood column in a person standing upright in the Earth's gravity field. The experiment will test how the cardiovascular system reacts to a controlled amount of blood pooling during weightless flight.
The LBNP experiment utilizes three basic units: (1) a cylindrical tank with a waist seal which encloses the lower half of the astronaut under test. The pressure in the tank can be lowered by as much as 15 to 20 percent below the ambient cabin pressure, thus exposing the lower body to a controlled series of negative pressures. (2) a leg volume measuring system (Leg Volume Plethysmograph) which senses the expansion of the legs by measuring the circumference of each leg at the level of the calf muscle. The amount of expansion is a measure of the amount of blood pooling in the legs. (3) the Blood Pressure Assembly, consisting of a pressure cuff attached to the upper arm, a microphone to pick up the sounds of blood flow, and the necessary electronic systems. A programming unit cycles the pressure cuff automatically. Recording and calibrating is accomplished through the Experiment Support System.
The experiment uses the Vectorcardiogram equipment from M093 and the Body Temperature Measuring System from M171. It will be performed on each astronaut every three days. The entire experiment takes about 60 minutes to perform; an attending astronaut is needed to assist the subject.
M093, Vectorcardiogram (Figs. 180, 181)
Measure the activity of the heart by recording electric signals (vector cardiographic potentials) of each astronaut during preflight, inflight, and postflight periods to obtain information on changes in heart functions induced by the flight conditions. Vectorcardiograms will be taken at regular ....
....intervals throughout the mission while the crewmen are at rest, and before, during, and after specific exercise periods with a bicycle ergometer (part of Experiment M171). This instrument will enable an astronaut to exercise at selected levels of energy consumption.
The Vectorcardiogram system consists of a harness with eight electrodes, a signal-shaping network (Frank Lead Network), calibration and timing circuits, and three Electrocardiogram (ECG) signal conditioner channels The system provides three ECG signals and a heart rate signal to the spacecraft system and to the Experiment Support System (ESS). The ESS will provide power, additional signal conditioning, and recording facilities.
M111, Cytogenic Studies of the Blood
Determine the frequency of chromosome changes in the peripheral blood leukocytes of the Skylab crew members before and after flight. Correlate the results with the radiation doses received by the astronauts ("in vivo" radiation dosimetry). Acquire data that will add to the findings of other Skylab cytologic and metabolic experiments to determine the genetic consequences of long duration space travel on man.
 Chromosomes, located in the nuclei of cells, provide the basis for control of most of the biochemical functions and activities within an organism. Their internal structures are susceptible to change under the influence of radiation' chemical reagents, and some other environmental factors, possibly including weightlessness.
Periodic blood samples will be taken before and after the flight, beginning one month before and ending three weeks after recovery. The leukocytes will be placed in a short-term tissue culture. During the first cycle of cell division in the isolated cultures, standard chromosome preparations of the leukocytes will be made.
The leukocytes from the cell culture will be removed during metaphase and "fixed." A visual analysis will be performed which involves counting the chromosomes, the number of breaks, and possibly the types of breaks, and then comparing the identifiable chromosome forms with groups of chromosomes comprising the normal human complement.
This experiment will provide chromosome aberration frequencies as they are found postflight in nine men. The relation between radiation dose experienced by each man and the number of chromosome breaks will be studied on the basis of these data.
M112, Man's immunity, in-Vitro Aspects
Determine any changes in man's cell chemistry that may result from prolonged exposure to weightlessness. Study the changes in humoral and cellular immunity as reflected by the concentration of plasma and blood cell proteins, blastoid transformations, and synthesis of ribonucleic (RNA) and desoxyribonucleic (DNA) acids by the Iymphocytes.
An organism's ability to combat infections or to repair injured tissues may be influenced by the lack of gravity as a consequence of a change in cell chemistry caused by zero gravity.
Data reflecting normal cell metabolism will be obtained 21, seven, and one day before launch from the crewmen, and from a control group composed of three men physically similar to the crewmen. This group will also serve as the ground control group during the flight. Inflight blood samples will be taken four times from each crewman during the first  mission and eight times from each crewman during the second and third missions. Seven days and 21 days after recovery, samples again will be taken from each crewman.
Blood will be analyzed for kinetics of Iymphocyte RNA and DNA, RNA and DNA distribution in Iymphocytes, observation of blastoid for mation, Iymphocyte morphology and antigen response, Iymphocyte functional response to antigen quantitation of plasma constituents, presence of immunoglobulins, albumin and globulin concentration, and total plasma protein. The Inflight Blood Collection System will provide the capability to draw venous blood and to centrifuge the samples for preservation. The blood samples will be frozen and returned to Earth for postflight analysis. The data from preflight, inflight, and postflight samples will be compared to detect any significant changes caused by the conditions of orbital flight.
M113, Blood Volume and Red Cell Life Span (Fig. 182)
Determine the effects of weightlessness on the blood plasma volume and the red blood cell population. Particular attention is to be paid to changes in total mass of red cells, red cell destruction, red cell life span, and red cell production rate.
Red blood cells transport oxygen from the lungs to all parts of the body. Decreases in the total mass of red cells will necessitate increased heart and breathing rates.
This experiment has four parts; in each, a different radioisotope tracer will be injected into crewmen's veins and into veins of a control group with similar physical characteristics on the ground.
The site of red blood cell (RBC) production in the mature adult is the marrow of membranous bones (e.g. sternum and vertebrae). The rate of production is dependent on metabolic demands and on the current red cell population. The rate of RBC production will be measured quantitatively by injection of a known quantity of a radioactive ion tracer into crew members.
Since the rate of RBC production acts with RBC loss to increase or decrease the total RBC mass present at a given time, any changes in the rates of RBC production and destruction will be necessarily reflected in the red cell mass. Such changes in red cell mass will be measured and analyzed in the flight crew members by injection of red cells tagged with radioactive chromium (in the form of sodium chromate).
To determine selective age-dependent RBC destruction and mean red cell life span, glycine tagged with radioactive carbon will be injected into a superficial arm vein of each crew member and control subject.
Finally, plasma volume changes will be measured by adding a known amount of radioiodinated human serum albumin to each crew member's blood.
The inflight Blood Collection System will provide the capability to draw venous blood and to centrifuge the samples for preservation; the blood samples will be frozen and returned to Earth for postflight analysis.
Blood samples of each crewman will be taken preflight (21, 20, 14, seven and- one days before launch); inflight (four times during the first and eight times during the second and third manned mission); and postflight (recovery day, one, three, seven, 14 and 21 days after recovery).
 M114, Red Blood Cell Metabolism
Study the effects of gravity on the membrane and the metabolism of the human red blood cell. Determine whether any metabolic changes or mem brane modifications occur as a result of exposure to the space flight environment This experiment will complement Experiment M113.
Blood samples of each crewman will be taken preflight (21, seven, and one days before launch), inflight (four times during the first and eight times during the second and third manned missions), and postflight (recovery day, one, and 14 days after recovery).
Blood will be analyzed for methemoglobin, glyceraldehyde-6-phosphate, dehydrogenase, phosphoglyceric acid kinase, reduced gluthathione, adenosme triphosphate, gluthathione reductase, lipid peroxide levels, acetylcholinestecare, phosphofructokinase, 2,3-diphosphoglycerate, and hexokmare.
The inflight Blood Collection System will provide the capability to draw venous blood and to centrifuge the samples for preservation. The blood samples will be frozen and returned to Earth for postflight analysis.
M115, Special Hematological Effects (Fig. 183)
Examine critical physiological blood parameters relative to a stable state of equilibrium between certain blood components and evaluate the effects of weightlessness upon these parameters. Provide other data on blood and blood circulation which will assist in the interpretation of hematology and immunity experiments (M111 series) and of nutrition and musculoskeletal function experiments (M071 series). The red blood cell represents a model system for the evaluation of physiological changes that might occur in man during prolonged exposure to weightlessness.
Blood studies made on Gemini and Apollo astronauts have shown that changes in red cell mass, blood constituents, and the fluid and electrolyte balance can be expected as a result of the space environment.
Blood samples of each crewman will be taken preflight (21, 14, seven, and one days before launch), inflight (four times on the first and eight times on the second and third manned missions), and postflight (recovery day, one, three, seven, 14, and 21 days after recovery).
Blood will be analyzed for sodium, potassium, single cell hemoglobin, red blood cell hemoglobin, RNA, protein distribution, hemoglobin characterization, electrophoretic mobility, red blood cell age profile, red blood cell electrolyte distribution, membrane and cellular ultrastructure, acid and osmotic fragility, critical volume, volume distribution, red blood cell count, white blood cell count, differential white cell count, microhematocrit, platelet count, hemoglobin, and reticulocyte count.
The Inflight Blood Collection System will provide the capability to draw venous blood and to centrifuge the samples for preservation. The blood samples will be frozen and returned to Earth for postflight analysis.
 M131, Human Vestibular Function (Fig. 184)
Examine the effects of weightlessness on the vestibular system, i.e. the system of semicircular canals of the ear which provides the perception of balance and orientation. Determine any changes in man's sensitivity to motion and rotation and any variations in his ability of coordination under prolonged weightlessness.
Test the astronauts' susceptibility to motion sickness in the Skylab environment, acquire data fundamental to an understanding of the functions of human gravity receptors under prolonged absence of gravity, and test for changes in the sensitivity of the semicircular canals. The following data are to be collected: threshold perception of rotation, motion sickness symptoms caused by out-of-plane head motions while being rotated, and ability of a crewman to determine his orientation with respect to spacecraft reference points without visual cues. Data will be collected before, during, and after flight.
The inflight equipment includes:
Rotating Litter Chair-This chair is a framed seating device which is convertible for operation in either a rotating or a tilt litter mode.
Drive Motor for Chair Rotation-This motor has the capability of rotating the seated subject within the limits of 1 to 30 mm at an accuracy of ± 1 percent.
Control Console-The console contains mode selector, speed selector, tachometer, indicators, timers, other devices for control, and a response matrix for coding a subject's response to the rotational tests.
Otolith Test Goggle This device is used to measure the visual space orientation in two dimensions. It provides the visual target for the oculogyral illusion test.
Custom Bite Boards-The bite boards are used to hold the otolith test goggle precisely and comfortably in position over the observer s eyes.
Reference Sphere and Magnetic Pointer with Readout Device These devices are used for measuring spatial localization using nonvisual clues. A magnetic pointer is held against the sphere and moved by the subject. This will determine the subject's ability to judge his orientation. The pointer position is measured by the three-dimensional readout device.
M133, Sleep Monitoring (Fig. 185)
Determine the quantity and quality of an astronaut's sleep during long periods of weightlessness through an analysis of electroencephalographic (EEG) and electro oculographic (EOG) activities. This information will complement other investigations concerning reactions of the central nervous system under space flight conditions. The following data are to be collected: preflight EEG and EOG data of a crewman for three consecutive nights of sleep, periodical inflight EEG and EOG data throughout a crewman's sleep period, and postflight sleep EEGs and EOGs on approximately the first, the third, and the fifth day after recovery.
One of the astronauts, selected for this experiment, will wear a fitted cap during his sleep periods with electrodes for electroencephalographic measurements of brain waves (EEG signals), with accelerometers to record motions of the head, and with electrodes near one eye ( electro-oculograph) to sense rapid movements of the eyeball during sleep. Signals from these sensors, recorded on magnetic tape and analyzed after return to Earth, will permit conclusions regarding the depth and length of the sleep stages. Signals will also be telemetered to the ground station in near real time. Inflight recordings will be compared with preflight and postflight observations made on the same crew member with the same sensors.
 M151, Time and Motion Study (Fig. 186)
Observe astronauts in motion. Compare their mobility and dexterity in various activities under weightlessness with their mobility and dexterity in similar activities under Earth conditions. Evaluate their zero-gravity behavior for designs and work programs of future spacecraft.
The following tasks have been selected for this observation:
Study the locomotion of crewmen as they move m the zero gravity environment with and without loads.
Study the fine and gross motor activities of crewmen in performing operations with and without the use of restraints.
Study crewmen performing tasks which require visual, tactile, or auditory feedback, or combinations of feedbacks.
Study intravehicular (IVA) and extravehicular (EVA) activities.
Study repeated activities performed early, midway, and late m the missions which will show adaptation to the zero-gravity environment.
Recording of this experiment will be achieved with the 16 mm movie camera, and with a portable high intensity photographic lamp, both of which will be used also for other purposes. In addition, verbal information by the astronauts about their experiences in zero-gravity operations will be tape-recorded for later evaluation.
Similar recordings have been made on the ground during crew training.
M171, Metabolic Activity (Fig. 187)
Determine man's metabolic effectiveness and its possible change while he is doing work in a zero-gravity environment. Obtain information on his physiological capabilities and limitations. Provide data useful in the design of future spacecraft and work programs.
 Physiological responses to physical activity will be deduced by analyzing inhaled and exhaled air, pulse rate, blood pressure, and other selected variables of a crew member performing controlled amounts of physical work with a bicycle ergometer.
Evaluate the bicycle ergometer as an exerciser on long-duration missions.
Collect data on ergometer work rate, ergometer RPM, oxygen uptake, carbon dioxide output, minute volume,9 vital capacity, respiratory quotient, heart rate, blood pressure, vectorcardiogram, body weight, body temperature, and Skylab environmental parameters.
Main component of this experiment is an ergometer (wheelless exercising bicycle) whose pedal wheel friction is controlled by a cardiotachometer in such a way that a preselected heart rate of the crew member remains constant. It can also be controlled for a constant, preselected workload. Equipment further includes a respiratory gas analyzer, a blood pressure measuring system, a body temperature measuring system, and a vectorcardiogram system (see Experiment M093). A metabolic analyzer, containing a spirometer and a mass spectrometer, will measure oxygen uptake, carbon dioxide output, and minute volume.
Each crew member will perform this experiment five times during the 28-day mission, and eight times during the 56-day missions.
M172, Body Mass Measurement (Fig. 188)
Determine the body mass of each crew member; observe changes in body masses during flight. Demonstrate the proper functioning and assess the utility of the Body Mass Measuring System in daily use.
Knowledge of exact body mass variations throughout the flight will greatly help in the correlation of other medical data obtained during flight.
Mass measurements under zero-gravity conditions can be achieved by application of Newton's second law (force equals mass tames acceleration) . The force is provided by a spring; the mass is attached to a platform suspended as a pendulum by four parallel flexing strips. An optical pickup and an electric timer measure the period of the spring-loaded pendulum in order to achieve a measurement, the astronaut sits in a....
....compact posture on the platform, cocks the spring, and releases the platform which will oscillate with a sinusoidal motion. Time signals are converted to provide a readout directly in kilograms. ( See Experiment M074). The Body Mass Measurement Device has been calibrated before launch with known masses up to 100 kg (220 lbs).
S015, Effects of Zero Gravity on Single Human Cells (Fig. 189)
- Southwestern Medical School
- Dallas, Texas
Observe the functioning of living human cells m a tissue culture while they are weightless. Determine the effects of gravity on individual cells by making complete surveys of cellular structures and biochemical functions.
Similar observations have been made on human cells under the Earth's gravity and under high acceleration forces. Cells will be observed during flight with time-lapse microscope photography. Two separate cell cultures will be examined for four-day and ten-day periods. After several biochemical experiments have been performed, the cells will be preserved and returned to Earth for further biochemical testing. Their DNA, RNA, and lipide 10 content and their enzyme activity will be determined.
Control groups of human cells will be subjected to similar tests under Earth gravity and in high-acceleration fields.
Instruments used for this experiment include a microscope-camera assembly and a growth curve module subsystem, both enclosed in a single hermetically sealed package. Two phase-contrast microscopes with magnifications of 20 and 40, each focused on its own specimen chamber, will provide images to the two 16 mm time-lapse cameras. The cameras will be cycled automatically by a built-in timing mechanism; each will run at 5 frames per minute for 40 minutes twice per day for the entire 28-day mission.
The specimen chambers will provide temperature-controlled environments for the cell cultures. Each chamber will have its own independent media exchange assembly to provide fresh nutrients to the cultures twice each day.
The Growth Curve Module consists of two operationally independent assemblies, each capable of maintaining living cells in nine chambers. At preprogrammed times, a fixative will be injected into eight chambers, one at a time. The cells will be returned for postflight analysis.
S071, Circadian Rhythm, Pocket Mice (Figs. 190, 191)
Determine whether the daily physiological rhythms of a mammal (pocket mouse, Fig. 140) are changed by a zero-gravity environment. Circadian rhythms (24-hour physiological wake-and-sleep cycles) of animals and man are suspected to be influenced to some extent by gravitational forces. Should an influence be discovered, this would be an indication that biorhythms at least of animals are timed and controlled by factors which include gravity.
Changed or affected rhythms alter the basic control of metabolism. It is important that normal biological rhythms in man be maintained for his well-being and effectiveness during space flight. If normal physiological rhythms are found to continue in the test animals, the conclusion can be drawn that space flight does not impose biorhythm restriction and that man can work in space without a degradation of his performance due to biorhythm disturbance.
The experiment includes six pocket mice placed in a completely dark cage at 15° C (60° F) temperature, relative humidity of 60° percent, and an atmospheric pressure equal to sea level pressure.
Three weeks before the mission, the mice will be placed in the cage. Body temperature and activity level will be automatically monitored to establish the natural period, phase, and stability of the rhythms under....
 ....Earth gravity conditions. The cage will be installed in the Service Module shortly before launch. The same measurements will be made during the flight. Data will he automatically recorded and telemetered to Earth for interpretation.
S072, Circadian Rhythm, Vinegar Gnats
Determine whether the daily emerging cycle of the vinegar gnat (drosophila) from the pupa to the fly is the same under weightlessness and on Earth.
Extensive experiments have shown that even though gnats in the pupa stage develop at different rates depending on temperature, the adult gnats will not emerge from their pupae until some kind of internal signal is given. This triggering signal is somehow timed to occur at an exactly fixed time delay after a flash of light. The signal occurs at the same constant time interval after the flash, independent of the temperature.
The experiment will measure the emergence times of four groups at 20° C (68° F) to find out whether space flight conditions change the mechanism which keeps the rhythm constant despite changes in temperatures.
Each group of pupae is divided into two subgroups. Flashes of light will initiate the emergence of the two subgroups at two different times. If the delayed subgroup shows the same rhythm of emergence response as the earlier group, it is probable that no external factor contributes to the rhythm and that the rhythms are internally synchronized with the light flashes.
This experiment is conducted in conjunction with the pocket mice experiment (S071 ) . If rhythms of both experiments are disrupted or altered during space flight, it can be assumed that space flight disrupts or alters the common basic rhythm mechanisms, and that man's biological rhythm mechanism is probably also affected by zero gravity.
This experiment is designed for automatic operation. After the initial white light flash has occurred for initiation of the emergence cycle, a dim red light will be turned on every 10 minutes, and 180 pupae photocells will be scanned electronically. After a gnat has emerged, its pupa shell will be transparent, and the pupa photocell will respond to the red light.
Emergence data will be stored and later telemetered to Earth.
Experiment Support System
This facility (Fig. 192), located in the Orbital Workshop, will provide normal power, special regulated power, controls and displays, data management  recording facilities, programmed time signals, pressurized gas, and calibration commands for the biomedical experiments M092, M093, M131, and M171. Specific subsystems will support blood pressure measurements, leg volume measurements, and vectorcardiogram measurements.
The Experiment Support System was developed and integrated by MSFC.
Chapter 5 continues here.
1 (1 nanometer = 1 nm = 10-meter = 10 Angstrom units)
2 Although this experiment is less significant than the ATM experiments, it is listed first because of the numbering system applied to the experiments.
3 Three times ionized oxygen, nine times ionized magnesium doubly ionized carbon, five times ,ionized oxygen, ionized hydrogen, and singly ionized carbon
4 Light below 912 Å emitted by hydrogen atoms.
5 The Rowland circle determines the locations of slit, grating, and detector in a concave grating spectrograph.
6 See pg. 133, Footnote [footnote 7]
7 The jaws of the slit of a spectrometer, being located in the focal plane of the imaging mirror of the spectrograph, carry an image of the light source, in this case the Sun. By making the surface of the slit jaws reflective, the solar image will be reflected and can be viewed by a TV camera. The spectrograph slit appears in this image as a thin black line. inspection of the image will help identify the precise location on the solar disc where the spectrum was taken.
8 MeV = million electron-volt, a measure of the energy of nuclear particles. ( 1 MeV= 1.602 x 10-13 Joule ).
9 Breathing volume per minute.