PI/Engineer: G. R. Carruthers, Hurlburt Center for Space Research, NRL, Wash. D.C.
Other Contacts: Thornton Page/JSC
Apollo Flight Nos.: 16
Apollo Exp't No. S 201
Discipline: Astronomy, UV; Earth atmosphere, aurora
Weight: 22 kg
Dimensions: 1 x 0.5 x 0.5 m (in zipped bag)
Manufacturer: Naval Research Lab, Applied Physics Lab (spectrometer)
A miniature observatory that acquired imagery and spectra in the far-UV range (below 1600 angstrom). An advantage of the electronographic technique used was that it was completely insensitive to visible and near-UV light. The unit was supported between two vertical stanchions on a table so that it could swing vertically from 0deg to 90deg. This table was supported by a tripod and could rotate 360deg horizontally. The main instrument was an f/1.0 Schmidt camera of 7.5 cm aperture. It had a 20deg field of view (FOV) in the imaging mode, 0.5deg x 20deg in the spectrographic mode. Either of two corrector plates (LiF or CaF2) could be selected for different bands of UV.
The goals of the experiment were to 1) determine composition and structure of the upper atmosphere of Earth from its spectra 2) determine the structure of the geocorona and study day and night airglow and polar aurorae 3) obtain direct evidence of intergalactic hydrogen in distant galaxy clusters 4) obtain spectra and imagery of the solar wind and other gas clouds in the solar system 5) detect gasses in the lunar atmosphere, including volcanic gasses, if any 6) obtain spectra and colors of external galaxies in the far UV 7) obtain spectra and colors of stars and nebulae in the Milky Way 8) evaluate the lunar surface as a site for future astronomical observatories.
Unloading from the LM:
John Young opened the plastic bag and removed it from the pallet in the Scientific Equipment Bay, and carried it to the shadow of the LM. There was no difficulty with this.
Transporting by foot or MET: Much easier than had been anticipated from 1 g training.
Loading/unloading tools/exp'ts on LRV: NA
Placed in the shadow of the LM for proper thermal conditions and to eliminate direct sunlight. Because of the delayed landing and EVA's, and the fact that the LM landed on a slope, the shadowed area behind the LM was considerably smaller than anticipated and the camera was located closer to the LM than originally planned. Hence, its field of view was somewhat restricted. It was moved even closer for EVA 2 and again for EVA 3 after the sun rose high enough to shine on it, thus eliminating two of the planned targets due to occultation by the LM. Once back in the shadow, there was no residual adverse affect from having been heated.
A checklist was attached to the camera. The CDR deployed it successfully in the shadow per the checklist. The three legs were unfolded and locked to form a tripod under a leveled table. The only way to level it on the slope, however, was to step down on 2 of the 3 legs, pushing them out of sight into the regolith. The battery was placed in the sun, for its optimal thermal conditions, but it was moved to the shade at the beginning of the 3rd EVA. The cable lines did not lay flat and tangled up in the CDR's legs almost every time he approached the camera. Fortunately, the battery moved rather than the camera. He had to level the unit and point it downsun to zero the azimuth. Pointing was accomplished by using two sets of graduated circles (in degrees) on an altitude-azimuth telescope mount. Pointing at Earth was accomplished by eye with a sighting tube. The A-16 timeline allotted ~8 minutes to offload and deploy the unit and another ~7 minutes to align it.
Check-out of experiment: For the first sequence, he pushed the "power on" switch.
Operation of experiment:
The CDR repointed the UVC 3 times during the first EVA, 4 times the second, and 3 on the third. Each time he had to press the "reset" switch, as planned. Actual exposures were controlled by an electronic sequencer. Aiming the unit was more difficult than had been anticipated. Because of high friction in the azimuth adjustment (the lubricant was a poor choice for the cold conditions since it became waxy below 10deg C), the camera often needed re-leveling after a new target was selected. The condition degraded with each adjustment. Because of this friction, the uneven and sloping surface, and the occasional camera moves to keep the camera in the LM shadow, it used more EVA time than anticipated. On the last EVA, some shots were aligned by eye. The first target was very bright relative to later targets and manual operation of the unit was used to get several short exposures. Inadequate film advance caused the first 7 exposures to be overlapped by adjacent frames (he was supposed to wait 3 seconds between shots but did not.) The overlapping did not adversely affect the science.
Once each operation was accomplished, the astronaut was to leave the vicinity of the camera as soon as possible due to the venting of waste gasses from the PLSS which could increase the local ambient pressure, thus causing the camera to stop operating, and/or contaminate the optics.
Repairs to experiment: none.
Recovery/take-down of experiment: Only the film was recovered.
Stowing experiment for return: Only the film cassette was returned.
Loading/unloading samples on LRV: NA
Loading of exp't/samples into the LM:
The film was retrieved and stowed in the LM at the end of the 3rd EVA.
Stowing of package once in the LM:
Camera not returned. The film magazines were transferred to the LM via the equipment transfer bag.
178 frames were obtained, including data on the airglow and polar auroral zones of Earth and the geocorona, and over 550 stars, nebulae, or galaxies.
There was a planned set of targets with altitude and azimuth settings for the camera. These had to be modified for the later EVAs.
Were there any hazards in the experiment?
i.e. hazardous materials (explosive, radioactive, toxic), sharp objects, high voltages, massive, bulky, tripping hazards, temperatures?
There was a strong magnet in the camera which was shown not to affect the watches worn by the crew.
Was lighting a problem?
The unit was deployed in the shadow of the LM. Since the landing was delayed, and thus the sun angle increased, it was placed closer to the LM than originally planned, thus restricting its field of view. Reflected light was adequate to view the settings on the altitude and azimuth adjustments.
Were the results visible to the crew?
No. Alignment devices were visible. The crew had received training with the qualification unit a week before launch and had discovered that the camera mode changes produced noise on the VHF radio. There was no other apparent electromagnetic interference resulting from the power supply operation.
Would you recommend any design changes?
New lubricant for azimuth bearing ring. Also, include this during tests of the instrument in environment chamber.
The back-up unit to A-16 was flown on Skylab 4. The unit was modified by removing the tripod and sealing it so that the internal atmosphere would not coat the optics. The mirror was also coated with Al + MgF2 rather than rhenium, as on the A-16 model. A clamp was added so that it could be mounted to the Apollo Telescope Mount (ATM) while on EVA. Images of the comet Kohoutek were thus obtained. For this operation it was pointed by eye. This experiment was called S201K. It was also used by placing it in the scientific airlock (SAL), during which there were mirrors used (articulated mirror system, or AMS) to enable pointing the FOV at the targets. During this general operation it was called S201G. After some time, the mirrors got clouded by contamination from Skylab. In the spectrographic mode, the PI recommended that future instruments include a coarse, venetian-blind collimator (a few degrees FWHM) ahead of the grid collimator.
Were any special tools required? No.
Was the orientation of the experiment (i.e. horizontal/vertical) important? Difficult?
It was important and very difficult. Setting the azimuth on the 3rd EVA moved the camera off level because of the torque force required. In several realignments, it was impossible to move the leveling bubble to the center of the ring because of the geometry of the 3 camera legs on the slopes and the time available for releveling.
Was the experiment successful? Yes.
Were there related experiments on other flights?
UV telescopes have flown in Earth orbit. One example was the OAO. Hand-held photography of the Earth and Moon was performed during many of the Apollo flights. On A-17 a far UV spectrometer in the SIM Bay of the SM, which was primarily used to study lunar atmospheric density and composition while in lunar orbit, was also used during TEC to observe Earth's atmosphere, zodiacal light, and galactic and extragalactic sources. As mentioned under "design changes," above, the back-up unit to A-16 was flown on Skylab 4. An extreme ultraviolet survey experiment flew on the Apollo-Soyuz test flight.
Where was it stored during flight? Quad III of the LM, scientific equipment bay.
Were there any problems photographing the experiment?
No. Photos clearly show the unit deployed on the surface. Some scattering of far UV light in the photos of the Magellanic cloud was attributed to lunar dust electrostatically suspended above the surface. See also Lunar Dust Detector - DTREM.
What pre-launch and cruise req'ts were there?
power, thermal, late access, early recovery?
A major requirement was to avoid gas contamination of the photocathode. The unit was placed into a bag. The bag was then purged with dry nitrogen continuously until 72 h before launch to keep out moisture while on the launch pad. The bag must have vented upon launch. The mass of this bag is included in the 22 kg.
What was different between training and actual EVA?
The sun angle was different than planned and trained under.
What problems were due to the suit rather than the experiment? None.
Any experiences inside the LM of interest from the experiment/operations viewpoint? No.
A-16 Preliminary Science Report, NASA SP-315, 1972
A-16 Mission Report
Apollo Scientific Experiments Data Handbook, JSC-09166, NASA TM X-58131, August, 1974, In JSC History Office.
Page, T. and G. R. Carruthers, S201 Far Ultraviolet Atlas of the Large Magellanic Cloud, NRL Report 8206, 1978.
George R. Carruthers, "Apollo 16 Far-Ultraviolet Camera/Spectrograph: Instrument and Operations, Applied Optics", Vol. 12, p. 2501 - 2508, Oct., 1973.
Thornton Page, personal communication with Thomas Sullivan
Thornton Page, "S201 Far-Ultraviolet Photographs of Comet Kohoutek From Skylab 4 (SL4), Preliminary Report", in Comet Kohoutek, Proceedings of a Workshop held at MSFC, June 13-14, 1974, pp. 37-75.
Apollo 16 Final Lunar Surface Procedures, March 16, 1972, MSC
Apollo Program Summary Report, section 3.2.31 Far-Ultraviolet Camera/Spectrograph, JCS-09423, April, 1975.
Apollo 16 Technical Crew Debriefing, 5 May 1972, in JSC History Office.