PI/Engineer: John H. Hoffman, Univ. of Texas/Dallas
Other Contacts:
Dallas E. Evans/JSC
R.R. Hodges, Jr. & F.S. Johnson, Univ. of Texas/Dallas
Apollo Flight Nos.: 17
Apollo Exp't No. S 205
Discipline: Lunar atmosphere
Weight: 9.1 kg
Dimensions:
33.7 x 16.5 x 31.8 cm
Manufacturer: Univ. of Texas/Dallas; Bendix
Description/Purpose:
The LACE was a 3 channel mass spectrometer designed to identify the composition of, and variation in, the lunar atmosphere. Its mass range was from 1 to 110 amu. It consisted of a magnetic deflection mass spectrometer, an electronics portion, and a dust cover which was not commanded open until the last explosive charge of the LSPE was detonated, 6 days after deployment.
Unloading from the LM: As part of ALSEP
Transporting by foot or MET: As part of ALSEP
Loading/unloading tools/exp'ts on LRV: NA
Site selection: As part of ALSEP
Deploying experiment:
The crew had to open a vent valve, remove 3 fasteners, rotate the unit upright, place it 45 feet NW of the central station, level it with a bubble, break the hermetic seal on the sensor, and recheck the level. The entrance aperture was oriented upward to intercept and measure the downward flux of gasses at the lunar surface - atoms and molecules have a ballistic trajectory under lunar conditions. This was sealed by a ceramic cap until opened by the crew. An arrow (sun orientation) and bubble level aided deployment.
Check-out of experiment: from Earth.
Operation of experiment:
From JSC via the ALSEP command system. It could not be operated in the lunar daytime because the electronics could not take the heat.
Repairs to experiment: None required or attempted.
Recovery/take-down of experiment: NA
Stowing experiment for return: NA
Loading/unloading samples on LRV: NA
Loading of exp't/samples into the LM: NA
Stowing of package once in the LM: NA
Sampling operations - soil, rocks: NA
Trenching: NA
Raking: NA
Drilling: NA
Coring: NA
Navigating/recognizing landmarks: NA
Were there any hazards in the experiment?
i.e. hazardous materials (explosive, radioactive, toxic), sharp objects, high voltages, massive, bulky, tripping hazards, temperatures?
High voltages in the instrument were not turned on until after departure.
Was lighting a problem? No.
Were the results visible to the crew? Just level and alignment.
Would you recommend any design changes? None made by crew.
Were any special tools required? UHT for deployment
Was the orientation of the experiment (i.e. horizontal/vertical) important? Difficult?
The entrance aperture was oriented upward to intercept and measure the downward flux of gasses at the lunar surface. It only needed to be within 15deg of level. The bubble level made this easy. An arrow aided the orientation of the instrument towards the sun.
Was the experiment successful?
Yes, although an error in thermal design and tempera-ture-sensitive components limited its operation to temperatures <325 K, which precluded operation during elevated lunar day temperatures when the atmosphere would have been most prevalent.
Were there related experiments on other flights?
The CCG (S058) on A-12, 14, & 15 was limited to total gas concentrations. The mass spectrometer (S-165) in the SIM bay of the SM on A-15 &16 also observed the lunar atmosphere at higher altitudes. Also, the Far Ultraviolet Spectrometer Experiment (S 169) in the SIM Bay of the SM of A-17 was used to measure the lunar atmosphere using resonance line scattering (none found except for a cloud just after LM descent.)
Where was it stored during flight? As part of ALSEP
Were there any problems photographing the experiment? No.
What pre-launch and cruise req'ts were there?
power, thermal, late access, early recovery?
What was different between training and actual EVA? No comments by crew.
What problems were due to the suit rather than the experiment? No comments by crew.
Any experiences inside the LM of interest from the experiment/operations viewpoint? No comments by crew.
References:
A-17 Preliminary Science Report
Personal conversation with Dallas Evans
Apollo 17 Mission Report
Apollo 17 Final Lunar Surface Procedures, Vol. 1: Nominal Plans, MSC, 11/6/72
Apollo Lunar Surface Experiments Package - Apollo 17 ALSEP (Array E) Familiarization Course - Handout for class of 1 September 1972, in JSC History Office
Apollo Scientific Experiments Data Handbook, JSC-09166, NASA TM X-58131, August, 1974, In JSC History Office.
Apollo Program Summary Report, section 3.2.26 Lunar Atmosphere Composition Exper-iment, JCS-09423, April, 1975.
ALSEP Array E Critical Design Review Presentation Material, NASA/MSC - Bendix Aerospace Systems Division, NAS9-5829, 14-18 June 1971, JSC History Office.
ALSEP Termination Report, NASA Reference Publication 1036, April 1979.