Experiment Operations During Apollo EVAs

Experiment: Apollo Lunar Surface Experiments Package

Acronym: ALSEP

ALSEP central station from Apollo 14. Note the mortar box for the active seismic experiment in the background to the right. The antenna mast was used as the "barbell" for carrying the two subpallets to the deployment site. (AS-14-67-9378)

PI/Engineer: Several PI's for indiv. expt's
Other Contacts: see indiv. expt's

Apollo Flight Nos.: 12, 14, 15, 16, 17
Apollo Exp't No. (contained several exp'ts)
A-12 incl'd PSE, SIDE, SWS, LSM, LDD, and CCG
A-13 was to have had PSE, CCG, HFE, and CPLEE
A-14 incl'd PSE, ASE, SIDE, CPLEE, LDD, and CCG
A-15 incl'd PSE, SIDE, SWS, LDD, LSM, HFE, and CCG
A-16 incl'd PSE, ASE, LSM, & HFE (HFE damaged during deployment)
A-17 incl'd HFE, LEAM, LSG, LACE, LSP

Discipline: several

Weight: varied, see individual missions
Dimensions: Several packages spread out on the lunar surface, connected by cables (which caused some problems)

Manufacturer: Bendix
(subcontractors had individual instruments)

A combination of experiments taken to a site sufficiently far from the LM was collectively called the ALSEP. There was a central processing station to which all of the peripheral experiments (and the RTG) were attached. It provided power distribution, communications with Earth, etc. The rest of the experiments connected to this station by cables. Power for all of the experiments was provided by the RTG. Each experiment was assigned its own name and number and is considered separately in this database. With several of the packages in place on the Moon, networks provided more information than any one could provide. For example, the seismometer network provide from ALSEPs emplaced by A-12, 14, 15, and 16 enabled the location of impacts and moonquakes to be determined. The network of 3 LSMs enabled the study of solar wind plasma movement by detection of its contained magnetic field. The ALSEP on A-17 carried different instruments once the networks had been established by earlier flights.

Unloading from the LM:
The ALSEP was stored in the Scientific Equipment Bay during flight. There were booms of some sort to prevent the crew from becoming unbalanced when removing the equipment, but these were not needed on A-15, perhaps because of the slope on which they landed. Lanyards were used to release the packages and allow them to swing free and then be lowered by pulley to the surface. The pulleys were removed for A-17 since the crew felt they weren't needed. The height of the pallets was at the limit for easy manual deployment on level terrain, and off-loading the pallets was hindered by a small crater 8 to 10 feet to the rear of the LM. However, sufficient working area was available in which to place a pallet and conduct fueling operations. The mission timelines show offloading as a coordinated activity and allowed 8 to 9 minutes of both crewmen.

Transporting by foot or MET:
It was packaged on two major subpallets in the LM which were removed and then attached by a "barbell" (which later became the antenna mast) to enable carrying. On the A-12 ALSEP, the whole pallet tended to rotate, especially the pallet containing the RTG. The crew commented that the necessity to grip the carry bar tightly was tiring to the hands. On A-14, Mitchell commented that the bouncing subpallets at the end of the "barbell" made it very difficult to carry and that he ended up carrying it across his arms. It was considerably heavier than he anticipated since the 1/6th g lightweight mock-up didn't respond in the same way. On A-15, Irwin decided to carry it in the crook of his elbow and had an easy time carrying it to the deployment site. Even once the LRV was available, the LMP carried the ALSEP while the CDR drove to the deployment site. On the A-16 ALSEP deployment traverse, the RTG fell off the subpallet. Lunar dirt in the subpackage socket had prevented the flanged end of the carry bar from sliding all the way into place so that the pin could lock. The LMP knocked the dirt out of the socket and re-attached the package. After reaching the deployment site, the LMP had to rest. It took 275 seconds to reach the site, during which his metabolic rate was as high as 2300 BTU/hr. He rested for 3 minutes afterward, while also describing the site. The total mass of the A-16 ALSEP was ~250 lbs, or 41.5 lbs moon weight. The A-17 LMP has commented that after just a short time on this long traverse his total attention was on how bad his arms hurt from holding onto it. The total mass for this ALSEP was ~360 lbs, or 60 lbs force on the moon.

Loading/unloading tools/exp'ts on LRV:
Even on A-15 to 17 the LMP carried the ALSEP subpallets to the site while the CDR drove the LRV.

Site Selection:
A level site was desired. Generally, 100 m to the west of the LM (but not in its shadow at sunrise) was seen as adequate. Craters and slopes were avoided since they would degrade the thermal control of the unit. A-14 had some trouble finding such a site. Also, a location far enough away from the LM to avoid the dust and debris of ascent and the seismic disturbance of the venting propellant tanks and thermally creaking structure was desired. Add to this the need for a reasonable straight and level area for a geophone line (on those missions with ASE or LSPE) and a clear area for mortar firings (for ASE) and a perfect site was difficult to find.

Deploying experiment:
See individual experiments. The central station (mass, 25 kg; stowed volume, 3.48 m3) was deployed and connected to the RTG and the separate experiments. Thirty minutes was allotted for this on the A-16 timeline. A-14 allotted ~20 min., A-17 allotted 17 minutes. Most, if not all, crews had difficulty erecting the sunshade on the central station due to its light weight, flimsy nature.

On A-12 the fuel element for the RTG would not come out of its cask easily and several minutes were spent working with the delicate element before it was removed satisfactorily. They had to hit the cask with a hammer while pulling on the element to coax it out. Also, the crew commented that there seemed to be no way to avoid getting dust on the exp't during unloading, transport, and deployment, and that this should be considered during the design.

A-14 had difficulty releasing one of the Boyd bolts on an ALSEP sub-pallet when the guide cup became full of dirt. They commented that there seemed to be no way to avoid getting the experiments dirty during transport and deployment. Also, there was always at least one side of the central station in the shade, which made seeing the bolts difficult. On the traverse to the deployment site, the pallets on either side of the antenna mast ("barbell") oscillated vertically and the mast flexed, making the assembly rather difficult to carry. However, they believed the "barbell" arrange-ment to be suitable for traverses of as much as 150 meters. When erecting the central station the sunshield did not lock in the "up" position, but the scientists in the back room at JSC noticed it and had the crew return to fix it. The communica-tion between these scientists and the crew on the surface was, by some accounts, too "filtered" to have good interaction under the tight timelines that existed.

A-15 and 16 reported no particular problems deploying ALSEP (but see A-16 HFE.) Some cords which were to release pins on the central station of A-15 broke and the pins had to be released by hand. A-16 deployment took 134 minutes, including travel preparation and obtaining a documented sample at the end (25 minutes).

The A-17 crew had trouble removing the dome from the fuel cask. The chisel end of the geological hammer was used to pry the dome off the cask. The remainder of the operation went nominally. They also had difficulty leveling the central station and antenna gimbal. The leveling was accomplished by working the edge of the station down to a level below the loose upper soil and placing a large, flat rock under the corner. In doing this, ~30% of the upper surface of the station sunshield was covered with a thin layer of dust, and no attempt was made to remove this dust. Also, soil became banked against the edge of the station. Later, upon request from ground personnel, this soil was removed by clearing a 15 - 20 cm wide moat around that edge of the station. Some dust and soil still adhered to the sides of the station, but the white thermal coating was visible through most of the dust.

During antenna gimbal leveling, both the N-S and E-W level bubbles appeared to be sticky and prevented precise leveling of the antenna gimbal. The N-S bubble eventually became free-floating, but the E-W remained at the E end of the fluid tube. Precise antenna pointing was not verified, but ground personnel reported that the signal strength appeared to be adequate. The time deficit resulting from these activities was compensated for by relocating the first traverse station to an area near the rim of Steno Crater.

Check-out of experiment: See individual experiments

Operation of experiment:
See individual experiments. The central station had 5 switches operable by the astronaut, all of which interfaced with the Universal Handling Tool. Two were for back-up operation only and would allow the crew to make ALSEP work despite certain possible failures. Also, the experiments were operated after crew departure from JSC via the ALSEP Command System. The commands took the form of an octal number which was entered manually via a thumbwheel and sent by pushing another button. On most days, tens to hundreds of commands were sent. Many would be routine commands for leveling experiments after terminator crossing or flipping magnetic field sensors, but many were at the request of the PIs for particular studies. A number of engineering tests of the ALSEP hardware and electronics were also performed. An ALSEP Termination Report (NASA Refer-ence Publication 1036, April, 1979) is available that lists these operations and tests.

Repairs to experiment:
During A-14 EVA 2, the crew was able to adjust the alignment of the central station antenna in an effort to strengthen the signal received at Earth. Photos show that the antenna aiming mechanism was not properly seated on the antenna mount and, despite the fact that the correct settings were used in aiming the antenna, it was pointed ~8deg off nominal. During erection of the central station on A-15, the rear-curtain retainer removal lanyard broke, requiring the LMP to remove the pins by hand.

Recovery/take-down of experiment:
See individual experiments, but nothing was returned from the ALSEP itself.

Stowing experiment for return: See individual experiments

Loading/unloading samples on LRV:
Even after the LRV was available, the ALSEP pallets were carried by hand to the deployment location ~100 meters from the LM.

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 was required for the emplacement of the HFE. Some drill cores were also taken near the ALSEP site and helped to characterize the area, which was helpful for interpretation of the seismic experiments. The Apollo Lunar Surface Drill (ALSD) was developed for these tasks and was considered, by some, as part of the ALSEP package.

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?
All the ALSEPS had SNAP-27 RTGs to generate power. The fuel capsules for these were kept in a separate cask for safety (they were at 500deg C and radioactive) until the astronaut on the surface removed it and placed it into the thermocouple assembly with the fuel transfer tool. The cask was mounted outside the descent stage of the LM. Redesign of the package or revision of procedures was necessary after the critical design review with the astronauts. The A-12 crew commented that the fuel cask guard was not needed and commented that heat radiating from the fuel element was noticeable through the gloves and during the walk to the deployment site, but was never objectionable.

The Active Seismic Experiment had small explosive charges in the "thumper", which see. The Lunar Seismic Profiling experiment had explosive charges which were deployed by the crew but not set off until after departure. See individual experiments for safety aspects.

Was lighting a problem? No

Were the results visible to the crew?
Silver and black decals were difficult to read in bright sunlight. A needle was not visible on a current meter on the A-12 RTG or central station - it was possible that the shorting plug had been depressed prior to the intended time.

Would you recommend any design changes?
A-12 crew commented that some sort of over-the-neck strap might be advantageous for deployment distances beyond 100 m. Also, the RTG fuel element was redesigned with looser tolerances for later flights.

Were any special tools required?
The Apollo Lunar Hand Tools (ALHT) were considered by some as part of the ALSEP package, but they were mostly used in the geological field work. The geological hand tool carrier was carried for 3 flights, A-12 to 14.

Two universal handling tools (UHT) were included to help carry and level many of the individual units on the surface. These were usually discarded after ALSEP activation, but on A-17 one was used as a handle for the LRV soil sampler. Also, a fuel transfer tool (FTT) was used to remove the fuel elements from their casks on the outside of the LM descent stage and place them in the RTG. A dome removal tool (RDT) was included, too, whose purpose was to operate the fuel cask dome. A-14 required several attempts to lock the dome removal tool onto the dome. A-17 also had trouble with the fuel cask dome. The A-12 crew commented that the tools should have been 2 to 5 inches longer. The change was made for later flights. The difficulty in fitting and locking both tools in most of the experiment receptacles was frustrating and time consuming. Looser tolerances would probably have eliminated the problem.

Was the orientation of the experiment (i.e. horizontal/vertical) important? Difficult?
The central station and most, if not all, of the individual experiments needed to be leveled to within 5deg of vertical and oriented with respect to the Sun. The central station was aligned within 5deg of the E-W line using the partial compass rose and its gnomon. This was for proper thermal control. - See also, individual experiments.

Was the experiment successful? Yes

Were there related experiments on other flights?
All landed missions had an ALSEP, except for A-11, which had EASEP.

Where was it stored during flight?
A-11 to 14 used the LM Modularized Equipment Stowage Area (MESA). A-15, 16, and 17 list the Scientific Equipment Bay (SEQ Bay)/Quad II as the storage area.

Were there any problems photographing the experiment?
No. A chart of desired photos of the ALSEP area was provided to the crew to document all orientations of the instruments. This task took ~20 to 25 minutes.

What pre-launch and cruise req'ts were there?
The radioisotope fuel capsule needed cooling before launch. This was due to the temperature of its fuel cask being above the ignition temperature of some of the fuels used on the spacecraft if this cooling were not provided.

What was different between training and actual EVA?
Installation of the RTG power cable connector to the central station was more difficult than it had been in training. The A-14 crew said that, by the end of training, they were consistently ahead of the timeline by 25 to 30 minutes, and felt that this would be adequate to take care of the extra time that they would use on the surface in being more careful, and to allow for problems. As it turned out, it wasn't enough. "The fact is that you're just a bit more careful with the actual flight equipment." They recommended a 25 to 30 % pad. The Apollo 16 Time and Motion Study looked at the ratio of time to perform tasks related to ALSEP deployment on the lunar surface on A-15 and A-16 vs. the time the crew took on their third 1-g training session. This ratio ranged from 1.16 for simple tasks to 2.18 for more complex ones. The average ratio on A-15 was 1.41, and that on A-16 was 1.66. The difference is not statistically significant. This suggests that tasks take about 50% longer to perform under the lunar EVA constraints than in training.

What problems were due to the suit rather than the experiment?
If the fuel element of the RTG were to brush against the suit it would have damaged it.

Any experiences inside the LM of interest from the experiment/operations viewpoint?
At the end of the last EVA, surface procedures called for a crewman to police the area around the LM, especially in the direction of the ALSEP, for material and loose equipment which could be blown by the ascent stage engine into the experiments. This loose gear and trash, much of which was brought out of the LM at the beginning of each EVA, was to be kicked underneath the descent stage.


Preliminary Science Reports, A-12, 14, 15, 16, 17

Mission Reports, A-12, 14, 15, 16, 17

"Alignment, Leveling, and Deployment Constraints for A-15 Lunar Scientific Experiments", document in JSC History Office

Memorandum from FC93/Head, Lunar Surface Section, 7 October 1971, RE: Apollo 14 ALSEP 4 Postmission Report.

The thermal control designs of 8 of the experiments and the central station are discussed in Apollo Experience Report # 17 - "Thermal Design of Apollo Lunar Surface Experiments Package"

Apollo Lunar Surface Experiments Package - Apollo 17 ALSEP (Array E) Familiarization Course - Handout for class of 1 September 1972, in JSC History Office.

Apollo Lunar Surface Experiments Package - ALSEP Familiarization Course - Handout for class of 15 January 1968, in JSC History Office.

Apollo Lunar Surface Experiments Package (ALSEP) Flight System Familiarization Manual, at JSC History Office

Final Systems Mission Rules for Apollo Lunar Surface Experiments Package - ALSEP 3, March 23, 1970

Apollo Scientific Experiments Data Handbook, JSC-09166, NASA TM X-58131, August, 1974, In JSC History Office.

Apollo Program Summary Report, JCS-09423, section 3.2 Lunar Surface Science, April, 1975

Apollo 15 Technical Crew Debriefing, 14 August 1971, in JSC History Office.

Apollo 14 Technical Crew Debriefing, 17 February 1971, in JSC History Office.

Personal communication with Herb Zook, 1 April 1993, re: ALSEP command procedures

ALSEP Termination Report, NASA Reference Publication 1036, April, 1979.

Personal communication with Jim Bates, 21 April, 1993, re: ALSEPs.

Apollo 16 Time and Motion Study (Final Mission Report), NASA, Manned Spacecraft Center, Houston, TX, July 1972