Experiment Operations During Apollo EVAs

Experiment: Lunar Portable Magnetometer

Acronym: LPM

The LPM instrument in use during Apollo 16 (AS-16-116-18721). A small rock has been placed on the instrument to measure its magnetic field. The smudge to the right of the instrument is due to a damaged negative; this entire roll of film has roller marks running vertically. See the LPM mounted on the MET during Apollo 14.

PI/Engineer: Palmer Dyal, Ames Research Center
Other Contacts:

Apollo Flight Nos.: 14, 16
Apollo Exp't No.: S 198

Discipline: lunar magnetometry

Weight: 4.6 kg
Dimensions: 56 x 15 x 14 cm, stowed
The sensor block stood 75 cm above the lunar surface when deployed.

Manufacturer: NASA Ames Research Center

The instrument stood on a tripod and had a bubble level (with 1 degree annular rings) and shadowgraph (with 3 degree markings) attached to the sensor block. It contained 3 orthogonal flux-gate sensors. A separate electronics/battery box was connected by a 15 m long cable and reel. The long cable allowed the astronaut to take the readings far removed from the sensor, so as not to perturb the measurement. It was used to measure the steady magnetic field at different locations at the A-14 and A-16 sites. The discovery of the unexpectedly high field at the A-12 site resulted in the concept of the LPM for A-14.

Unloading from the LM:
Had been stored in the LM Scientific Equipment Bay. It took both crewman to unload it on A-14.

Transporting by foot or MET:
A-14 carried it in special stowage areas on the MET for each of the subassemblies (tripod with sensor, electronics box.) It needed to be a minimum of 100 m from the LM to eliminate it as an artificial field source. Also needed to be a minimum of 11 m from the MET on A-14 or LRV on A-16.

Loading/unloading tools/exp'ts on LRV: A-16 carried it on the LRV.

Site selection:
Used at 2 site on A-14 and 4 sites on the A-16 traverses. (Along with the LSM at A-16, 5 measurements were thus made at this landing area.)

Deploying experiment:
Carried on 2nd EVA of A-14 on the modularized equipment transporter (MET). The electronics were turned on when first loaded to allow them to warm up and stabilize. Two measurements were made during the traverse on A-14. The readings were relayed to Mission Control. They had trouble when attempting to reel in the LPM cable. The set in the cable was such that, if the handle was released, the cable would unwind 3 or 4 turns. They wound it in enough to keep it off the ground and proceeded with the traverse. Later in that EVA they deployed the LPM again . After some difficulty in leveling the instrument, they relayed the reading on the voice link. The LPM was discarded at the completion of this reading.

On A-16, the deployment and operation of the LPM was normal in all respects and leveling, orientation, positioning, and switching, were accomplished without difficulty. Cable unwinding got harder and harder, however, eventually giving the impression that the cable would break before it completely unwound. Winding it up was not difficult. It was also easy to set up and operate according to this crew.

Check-out of experiment:
No set procedure for check-out, but a zero offset measurement was made.

Operation of experiment:
The instrument needed to be at least 35 feet (10.7 m) from the MET, electronics box, and the PLSS's. A stripe on the cable indicated that 40 feet (12.2 m) of cable had been reeled out. The astronaut had to select a range switch (high/low) as required by the readings on the meter, and report it when reporting the readings. The astronaut had to wait 60 seconds for meter stabilization before reporting the readings. At the first site only, two sets of additional readings were taken with the sensor block rotated first 180 degrees about a horizontal axis, then 180 degrees about a vertical axis. These allowed determination of a zero offset for each axis. Also on A-16, the magnetic field of a rock was measured in situ by placing the rock on the instrument. This same rock (sample 331) was returned to Earth as a sample for laboratory measurements. Also on A-16, to measure any fields that may have been induced by the spacecraft or otherwise during trans-Earth coast, a demagnetized sample from A-12 was returned and its field measured there. The sample reacquired a "soft" component of magnetism, indicating that the exposure to magnetic fields during trans-lunar coast accounted for at least some of the field measured in samples returned to the Earth. After the last site measurement, the astronaut had to turn it off and read the temperature indicator labels before disposing of the LPM.

Repairs to experiment: None required.

Recovery/take-down of experiment:
Discarded after second reading on A-14. The cable was somewhat difficult to rewind after the first readings. Also discarded after use on A-16.

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

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?

Was lighting a problem?:
No. It was even easy to read in the sun. If necessary, a hand could provide any needed shade to allow the numbers to be read.

Were the results visible to the crew?: Yes

Would you recommend any design changes?:
Based on the A-14 experience with cable rewinding, corrective action for A-16 consisted of adding a ratchet and pawl assembly for actuation with the gloved hand, and providing a better grip for the reel and crank. See fig 14-32 in Mission Report.

Were any special tools required?: No.

Was the orientation of the experiment (i.e. horizontal/vertical) important? Difficult?
Yes. The instrument had to be level within 5 degrees using a leveling bubble. A sun compass was used to align it within 3 degrees of a sunline using a shadowgraph. Leveling was somewhat difficult for the second reading of A-14.

Was the experiment successful?: Yes.

Were there related experiments on other flights?:
See Lunar Surface Magnetometer (S 034) on A-12, 15, and 16.

Where was it stored during flight?: LM Quad II Scientific Equipment Bay.

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.


Preliminary Science Reports, A-14, 16

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

Apollo Program Summary Report, section 3.2.13 Lunar Portable Magnetometer Experi-ment, JCS-09423, April, 1975.

Apollo 16 Technical Crew Debriefing, 5 May 1972, in JSC History Office.