Moon Dust – 40 Years Ago and Today

Apollo 12 Moon Dust Experiements

NOTE, this post has some errors and needs to be read with that in mind. I believe that they are especially in the NASA content. Please note the letter from Prof Brian O’Brien at the end of this post.

Moon Dust – it is a crucial part of what we must overcome if we are to return to the moon. Learn about the Apollo moon dust experiments and the danagers facing us on our return.

Echoes of Apollo has recently been in contact with Prof Brian J. O’Brien and we are pleased to report that he has been gracious enough to assist with information about moon dust – in particular Apollo moon dust. O’Brien is based in Australia and has the distinction of creating the extremely small moon dust detectors that rode on many of the Apollo missions including Apollo 11 and 12.

Echoes will publish an in depth story on the dust experiments, but here is a little to keep you interested. The picture at right shows the Apollo 12 ELSEP unit deployed (all photos courtesy of NASA unless indicated)

Apollo Lunar Surface Experiment Package (ALSEP)

During Apollo 12′s first moonwalk, they deployed an Apollo Lunar Surface Experiment Package (ALSEP), which returned scientific data directly to Earth for more than seven years. This unit connected to several other experiments and provided the radio relay back to earth for the experiments. Each Apollo ALSEP provided about of 9 million measurements per ALSEP per day. By the end of the apollo missions and with 5 ALSEPs deployed, scientists were swamped with 45 million measurements per day! Although this could fit on a fraction of a home computer hard drive today, this data consumed an enormous number of data tapes and computer time.

The Apollo 12 package was the first full ALSEP package to be deployed on the moon due to the experimental nature of the first landing (Apollo 11). The mechanics of getting to the lunar surface and back meant that science took a lesser role with Apollo 11. Apollo 11 had a simpler version known as the Early Apollo Surface Experiments Package (EASEP).

Lunar dust remains a complex of major unsolved environmental problems for lunar astronauts. Considering the consequences of dust contamination, we still know little about it. The only direct, active, continuous measurements were by matchbox-sized Dust Detector Experiments (DDE) that flew on the Apollo missions. The Apollo 12 DDE provide the first measurements of the strength of lunar adhesion forces (“stickiness”). The adhesive force increases as solar intensity increases, so that for a vertical surface the dust fell off after mid-morning. This means that it is likely that astronauts during the middle of the lunar day (a bit less than one Earth month long) in future missions will encounter much greater stickiness than met by Apollo astronauts.

Lunar Dust Detector Experiment Description

From nasa.gov

The purpose of the Lunar Dust Detector Experiment (also referred to as the Dust, Thermal, and Radiation Engineering Measurements package, or DTREM) on the Early Apollo Surface Experiments Package (EASEP) was to assess the long term effects of the lunar environment on silicon solar cells by measuring power output reduction caused by high-energy cosmic particle and ultraviolet radiation damage and dust accumulation, and to measure temperatures, including reflected infrared brightness temperatures in computing lunar surface temperatures. Another objective was to determine if protective cover glass was necessary on the cells.

The Dust Detector had two components – a sensor package mounted on a housing on top of the central station sun shield and a printed circuit board located within the central station that interfaced with a preamplifier and the power distribution unit of the ALSEP data subsystem. The sensor package had three 10-ohm-cm n-on-p silicon solar cells, each 1 x 2 cm. The power output of each cell varied from 0 to 150 mV. They were mounted on the top horizontal surface of the dust detector housing. One cell was exposed directly to the environment. The other two were covered with clear fused silica shields of 0.15 mm and 0.51 mm thickness, respectively. The particle energy required to damage the cells is determined by the thickness of the shield. The energy threshold for the uncovered cell was 173 keV electrons and 60 keV protons, for the 0.15 mm covered cell 175 keV electrons and 4.25 MeV protons, and for the 0.51 mm covered cell 380 keV electrons and 8.5 MeV protons. Three temperature sensors were also mounted on the housing, one beneath the solar cells and two, one internally and one externally, on a vertical side of the housing. The sensors are high-precision nickle resistance thermometers with a range of 84 to 408 K.

Data from this experiment consisted of the photovoltaic output of the solar cells and temperatures measured by the three thermistors (internal temerature, cell temperature, and external infrared temperature) as a function of time during daytime conditions. The voltage drop across a precision 1.00 ohm resistor was measured to determine the photovoltaic output. Measurements were made over the course of each lunar day, returned to Earth, and stored on magnetic tape. Selected data were plotted. The original tapes were subsequently misplaced before they could be archived, the only existing data from these experiments are on the plots (Bates and Fang, 2001). No data from this experiment were ever archived with the NSSDC.

The Dust Detector was originally designed to measure only dust accumulation but was expanded to include the particle, radiation, and temperature studies when it was determined from Surveyor engine firings on the surface that the dust accumulation would not be as heavy as anticipated. (The original dust accumulation design was flown on the Apollo 12 mission.) The expanded experiments were flown on the Apollo 11, 14, and 15 missions and were identical to each other except that the Apollo 14 and 15 experiments had a pre-irradiated cell covered by a 0.15 mm glass shield in place of the normal cell covered by 0.51 mm glass on Apollo 11.

The Dust Detector began operation with deployment of the Apollo 11 EASEP on 21 July 1969 and ended in December 1969.

Facts in Brief

Mass: 0.27 kg
Power (avg): 0.5 W

Funding Agency

National Aeronautics and Space Administration (United States)

Discipline

Planetary Science: Geology and Geophysics

Personnel

Name	Role	Original Affiliation	E-mail
Dr. Brian J. O’Brien	Principal Investigator	Department of Environmental Protection	brianjobrien@ozemail.com.au
Mr. James R. Bates	Other Investigator	NASA Johnson Space Center	jbates@ems.jsc.nasa.gov

The photo above shows Dr O’Brian working on the Injun 1 satellite which unfortunately failed to separate from another satellite after launch.

Lunar Surface Experiments

(from nasa.gov)

The lunar surface experiments were of two kinds:

The Apollo Lunar Surface Experiments Package (ALSEP) systems, which were left on the lunar surface by the astronauts and which continued sending telemetry data until turned off Sept. 30, 1977, and
experiments conducted on the lunar surface by the astronauts and returned to earth in the command module.

The dates and lunar coordinates are given in the following listing. The ALSEP-related experiments are listed next, by experiment number, with Apollo mission numbers.

Apollo 12:: Deployed on Nov 19, 1969, at latitude 3 degrees 11′ S, longitude 23 degrees 23′ W in Oceanus Procellarum.
Apollo 13:: Because of service module problems, a lunar landing was not accomplished during the Apollo 13 mission.
Apollo 14:: Deployed on Feb 5, 1971, at latitude 3 degrees 40′ S, longitude 17 degrees 27′ W in the Fra Mauro formation.
Apollo 15:: Deployed July 31, 1971, at latitude 26 degrees 06′ N, longitude 3 degrees 39′ E in the Hadley-Apennine region.
Apollo 16:: Deployed April 21, 1972, at latitude 8 degrees 59′ 34″ S, longitude 15 degrees 30′ 47″ E in the Descartes Highlands.
Apollo 17:: Deployed on Dec 12, 1972, at latitude 20 degrees 09′ 55″ N, longitude 30 degrees 45′ 57″ E in the Taurus-Littrow region.

Apollo ALSEP Experiments

                                                    Apollo Mission
Number & Experiment                             12   14   15   16   17
===================                             ===  ===  ===  ===  ===
S 031 Passive Seismic                            X    X    X    X
S 033 Active Seismic                                  X         X
S 034 Lunar Surface Magnetometer                 X         X    X
S 035 Solar-wind Spectrometer                    X         X
S 036 Suprathermal Ion Detector                  X    X    X
S 037 Heat flow                                             X   (1)   X
S 038 Charged Particle                                X
S 058 Cold Cathode Gage                          X    X    X
S 059 Lunar Geology                              X    X    X    X    X
S 078 Laser Ranging Retroreflector               X    X    X
S 152 Cosmic Ray Detector                                       X
S 198 Portable Magnetometer                           X         X
S 199 Traverse Gravimeter                                            X
S 200 Soil Mechanics                             X    X    X    X    X
S 201 Far UV Camera/Spectrograph                                X
S 202 Lunar Ejecta and Meteorites                                    X
S 203 Lunar Seismic Profiling                                        X
S 204 Surface Electrical Properties                                  X
S 205 Lunar Atmospheric Composition                                  X
S 207 Lunar Surface Gravimeter                                       X
S 229 Neutron Probe                              X    X    X    X    X
M 515 Dust Detector                              X    X    X

(1) Cable broken during deployment.

Further information can be found here on the effects of dust:
http://history.nasa.gov/alsj/TM-2005-213610.pdf

Our Friends at Honeysuckle Creek have very interesting detail on the experiements: 
http://www.honeysucklecreek.net/msfn_missions/ALSEP/hl_alsep.html

Background information on Professor O'Brian:
http://www.churchholytrinity.com/notices/20090711/newsletter_28.pdf

Eugene Cernan (A17) after a day of moonwalking - his spacesuit is covered in moon dust

FOOTNOTE from Prof Brian O’Brien:

Thanks Robert.

The article looked attractive, but I’m afraid it has various errors.

I don’t have time to discuss them here, but in particular I was disappointed that some of the extracts from reference sites had significant omissions and are not accurate.

My peer-reviewed paper published in 6 May 2009 Geophysical Research Letters has a few very brief comments, but did not give a comprehensive discussion of the site.

I’d be happy to talk with you mid-February. Thanks again for your interest.

Prof Brian J. O’Brien

NOTE* Echoes of Apollo will correct the ommissions and any other errors in February with thanks to Prof O’Brien

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