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Lunar Dust Detector

NSSDCA ID: 1969-059C-05

Mission Name: Apollo 11 Lunar Module / EASEP
Principal Investigators:Mr. James R. Bates
Principal Investigators:Dr. Brian J. O'Brien


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.

The Dust Detector was originally designed to measure only dust accumulation but was expanded to include the particle, radiation, and temperature studies before it was flown on Apollo 11. (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 EASEP on 21 July 1969 and ended in late August 1969 near sunset of the 2nd lunation.

Alternate Names

  • Apollo11EASEP/LunarDustDetector
  • Dust, Thermal, and Radiation Engineering Measurements Package
  • M515

Facts in Brief

Mass: 0.27 kg
Power (avg): 0.5 W

Funding Agency

  • National Aeronautics and Space Administration (United States)


  • Planetary Science: Geology and Geophysics

Additional Information

Questions and comments about this experiment can be directed to: Dr. David R. Williams



NameRoleOriginal AffiliationE-mail
Dr. Brian J. O'BrienPrincipal InvestigatorDepartment of Environmental
Mr. James R. BatesPrincipal InvestigatorNASA Johnson Space

Selected References

  • O'Brien, B. J., et al., Degradation of Apollo 11 deployed instruments because of lunar module ascent effects, J. Appl. Phys., 4, No. 11, 4538-4541, doi:10.1063/1.1658493, Oct. 1970.
  • Bates, J. R., et al., The modified dust detector in the Early Apollo Scientific Experiments Package, in Apollo 11 Prelim. Sci. Rept., NASA SP-214, Wash., DC, 1969.
  • Bates, J. R., and P. H. Fang, Some astronomical effects observed by solar cells from Apollo missions on lunar surface, Solar Energy Materials Solar Cells, 68, No. 1, 23-29, Apr. 2001.

Related Information at NSSDCA

Image of EASEP

EASEP central station

Apollo 12 Dust Detector Experiment
Apollo 14 Dust Detector (DTREM) Experiment
Apollo 15 Dust Detector (DTREM) Experiment

Lunar Science
Moon Page

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