Degradation of Apollo 11 Deployed Instruments because of Lunar Module Ascent Effects

Abstract

Three similar horizontal solar cells were deployed by the Apollo 11 astronauts to measure whether the lunar module ascent caused degradation of their surface properties and resultant thermal control. The outputs of the cells at lunar module ascent decreased approximately 18%, 7%, and 0%. The average absorptivity thus decreased approximately 8%, while the average emissivity decreased approximately 12%, resulting in overheating. The results are discussed and several possible causes are suggested. Subsequently, the surface absorptivity and emissivity of each cell changed less than 1%–2% during the following month. Lunar module ascent effects for the closely deployed Apollo 11 instruments were therefore much more important than the long-term exposure to the lunar environment. The relevance of these findings to future deployment of lunar instruments is discussed.

Apollo measurements of lunar dust amidst geology priorities

“…This report describes measurements by the DDEs deployed on Apollo 11 (Figure 2), 12 (Figure 3), 14 and 15 (Table 1). Not unexpectedly, the Apollo 11 DDE measured contamination at the LM ascent (O'Brien et al 1970) but the official NASA Apollo 11 Preliminary Science Report denied it (Bates et al 1969). The Passive Seismometer overheated by about 308C and operated for only 21 days.…”

“…As recently as 2007 an important review of the lunar regolith and processes occurring on it (Colwell et al 2007) did not reference either Apollo 11 findings about lunar dust with DDE by O'Brien et al (1970) or Apollo 14 findings of cohesive forces by Gold (1971) with TDS. Neither reference appears to be cited until O'Brien (2009O'Brien ( , 2011.…”

“…By contrast, Figure 4 shows over 600 data points, not 2, at 54 s intervals over the relevant 10 h. LM ascent took 10 s, clearly detected in DDE data. However, O'Brien et al (1970) with fine detail of Figure 4 was not published in a peer-reviewed journal until October 1970. By that time the Apollo 12 ALSEP had been deployed successfully, Apollo 13 had been aborted safely, and the Apollo 14 ALSEP was packaged and ready for a successful landing in early February 1971.…”

“…Contamination was proven by the DDE to occur for the pioneering Apollo 11 expedition (O'Brien et al 1970), when for reasons of safety Buzz Aldrin deployed experiments only 17 m from the LM. The Passive Seismometer overheated by almost 308C and was terminated by ground command after only 21 Earthdays' operation, the consequence of overheating because of dust deposition at the LM ascent (Harris 1972).…”

“…There were a telemetry fade and high noise during the LM ascent. Decreases in outputs were estimated to be zero, minus 7% and minus 17%(O'Brien et al 1970).…”