Page 56 - Apollo Moonships

54 On bOard apOllO mOOnships
INTO THE LUNAR ORBIT
While two of the three astronauts on Apollo missions flew down to the moon on board the Lunar Excursion Module (LEM) to explore its surface, the third member of the crew— the Command Module (CM) pilot—remained in the mother ship orbiting the satellite. The lunar parking orbit used by Apollo missions was situated between 170 nautical miles and 60 nautical miles above the moon’s surface. The Command- Service Module (CSM) completed one revolution around
the moon between 48 minutes and two hours, depending on several factors. Pending for the return of his comrades, the solitary journey of the pilot around the moon could last several days (the record corresponds to Apollo 17 Astronaut Ronald Evans, who was the most distant solo traveler during four days), but his role was critical: he patiently waited
for a call from his partners saying the LEM successfully blasted from the lunar surface and immediately went to find them with the mother ship. If the rendezvous and docking maneuvers between both spacecrafts failed, there was no hope for recovery for the two astronauts on board the Lunar Module. Too far from the Earth to be rescued, they would be stranded in low orbit around the moon with few reserves of oxygen, food, and water. Eventually, the lunar lander would fall towards the moon and crash back against its surface. For that reason, the CM pilots were some of the most experienced aviators in the world.
ORBITAL EXPERIMENTS
While the Command Module pilot remained in the lunar parking orbit, he performed several experiments to study the moon and the space environment. The first lunar missions completed only a limited number of studies, but Apollo 15, 16, and 17 (J-missions) were especially equipped for the
job. In those missions, the previously vacant sector 1 of
the Service Module (SM) contained a Scientific Instrument Module (SIM), which carried specialized cameras and instrumentation for gathering lunar orbit scientific data.
For example, the SIM Bay of Apollo 15 included an X-ray fluorescent detector, a gamma ray spectrometer, an alpha particle spectrometer, both panoramic and mapping cameras, one laser altimeter, a dual-beam mass spectrometer, and a small satellite (31 inches long and 14 inches of hexagonal diameter), which was released to study the space in the vicinity of the moon. During the translunar coast, SIM Bay was covered by a door that was jettisoned a few hours
prior to lunar orbit insertion to expose the cameras and scientific instruments. After leaving the moon, during the transearth coast, each command pilot of J-missions had to perform a space walk to retrieve the film cassettes inside the mapping and panoramic cameras placed in the SIM Bay. The orbital experiments conducted by Apollo missions helped scientists determine the internal structure of the moon,
the composition of its tiny atmosphere, and the moon’s gravitational acceleration, among other things.
SUBSATELLITE EJECTION
The small subsatellite ejected into the Lunar orbit by Apollo 15 carried three experiments: the S–band transponder experiment, the particle shadow – boundary layer experiment and the magnetometer experiment. The satellite remained operational about a year, powered by a solar cell array for day operation and a rechargeable battery for night.