Apollo 15 & Apollo 16
Apollo 15 and 16 were launched on 26 July 1971 and 16 April 1972,
respectively. Splashdowns were 7 August 1971 and 27 April 1972. Both
released sub-satellites while in orbit around the Moon to do studies on
lunar gravity and magnetic fields. Apollo 16 astronauts John Young and
Charles Duke deployed a UV electrographic camera/spectrograph on the
lunar surface. The instrument observed the Sun, the Earth's geocorona
and various astronomical objects. Both Apollo 15 & 16 Command Service
Modules carried gamma-ray spectrometers. These spectrometers studied
the Moon and the gamma-ray background.
Apollo 15 and 16 carried a 512-channel cylindrical NaI(Tl) scintillation
gamma-ray spectrometer, 76x76 mm in size, covered with a plastic
scintillator for charged particle rejection. The instrument covered the energy
range 0.55-8.6 MeV. The resolution of the spectrometer was about 8%.The
sensor was mounted on a 7.6 m long boom.
Primarily intended to study the Moon's radioactivity, it made measurements
of the cosmic gamma-ray background during its trip. A flux density of
quanta/m2/s was observed.