NASA launched first satellite into lunar orbit from manned spacecraft on this day in 1971

NASA successfully launched its first satellite into the lunar orbit from a manned spacecraft on this day, 49 years ago. The Apollo 15 subsatellite was lifted off from Launch Complex 39A at Cape Canaveral, Florida, the United States on August 4, 1971, and it ended up providing at least six months of data coverage before the electronics failures occurred in February 1972. All objectives of the historic mission were accomplished according to NASA that was placed in the orbit from the Apollo 15 Service Module. 

The main aim of sending Apollo 15 subsatellite was to study the plasma, particle, and magnetic field environment of the Earth’s satellite and map the lunar gravity field. NASA has explained, “Specifically it measured plasma and energetic particle intensities and vector magnetic fields, and facilitated the tracking of the satellite velocity to high precision.” The basic requirement of the satellite was to acquire fields and particle data everywhere on the orbit around the Moon. Later on, a similar satellite was deployed by Apollo 16. 

Apollo 15 crew, subsatellite. Credit: NASA

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Probe was 35.6-centimeter-diameter

The satellite was small and was designed around 35.6-centimeter-diameter hexagonal structure that was equipped with three instrument booms and was deployed by Apollo 15, the ninth crewed mission, shortly before leaving lunar orbit. The power supply for the probe came from the solar panels and also the chemical batteries. 

The instruments on the satellite measured the strength and direction of interplanetary and terrestrial magnetic fields, detected variations in the lunar gravity field, and also measured proton and electron flux. The satellite even confirmed Explorer 35's finding that while “Earth's magnetic field deflects the incoming solar wind into a tail, the Moon acts as a physical barrier due to its weak field and creates a "hole" in the wind.”

Credit: NASA

Before deploying the subsatellite, the Apollo 15 astronauts David Scott and James Irwin deployed the first Lunar Roving Vehicle (LRV) on Earth’s natural satellite. It was the first off-planet automobile ride that the astronauts too to explore the landing site which was Hadley-Apennine. The NASA astronauts on Lunar module ‘Falcon’ spent nearly three days on the Moon and in totality, the first rover, traversed at least 28 kilometres (17 miles) on the lunar surface. The Apollo 15 mission returned about 76 kilograms of moon rocks to planet Earth. 

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