Historical Lunar Exploration
Section M 2.
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Japanese Planetary Missions

SAKIGAKE (MS-T5) was launched from the Kagoshima Space Center by ISAS on January 8, 1985, and approached Halley's Comet within about 7 million km on March 11, 1986. The spacecraft is carrying three instruments to measure interplanetary magnetic field/plasma waves/solar wind, all of which work normally now, so ISAS made an Earth swingby by Sakigake on January 8, 1992 into an orbit similar to the Earth's. The closest approach was at 23h08m47s (JST=UTC+9h) on January 8, 1992. The geocentric distance was 88,997 km. This is the first planet-swingby for a Japanese spacecraft.

During the approach, Sakigake observed the geotail. Some geotail passages will be scheduled in some years hence. The second Earth-swingby will be on June 14, 1993 (at 40 Re (Earth's radius)), and the third October 28, 1994 (at 86 Re).

HITEN, a small lunar probe, was launched into Earth orbit on January 24, 1990. The spacecraft was then known as MUSES-A, but was renamed to Hiten once in orbit. The 430 lb probe looped out from Earth and made its first lunary flyby on March 19, where it dropped off its 26 lb midget satellite, HAGOROMO. Japan at this point became the third nation to orbit a satellite around the Moon, joining the Unites States and USSR.

The smaller spacecraft, Hagoromo, remained in orbit around the Moon. An apparently broken transistor radio caused the Japanese space scientists to lose track of it. Hagoromo's rocket motor fired on schedule on March 19, but the spacecraft's tracking transmitter failed immediately. The rocket firing of Hagoromo was optically confirmed using the Schmidt camera (105-cm, F3.1) at the Kiso Observatory in Japan.

Hiten made multiple lunar flybys at approximately monthly intervals and performed aerobraking experiments using the Earth's atmosphere. Hiten made a close approach to the moon at 22:33 JST (UTC+9h) on February 15, 1992 at the height of 423 km from the moon's surface (35.3N, 9.7E) and fired its propulsion system for about ten minutes to put the craft into lunar orbit. The following is the orbital calculation results after the approach:

        Apoapsis Altitude:      about 49,400 km
        Periapsis Altitude:     about 9,600 km
        Inclination:            34.7 deg (to ecliptic plane)
        Period:                 4.7 days

Historical Lunar Exploration

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