Hiten
Encyclopedia
The Hiten Spacecraft
Spacecraft
A spacecraft or spaceship is a craft or machine designed for spaceflight. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and transportation of humans and cargo....

 (hiteɴ), given the English name Celestial Maiden and known before launch as MUSES-A (Mu Space Engineering Spacecraft A), part of the MUSES Program, was built by the Institute of Space and Astronautical Science
Institute of Space and Astronautical Science
is a Japanese national research organization of astrophysics using rockets, astronomical satellites and interplanetary probes. It is a division of Japan Aerospace Exploration Agency .- History :...

 of Japan and launched on January 24, 1990. It was Japan's first lunar probe, the first robotic lunar probe since the Soviet Union
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

's Luna 24
Luna 24
-External links:*...

 in 1976, and the first lunar probe launched by a country other than Soviet Union or the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

.

Hiten was to have been placed into a highly-elliptical Earth orbit with an apogee of 476,000 km, which would be swing past the moon. However, the injection took place with a delta-v
Delta-v
In astrodynamics a Δv or delta-v is a scalar which takes units of speed. It is a measure of the amount of "effort" that is needed to change from one trajectory to another by making an orbital maneuver....

 deficit of 50 m/s, resulting in an apogee of only 290,000 km. The deficiency was corrected and the probe continued on its mission.

On the first lunar swing-by, Hiten released a small orbiter, Hagoromo (named after the feather mantle of Hiten), into lunar orbit. The transmitter on Hagoromo failed, but its orbit was visually confirmed from Earth. After the eighth swing-by, Hiten successfully demonstrated the aerobraking
Aerobraking
Aerobraking is a spaceflight maneuver that reduces the high point of an elliptical orbit by flying the vehicle through the atmosphere at the low point of the orbit . The resulting drag slows the spacecraft...

 technique on March 19, 1991. This was the first aerobraking maneuver by a deep space probe. After the ninth lunar swing-by and second aero-braking maneuver on March 30, 1991, the primary mission of the probe was concluded.

First ballistic capture into lunar orbit

Edward Belbruno
Edward Belbruno
Edward Belbruno is a mathematician whose interests are in celestial mechanics, dynamical systems, dynamical astronomy, and aerospace engineering....

 of the Jet Propulsion Laboratory
Jet Propulsion Laboratory
Jet Propulsion Laboratory is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. The facility is headquartered in the city of Pasadena on the border of La Cañada Flintridge and Pasadena...

 had been working for several years on numerically modelling low-energy (weak stability boundary) trajectories
Low energy transfers
A low energy transfer, or low energy trajectory, is a route in space which allows spacecraft to change orbits using very little fuel. These routes work in the Earth-Moon system and also in other systems, such as traveling between the satellites of Jupiter...

. He had heard of the probe's problems and developed a ballistic capture trajectory that would enable the main probe to enter lunar orbit using zero delta-v. On June 21, 1990, Belbruno faxed over an unsolicited proposal to the Japanese space agency, which responded favorably and called it an "amazing result."

After the probe's primary mission had been completed, it was placed onto the Belbruno trajectory. This represented the first time that a probe had been placed into lunar orbit using zero delta-v
Delta-v
In astrodynamics a Δv or delta-v is a scalar which takes units of speed. It is a measure of the amount of "effort" that is needed to change from one trajectory to another by making an orbital maneuver....

 for orbital capture. On October 2, 1991, Hiten was captured temporarily into lunar orbit.

After that, it was put into a looping orbit which passed through the and Lagrange points
Lagrangian point
The Lagrangian points are the five positions in an orbital configuration where a small object affected only by gravity can theoretically be stationary relative to two larger objects...

 to look for trapped dust particles. The only scientific instrument on Hiten was the Munich Dust Counter (MDC), and no increase over background levels was found. On February 15, 1993, Hiten was placed into a permanent lunar orbit, where it remained until it was deliberately crashed into the lunar surface on April 10, 1993 at , between the craters Stevinus
Stevinus (crater)
Stevinus is a lunar impact crater located in the southeast part of the Moon. To the southeast is the large crater Furnerius. Just to the northeast is Snellius and the Vallis Snellius crater valley. To the west-northwest lies Reichenbach...

 and Furnerius
Furnerius (crater)
Furnerius is a large lunar crater located in the southeast part of the Moon, in the area close to the southwestern limb. Because of its location, the crater appears oval in shape due to foreshortening but is actually nearly circular. Notable nearby craters include Stevinus to the northwest and...

.
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