The Hiten

spacecraft A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, ...

(ひてん, ), 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 (ISAS) is a Japanese national research organization of astrophysics using rockets, astronomical satellites and interplanetary probes which played a major role in Japan's space development. Since 2003, it is a division of Japan Aerospace Ex ...

of Japan and launched on January 24, 1990. It was Japan's first

lunar probe The physical exploration of the Moon began when ''Luna 2'', a space probe launched by the Soviet Union, made an impact on the surface of the Moon on September 14, 1959. Prior to that the only available means of exploration had been observatio ...

, the first robotic lunar probe since the Soviet Union's

Luna 24 ''Luna 24'' was a robotic probe of the Soviet Union's Luna programme. The last of the Luna series of spacecraft, the mission of the ''Luna 24'' probe was the third Soviet mission to return lunar soil samples from the Moon (the first two sampl ...

in 1976, and the first lunar probe launched by a country other than the

Soviet Union The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen nationa ...

or the United States. The spacecraft was named after flying heavenly beings in

Buddhism Buddhism ( , ), also known as Buddha Dharma and Dharmavinaya (), is an Indian religion or philosophical tradition based on teachings attributed to the Buddha. It originated in northern India as a -movement in the 5th century BCE, and gra ...

. Hiten was to be placed into a highly elliptical Earth orbit with an apogee of 476,000 km, which would swing past the Moon. However, the injection took place with a

delta-v Delta-''v'' (more known as " change in velocity"), symbolized as ∆''v'' and pronounced ''delta-vee'', as used in spacecraft flight dynamics, is a measure of the impulse per unit of spacecraft mass that is needed to perform a maneuver such as ...

deficit of 50 m/s, resulting in an

apogee An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any ellip ...

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 (はごろも, named after the feather mantle of ''Hiten''), into lunar orbit. The transmitter on Hagoromo failed, and even though ignition of Hagoromo's deceleration rockets was confirmed by ground observation, it could never be confirmed if the spacecraft had successfully inserted itself into

lunar orbit In astronomy, lunar orbit (also known as a selenocentric orbit) is the orbit of an object around the Moon. As used in the space program, this refers not to the orbit of the Moon about the Earth, but to orbits by spacecraft around the Moon. The ...

or failed to capture, entering a

heliocentric orbit A heliocentric orbit (also called circumsolar orbit) is an orbit around the barycenter of the Solar System, which is usually located within or very near the surface of the Sun. All planets, comets, and asteroids in the Solar System, and the Sun i ...

. After the eighth swing-by, Hiten successfully demonstrated the aerobraking technique on March 19, 1991, flying by the Earth at an altitude of 125.5 km over the Pacific at 11.0 km/s. Atmospheric drag lowered the velocity by 1.712 m/s and the apogee altitude by 8665 km. This was the first aerobraking maneuver by a deep space probe. After the ninth lunar swing-by and second aerobraking maneuver on March 30, 1991, the primary mission of the probe was concluded.

First ballistic capture into lunar orbit

Edward Belbruno Edward Belbruno (born August 2, 1951, as a U.S. Citizen in Heidelberg, Germany) is an artist, mathematician and scientist whose interests are in celestial mechanics, dynamical systems, dynamical astronomy, and aerospace engineering. His artistic m ...

and James Miller of the Jet Propulsion Laboratory heard of the failure of the Hagoromo orbiter and helped to salvage the mission by developing a so-called ballistic capture trajectory that would enable the main Hiten probe to enter lunar orbit. Belbruno had been working on numerically modelling low-energy trajectories, and heard of the probe's problems. He developed a trajectory solution and on June 22, 1990, sent an unsolicited proposal to the Japanese space agency. They responded favorably, and later implemented a version of the proposal. The trajectory Belbruno and Miller developed for Hiten used

Weak Stability Boundary Weak stability boundary (WSB), including Low-energy transfer, is a concept introduced by Edward Belbruno in 1987. The concept explained how a spacecraft could change orbits using very little fuel. Weak stability boundary is defined for the thre ...

Theory and required only a small perturbation to the elliptical swing-by orbit, sufficiently small to be achievable by the spacecraft's thrusters. This course would result in the probe being captured into temporary lunar orbit using zero (called a ballistic transfer), but required five months instead of the usual three days for a

Hohmann transfer orbit In astronautics, the Hohmann transfer orbit () is an orbital maneuver used to transfer a spacecraft between two orbits of different altitudes around a central body. Examples would be used for travel between low Earth orbit and the Moon, or an ...

. This was the first time a satellite had used

low-energy transfer A low-energy transfer, or low-energy trajectory, is a route in space that allows spacecraft to change orbits using significantly less fuel than traditional transfers. These routes work in the Earth–Moon system and also in other systems, such as ...

to transfer to a Moon orbit. On October 2, 1991, Hiten was captured temporarily into lunar orbit. After that, Hiten was put into a looping orbit which passed through the and

Lagrange points In celestial mechanics, the Lagrange points (; also Lagrangian points or libration points) are points of equilibrium for small-mass objects under the influence of two massive orbiting bodies. Mathematically, this involves the solution of th ...

to look for trapped dust particles: the then-tentatively observed

Kordylewski cloud Kordylewski clouds are large concentrations of dust that exist at the and Lagrangian points of the Earth–Moon system. They were first reported by Polish astronomer Kazimierz Kordylewski in the 1960s, and confirmed to exist in October 2018. D ...

s. 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 and Furnerius. Because the orbit was unstable and would have resulted in the spacecraft crashing into the far side of the Moon, it was decided to use the last fuel to move the impact location to the front side of the Moon so that it could be observed.

References

{{Orbital launches in 1990 Missions to the Moon Japanese Lunar Exploration Program Japanese space probes Spacecraft that orbited the Moon Spacecraft that impacted the Moon Spacecraft launched in 1990 Japanese inventions 1990 establishments in Japan 1993 on the Moon

First ballistic capture into lunar orbit

See also

References