Overview

Hiten (MUSES-A) is a spacecraft developed by the Institute of Space and Astronautical Science (ISAS) to demonstrate lunar exploration techniques. Its main objectives are follows:

1. Experiments on a fault-tolerant on-board computer and packet telemetry
2. Experiment of aerobraking between the Earth and the Moon
3. Detection and measurement of mass and velocity of micrometeorite particles

It was launched by M-3SII Rocket No.5 from the Kagoshima Space Center (currently Uchinoura Space Center) on January 24, 1990.
It successfully completed all major missions by the end of March 1991 and conducted the world’s first two earth-to-month aerobraking experiments.
Subsequently, the following additional missions were also accomplished:

1. Exploration of the Lagrangian points (L4 and L5) in the Earth-Moon system
2. Insertion of the HITEN spacecraft into lunar orbit
3. Hard landing on the Moon

At 18:08:45 UTC on April 10, 1993, all telemetry from Hiten ceased and the probe was estimated to have impacted the lunar surface at 55.6°E, 34.3°S, near Frenelius Crater.

Hiten was cylindrical in shape, 1.4 m in diameter and 0.8 m high, and carried the 26-hedron lunar orbiter “Hagoromo” on its top surface with a face-to-face dimension of 40 cm. 197 kg (42 kg of which was hydrazine fuel and 12 kg was the lunar orbiter Hagoromo) at launch.
The spacecraft was spin stabilized at 20 rpm, and its spin axis was kept nearly perpendicular to the ecliptic plane at all times.

DARTS archives raw telemetry and orbit data from Hiten. However, data processing and analysis software are not archived, which may limit the ability to support scientific data analysis.

Observation Instruments

Dust Counter (MDC)

MDC is a microparticle detection device onboard HITEN. Designed to detect microscopic dust and particles in space, MDC identifies the number and size of particles by measuring the electrical signals generated when they collide with the sensor. The wavelength and bandwidth used for the measurement are not specified, but are based on the principle of detecting the electrical signal caused by particle collisions.

MDC’s ability to measure the distribution and density of microscopic dust and particles with high precision has led to a better understanding of the spatial environment around the Moon.

Optical Navigation System (world-first for a spin-stabilizing satellite)

The Optical Navigation System was the world’s first optical navigation system installed by Hiten on a spin-stabilized satellite. This system was used to accurately control the satellite’s orbit by capturing images of the Earth and Moon and locating its position.

The system consists of a camera and an image processor. By analyzing the images taken, the satellite’s position and velocity can be determined with high precision. The observation capability of the optical navigation system contributed greatly to the success of the mission by enabling the satellite’s orbit to be controlled with high precision.

Achievements

Hiten successfully completed the world’s first Earth-Moon aerobraking experiment and collected data on the mass and velocity of micrometeorite particles. Hiten also achieved many other accomplishments, including exploration of the Lagrangian point in the Earth-Moon system, insertion into lunar orbit, and a hard landing on the Moon’s surface. This has greatly contributed to the improvement of Japanese space exploration technology.