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Nozomi (Japanese for Hope and known before launch as Planet-B) was to have been a Mars orbiting aeronomy mission designed to study the Martian upper atmosphere and its interaction with the solar wind and to develop technologies for use in future planetary missions. However propulsion failures led to its arrival at Mars being delayed from 1999 to 2003. When it finally arrived at Mars its main engine failed, and the spacecraft passed by 1000 km over the surface and then into solar orbit.
Instruments on the spacecraft were to have measured the structure, composition and dynamics of the ionosphere, aeronomy effects of the solar wind, the escape of atmospheric constituents, the intrinsic magnetic field, the penetration of the solar-wind magnetic field, the structure of the magnetosphere, and dust in the upper atmosphere and in orbit around Mars. The mission also would have returned images of Mars' surface.
The Nozomi orbiter was a 0.58 meter high, 1.6 meter square prism with truncated corners. Extending out from two opposite sides were solar panel wings containing silicon solar cells which provided power to the spacecraft directly or via Ni-MH (nickel metal hydride) batteries. On the top surface was a dish antenna, and a propulsion unit protruded from the bottom. A five meter deployable mast and a 1 meter boom extended from the sides, along with two pairs of thin wire antennas which measured 50 m tip to tip. Other instruments were also arranged along the sides of the spacecraft. Spacecraft communications were via X-band at 8410.93 MHz and S-band at 2293.89 MHz.
The 14 instruments carried on Nozomi were an imaging camera, neutral mass spectrometer, dust counter, thermal plasma analyzer, magnetometer, electron and ion spectrum analyzers, ion mass spectrograph, high energy particles experiment, VUV imaging spectrometer, sounder and plasma wave detector, LF wave analyzer, electron temperature probe, and a UV scanner. The total mass budgeted for the science instruments was 33 kg. Radio science experiments were also possible using the existing radio equipment and an ultra-stable oscillator. The total mass of Nozomi at launch including 282 kg of propellant was 540 kg.
Nozomi used multiple lunar and Earth gravity assist passes to increase its energy for solar orbit insertion and the cruise to Mars. Nozomi was to have been inserted into a highly eccentric Mars orbit with a periapsis 300 km above the surface, an apoapsis of 15 Mars radii, and an inclination of 170 degrees with respect to the ecliptic plane. Shortly after insertion the mast and antennas would have been deployed. The periapsis would then be lowered to 150 km, the orbital period to about 38.5 hours.
The spacecraft would be spin stabilized at 7.5 RPM with its spin axis (and the dish antenna) pointed towards Earth. The periapsis portion of the orbit would have allowed in-situ measurements of the thermosphere and lower exosphere and remote sensing of the lower atmosphere and surface. The more distant parts of the orbit would allow study of the ions and neutral gas escaping from Mars and their interactions with the solar wind.
The nominal mission was planned for one Martian year (approximately two Earth years). An extended mission would have allowed operation of the mission for three to five years. The spacecraft also was to have pointed its cameras at the Martian moons Phobos and Deimos.
AKA: Planet-B.
Gross mass: 258 kg (568 lb).
Unfuelled mass: 234 kg (515 lb).
Height: 0.58 m (1.90 ft).
First Launch: 1998.07.03.
Number: 1 .