Nozomi (spacecraft)

Mission profile

After launch on the third M-V launch vehicle, Nozomi entered an elliptical geocentric parking orbit with a perigee of 340 km and an apogee of 400,000 km. It performed a lunar swingby on September 24, 1998, and another on December 18, 1998, to increase its apogee. On December 20, 1998, it flew by Earth at a perigee of about 1000 km; the gravitational assist and a 7-minute burn of the bipropellant rocket placed it on an escape trajectory toward Mars, with arrival scheduled for October 11, 1999, at 7:45:14 UT.

However, a malfunctioning valve during the Earth swingby caused fuel loss, leaving insufficient acceleration for the planned trajectory. Two course correction burns on December 21 used more propellant than planned, further depleting fuel. A revised plan kept Nozomi in heliocentric orbit for four more years, including Earth flybys in December 2002 and June 2003, to encounter Mars at slower relative velocity in December 2003 or January 1, 2004. On April 21, 2002, powerful solar flares damaged communications and power systems; an electrical short in a power cell for the attitude control heating system allowed hydrazine fuel to freeze.

The fuel thawed as the craft approached Earth, and maneuvers for the Earth flyby succeeded. Another Earth flyby within 11,000 km occurred on June 19, 2003.

On December 9, 2003, efforts to orient the craft for a December 14 main thruster orbital insertion burn failed, and mission-saving efforts were abandoned. Small thrusters were fired on December 9, moving the closest approach to 1,000 km to avoid inadvertent impact on Mars. The spacecraft flew by Mars on December 14, 2003, entering a roughly 2-year heliocentric orbit.

Spacecraft and subsystems

The Nozomi spacecraft was shaped like a square prism with its corners cut off, standing 0.58 meters tall and measuring 1.6 meters across. Two solar panel wings, fitted with silicon solar cells, jutted out from opposite sides to supply power either directly or through nickel-metal hydride batteries. A dish antenna sat on top, while a propulsion unit stuck out from the bottom. From the sides extended a 5-meter deployable mast, a 1-meter boom, and two pairs of thin wire antennas spanning 50 meters tip to tip.

Communications used X-band at 8410.93 MHz and S-band at 2293.89 MHz. The orbiter carried 14 instruments, including 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 science payload had a total budgeted mass of 33 kilograms.

Canada contributed a $5 million thermal plasma analyzer, marking the Canadian Space Agency’s first involvement in an interplanetary mission.