Vesta Mission - Vesta Spacecraft Design

Vesta Spacecraft Design

Around 1985 Vesta was changed to be a Mars mission, with the asteroid-part unchanged. Detailed studies indicate each probe would have visited four small bodies, including asteroids belonging to different classes - providing a representative sample of the diversity of asteroids - and probably one or two comets as well.

Visiting at least one Apollo-Amor (Earth-nearing) asteroid was also given a preference.

Preliminary studies called for at least the following scientific instruments to be included:

• a wide angle camera (~6.5° field of view, 512x512 pixel CCD)
• a narrow angle camera (~0.5° field of view, 512x512 pixel CCD - 3.9 arcsec/pixel)
• a near-infrared spectrometer (measuring between 0.5-5 micrometers with lambda/delta lambda = 50, 5 arcminutes per pixel)

Possible further instrumentation:

• UV spectrometer (for imaging during a comet flyby)
• radar altimeter/radiometer
• a dust detector
• ion or neutral gas detector

Onboard memory would be about 240 Mbits. Images at closest approach (~500 km) could have a resolution of 10 m/pixel. Worst case downlink rate is 600 bit/second (if not using Deep Space Network (DSN)). The scientific payload is about 100 kg. The spacecraft has 750 kg dry mass, and carries 750 kg propellants, and possibly a 500 kg penetrator. 20 square meters of solar panels provide 350 Watts of power.

If DSN support could be obtained, Doppler tracking of the Vesta spacecraft's movement can be used to accurately determine the mass of the encountered bodies. In the other case, another possibility was considered: releasing a test mass, and observing its movement near the target asteroid.

The spacecraft's structure is derived from telecommunication satellites (INMARSAT), having the required mass, volume, and delta-v capabilities (3-axis stabilized, with a pointing platform with 2 axes of freedom for scientific instruments).