Radio observations of the Sun, planets, and minor bodies such as planetary satellites, comets, and asteroids present special problems to synthesis telescopes: all have relatively large apparent motions, many display brightness variations on short timescales due to rotation and/or intrinsic variability, and many possess complex brightness distributions. Yet solar system objects also present special opportunities. The Sun offers an environment where astrophysical phenomena - particle acceleration, MHD shocks, energy transport - can be studied at a level of detail impossible for more distant objects. Similarly, the planets offer a variety of environments where space plasmas, aeronomy, meteorology, and geology can be studied. Furthermore, the interplanetary medium (IPM) is accessible to observation through indirect means which complement in situ observations by spacecraft.
Observations of sources in the solar system have led to novel and unanticipated uses of the VLA. The VLA was successfully employed as a downlink for the Voyager fly-by of Neptune in the 8.4 GHz band. The addition of the 2.4 GHz band will greatly augment the VLA's ability to offer continued and expanded support in this capacity. As a consequence of the installation of 8.4 GHz receivers in support of the Voyager fly-by, bistatic radar experiments with the Goldstone 70 m antenna became possible. Again, the addition of the 2.4 GHz and the 33 GHz bands, will broaden the opportunities for planetary radar experiments.
The special observational opportunities and challenges posed by solar system objects and the IPM set demanding standards for the instrument proposed in the VLA Development Plan. If these standards are met, the VLA will continue to play a major rôle in the exploration of the solar system.