The earliest flights to concentrate solely on the nature of particular asteroids will probably be of the simple flyby or rendezvous type. That is, data will be obtained by close investigation of these bodies without actually coming in contact with their surface. The technology of flyby missions to bodies at planetary distances is well established; there have been five successful Mariners to date and more flights are scheduled. Unfortunately, ballistic flyby missions suffer from the fact that the spacecraft is near the body of interest for a short period of time (relative velocities at asteroid encounters are 5 to 12 km/s). This problem is acute because spatial resolution of the onboard instruments must be very high, and typical flyby velocities will preclude detailed observations.