First Small Explorer mission; Solar Anomalous and Magnetospheric Particle Explorer. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B).

Second Small Explorer mission.

NASA's third Small Explorer, the Transition Region and Coronal Explorer (TRACE), was successfully launched by an Orbital Pegasus XL. The L-1011 carrier aircraft took off from Vandenberg and dropped the Pegasus over the Pacific Ocean. TRACE, a project led by Lockheed's solar physics group, carried a 30-cm extreme ultraviolet imaging telescope which will study the Sun. The telescope mirrors were made by the Smithsonian Astrophysical Observatory. TRACE had an 8.5 arcmin field of view and 1 arcsecond resolution.

On December 3 the Orbital Sciences L-1011 Stargazer took off from Vandenberg AFB Runway 30/12 carrying a Pegasus XL launch vehicle with the SWAS satellite aboard. It reached the drop box at 36.0N 123.0W over the Pacific, but due to a software-related problem the range ordered the launch scrubbed and the L-1011 returned to base. After a further delay due to weather, the L-1011 took off at 23:58 GMT on December 5 and SWAS reached orbit and separated from the third stage at 01:09 GMT. SWAS, the Sub-millimetre Wave Astronomy Satellite, had a 0.6m telescope with a 490 to 550 GHz sub-millimetre receiver and an acousto-optical spectrometer. SWAS was used to study the cooling of molecular cloud cores, the sites of star formation in our galaxy, by measuring lines from molecular oxygen and water.