TERRIERS was part of NASA's Student Explorer Demonstration Initiative (STEDI), which was a precursor program to the UNEX (University Explorer) series. STEDI was managed by USRA (the Universities Space Research Association) for NASA, while UNEX was to be more directly managed by NASA-GSFC. TERRIERS was to be operated by the space physics group at Boston University for ionosphere studies, and carried TESS, a set of extreme ultraviolet (EUV) spectrographs to get electron density and thermosphere emission profiles. The GISSMO instrument measured the solar EUV flux. The spacecraft was built by AeroAstro and based on HETE. TERRIERS was placed in the correct orbit, but it failed to orient its solar panel to the Sun and ran out of battery power by May 20. Controllers were optimistic that when its orbit processes to a better sun angle the satellite could be revived.
Launch went according to plan. The L-1011 Stargazer aircraft took off from Vandenberg's runway 30/12 at 04:12 GMT on May 18 and headed to the drop box over the Pacific at 36.0 N 123.0 W. Stargazer dropped the Pegasus at 05:09 GMT and the first stage solid motor ignited five seconds later. At 05:18 UTC the third stage motor burned out and separated, leaving the payload stack in a 405 km x 548 km x 97.7 degree orbit. The PRIMEX HAPS-Lite stage then made the first burn of its hydrazine engine and entered a 540 km x 553 km x 97.7 degree orbit. The box-shaped Terriers satellite was deployed at 05:20 GMT.