Using a combination of ground based and space instruments, TERRIERS surveys the upper atmosphere using a technique called tomography, measuring ultraviolet light emissions, to construct an image of Earth's ionosphere. While the ionosphere has been studied in detail in the past, there is currently no other means to obtain these types of global three dimensional maps of electron density. Such measurements are of crucial importance in understanding many upper atmosphere phenomena. As secondary goals, TERRIERS examines related upper atmospheric phenomena, and tests the utility of long term solar irradiance measurements. Spacecraft: Spins at 3 rpm in "Thompson Spinner" configuration. Attitude and spin rate control with 3 magnetic torque coils. Attitude determination with sun sensors, magnetometers and horizon crossing indicators. Satellite uses 16W of orbit-averaged power and can downlink telemetry at 250 kbit/s in S-band. Spacecraft Bus is based on, though not an exact copy of AeroAstro's HETE design. Payload: Primary payload is 5 imaging spectrometers, 4 of which operate in the night portion of the orbit. TERRIERS also carries 2 photometers, and a Gas Ionisation Solar Spectral MOnitor (GISSMO) which is an optics-free solar EUV spectrometer. Riding piggyback at the base of the spacecraft bus is a small payload built by Cleveland Heights High School.
Design Life: 1 year.
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. Additional Details: TERRIERS.