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The Tomographic Experiment using Radiative Recombinative Ionospheric EUV and Radio Sources (TERRIERS) project is the second satellite in NASA's Student Explorer Demonstration Initiative (STEDI) program. STEDI, managed for NASA by USRA, is a pilot program to demonstrate that high-quality space science can be carried out with small, low-cost (<$4.4 Million) free-flying satellites on a time scale of two years from go-ahead to launch.

TERRIERS is a collaboration between the Center for Space Physics at Boston University, AeroAstro Inc. (satellite and ground station), the University of Illinois at Urbana-Champain, the Naval Research Laboratory, MIT's Haystack Observatory, Phillips Laboratory and Cleveland Heights High School. TERRIERS' primary goal is to demonstrate meridional 2-D (latitude-altitude) and global 3D imaging of the ionospheric electron density and thermospheric photo-emission profiles using EUV emissions and tomographic techniques. A secondary goal is the study of several ionospheric and thermospheric phenomena and a tertiary goal is to test the utility of a new technique for long term solar EUV irradiance measurements (GISSMO).

The TERRIERS spacecraft is based on the High energy transient Experiment (HETE) spacecraft. The spacecraft is highly autonomous. After initial orbit insertion, it will place itself in the safe orbital configuration and contact the ground station to begin mission operation. Science operations will be conducted from Boston University through a single ground station.

Instrumentation consists of five Tomographic EUV spectrographs (TESS) for nightglow and dayglow observations (80-140 nm,1-2 nm resolution), the Gas Ionization Solar Spectral Monitor (GISSMO) measuring solar EUV with high sensitivity over long time periods, two photometers for 630 nm night airglow, a dual-frequency radio beacon for electron content measurements.

Note added November 16, 1999: Due to attitude control problems further detailed in the Boston University TERRIERS web page, the spacecraft battery power was quickly expended and no good data have been acquired. As of this writing, recovery efforts continue.

Alternate Names

  • Explorer 76
  • 25735

Facts in Brief

Launch Date: 1999-05-18
Launch Vehicle: Pegasus
Launch Site: Vandenberg AFB, United States
Mass: 120.0 kg
Nominal Power: 16.0 W

Funding Agency

  • NASA-Office of Space Science (United States)


  • Solar Physics
  • Space Physics

Additional Information

Questions or comments about this spacecraft can be directed to: Dr. Dieter K. Bilitza.



NameRoleOriginal AffiliationE-mail
Dr. Daniel CottonMission Principal InvestigatorBoston

Selected References

Chakrabarti, S., Space physics mission gives hands-on experience to students, EOS Trans., AGU, 77, No. 39, Sept. 1996.

Other TERRIERS Data/Information at NSSDCA

Status report (19 May 1999)

Other Sources of TERRIERS Data/Information

TERRIERS Project page (Boston U.)

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