Triana data will assist scientists in constructing more accurate models of the Earth's climate and in determining how solar radiation affects climate. Dr. Francisco Valero of Scripps is the Triana mission principal investigator. Scripps is managing the Triana mission in conjunction with NASA's Goddard Space Flight Center, which is also providing the Triana spacecraft and instrument integration.

The Scripps-NIST advanced radiometer, or Scripps-NISTAR instrument, will measure radiation emitted and reflected by the entire sunlit Earth. The four-channel radiometer contains three absolute radiometric cavities and one photo-diode provided by NIST.

Ball Aerospace performed the instrument system engineering, design, fabrication, assembly, and test for the canister that housed the NIST-provided detectors along with shutters for each channel, selectable optical filters, and the thermal control system. Ball Aerospace also developed the high-gain, high-precision servo-control electronics used to control the detectors and to interface Scripps-NISTAR with the Triana spacecraft.

Scripps-NISTAR uses an electrical substitution measurement technique employed by Dr. Steven Lorentz, the instrument principal investigator from NIST. The radiometric cavities are maintained at a constant temperature.

When the shutters are open, the cavity temperatures begin to increase as radiation is absorbed. The electronics detect the very small temperature changes and reduce the power to hold the cavity temperature constant. The change in power used to keep the cavity temperature constant is a measurement of how much radiation is entering the instrument.

"Scripps-NISTAR was completed as a true integrated product team with our technical customer involved in the design, fabrication, assembly and testing phases. The team performed a lot of work in a short amount of time -- just nine months -- because the original intent was to deliver Scripps-NISTAR by the end of October 1999. We worked at a pace to accomplish that," said Bob Parizek, Ball Aerospace NISTAR program manager.

The Triana mission was halted in October 1999 per congressional direction and restarted in March 2000. The instrument was originally shipped to NIST in November 1999 and returned to Ball for additional development work and testing in the spring of 2000. The instrument is currently being characterized and calibrated at NIST.

Triana's 1 million-mile journey is slated to begin with a 2002 space shuttle launch, arriving at its L-1 destination about six months later. The gravitational field from the sun at L-1 is balanced by the gravitational field of the Earth; therefore Triana will orbit the sun always remaining on a line between the sun and the Earth.

The Triana visible images, taken by a different instrument, will be distributed continuously on the Internet, providing the public with a full disk image of the Earth. Triana is the first Earth-observing mission to L-1. The L-1 perspective provides a unique global, sunrise-to-sunset view of Earth. This permits a large number of daily measurements over the entire sunlit Earth for the life of the mission.

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Scripps Institution of Oceanography
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