NIST SCIENTISTS ENSURE THE ACCURACY OF MEASUREMENTS MADE BY THE TRIANA SATELLITE.

Physicists from NIST are working with scientists from the Scripps Institution of Oceanography at the University of California, San Diego, and a private company to ensure the reliability of measurements made by the Scripps Earth Polychromatic Imaging Camera (Scripps-EPIC) instrument. This unique spectroradiometer is one of three instruments aboard the Triana satellite scheduled to be launched aboard the space shuttle early in 2002. The Triana EPIC mission is designed to study the Earth, for the first time, from a vantage point of a million miles away and promises to offer new insights into how the planet's climate works as an integrated system.

Once it reaches its destination, Scripps-EPIC will begin to transmit a full-color image of the entire sunlit side of the Earth, with 8 km spatial resolution, every 15 minutes. These images will then be continuously distributed over the Internet. To perform these measurements, Scripps-EPIC uses a 4 million element charge coupled detector array attached to a 30 cm Cassegrain telescope with 10 wavelength channels in the ultraviolet, visible, and near-infrared spectral regions. The scientists performed the instrument's radiometric calibration, which is vital to obtaining useful scientific data since it determines the response of the instrument to the light it receives from Earth. The guiding principle for the calibration was to perform separate, controlled experiments for each parameter affecting the conversion from light to signal; these parameters are dark signal, linearity, exposure time, and spectral radiance responsivity.

Except for a few planetary fly-bys, such as Galileo, NASA has not deployed a spacecraft to provide the public with a full disk image of the Earth since Apollo.