On-orbit calibration of the Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS)

Abstract

The Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) sensor has been designed to provide highly accurate radiometric and spectral radiances in order to meet the requirements of remote sensing of atmospheric motion from a geostationary orbit. The GIFTS sensor was developed under NASA New Millenium Program funding to demonstrate the tracking of infrared water vapor features in the atmosphere with high vertical resolution. A calibration concept has been developed for the GIFTS instrument design which meets the top level requirement to measure brightness temperature to better than 1 K. The in-flight radiometric calibration is performed using views of two on-board blackbody sources along with cold space. For the GIFTS design, the spectral calibration is established by the highly stable diode laser used as the reference for interferogram sampling, and verified with comparisons to atmospheric absorption line positions. The status of the GIFTS on-orbit calibration approach is described and accuracy estimates are provided. GIFTS is a collaborative activity among

On-orbit absolute radiance standard for the next generation of IR remote sensing instruments

“…This technology was also part of the IIP and is discussed in detail by Gero et al 8,9 The OARS design is a derivative of an earlier UW development for NASA's Geostationary Imaging Fourier Transform Spectrometer (GIFTS). [10][11][12][13][14][15] The phase transition technology was originally demonstrated at UW under internal funding, using a prototype GIFTS blackbody and controller. This work laid the foundation for the advancement of this technology under the IIP, under which the OARS was brought from TRL 3 to 6.…”

Modeled vs. actual performance of the Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS)

“…The IR radiation in these two bands is then focused on the LWIR and SMWIR focal plane arrays (FPAs). A flip-in mirror can be inserted into the optical path between M2 and M3 to allow the FPAs to view one of two internal blackbodies designed by the University of Wisconsin-Madison Space Science and Engineering Center 3,4 . A cold shutter at 60 K can be moved into the optical path in front of the Lyot stop to block all incoming radiation to make measurements of the detector dark offset levels.…”

Far infrared spectroscopy of the troposphere (FIRST): flight performance and data processing

“…Calibrating FIRST required addressing basic issues of absolute radiometric response, frequency scale, instrument line shape, phase alignment and self-apodization. Techniques for quantifying and modeling these effects were applied to FIRST 10,11,12,13,14,15 during its calibration. For Earth scene calibration, FIRST utilized the same calibration scheme adopted by the NPOESS Cross Track Infrared Sounder (CrIS) sensor with calibration information from space view (cold BB) and then the warm flight blackbody.…”