HR: 0830h
AN: A31E-0099    [PDF]
TI: On-orbit SI Traceability of the Calibration of a Spectrally Resolved Measurement of Atmospheric Thermal Radiances
AU: * Dykema, J A
EM: dykisma@deas.harvard.edu
AF: Harvard University, 12 Oxford Street, Cambridge, MA 02138 United States
AU: Gero, P J
AF: Harvard University, 12 Oxford Street, Cambridge, MA 02138 United States
AU: Goody, R M
AF: Harvard University, 12 Oxford Street, Cambridge, MA 02138 United States
AU: Anderson, J G
AF: Harvard University, 12 Oxford Street, Cambridge, MA 02138 United States
AB: The Climate Change Research Initiative (CCRI) prioritizes the development of specialized observational datasets intended to improve the quality of high-end model forecasts of future climate. Because of the evolution of climate change signals over periods of years to decades, distinct from the synoptic timescales characteristic of the meteorological observing network, measurement accuracy is prioritized over measurement precision. This accuracy must be demonstrable to future investigators from any agency or country for all time. This demanding standard for accuracy requires the measurement to be traceable to the SystŠme International d'Unit‚s (SI). The SI provides an internationally recognized and reproducible standard that makes the measurement results intrinsically comparable between scientists and across instruments. With the development of new calibration facilities in collaboration with standards laboratories such as NIST (Rice and Johnson 2001), the traceability of space-based remote sensing measurements to the SI can be clearly demonstrated in the pre-launch. It is another challenge altogether to maintain this traceability on-orbit, as these remote sensing instruments are typically not recovered after the mission terminates. On-orbit calibration systems provide some information about the radiometric stability, but the question of absolute drift from the SI value is a vexing question. One solution under consideration is the development of the moon and certain stars as space-based SI standards. For infrared instruments with large viewing apertures, this solution still contains intolerable uncertainties. Here we describe a second solution: to include a redundant calibration system that provides an on-orbit measurement of every significant component uncertainty in the instrument error budget. We present preliminary lab results from a prototype spectrally resolved infrared radiometer designed to measure the earth's thermal radiation spectrum to an SI-traceable accuracy of 0.1 K. These results simulate the on-orbit tests to verify the instrument's native infrared radiance scale, derived from blackbody sources.
DE: 0360 Transmission and scattering of radiation
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting