Abstract
The FIRST (Far-InfraRed Spectroscopy of the Troposphere) instrument is a 10 to 100 micron spectrometer with 0.64 micron resolution designed to measure the complete mid and far-infrared radiance of the Earth's Atmosphere. A Fourier transform interferometer provides the spectral resolution. FIRST has been successfully used to obtain high-quality atmospheric radiance data from the ground and from a high-altitude balloon. When used to observe the atmosphere from the ground, FIRST uses ambient and warm on-board blackbodies for calibration and when used from a balloon a warm blackbody and view of cold space are used. FIRST was calibrated previously for absolute accuracy using a warm and ambient blackbody, and found to be accurate to 0.2 K for temperatures near the blackbodies, but with increasing inaccuracy for temperatures farther from the blackbodies because of the required extrapolation. To avoid this extrapolation and to better simulate operations from a balloon, first was recently calibrated using a warm blackbody and a cold (77 K) blackbody. This presentation will discuss this recent re-calibration of FIRST and compare results to the pervious calibration with a warm and ambient blackbody. The LWRICS (Long Wave Infrared calibration source) blackbody, which is accurate to the ~100 mK level in brightness temperature was used as the calibrator.
Absolute Radiance Recalibration of FIRST using a Cold Blackbody
The FIRST (Far-InfraRed Spectroscopy of the Troposphere) instrument is a 10 to 100 micron spectrometer with 0.64 micron resolution designed to measure the complete mid and far-infrared radiance of the Earth's Atmosphere. A Fourier transform interferometer provides the spectral resolution. FIRST has been successfully used to obtain high-quality atmospheric radiance data from the ground and from a high-altitude balloon. When used to observe the atmosphere from the ground, FIRST uses ambient and warm on-board blackbodies for calibration and when used from a balloon a warm blackbody and view of cold space are used. FIRST was calibrated previously for absolute accuracy using a warm and ambient blackbody, and found to be accurate to 0.2 K for temperatures near the blackbodies, but with increasing inaccuracy for temperatures farther from the blackbodies because of the required extrapolation. To avoid this extrapolation and to better simulate operations from a balloon, first was recently calibrated using a warm blackbody and a cold (77 K) blackbody. This presentation will discuss this recent re-calibration of FIRST and compare results to the pervious calibration with a warm and ambient blackbody. The LWRICS (Long Wave Infrared calibration source) blackbody, which is accurate to the ~100 mK level in brightness temperature was used as the calibrator.