The TIRCIS instrument is not subject to the same volume constraints so a traditional blackbody paddle scheme will be employed for radiance calibration (Figure 5). Two paddles will be actively heated or cooled by thermoelectric modules in order to achieve ideal “hot” and “cold” calibration temperatures determined by the scene temperatures of interest. A third blackbody paddle will be allowed to float at ambient and will be temperature monitored. Cooling straps will be used to channel excess heat to the chassis in the case of vacuum operation. A blackbody wheel containing a hot, cold, and ambient blackbody again heated and cooled using thermoelectric modules will also be employed between the interferometer and relay lens for flat field correction; however, a goal of this project is to improve removal of fringes from the paddle blackbody data collects and use these data for flat field correction to assess whether the interior blackbody can be retired from future designs
Wavelength calibration for both sensors to convert from optical path difference on the detector to wavelength is done using narrow band filters. Since the interferometer design we employ has no moving parts, once determined, wavelength calibration should be unchanged during operation. However, once in orbit, the continuing quality of the wavelength calibration for SUCHI can be checked against the ozone feature at 9.6 microns.