application of polyimide kapton heater
Both instruments calibrate  data to radiance using  a two-point temperature calibration.  The strict  volume constraints imposed on SUCHI because of its satellite bus drove the design of an innovative blackbody shutter calibration system (Figure 4).  Teflon-coated, vacuum compatible iris shutters were used to minimize volume consumed by the calibration system.  The blackbody shutters are heated using low-profile Kapton heater  modules and temperature is monitored by analog temperature transducers to maintain knowledge of blackbody temperature to within 0.5° C.  SUCHI employs four shutters, two located between the interferometer and the relay optic for flat field correction, and two located at the end of the stack beyond the  objective  lens.  One shutter  of  each  pair  is actively heated,  while  the  other  will act as the  “cold” blackbody and will be temperature monitored and allowed to float at ambient.  However, all four shutters are capable of being heated for redundancy in case either of the two designated “hot” blackbodies fails.

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.