The Cold Focal Plane Assembly is mounted on the cold stage of the Radiative Cooler, and operates at a nominal temperature of 90°K ±2°K and can be controlled to one of three set points (90° K, 95° K or 105° K) by a heater on the back of the substrate. The higher temperatures are backup in case the Radiative Cooler efficiency degrades. The characteristics of the Cold Focal Plane Assembly are listed in Table 3.6. The Cold Focal Plane Assembly contains the detector arrays for Bands 5, 6 and 7. Each band is a separate array. The three arrays are mounted on a monolithic substrate. The Band 5 and Band 7 arrays contain 16 detector elements, and are fabricated from indium antimonide. These photovoltaic indium antimonide arrays show very little change in responsivity from 90° K to 105° K. The nominal spatial resolution of Bands 5 and 7 is the same as Bands 1 through 4. The Band 6 array is fabricated from mercury cadmium telluride. This photoconductive array shows a significant decrease in responsivity from 90° K to 105° K. The Band 6 array contains 8 detector elements. The input stages and the feedback resistors of the preamplifier for the Band 5 and 7 (photovoltaic) detectors are mounted with the detectors on the cold stage of the Radiative Cooler. The Band 6 preamplifier and the remainder of the Bands 5 and 7 preamplifier are mounted on a circular housing adjacent to the radiative cooler. The connections within the Radiative Cooler from the cold focal plane area to the ambient temperature connectors for the preamplifiers are made via special low thermal conductivity ribbon cables.

Table 3.6 Cold Focal Plane Design Parameters
Parameter	Bands 5 and 7	Band 6
Number of detectors	16 per band	8
Detector Size	0.00190 in x 0.00204 in	0.00408 in x 0.00408 in
Detector Area
IFOV size	42.5 µrad x 39.4µrad	42.5 µrad x 85.0 µrad
Center to center spacing along track	0.00204 in	0.00408 in
Center to center spacing between rows	0.00510 in	0.01020 in

Back to Chapter 3

Last Update: February 21, 2002