Advanced Geosynchronous Studies Imager thermal design

Abstract

The AGSI instrument contains four focal plane arrays (FPAs) including the long wave IR (LWIR), medium wave IR (MWIR), short wave IR (SWIR), and the visible (VIS) FPA. The LWIR and MWIR FPAs are housed in a dewar. The SWIR FPA is housed in a separate dewar. The visible FPA will be located outside of the dewar. The AGSI instrument thermal subsystem is required to maintain the LWIR and MWIR FPAs at 65K, the SWIR FPA at 210 K, and the visible FPA between 210 K and 300 K. The stability of all four FPAs must be +/- 0.1 degrees C. The remainder of the optical system, telescope structure and instrument electronics must be maintained between 0 degrees C and 40 degrees C. Telescope alignment must also be maintained through the cooldown of the instrument optical bench, and during the diurnal and seasonal variations in orbital environment. The thermal design will accommodate such directly in the field-of-view for short periods of time without damage to the instrument, and with the ability to recover science operation quickly. This paper will discuss the thermal design needed to achieve these goals as well as detail the cryocooler and solar intrusion issues.