The thermal background of HST as measured by HST-NICMOS

摘要

The overall temperature environment of the NICMOS detectors onboard the Hubble Space Telescope (HST) has changed since initial operation in 1997. These changes include an increased detector operating temperature and increases of the temperatures at the aft end of HST and the NICMOS enclosure. The aft shroud of HST is warmer due to on-going degredation of the MultiLayer Insullation (MLI) and increased power from the instruments installed during Servicing Mission 3B (The Advanced Camera for Surveys (ACS) and the NICMOS Cryocooling System (NCS)). This warms the NICMOS fore-optics, affecting the thermal background in long wavelength camera 2 and camera 3 filters. These trends are well described by both direct engineering data from the telescope and thermal emission models which are able to estimate the total thermal contribution to an exposure by knowing the etendue, reflectance, emissivity and temperature of each of the optics. This work reflects the first evidence of spacecraft heating directly affecting science observations onboard HST.