On-Orbit Performance of the TES Pulse Tube Coolers and Instrument — A First Year in Space

Abstract

Launched on NASA’s Aura spacecraft on July 15, 2004, JPL’s Tropospheric Emission Spectrometer (TES) instrument has completed a successful first year in space and captured a number of important lessons. The instrument contains four focal plane arrays in two separate housings cooled to 65 K by a pair of NGST pulse tube cryocoolers. The instrument includes a two‐stage passive cooler to cool the optical bench to 180 K. The cryocooler system design is tightly coupled with the overall thermal control design to maximize performance. Soon after cooling the optical bench and focal planes to their operating temperatures on August 20, 2004, ice contamination of the focal planes led to the need of a decontamination cycle. Ice buildup of cryogenic surfaces led to increased cryocooler heat loads. After six months of successful science operations, plans were developed to increase the optics temperature to 187 K to improve the interferometer optical alignment and obtain higher quality science data. The plan is in place and will be implemented in the near future. This paper provides a general overview of the cryogenic system design and reviews the instrument cryogenic performance over the past year.