Thermal architecture of the galaxy evolution probe mission concept

Abstract

The Galaxy Evolution Probe (GEP) is a proposed far infrared-optimized observatory designed for zodiacal-light-limited imaging and spectroscopy in the 10 to 250 micron band. The GEP telescopes and instruments are planned to be actively cooled with the system in a sun-earth L2 halo orbit. A detailed description of the GEP mission concept is documented in [1]. Crucial to the scientific performance of GEP is the thermal architecture; it must support a range of cryogenic elements, ranging from the full telescope optical assembly at around 4 K to the far-IR focal planes consisting of kinetic inductance detector (KID) arrays cooled to 100 mK. Given the mass operating at these low temperatures, the thermal system is one of the main drivers of mission cost and complexity. We present a solution to the GEP thermal design that is realizable within a probe-class envelope. The baseline system utilizes a multi-stage adiabatic demagnetization refrigerator (ADR) for the 100mK base; the ADR system also provides an intercept at 1K. ADR systems similar to that in our design have flown, and among sub-K options, ADRs offer high Carnot efficiency. The ADR rejects heat to a hybrid Joule Thompson (JT) and Stirling or PT Cryocooler with a lowtemperature stage at 4 K as well as an intercept at 20 K. These coolers are also mature systems with flight heritage on most subcomponents.