Thermal/Mechanical System Level Test Results of the GIFTS 2-Stage Pulse Tube Cryocooler

The Space Dynamics Laboratory (SDL), in partnership with NASA Langley Research Center, is building the Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) instrument. The GIFTS focal plane assemblies (FPAs) must operate below 60 K to work properly. The aft optics and interferometer of the instrument must operate below 150 K. These two temperature zones will be cooled by a 2-stage pulse tube cryocooler built by Lockheed Martin. This cryocooler was designed to cool 1.5 watts at 55 K and 8.0 watts at 140 K with a 300 K reject temperature. System power consumed was to be less than 160 watts. SDL recently completed system level testing of the 2-stage cryocooler integrated into the GIFTS system. The thermal performance of the cryocooler as well as mechanical vibration characteristics observed during these tests will be presented. Preliminary analysis of the thermal data shows that cooling performance was achieved on both stages of the cryocooler with adequate thermal margin. Mechanical vibrations from the cryocooler were also found to be sufficiently low in that the perturbations did not prevent the instrument from meeting the NESR (Noise Equivalent Spectral Radiance) requirements. This paper discusses the effects of the cryocooler vibration on the performance of the GIFTS interferometer, which is highly susceptible to even the smallest vibration inputs. This paper also discusses the thermal performance data obtained dur-