Cooler Electronics
Instrument
The cryocooler control electronics (see photo) operate off a 28 Vdc spacecraft bus and provide high efficiency, synchronized drive to the compressor pistons. Cold head temperature (+/-10 mK) and compressor vibration output (<0.5 Newton) are controlled by software feedback loops based on a cold head temperature sensor, a capacitive piston position sensor, and an accelerometer mounted on the compressor. The overall mass of the AIRS cryocooler system is 37 kg including both redundant assemblies along with the support structure.
The development of the space qualified pulse tube cryocooler was a key accomplishment for the program and represents a major advance in cryogenic technology. The AIRS pulse tube cryocooler has demonstrated excellent performance in terms of temperature control, operating efficiency and vibration output. Both cryocoolers achieved a thermodynamic efficiency (system input power/cooling capacity) of approximately 62 W/W at 55 K operation with a net cooling capacity of 1.5 Watts. Cold head temperature control has been measured to be better than +/-10 mK at 55 K. Vibration output as measured during cryocooler acceptance testing was well within specification for nearly all cryocooler harmonics and subsequent system level tests have shown no evidence of cryocooler vibration interference.
