MOPITT On-Orbit Stirling Cycle Cooler Performance

Abstract

The Measurements of Pollution In The Troposphere (MOPITT) instrument was launched aboard the Terra spacecraft (formerly known as EOS AM-1), from Vandenburg Air Force Base, California on Dec 18^th 1999. At present the instrument is in normal operations mode, having undergone its outgas and activation phases.

The instrument uses a pair of Matra Marconi 50–80K Stirling Cycle Coolers interfaced to a set of Lockheed Martin low vibration cooler drive electronics (CDE). The cooler sub-system is mounted to the MOPITT baseplate, directly over a capillary pump heat transfer system (CPHTS). The CPHTS allows the coolers to dump their heat via a remote radiator panel. The displacers are in a back to back configuration and each cold tip is interfaced to a detector nest holding sixteen indium antimonide detectors cooled to less than 100K. The coolers are also run in a vibration cancellation mode using the CDE position digital error correction system (PDECS), in order to minimise focal plane jitter.

This paper will describe the MOPITT cooler sub-system performance during the instrument’s activation and normal operation sequence (March 3^rd to June 1^st 2000). In particular the cooler characteristics are presented. This includes cooler cold tip and detector thermal performance, any affects of orbital temperature fluctuations on the cooler sub-system and contamination (ice) build up on the cold tip and detectors. Finally, the vibration levels will be characterised.

MOPITT is one of the first instruments to use the Matra Marconi 50–80K coolers on-orbit, hence the data should provide an interesting insight into cooler performance and longevity.

The MOPITT instrument has been funded by the Canadian Space Agency, built by COM DEV International and operated by the University of Toronto Instrument Operations Team (IOT).