Launched on India's Chandrayaan-1 spacecraft on October 22, 2008, JPL's Moon Mineralogy Mapper (M3) instrument has successfully completed over six months of operation in space. M3 is one in a suite of eleven instruments, six of which are foreign payloads, flying onboard the Indian spacecraft. Chandrayaan-1, managed by the Indian Space Research Organization (ISRO) in Bangalore, is India's first deep space mission. Chandrayaan-1 was launched on the upgraded version of India's Polar Satellite Launch Vehicle (PSLV-XL) from the Satish Dhawan Space Centre, SHAR, Sriharikota, India. The primary science objective of the M3 instrument is the characterization and mapping of the lunar surface composition in the context of its geologic evolution. Its primary exploration goal is to assess and map the Moon mineral resources at high spatial resolution to support future targeted missions. M3 is a cryogenic state of the art “push-broom” near infrared imaging spectrometer with high signal to noise ratio and spatial and spectral uniformity. The mission lifetime for the instrument is 2 years with 3 months of primary science imaging every 6 months.
Thermal control makes use of passive cooling to provide three temperature zones needed for efficient cryogenic staging, namely 150 K, 170 K and 210 K. A three-stage passive cooler provides cooling for the low temperature zones while a flat plate radiator provides 300 K cooling for the electronics. M3 contains a single mercury cadmium telluride focal plane array cooled to near 150 K by means of the passive cooler 3rd stage. The passive cooler 2nd stage cools the spectrometer optics bench to 170 K while the 1st stage provides cooling to a thermal shield at 210 K surrounding the optics bench. Aluminum flexible thermal straps connect the detector and optics bench to the passive cooler stages. In survival mode, the instrument is off and survival heater power is used to maintain non-operating allowable flight temperatures.
At launch plus 2 hours, M3 survival heater power was enabled and the detector decontamination heater was powered on 6.5 hours later. The spacecraft trajectory required five liquid apogee motor burns at perigee to place the spacecraft into the lunar transfer trajectory. Lunar orbit insertion occurred at launch plus 17 days and 5 days later a stable 100 km circular orbit was achieved. India's Moon Impact Probe was first powered on and successfully released after achieving a stable orbit. M3 was powered on November 18, 2008 after 27 days in decontamination mode. Two days after M3 was powered on, the detector was sufficiently cold to begin acquiring science data. This paper provides a brief overview of the overall thermal control approach, reviews the on-orbit instrument performance and identifies important lessons learned.
