The design of the compact reconnaissance imaging spectrometer for mars (crism) instrument
- Paper number
IAC-06-A3.P.3.02
- Author
Mr. Jeffrey Lees, The John Hopkins University Applied Physics Laboratory, United States
- Coauthor
Mr. Scott L. Murchie, The John Hopkins University, United States
- Year
2006
- Abstract
The compact Reconnaissance Imaging Spectrometer for Mars (CRISM) will use targeted observations to search for evidence of aqueous activity and to characterize the geology and composition of surface features (Fig. 1). Global measurements acquired repeatedly throughout the Martian year will provide information on atmospheric water vapor, CO, and aerosols complementary to that from other MRO instruments. When not conducting targeted measurements, CRISM will perform a comprehensive planetary survey in 50 key wavelengths to identify new sites with high science potential for future investigation. CRISM covers the wavelength region 400-830 nm at 8 nm/channel and 830-4050 nm at 7 nm/channel. CRISM’s extended wavelength range provides sensitivity to carbonates even at very low abundances, and its high spatial resolution (24 m/pixel at 400 km altitude) enables measurement of deposits at the scale of outcrops. This paper will discuss the design of each subsystem comprising the CRISM instrument: optical assembly; focal planes; cryogenic system; and the gimbal bearing assemblies and present some of the first images produced by CRISM. The Optical Sensor Unit (OSU) consists of an optical system, a cryogenic system, and focal plane electronics gimbaled about a single axis to allow scanning over +/-60C from nadir. The gimbal bearings are a precision assembly designed to operate in a -60C environment. The gimbal is driven directly by a brushless DC motor paired with a 20-bit incremental position encoder. The electrical signals and purge are passed through a twist capsule in the center of the motor/encoder bearing assembly. A second bearing pair is mounted in a parallel diaphragm bearing housing that provides high stiffness in the lateral directions to the gimbal axis and flexibility along the gimbal axis to compensate for differential expansion between the instrument and spacecraft. The optical assembly is mechanically and thermally isolated from the main gimbal housing by titanium flexures. The spectrometer housing is passively cooled to -90°C through a flexible link to the anti-sunward radiator that passes through the center of the diaphragm bearings, and thus rotates with the OSU; its FOV being independent of the gimbal position. A deployable cover at the aperture of the baffle assembly protects the optical assembly from contamination. Once aerobraking has completed, a HOP actuated release mechanism will deploy the spring loaded door assembly.
- Abstract document
- Manuscript document
IAC-06-A3.P.3.02.pdf (🔒 authorized access only).
To get the manuscript, please contact IAF Secretariat.