Mars Orbiter uses Rockwell Scientific sensors

Feb. 1, 2006
When NASA launched its Mars Reconnaissance Orbiter from Cape Canaveral Air Force Station in Florida on Aug.

By Ben Ames

THOUSAND OAKS, Calif. - When NASA launched its Mars Reconnaissance Orbiter from Cape Canaveral Air Force Station in Florida on Aug. 12, 2005, it carried six scientific instruments.

Rockwell Scientific Co. in Thousand Oaks, Calif., supplied two imaging sensor components for one of those, the CRISM (Compact Reconnaissance Imaging Spectrometer for Mars).

CRISM is a visible-infrared hyperspectral mapper developed by the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. NASA will use it to search for evidence of minerals that form in the presence of water, which might have been left by hot springs, thermal vents, lakes, or ponds far back in Mars’ history when water may have been present on the surface. They will also use CRISM to aid in mapping the geology, composition, and stratigraphy of Mars’ surface features.

Rockwell Scientific contributed a midwave-infrared (MWIR) and visible-IR subsystem to the project.

The MWIR subsystem is composed of an MWIR sensor and a three-zone order-sorting multilayer interference filter packaged in a cold shield. The MWIR sensor is a mercury cadmium telluride (HgCdTe) array with 640 (spatial) by 480 (spectral) pixel format for high resolution with a 980- to 3960-nanometer spectral bandpass.

The three-zone filter consists of two broadband filters and one linear variable filter. The visible subsystem uses a silicon photodiode array with a 380-to-1050-nanometer spectral bandpass and a two-zone order-sorting filter. The visible array has the same pixel format and read-out integrated circuit (ROIC) as the MWIR sensor, greatly simplifying the data-acquisition system.

The combination of the high-resolution sensors and the multizone order-sorting filters provides the CRISM instrument a greater capability to map spectral variations than any similar instrument sent to Mars.

The visible and infrared spectrometers will track regions on the Mars surface and map them at scales as small as 60 feet across, from an altitude of 186 miles. The instruments will read 544 “colors” to detect minerals in the Mars surface.

Its highest resolution is about 20 times sharper than any previous look at Mars in midwave infrared wavelengths, and boasts five times better spatial resolution than any previous look in the thermal infrared spectral region.

“CRISM plays such an important role in Mars exploration, and our sensor systems are critical in collecting the data to identify the sites most likely to have contained water and which would make the best potential landing sites for future Mars exploration missions,” says Jianmei Pan, program manager of the CRISM program at Rockwell Scientific.

Rockwell Scientific builds high-performance sensor designs and develops focal plane-arrays (FPAs) that operate within a broad spectrum of light from below 0.3-micron ultraviolet to 18-micron long-wave infrared for defense, astronomy/scientific, and commercial applications.

The company supplied NASA’s Hubble Space Telescope with extremely sensitive FPA mosaics to capture light from distant galaxies, and will provide IR FPAs for Hubble’s successor-the 2011 James Webb Space Telescope.

The company has meshed its engineering expertise in sensor and ROIC design to offer complete subsystem packages that incorporate state-of-the-art sensors with custom mixed-signal CMOS ROIC design and fabrication.

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