Sharma, Rajeev K. | Search NASA

NASA NTRS2007

JWST NIRSpec Cryogenic Light Shield Mechanism

The focal plane detectors for the Near-Infrared Spectrometer (NIRSpec) instrument on the James Webb Space Telescope (JWST) require a light tight cover for calibration as well as an open field-of-view during ground performance testing within a cryogenic dewar. In order to achieve the light attenuation requirements when closed as well as provide a open field of view for the detectors within the cryogenic dewar, a light shield mechanism was designed. This paper discusses the details of the light shield mechanism design, development, and test results.

Sharma, Rajeev K.↗

NASA NTRS2001

The Role of Bearing and Scan Mechanism Life Testing in Flight Qualification of the MODIS Instrument

This paper describes the results of accelerated and operational life tests on bearings for the Moderate Resolution Imaging Spectroradiometer (MODIS). It also describes the post test analysis of the disassembled bearings. Analysis was performed using micro-Raman, micro-FTIR, X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), and Size Exclusion Chromatography (SEC). In general, the three sets of bearings in each of three test stations were in very good condition after accumulating 68, 144, and 209 million cycles, respectively. Some of the bearings exhibited lubricant degradation, indicated by viscous lubricant deposits on the cage and raceways.

VanDyk, Steven G.↗