This is a comparison of NOGAPS synoptic weather fields for 82 km for 18 UT (Universal Time) on June 13, 2007. Shown are maps of (a) temperature, (b) abundance of water vapor (parts per million by volume) and (c) resultant saturation (proportional to relative humidity). Values greater than 1 represent super saturated air. The three red dots are locations of ice clouds observed by SHIMMER near this time. No clouds were seen in the sub-saturated air. Credit: Naval Research Laboratory

The STPSat-1, built for the Department of Defense (DoD) Space Test Program (STP) and operated by the DoD STP for the first year then transitioned to NRL for the last 16 months, was decommissioned on October 7th after completing almost 2 ½ years of successful on-orbit operation. The satellite's two payloads, both designed and built by the Naval Research Laboratory (NRL), provided unique measurements of middle atmospheric hydroxyl, polar mesospheric clouds and the low latitude ionosphere.

The DoD STP launched STPSat-1 on March 8, 2007, into Low Earth Orbit as one of the payloads on the demonstration flight of the EELV Secondary Payload Adapter (ESPA) ring aboard an Atlas V (AV-013) as part of the STP-1 mission. It was built by Comtech AeroAstro, a subsidiary of Comtech Telecommunications Corp. The primary payload was the Spatial Heterodyne Imager for Mesospheric Radicals (SHIMMER); the PI was Dr. Christoph Englert of the NRL Space Science Division. SHIMMER's objective was to demonstrate the viability of a new optical technique, Spatial Heterodyne Spectroscopy (SHS), for satellite-borne observations of the Earth's atmosphere from space. SHS is an optical technique which combines the high throughput and high spectral resolution of a Fourier transform spectrometer with the relatively simpler optical and mechanical design associated with more conventional grating spectrometers. NRL is a key institution in the development of this novel technique and is pioneering SHS applications from ultraviolet to and in measuring air motions (winds). SHIMMER's key scientific objective was to make high resolution spectral measurements, using UV resonance fluorescence, of mesospheric hydroxyl (OH), an atmospheric trace constituent which is important for chemistry. The first space-based measurements of middle atmospheric OH had been obtained by NRL during the 1990s; however, the earlier measurements were limited in scope and were made with a spectrograph so large it could only be delivered to orbit using the space shuttle. SHIMMER's distinguishing feature was the use of a monolithic interferometer that enabled the required very high spectral resolution measurements to be made with an instrument package many times smaller and lighter than the earlier shuttle experiment.

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