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The High Resolution Doppler Imager

The High Resolution Doppler Imager (HRDI) was one of the instruments on board the Upper Atmospheric Research Satellite (UARS). The satellite was launched on 12 September 1991 as a part of NASA's effort to study the Earth's stratosphere and mesosphere. UARS was the first satellite in NASA's Mission to Planet Earth. HRDI observed the emission and absorption lines of molecular oxygen (and other atmospheric components) in small volumes (4 km in height by 50 km in width) above the limb of the Earth. From the Doppler shift of the lines, the horizontal winds can be determined to an accuracy of ~5 m s-1, while the line shapes and strengths yield information about the temperature and atmospheric species, such as mesospheric ozone. The HRDI instrument conducted scientific measurements from November 1991 until April 2005. The UARS spacecraft was deactivated on 14 December 2005 at 17:16:37z, completing 78084 orbits over 5208 mission days. The UARS spacecraft is believed to have entered the Earth's atmosphere around 04:00 GMT on 24 September 2011 over the Pacific Ocean at approximately 14.1 degrees south latitude and 189.8 degrees east longitude.

Wind measurements from the TIDI instrument on the TIMED satellite provide overlapping measurements with HRDI from early 2002 through the end of the UARS mission. TIDI observations continue to the current time.

The primary purpose of this site is to make HRDI data available to the scientific community. A secondary goal is to provide information about the instrument technical details and operational performance.