|Mission type||Earth observation|
|Mission duration||~7 years|
|Manufacturer||Jet Propulsion Laboratory|
|Launch mass||437 kg (963 lb)|
|Start of mission|
|Launch date||October 6, 1981, 11:27UTC|
|Launch site||Vandenberg AFB SLC-2W|
|Perigee altitude||535.0 kilometers (332.4 mi)|
|Apogee altitude||551.0 kilometers (342.4 mi)|
|Argument of perigee||259.5734 degrees|
|Mean anomaly||100.6126 degrees|
|Epoch||5 March 1991, 04:02:01 UTC|
|Ultraviolet ozone spectrometer|
1.27 micrometer spectrometer
nitrogen dioxide spectrometer
four-channel infrared radiometer
solar ultraviolet monitor
solar proton alarm detector
The Solar Mesosphere Explorer (also known as Explorer 64) was a U.S. uncrewed spacecraft to investigate the processes that create and destroy ozone in Earth's upper atmosphere. The mesosphere is a layer of the atmosphere extending from the top of the stratosphere to an altitude of about 80 km (50 mi). The spacecraft carried five instruments to measure ozone, water vapor, and incoming solar radiation.
Launched on October 6, 1981, on a Delta rocket from Vandenberg Air Force Base, in California, the satellite returned data until April 4, 1989. The spacecraft reentered Earth's atmosphere on March 5, 1991.
Managed for NASA by the Jet Propulsion Laboratory, the Solar Mesosphere Explorer was built by Ball Space Systems and operated by the Laboratory for Atmospheric and Space Physics of the University of Colorado where one hundred undergraduate and graduate students were involved.