The Aerosol Polarimetry Sensor (APS), an advanced scientific instrument that will be launched on the Glory satellite, has successfully completed environmental testing and was officially turned over to NASA on March 11 by the Raytheon Company, Waltham, Mass., which built the instrument. APS was delivered on March 9 to the Orbital Sciences Corporation in Dulles, Va., for integration with the Glory spacecraft.

The milestone comes after four months of testing at a Raytheon facility in El Segundo, Calif., during which the APS underwent a series of vibration, electromagnetic compatibility, calibration, and thermal vacuum tests.

"APS is on track and ready to go," said Jeff Hein, the APS instrument manager for Glory at NASA's Goddard Space Flight Center in Greenbelt, Md. "It was a very robust set of tests, and the instrument performed well."

With this round of environmental tests complete, engineers and technicians at Orbital Sciences, the spacecraft and launch vehicle provider, can now install APS on the spacecraft. After APS is integrated, the entire spacecraft will undergo additional system-level environmental tests in preparation for launch.

"The APS performance was excellent at the beginning of the test program and has been essentially unchanged throughout all of the testing," said APS instrument scientist Brian Cairns of NASA's Goddard Institute for Space Studies. "The instrument should provide extremely precise measurements that will allow us to provide the highest-quality aerosol observations ever retrieved from space."

Once in orbit, APS will study tiny airborne aerosol particles to better understand their influence on climate. The instrument will view aerosols through polarizing filters that screen out certain orientations of light waves. The technique will allow scientists to measure and characterize aerosols that would otherwise be obscured by background glare from the Earth's surface and from atmospheric gases.

Aerosols are of great interest to climatologists. Some types, including black carbon from traffic exhaust, promote warming by absorbing sunlight. Others, such as sulfates from coal power plants, exert a cooling effect by reflecting incoming solar radiation back into space. For some types of aerosols -- including naturally occurring mineral dust particles -- it isn't clear how they might affect climate. Overall, aerosols represent one of the greatest areas of uncertainty in understanding the climate system.

In addition to APS, Glory will carry a second instrument -- the Total Irradiance Monitor (TIM) -- that will measure the sun's energy output. The TIM instrument recently completed calibration at a first-of-its-kind radiometer facility -- the TSI Radiometer Facility -- at the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.

Related Links:

Glory APS Science http://glory.giss.nasa.gov/aps/

Glory Mission Page http://glory.gsfc.nasa.gov/index.html