SAGE III on ISS

SAGE III on ISS is the fourth generation of a series of NASA Earth-observing instruments, known as the Stratospheric Aerosol and Gas Experiment. The first SAGE III instrument was launched on the Russian Meteor (satellite) spacecraft. The recently revised SAGE III will be mounted to the International Space Station where it will use the unique vantage point of ISS to make long-term measurements of ozone, aerosols, water vapor, and other gases in Earth's atmosphere.

The first SAGE instrument was launched February 18, 1979, to collect data on the various gases in the atmosphere, including ozone. The data collected on SAGE I and the following instrument SAGE II, which began taking measurements in October 1984, were critical to the discovery of the Earth's ozone hole and the creation of 1987 , which banned ozone-depleting substances, such as chlorofluorocarbon (CFC).

SAGE III on ISS is a nearly exact replica of SAGE III Meteor-3M, sent into orbit in 2001 on a Russian satellite. SAGE III Meteor-3M went out of service in March 2006 when the satellite's power supply stopped working. The new instrument was built in anticipation of being attached to the space station in 2005. A change in ISS design, however, put those plans on hold. The instrument was stored in a Class 100 clean room in a sealed shipping container under a continuous gaseous nitrogen purge. The purge kept clean dry "air" inside the instrument.

Recently, the opportunity arose for SAGE III to be placed on ISS, and build on the long record of stratospheric gas data that its ancestors created. The week of February 14, 2011, scientists at NASA Langley Research Center pulled the instrument from storage to begin initial testing and calibrations in preparation prepping it for launch.

The 76-kilogram (168 lb)SAGE III instrument is a grating spectrometer that measures ultraviolet and visible energy. It relies upon the flight-proven designs used in the Stratospheric Aerosol Measurement (SAM I) and first and second SAGE instruments. The SAGE III design incorporates Charge Coupled Device (CCD) array detectors and a 16 bit A/D converter. Combined, these devices allow for wavelength calibration, a self-consistent determination of the viewing geometry, lunar occultation measurements, and expanded wavelength coverage.

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