Concept information
Preferred term
SAGE II
Definition
- The Stratospheric Aerosol and Gas Experiment II (SAGE II) on the Earth Radiation Budget Satellite (ERBS) was a seven-channel sunphotometer which measured stratospheric aerosols, ozone, water vapor, and nitrogen dioxide during spacecraft sunrise and sunset. The SAGE II mission objectives were to (1) develop a long-term global climatology of stratospheric aerosol extinction, (2) monitor transient events (e.g. volcanic eruptions), (3) develop a high-altitude cloud climatology, and (4) provide stratospheric ozone, water vapor, and nitrogen dioxide concentration profiles at 1 km vertical resolution. The SAGE II was a two-axis gimbaled system capable of rotating in azimuth. The sun was acquired when two azimuth sun sensors were activated and rotated in azimuth until SAGE II was pointed at the radiometric centroid of the sun. A scan mirror moved at fast rate of 3 deg/sec to acquire the sun. The mirror scanned across the sun at a slow rate of 15 min/sec. When the limb of the sun was reached, the servo mechanism reversed and scanned the sun again. The sunlight was reflected into a Cassegranian telescope and focused on an aperature that defined a 0.5-minute elevation angle by 2.5 minute azimuth angle instantaneous field-of-view (IFOV). The aperature was the entrance slit to the spectrometer, which used a holographic grating and filters to isolate the seven wavelength bands (0.385 to 1.02 micrometer). Channels 1,2,3,4, and 7 used neutral density filters and channels 2,5, and 6 used bandpass filters. All seven channels were sampled within 1 ms at 64 Hz and digitized to a 12-bit word. The SAGE II instrument measured the solar irradiance during each spacecraft sunrise and sunset so that two profiles from specific locations above the Earth were obtained during each spacecraft revolution. SAGE II made about 15 sunrise and sunset measurements each day, seperated by 24.5 degrees in longitude and slightly in latitude. The maximum latitudes covered were 80 N to 80 S. For more information see: http://eosweb.larc.nasa.gov/project/sage2/table_sage2.html Group: Instrument_Details Entry_ID: SAGE II Group: Instrument_Identification Instrument_Category: Earth Remote Sensing Instruments Instrument_Class: Passive Remote Sensing Instrument_Type: Spectrometers/Radiometers Instrument_Subtype: Spectrometers Short_Name: SAGE II Long_Name: Stratospheric Aerosol and Gas Experiment II End_Group Online_Resource: http://oea.larc.nasa.gov/PAIS/SAGE.html Online_Resource: http://eosweb.larc.nasa.gov/PRODOCS/sage2/table_sage2.html Online_Resource: http://data.giss.nasa.gov/sageii/ End_Group (en)
Broader concept
- Spectrometers (en)
URI
https://gcmd.earthdata.nasa.gov/kms/concept/85882054-d455-492f-976e-d2ea12f35578
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