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Validation of 1985-1997 Active Cavity Radiometer Spacecraft Measurements of Total Solar Irradiance VariabilitySince 1978, long-term variations in the total solar irradiance (solar constant) have been monitored using spacecraft radiometers, at the 0.01% precision level. The irradiance measurements were performed from the Earth Radiation Budget Satellite [ERBS], Nimbus-7, Solar Maximum Mission [SMM], Upper Atmosphere Research Satellite [UARS], European Retrievable Carrier (EURECA), Solar and Heliospheric Observatory [SOHO], and the Space Shuttle Atmospheric Laboratory for Applications and Science [ATLAS] spacecraft platforms. Radiometer responses can drift or shift at precision levels of a few hundreds of a percent. In-flight calibration sources are not available to detect radiometer response changes at radiometric accuracy or precision levels near the 0.01% (0.1 W/sq m) level. Inconsistent trends among the sets were used to identify possible instrumental drifts or shifts which may be incorrectly interpreted as solar irradiance changes while consistent trends among the different measurement sets were used to detect long-term irradiance variability components. In this paper, 1991-1998 corresponding ERBS, UARS, SOHO, and ATLAS irradiance measurements are inter-compared with each other as well as with the ERBS empirical irradiance fit. The empirical irradiance fit is based upon 10.7-cm solar radio flux (F10) and photometric sunspot index (PSI), indices of solar magnetic activity. Analyses of recent data sets identified no long-term shifts and drifts in the ERBS, SOHO, or UARS data sets. The typical value of the total solar irradiance is approximately 1365 Watts per meter squared (W/sq m).
Document ID
19990052598
Acquisition Source
Langley Research Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Lee, Robert B., III
(NASA Langley Research Center Hampton, VA United States)
Wilson, Robert S.
(Science Applications International Corp. Hampton, VA United States)
Date Acquired
August 19, 2013
Publication Date
July 1, 1998
Publication Information
Publication: International Society of Optical Engineering
Volume: 3439
ISSN: 0277-786X
Subject Category
Solar Physics
Meeting Information
Meeting: Earth Observing Systems III
Location: San Diego, CA
Country: United States
Start Date: July 1, 1998
Distribution Limits
Public
Copyright
Other

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