1984 - 2003, Earth Radiation Budget Satellite (ERBS)/Earth Radiation Budget Experiment (ERBE) TSI Measurements



Authors:  Robert B. Lee III (1), and Robert S. Wilson (2)

Affiliation:    1) NASA Langley Research Center

                     2) Science Applications International Corporation (SAIC), Hampton, Virginia


            An Earth Radiation Budget Experiment (ERBE) active cavity radiometer (ACR), called the solar monitor, was used to produce a continuous 19-year (October 1984 through December 2003) data set of total solar irradiance (TSI) variability measurements.  The solar monitor is located on the NASA Earth Radiation Budget Satellite (ERBS).  The ERBS/ERBE TSI data set exhibited long-term TSI variations of the order 0.1%, which varied directly with solar magnetic activity associated with recent 10-year sunspot cycles.  The data set defined 1365 Wm-2 level as the most likely magnitude of the quiet sun, normalized to the mean earth-sun distance.  Maximum TSI values occurred during the 1989-1991, and 1998-2002, time frames; while minimum (quiet sun) levels occurred during 1986 and 1996.  The 2002-2003 TSI values appear to be decreasing to minimum levels in the 2005-2007, as forecasted.  In this paper, the resulting October 25, 1984 through August 6, 2003, solar monitor measurements, along with the other spacecraft measurements, are evaluated, as well as the 1986 and 1996 TSI minimum levels to identify additional TSI variability components, which may have cycle periods, which are greater than 10 years.  After 19 years, the ERBE solar monitor is operating nominally with no instrument response or spacecraft telemetry/command problems.