NIMBUS-7 SOLAR TOTAL IRRADIANCE
16 Nov 1978-13 Dec 1993
The final Nimbus-7 solar total irradiance values for 16 November 1978-13 December 1993 are given here. There will be no more total solar irradiance measurements made by Nimbus-7. Values are in watts per square meter. In contrast to previous data releases, data for missing days are not filled, but rather omitted. Also, starting in 1990 a daily cycle appeared in the solar irradiances from unknown causes. This problem is corrected by excluding measurements from 1 to 6 hours UT in calculating the daily means from 1/1/90 to the end of the experiment.
The paper "The Nimbus-7 Solar Total Irradiance: A New Algorithm for its Derivation" by D.V. Hoyt, H.L. Kyle J.R. Hickey, and R.H. Maschhoff (JGR, Vol. 97, pp. 51-63) describes the methodology used to derive the values.
In 1992, there are two data gaps: a) The days 15 to 24 are missing due to instrumental problems, and b) the days 170 through 246 are missing since the instrument could not acquire the Sun. In 1993 most of the days are missing since the Sun could not be acquired. Finally, daily averages formed with 3 or fewer observations should be considered less reliable than other days. Users may want to omit them or replace them with interpolated values. The complete data set (number of orbits for which good observations are available on a given day, daily mean solar irradiance, and standard deviation of the mean solar irradiance) is available on-line at NGDC ftp anonymous--click here.
Click here to go back to the solar irradiance introduction page and see a plot of the data.
For more information about the data or to obtain the comprehensive database (all data points taken), please contact Dr. H. Lee Kyle, NASA/GSFC, Code 636, Greenbelt, MD 20771 USA, (301)286-9415.