Space Science Reviews

, Volume 94, Issue 1, pp 15–24

Observations of Irradiance Variations

  • Claus Fröhlich

DOI: 10.1023/A:1026765712084

Cite this article as:
Fröhlich, C. Space Science Reviews (2000) 94: 15. doi:10.1023/A:1026765712084


Since November 1978 a complete set of total solar irradiance (TSI) measurements from space is available, yielding a time series of 21 years. From measurements made by different space radiometers (HF on NIMBUS-7, ACRIM I on SMM, ACRIM II on UARS and VIRGO on SOHO) a composite record of TSI can be compiled. The corrections which are needed for each radiometer, mainly to compensate for degradation, but also for operational influences are described. ACRIM I (1980–1989) and ACRIM II (1992–1995) are taken as reference because their degradation was monitored by inflight comparisons with spare radiometers; since 1996 VIRGO is used as reference. The scale of ACRIM II is adjusted to ACRIM I by comparison with NIMBUS-7 and ERBE. The reliability of this adjustment depends strongly on the stability of the HF and ERBE radiometer during the period of the gap between the ACRIMs which is discussed in detail together with an assessment of the overall precision of the composite.

solar variabilitytotal solar irradiancesolar activity

Copyright information

© Kluwer Academic Publishers 2000

Authors and Affiliations

  • Claus Fröhlich
    • 1
  1. 1.Physikalisch-Meteorologisches Observatorium DavosWorld Radiation CenterDavos DorfSwitzerland