HR: 1340h
AN: SH53A-0301    [Abstracts]
TI: Re-analysis of the long-term changes of the NIMBUS-7 radiometer and behaviour of total solar irradiance during solar cycle 21
AU: * Frohlich, C
EM: cfrohlich@pmodwrc.ch
AF: Physikalisch-Meteorologisches Observatorium Davos, World Radiation Center, Dorfstrasse 33, Davos Dorf, 7260 Switzerland
AB: Only one radiometer - called Hickey-Frieden (HF) - is within the ERB package on NIMBUS-7 for the measurement of total solar irradiance (TSI) and thus changes due to exposure to solar radiation cannot be directly determined by comparison with a less exposed radiometer on the same spacecraft. The geometry and optical property of the cavity of HF is, however, very similar to the PMO6-type radiometers, it is essentially a copy of it with increased size. For the PMO6V on VIRGO/SOHO two main effects have been identified, a rapid early increase and a slow decrease, normally termed degradation, which can be modelled with a hyperbolic function taking the actual dose into account (Fr\"{o}hlich, 2003). The corrections used by Fr\"{o}hlich and Lean (1998) for the composite were based on early results from VIRGO and used simple exponential functions. With the recent results from VIRGO a re-analysis of the long-term behaviour of HF is necessary. The results are not only important for solar radiometry from space, but also to improve the reliability of TSI before the start of ACRIM-I in early 1980. The latter will allow to better quantify the behaviour of solar cycle 21 and to compare it with the two recent ones which differ in several aspects. C. Fr\"{o}hlich. Long-term behaviour of space radiometers. Metrologia, 40:60--65, 2003. C. Fr\"{o}hlich and J. Lean. The sun's total irradiance: Cycles and trends in the past two decades and associated climate change uncertainties. Geophys. Res. Lett., 25:4377--4380, 1998.
DE: 7529 Photosphere
DE: 7536 Solar activity cycle (2162)
DE: 7538 Solar irradiance
DE: 7594 Instruments and techniques
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2004 AGU Fall Meeting