PMOD/WRC Instrument: SOVIM
PMOD/WRC constructed SOVIM (Solar Variations and Irradiance Monitor), onboard the ISS SOLAR experiment. SOVIM was conceived in 1998 but, due to the catastrophe of the Columbia Space Shuttle, was only installed on the International Space Station (ISS) on 7 February 2008 with the Atlantis Space Shuttle (STS-122). SOVIM was equipped with 4 absolute radiometers and 2 solar photometers and was based on the SOVA design of the EURECA satellite. SOVIM was foreseen as a replacement for VIRGO, but unfortunately failed in April 2008.
SOVIM
SOVIM was part of the SOLAR experiment. During the early utilisation phase on the ISS, SOLAR was accommodated onto one dedicated CEPA (Columbus External Payload Adapter). The CEPA was installed on the CEPF (Columbus External Payload Facility) of the ISS where the baseline position was the Zenith side.
The Total Solar Irradiance (TSI) was observed with active cavity radiometers (PMO6 and DIARAD) which were traceable to the SI scale of irradiance through direct comparison with cryogenic radiometers on the ground and in vacuum for PMO6, and through characterisation in the laboratory for the DIARAD.
Spectral Solar Irradiance (SSI) measurements were conducted with sun-photometers. A detector-based calibration method, directly traceable to the scale established by cryogenic radiometers, was used to calibrate the SPM with high accuracy.
SOVIM consisted of one package containing the following instruments:
- One absolute radiometer (DIARAD)
- Two PMO6V absolute radiometers
- One PMO6R absolute radiometers
- Two three-channel sunphotometers (SPM)
- A pointing sensor (TASS)
Scientific Objectives
- Obtain quasi-continuous high quality measurements of the solar irradiance variation.
- Determine with high accuracy the amount of spectral re-distribution of the solar output.
- Search for the long periodicity or quasi-periodicity found in other solar parameters.
- Study the influence of active regions and other large scale solar structures on the solar irradiance.
- Investigate the energy storage in the convection zone in connection with the energy blocking of active regions.
- Investigate the mechanisms of solar radiative forcing of climate change on seasonal to decadal timescales.
- Continue the historical TSI monitoring record by linking present and future measurements.
Status
SOVIM unfortunately failed in April 2008 after several months in operation.
Source and credits: NASA, ESA, PMOD/WRC