SUN MONITORING ON THE EXTERNAL PAYLOAD FACILITY OF COLUMBUS –SOLAR SPECTRAL
IRRADIANCE MEASUREMENTS (SOLAR-SOLSPEC)
Research Area: Heliophysics
Expedition(s): 16-ongoing
Principle Investigator(s): ● Gerard Thuillier, CNRS, Verrieres le Buisson, France
● Thomas Foujols, CNRS, Verrieres le Buisson, France
● David Bolsée, Belgian Institute for Space Aeronomy, Belgium
RESEARCH OBJECTIVES
The SOLar SPECtral Irradiance Measurements (SOLSPEC) instrument operates at a high spectral
resolution in the range of 180 to 3,000 nanometers (nm), with an accuracy of 2% in ultravaiolet
(UV) and 1% in visible and infrared (IR) light for the purpose of measuring solar spectral
irradiance (SSI) from the sun.
RESULTS
SOLAR facility measurements were the first ones with in-orbit recalibration capability for the
total spectral range of interest. In the extreme UV (EUV) spectral range, SolACES used ionization
chambers that are considered a primary detector standard. Within SOLSPEC, several sources
allowed checking instrument stability.
In August/September 2009
period, the EUV data showed a
distinct minimum during the
extended solar minimum
period between solar cycles 23
(beginning in May 1996 and
ending in January 2008) and
24 (from January 2008 until
now, with several irregularities
in terms of sun behavior),
while at UV wavelengths this
minimum appeared before.
Using SolACES, SOLSPEC, and
SOLSTICE SSI to fill the spectral
gap between the 2
instruments, 2 spectra SOLAR
1 and SOLAR 2 have been
developed, which differ
between 1100 and 2400 nm
by using ATLAS 3. In this
range, SOLAR 2 showed a lower SSI reaching 10% at 1 700 nm. An exhaustive investigation has
been carried to understand this difference (though currently no explanation has been found).
An important aspect of SSI measurements was the validation/comparison with the theoretical
SOLAR consists of 3 complementary instruments: SOlar Variable and
Irradiance Monitor (SOVIM) covers the near-ultraviolet, visible and
thermal-infrared regions of the spectrum; SOLar Auto-Calibrating Extreme
UV/UV Spectrophotometers (S ol-ACES) measures the extreme
ultraviolet; and SOLar SPECtral Irradiance measurements (SOLSPEC)
covers the 180– ,000 nm wavelength range. ESA image.