On May 17th, a unique collaboration between instruments on the ISS and Venus Express was set up. Between 19h00 and 22h30, SOLSPEC, in Earth-orbit on the ISS, and SPICAV, in Venus-orbit on Venus Express, were simultaneously observing the sun. The goal of this synchronisation is to perform an absolute calibration of SPICAV.
SOLSPEC is part of the SOLAR payload, mounted on the exterior of the Columbus Module of the ISS and operated by B.USOC. The instrument is composed of three spectrometers that together cover the wavelength domain extending from 165 nm to 3100 nm, studying the Solar spectral irradiance and its variability. SOLSPEC completed its 4th year in space in February 2012.
SPICAV, short of "SPectroscopy for Investigation of Characteristics of the Atmosphere of Venus", is mounted on Venus Express. SPICAV is an imaging spectrometer for ultraviolet and infrared radiation, and it investigates the Venus atmosphere by measuring the interactions of the light coming from the sun with the components constituting the atmosphere of Venus. To derive reliable results, it needs to be known very accurately what the output of the sun is.
This simultaneous measurement will be repeated on May 24th, again between 19h00 and 22h30 local time.