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The second day of the laboratory measurements involved the calibration of all the participants radiometers. These are the actual instruments that make the measurements in the field. It is therefore important to know if there are any discrepancies in the calibration of these instruments. This was done via a calibrated radiance source. The source, a Transfer Standard Absolute Radiance Source or TSARS for short, was provided by NPL for this purpose. It is calibrated directly against national standards.

Transfer Standard Absolute Radiance Source (TSARS)

The participants were briefed by Andrew Deadman from the pilot lab, NPL, before the measurements began. The fibre optic input from each participants radiometer was set up in the pre-aligned "pistol grip" in front of TSARS. The "pistol grip" was used in order minimise any effects due to mis-alignment. The measurements from each radiometer were repeated a number of times.

Andrew Deadman briefs the participants	Larry Leigh, SDSU, careful inserts the fibre optic into the "pistol grip"

More pictures from the radiometer calibrations can be seen in the Multimedia Gallery at calvalportal.ceos.org/web/guest/multimedia-gallery .

There were two groups who were not able to measure TSARS. The group from Thailand whose equipment had still not arrived, we are hoping it will arrive tomorrow, and the group from Brazil who have an instrument without a fibre optic input. This instrument will however be set up to measure TSARS when these measurements are repeated after the field measurements on 26 August.

Tomorrow, 16th August, all the participants together with the hosts from Turkey, will travel the 150 km or so to Tuz Golu, the literal translation of which is salt lake. Here the participants will brave soaring temperatures while they  set-up their equipment in readiness for the 9 days of measurements on the lake that will follow.