Experimental verification

According to charter item 2 the new procedure for refraction correction should be verified experimentally. It is proposed to use two techniques:

1. tracking satellites at elevations lower than 30 degrees
2. two colour SLR

It is to note that up to now there is no operational two colour ranging station. Two colour laser ranging data will be supplied routinely from the TIGO-SLR system as soon as it is set up in Concepcion/Chile for the wavelengths of 847nm and 423.5nm. The WLRS is expected to supply two colour data starting in early 2001 for the wavelengths 1064nm and 532nm. The Matera laser ranging system is expected to provide two colour data for the wavelengths 532nm and 355nm. The expected accuracy of this verification procedure is at the level of a few centimeters.
Moreover we are grateful to Erricos Pavlis, who is analysing the low elevation tracking data. The accuracy of this verification procedure is limited to the satellite orbit accuracy, since the zenith path delay shoulb be verified as well.