MICROWAVE RADIOMETRY OF THE ATMOSPHERE - AN EXPERIMENT FROM A SEA-BASED PLATFORM DURING ERS-1 ALTIMETER CALIBRATION

A steerable dual-channel microwave radiometer was installed on top of an oceanographic tower off shore from the Venice lagoon (Italy) during the calibration experiment of the ERS-1 radar altimeter organized by the European Space Agency. Measurements of atmospheric brightness temp erature were carried out over more than two months in the summer 1991. The main objective of the experiment was to obtain the tropospheric e lectromagnetic excess path length (Delta H) required for the correctio n of the radar altimeter on board the satellite. The instrument calibr ation and the parameter retrieval algorithms were the main problems to be addressed. The retrieval of other meterological parameters, namely the precipitable water vapour (V) and the integrated cloud liquid (L) , was also assessed. An accuracy (r.m.s.) of about 0.8cm in Delta H, 0 .1cm in V and 0.04 mm in L is expected, resulting in a significant imp rovement when compared to those available from conventional meteorolog ical data.