3.2 Data availability
There are two main periods of time during which instrument failures prevented operational measurements. Between May 2003 and July 2003, due to a steering system problem and the consequent progressive reduction of the instrument Field of View, the measurement efficiency was lower. The measurement frequency resumed after the switch to the redundant electronics chain. A second steering system problem (failure of the Elevation voice-coil) occurred in early January 2005 and prevented operational measurements until July 2005, when a new mission scenario with a reduced azimuth range was implemented. This new scenario affects the effective global coverage of the measurements (see section 1.4 of this document).