ITOS (Improved TIROS Operational System) was the follow-on to the TIROS series. They were the second generation of operational polar orbiters. Once operational, the satellite's designator was change to NOAA (National Oceanic and Atmopheric Administration Satellite). The primary objective of the ITOS Series of Sun-synchronous meteorological satellites was to provide improved operational infrared and visual observations of Earth cloud cover for use in weather analysis and forecasting. Secondary objectives included measuring snow and ice and the sea surface, and gathering information on the vertical structure of temperature and moisture in the atmosphere on a regular daily basis. Additional instruments, starting with ITOS-D/NOAA -2, also provided both global daytime and nighttime daily direct readout real-time cloudcover data.