1960-04-01 USA Tiros 1

TIROS-1 was the first full-scale weather satellite (the Vanguard 2 satellite had been the first experimental/prototype weather satellite) and marked the beginning of a series of Television Infrared Observation Satellites launched into low-Earth orbit.

TIROS-1 launch cover with Sarzin cachet.
The TIROS Program was NASA's initial experimental initiative to assess the potential of satellites for studying the Earth. At that time, the efficacy of satellite observations had not yet been established. Given that satellites were a new technology, the TIROS Program also addressed various design challenges for spacecraft, including instruments, data, and operational parameters. Its aim was to enhance satellite applications for making Earth-based decisions, such as determining whether to evacuate coastal areas due to a hurricane. The primary focus of the TIROS-1 Program was the development of a meteorological satellite information system, as weather forecasting was considered the most promising application for space-based observations.

(Reference from TIROS-1)