Page "Television Infrared Observation Satellite" Paragraph 6

TIROS continued as the ESSA TIROS Operational System, and was eventually succeeded by the NOAA ITOS ( Improved TIROS Operational System ), or TIROS-M, and then by the TIROS-N and Advanced TIROS-N series of satellites.

The naming of the satellite becomes a little confusing because the satellites share the same name as the over-seeing organization, such as ESSA & ESSA 1 and NOAA & NOAA M. NOAA-N Prime is the last in the TIROS series of NOAA satellites that observe Earth ’ s weather and the environment.