images of
Earth from space, taken by
TIROS-1 in April 1960|alt=Grayscale photograph of the limb of Earth, showing land, sea, and clouds The TIROS project emerged from early efforts examining the feasibility of
surveillance from space for meteorology and intelligence gathering which began in the U.S. as early as the late 1940s. The
Radio Corporation of America conducted a study for the
RAND Corporation in 1951, concluding that a spaceborne
television camera could provide worthwhile information for general reconnaissance. In 1956, the RCA received funding from the
U.S. Army to develop a reconnaissance satellite program, initially called Janus, under the administration of the
Army Ballistic Missile Agency (ABMA). The project remained under the administration of ABMA but was transferred to the
Advanced Research Projects Agency (ARPA, now
DARPA) in 1958. The contract called for the development of a spacecraft to be launched using the
Jupiter-C launch vehicle, which was eventually revised to the
Juno II launch vehicle. Janus and Janus II, prototype satellites without
directional stability and a single onboard camera, were built as part of the project. In May 1958, a committee chaired by
William Welch Kellogg of the RAND Corporation with representatives from the U.S. Armed Forces, the
U.S. Weather Bureau, the
National Advisory Committee for Aeronautics, and the RCA was convened to discuss a satellite meteorological program and design objectives. The committee recommended that such a program should provide observations of
cloud cover with television cameras at coarser and finer resolutions, accompanied by
infrared measurements of
Earth's radiation; the goal of the first meteorological satellites would be to trial experimental television techniques, validate
sun- and horizon-based sensors for
spacecraft orientation, and collect meteorological data. While Janus was in development,
Herbert York, the
Director of Defense Research and Engineering, moved
Department of Defense reconnaissance satellites out of the purview of the U.S. Army. With
meteorological satellites flagged as a high-priority requirement by the U.S. government, the RCA shifted the goals of the Janus project towards meteorological applications, whose relaxed resolution requirements for cameras enabled smaller and lighter satellite systems. Accordingly, the resolution of the television cameras planned for Janus was lowered, relying on off-the-shelf refractive optics rather than the more sophisticated systems originally planned. The U.S. Army also granted an ARPA request to develop a
larger launch vehicle for larger satellites, allowing the RCA to change the Janus design to a larger
spin-stabilized spacecraft. The Janus project was renamed to Television Infrared Observation Satellite (TIROS) following the changes and the project was declassified. Development of the TIROS satellite payload was contracted to the
Army Signal Corps Laboratories and $3.6 million was allocated to
Air Force Systems Command for use of the
Thor launch vehicle. Before signing the
National Aeronautics and Space Act that created the
National Aeronautics and Space Administration (NASA), President
Dwight D. Eisenhower determined that NASA should handle meteorological satellite development.
Edgar Cortright, the ARPA committee overseeing the TIROS project, arranged the transfer of TIROS to NASA's
Goddard Space Flight Center on April 13, 1959. The acquisition of the TIROS project from ARPA by NASA was seen as a means to provide good publicity and validate the existence of the nascent civilian agency. The agency treated the project as an experimental testbed rather than as an operational aid or as a platform for taking scientific observations. The
United States Weather Bureau and
Department of Defense Weather Services favored operational use of early TIROS data. This tension led to the formation of the Panel on Operational Meteorological Satellites, an interagency group, in October 1960 to ascertain the objectives of an operational meteorological satellite program. The initial TIROS mission design called for three satellites. Each satellite was to carry a two-lens optical television system built by the RCA, an improved infrared scanning system drawn from the
Vanguard 2 spacecraft, and a
radiometer developed by
Verner E. Suomi to measure
Earth's energy budget. However, only the optical system was included in the first TIROS payload,
TIROS-1, launched on April 1, 1960, as the first U.S. satellite to carry a television camera. The originally planned instruments were included in the subsequent launches of
TIROS-2,
TIROS-3, and
TIROS-4 over the following two years. Despite the early success of TIROS, early difficulties with handling TIROS data and political pressure to develop an operational weather satellite system based around a second spacecraft in development,
Nimbus. However, delays and the high cost of the Nimbus program ultimately led to TIROS-based spacecraft serving as the United States' fleet of operational weather satellites. The second generation of TIROS satellites, designated as
ESSA, fulfilled this role as the TIROS Operational System (TOS) beginning in 1966. Nine ESSA satellites were launched during 1966–1969. The odd-numbered ESSA satellites provided meteorological data to national meteorological services while television images from the even-numbered ESSA satellites could be received from simple stations globally through an
Automated Picture Transmission (APT) system. A third generation of TIROS satellites, named the Improved TIROS Operational System (ITOS), was developed and launched in the 1970s, combining the capabilities of the two types of ESSA satellites and serving in an operational capacity. Unlike the preceding TIROS generations, the ITOS spacecraft featured
three-axis stabilization. Later ITOS satellites included additional instruments and improved versions of the preceding instruments, including the Very High Resolution Radiometer. In 1978, RCA completed the first spacecraft in the TIROS-N series, the fourth generation of TIROS satellites. These offered a new suite of instruments including the
Advanced Very-High-Resolution Radiometer (AVHRR). Later TIROS-N satellites, beginning with
NOAA-E in 1983, had higher data-handling capacity and carried new instruments on a slightly larger
spacecraft bus; these satellites were collectively known as Advanced TIROS-N (ATN).
NOAA-N Prime (later designated NOAA-19) was the last spacecraft in the TIROS series, launching in February 2009. == Series ==