For just about anyone under the age of fifty, satellite pictures of Earth’s cloud cover have been a staple of weather reports on television and, more recently, on-line for almost as long as we can remember. But before 1960, such images and the other vital data returned by weather satellites simply did not exist. During this almost forgotten era, meteorologist had to rely on observations taken by ships at sea and fixed weather stations scattered across the globe to track the weather and make predictions. Tracking storms, especially those at sea, was especially difficult because of a lack of synoptic data. Earth orbiting satellites are able to provide such data like no other platform.
The Origin of the Concept
After World War II, a number of artificial Earth satellite studies were performed because the availability German rocket technology started to make such a concept practical. One of the most famous of these was Preliminary Design for an Experimental World Circling Spaceship performed by the Rand Corporation under the sponsorship of the US Army Air Force (the predecessor of today’s USAF). Released on May 2, 1946, this report listed weather reconnaissance as a possible satellite application. Five years, later Rand researchers produced another secret report entitled Feasibility of Weather Reconnaissance from a Satellite Vehicle which further addressed the attractiveness of weather satellites.
There was also growing interest in weather observations from space in more open sources of the time. In January of 1949, USAF Major Dwain L. Crowson published a paper on the use of television camera-equipped rockets to track storms. The first public mention of weather satellites themselves came in a 1954 paper written by Harry Wexler of the US Weather Bureau (the predecessor of today’s National Weather Service). On October 5 of that year, a US Navy Aerobee suborbital sounding rocket took a series of photographs that gave a spectacular view of a tropical storm over Texas – the first time such a storm had been seen from space. Slowly the value of space-based weather observations was becoming apparent to a large number of weather experts.
But like most other spacecraft concepts during this time, weather satellite development languished for lack of substantive support. While potentially useful, no one had ever launched a satellite of any sort before and there was resistance about funding a project based on unproven technology. But this was about to change. In March of 1955 the USAF issued a secret directive for the development of a reconnaissance satellite which eventually lead to the WS-117L satellite reconnaissance program (see “Spy in the Sky”). In the more open realm, President Eisenhower publicly announced on July 5, 1955 that the United States would launch a scientific satellite as part of the American contribution to the International Geophysical Year – an international, multidisciplinary scientific project to study the Earth and its interaction with the Sun running from July 1, 1957 to December 31, 1958. Two months later the Naval Research Laboratory’s satellite proposal, later named Vanguard, was chosen for the task. Among the experiments proposed for Vanguard were some that would gather data vital to the development of an operational weather satellite (see “Vintage Micro: The Original Standardized Microsatellite”).
In one of Vanguard’s experiments, Verner Soumi of the University of Wisconsin proposed to measure the Earth’s energy balance using simple radiometers. Knowing how much of the Sun’s energy the Earth and its atmosphere reflected and how much infrared radiation it emitted is vital to understanding weather. Another experiment also approved for Vanguard was proposed by William G. Stroud and William Nordberg from the US Army Signal Research and Development Laboratory (USASRDL). They proposed to place small photocells on the exterior of the spinning Vanguard satellite. Each would scan a slightly different part of the scene below during each rotation while the forward motion of the satellite would then allow a series of pictures to be built up line by line. The crude pictures from this experiment would provide data on the brightness and appearance of the Earth and its clouds from orbit – much needed information for developing cameras for weather satellites.
While studies relating to weather satellites continued under the sponsorship of various military and civilian groups, real progress did not begin until the launch of the first Sputnik satellites by the Soviet Union when a range of space concepts received renewed interest. As with most American space programs, work on weather satellites came under the purview of the Department of Defense’s ARPA (Advanced Research Projects Agency) by the middle of 1958. While all the military services and the US Weather Bureau supplied inputs based on their own research, ARPA eventually gave responsibility for the development of a weather satellite (now considered a high priority) to USASRDL. They already had a satellite concept under development that could be used as a weather satellite.
TIROS is Born
Throughout the 1950s, RCA (Radio Corporation of America – a leading electronics manufacturer of the time) worked closely with the Department of Defense examining a variety of applications for television-equipped satellites including in the WS-117L program. But after the WS-117L program opted for a photographic-based imaging system that eventually evolved into the Corona program, RCA was forced to look for a customer elsewhere for its satellite-based camera expertise. After some convincing, the Army Ballistic Missile Agency (ABMA), which was busy pushing their own satellite proposal that resulted in the launch of the first Explorer satellites in 1958 (see “Project Orbiter: Prelude to America’s First Satellite”), issued a contract to RCA in 1956 to study television-based reconnaissance concepts. Shortly afterwards a second contract was let to RCA and control of the program, called Janus, was transferred to the USASRDL.
Originally Janus would be launched on a Juno I based on the Redstone missile and, like the first Explorer satellites that used the same rocket, would be rod shaped with a total mass of no more than nine kilograms. But this shape had a tendency to tumble unstably once in orbit and the mass restrictions proved to be almost impossible to meet. In 1958 the Juno II based on the larger Jupiter IRBM, with a 39 kilogram payload capability, became available. Now the television-equipped satellite took on a drum-shape which would spin more stably about its principle axis. Once the Army redirected the program towards developing a weather satellite to meet the ARPA mandate, the satellite design and its payload were optimized for its new role and christened TIROS (Television and InfraRed Observation Satellite). Soon thereafter the launch vehicle was switched again to the still more capable Juno IV with a planned payload capacity of 230 kilograms. After ABMA cancelled development of the Juno IV in August of 1958, the Thor-Able was chosen as the new launch vehicle and the USAF took control of the TIROS program.
But as the TIROS design rapidly neared completion, project responsibility would change hands one last time. Despite its obvious military applications, the TIROS program was transferred by President Eisenhower to the six-month old NASA on April 13, 1959 because of its perceived benefits to the peaceful promotion of space. And from the start, the new civilian space agency was committed to getting TIROS into space.
As with all of its other space science programs, NASA leaders gave responsibility of TIROS to the new Goddard Space Flight Center (GSFC) located in the Washington suburb of Greenbelt, Maryland. At NASA headquarters, Morris Tepper led the program and Stroud was transferred from USASRDL to GFSC to run the project from there. Considering the advance state of development, it was decided that overall spacecraft design responsibility would remain with USASRDL and RCA would continue development of the camera system at least until the launch of the first TIROS satellite, now designated A-1. NASA also preferred to launch TIROS their Thor-Delta rocket (a significantly improved version of the unreliable Thor-Able that was later simply called Delta) then under development to handle NASA’s medium-size scientific satellites. It was decided to stay with the temperamental Thor-Able for the launch of A-1 at least, again to keep the program on track. Afterwards a more thorough reorganization would allow NASA to assume more direct control of the program.
The First Missions
On July 29, 1959 assembly of the first prototype satellite, T-1, began. All of the satellite’s components were mounted on a rigid structural base plate. When assembled, TIROS looked like a squat cylinder 107 centimeters in diameter and 48 centimeters tall. The sides of the spacecraft actually consisted of 18 rectangular panels covered with solar cells that provided an average of 20 watts of electrical power to recharge the satellite’s nickel-cadmium batteries. The spin-stabilized TIROS employed magnetic torquers to change its attitude by “pushing” against the Earth’s own magnetic field. The spacecraft could either be commanded directly from the ground in real time or be programmed to make observations automatically when out of contact with its tracking stations.
The instrument of most interest carried by TIROS was its pair of RCA-developed television cameras looking downward from the base plate. One camera was fitted with a wide-angle lens with a 104° field of view which yielded an image about 1,200 kilometers on a side from TIROS’ nominal 740-kilometer orbit when looking straight down. The second camera had a narrower 12.7° field of view that would cover an area about 120 kilometers on a side in a nadir view. Both cameras were fitted with yellow filters to reduce the effects of light scattered by the atmosphere and improve the visibility of cloud. The 500-line images, which had a ground resolution of about 5 and 0.5 kilometers for the wide and narrow-angle lenses, respectively, could either be readout for direct transmission to a ground station or recorded for later transmission. The tape recorder, an early version of which was flown into orbit on Project SCORE experimental communication satellite (see “Vintage Micro: The Talking Atlas”), stored up to 32 images and could be downloaded to the ground in three minutes.
The first prototype of the RCA camera was connected to ground equipment on January 15, 1959 and worked as intended. On February 17, Vanguard 2 was launched into orbit carrying Stroud and Nordberg’s cloud imaging experiment. Although the satellite wobbled uncontrollably once in orbit making it impossible to assemble coherent pictures, this raw data plus photographs returned by other rockets did provide enough information to confirm the TIROS camera’s specifications. The other set of instruments carried by TIROS were a trio of radiometers to measure the Earth’s emissions in the infrared. Among these was a one built by Verner Soumi and his team. While his original instrument was a victim of a Vanguard launch failure, he did fly a similar one later on Explorer 6 launched on October 13, 1959 which also secured the first primitive image of the Earth from orbit (see “The Early Explorers”).
Assembly of the second TIROS prototype, T-2, was completed on September 10, 1959 and performed satisfactorily during a demonstration 15 days later. Work then started on the first flight model, A-1, which would only carry television cameras. The A-1 satellite did not have the IR radiometer suite or the magnetic torquers to keep the mission simple and the schedule on track. The first TIROS could complete its mission in the attitude it assumed after an early morning launch. In November 1959 preparations for launch at Cape Canaveral began. While there were a number of problems found during testing that needed correction, final testing of A-1 was completed on February 28, 1960 and the satellite was shipped to the Cape for launch.
Finally on April 1, 1960 at 6:40:09 AM EST, the 119-kilogram TIROS 1 was successfully launched from Launch Complex 17A into a 690 by 750-kilometer orbit inclined 48.4° to the equator by the last Thor-Able to fly. On its first day in orbit, TIROS 1 started returning pictures – dozens followed by hundreds then thousands as the mission progressed. The only major malfunction following launch was in the control system for the narrow angle camera. But after over a month in orbit, it began operating again on its own.
Nine days after launch, TIROS 1 discovered its first cyclone north of New Zealand. The first samples of the ensuing flood of findings were presented to an eager audience later that month at a combined meeting of the American Meteorological Society and the American Geophysical Union in Washington, DC. TIROS 1 remained active until June 15 when a power failure permanently knocked out the cameras. During its 77 day useful lifetime, TIROS 1 took a total of 22,952 pictures which meteorologists eagerly waded through to gain new insights into Earth’s weather.
With the value of weather satellites demonstrated, the 126-kilogram TIROS 2 was launched on November 23, 1960 on the third flight of the new Delta A rocket. Unlike its predecessor, TIROS 2 carried a full complement of instruments and equipment. This included IR radiometers and magnetic torque device to change the attitude of the spinning satellite once it was in orbit to optimize its view of the Earth. Although the picture quality was disappointing, TIROS 2 returned 36,154 television images mostly during its first 76 days in orbit along with 141 days worth of IR data. Although technical issues limited the usefulness of TIROS 2 afterwards, it continued to operate for a total of 376 days in orbit.
Next came TIROS 3 on July 12, 1961 which was launched in time for the Atlantic hurricane season allowing it to spot tropical storms while they were far out at sea. In order to increase the areal coverage, the narrow-angle camera was replaced with a second wide-angle camera for this flight. During its 230-day useful life, TIROS 3 managed to return over 35,000 images some of which were used by meteorologists to issue 70 storm bulletins – a first for the weather satellite program. With their value proven, NASA would almost continuously monitor the weather from orbit with a succession of increasingly sophisticated weather satellites in polar and then later geosynchronous orbit in a series of programs that continues to this day.
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Here is a brief NASA video from 2010 to commemorate the 50th anniversary of the launch of TIROS 1 and the subsequent weather satellite achievements it spawned.
“Vintage Micro: The Original Standardized Microsatellite”, Drew Ex Machina, July 5, 2014 [Post]
“Vintage Micro: The Talking Atlas”, Drew Ex Machina, December 18, 2014 [Post]
“Spy in the Sky”, Space Views, March 1, 1999 [Article]
“Project Orbiter: Prelude to America’s First Satellite”, Space Views, Volume Year 1998, Number 1, pp. 1, 5-7, January 1998 [Article]
“The Early Explorers”, Space Views, August 8, 1999 [Article]
John Jakes, Tiros: Weather Eye in Space, Julian Messner, 1966
W.G. Stroud and W. Nordberg, “Meteorological Measurements from a Satellite Vehicle”, in Scientific Uses of Earth Satellites, edited by James A. Van Allen, University of Michigan Press, pp. 119-132, 1956
H. Wexler, “TIROS Experiment Results”, Space Science Reviews, Vol. 1, No. 1, pp. 7-27, 1962
William Widger Jr., Meteorological Satellites, Holt, Rinehart, and Winston, Inc., 1966