The TIROS series of cloud-cover meteorological satellites not only pioneered reconnaissance of large-scale weather systems but also provided the first television picture from space. The weather satellite program led to vast improvements in weather forecasting capabilities.
The first experimental weather satellite, TIROS 1, was launched from Cape Canaveral on April 1, 1960, by a Thor-Able launch vehicle. TIROS 1 was inserted into an elliptical orbit ranging from 696 to 749 kilometers. This orbit was inclined 49.3 degrees to the equator; thus TIROS flew over a large portion of Earth’s inhabited landmasses. As a result, TIROS covered the area from Montreal, Canada, to Santa Cruz, Argentina, in the Western Hemisphere. TIROS completed an orbit every ninety-nine minutes and, when launched, was expected to survive at least three months in space, returning thousands of images of large-scale weather systems.
TIROS 1 was built in the shape of an 18-sided drum, 48.25 centimeters high and 106.7 centimeters in diameter. It weighed a mere 123 kilograms. The polygonal drum shape maximized available surface area on the spin-stabilized satellite for solar cells to gather solar radiation and generate electricity. A total of 9,260 solar cells covered the top and sides of TIROS 1. These charged a nickel-cadmium battery pack to which all electrical systems were connected. Images taken by TIROS optical systems were transmitted to ground stations by a pair of 2-watt FM transmitters operating at 235 megacycles.
TIROS 1 was equipped with a pair of vidicon scanner television cameras, one equipped with a wide-angle lens and the other with a narrow-angle lens. Both cameras created pictures with five hundred lines per frame at a shutter speed of 1.5 milliseconds. Each television camera’s imaging data were stored on their own magnetic tape storage unit for downloading when TIROS 1 was in contact with a ground station. A total of thirty-two images could be stored on each tape unit during a single orbit. The wide-angle lens provided a low-resolution view of a coverage area of 2,048 square kilometers. The narrow-angle lens had a resolution of half a kilometer, but covered only 205 square kilometers.
The imaging system operated in two different modes. When TIROS was in contact with a ground station, the television cameras could bypass the tape-recording system and transmit data directly to Earth. When out of range of a ground receiving station, the television cameras recorded images on magnetic tape every thirty seconds until a maximum of thirty-two pictures were stored. Once back over a ground station, data would be downlinked. It required less than eight minutes to play back completely thirty-two recorded images. Typically, a pass within range of a ground station would last twelve minutes; thus live images were possible after downloading those images recorded when out of radio contact.
TIROS transmitted its data to ground stations, which displayed the data on televison displays. Photographs of these displays were then made for permanent records. TIROS weather data were sent to the Naval Photographic Interpretation Center for detailed meteorological analysis. Next, the photographs were passed along to the National Weather Bureau for further study. TIROS was controlled principally from two ground stations, one operated by the Army Signal Corps located at Fort Monmouth, New Jersey, and one operated by Lockheed Missile and Space Division located at Kaena Point, Hawaii. In addition to these primary ground stations for satellite data retrieval and control, backup ground stations at Cape Canaveral and in Princeton, New Jersey, were available for data acquisition only. An onboard electronic timing system could be set five hours in advance of execution by ground control commands from either Fort Monmouth or Kaena Point. Then the electronic timing mechanism would selectively trigger the camera shutters for proper exposures to image selected weather systems and electronically record the image on magnetic tape.
TIROS caused some controversy because it was able to image large areas of the communist world: the Soviet Union, Cuba, and Mongolia. The weather satellite’s imaging system was not particularly useful as a spy satellite. The highest resolution available on TIROS photographs was only 0.3 kilometer; thus only large-scale surface features were visible in the images. Nevertheless, the National Aeronautics and Space Administration
The Television Infrared Observation Satellite (TIROS) before launch in 1960.
TIROS could image weather systems only for certain periods of each orbit. The satellite was constructed so that its receiving antenna was on the top surface and the two television cameras and four transmitting antennae were mounted on the satellite’s bottom surface. TIROS was spin-stabilized, rotating twelve times per minute about its symmetry axis, which was aligned in inertial space rather than simply pointing down to the earth. As a result, TIROS was able to image weather only on the daylight side of an orbit, when the satellite’s bottom faced toward Earth. The combination of TIROS orbital mechanics and Earth’s rotation permitted the satellite to provide intermittent coverage of the area between north and south 50 degrees latitude.
TIROS 1 was not in orbit very long before it made significant and startling discoveries. This satellite was the first to document that large storms have vortex patterns, unmistakable pinwheel swirl patterns. Within its lifetime, TIROS photographed more than forty northern mid-latitude storm systems, and each one had a vortex at its center. These storms were in various stages of development and were between 800 and 1,600 kilometers in diameter. The storm vortex in most of these was located inside a 560-kilometer-diameter circle around the center of the storm’s low-pressure zone. Nevertheless, TIROS images did not reveal at what stage in a storm’s development the vortex pattern formed. This was typical of TIROS data. The satellite was truly an experiment and, like most initial experiments, various new phenomena were uncovered but not fully understood. TIROS data showed clearly that weather systems could be investigated from orbit and future weather satellites could be outfitted with sensors that would lead to better understanding of meteorology on a global scale.
TIROS 1 did suffer from a few difficulties during its lifetime in orbit. Low contrast in the television imaging system often made it difficult to distinguish between cloud and snow cover. Following the twenty-second orbit only, the satellite’s high-resolution television camera was no longer capable of recording images on magnetic tape for later playback. TIROS responded to Earth’s magnetic field in a way that tended to move it away from an advantageous Earth observation attitude. Experience with TIROS 1 led to improvements on later TIROS and other weather satellites.
After completing 1,302 orbits, the operational lifetime of TIROS 1 concluded. Between launch and June 14, fourteen thousand useful photographs had been collected by the experimental weather satellite, proving the utility of an orbital imaging platform for the collection of meteorological data. TIROS 1 data provided information about large-scale meteorological structures not known previously to exist. The success of TIROS 1 justified the existence of the TIROS program and ultimately led to nine other TIROS satellites and the modern weather satellites available for weather monitoring and forecasting.
The space age has spawned numerous important benefits to daily life and accelerated the evolution of several existing technologies. Many of these space-derived technologies are taken for granted: high-speed global communication, vast memory computer systems, and worldwide weather forecasting, for example. Prior to TIROS 1, weather monitoring was done with networks of ground-based instrumentation centers, airborne balloons, and instrumented aircraft. Brief high-altitude rocket flights provided limited coverage of cloud systems from above. TIROS 1was the first step in the development of a permanent monitoring of weather systems. The resulting savings in both property damage and loss of human life from hurricanes alone that has resulted from early detection and accurate tracking of such storms by weather platforms in space has paid for the development and operational costs of all weather satellites from TIROS to the present many times over.
The first suggestion of using a space-based platform for weather observation appears to have been included in a 1951 Rand Corporation report to the U.S. Air Force written by Stanley M. Greenfield and William W. Kellogg. In 1954, Harry Wexler, of the National Weather Bureau, proposed providing such a space-based platform with television cameras, infrared sensors, and radar. Serious work on a weather satellite began in 1957, when researchers at the Air Force Geophysics Research Directorate outlined a design for the infrared sensors that would be used ultimately on TIROS 1. The remainder of TIROS systems were defined the following year by the Advanced Research Projects Agency. Shortly thereafter, TIROS project authority was transferred to the newly formed civilian NASA space program. NASA awarded the contract to build TIROS 1 to the RCA Astro-Electronics Division.
TIROS was designed purely as an experimental project, not as an operational weather satellite. The Weather Bureau,
As a result of the TIROS 1 experiment, meteorologists were not ready to discard ground-based and airborne weather systems in favor of orbital platforms. Such systems could not provide data about pressure, humidity, and temperature, for example. Because of TIROS 1, meteorologists clearly viewed weather satellites as a necessary supplement to ground-based and airborne systems for large-scale monitoring of weather systems and storms. Satellites could provide more reliable expansive coverage at a far lower cost than a large contingent of aircraft. TIROS 1 was followed by many other similar spacecraft and paved the way for modern operational weather satellite systems.
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Ahrens, C. Donald. Essentials of Meteorology: An Invitation to the Atmosphere. 4th ed. Pacific Grove, Calif.: Thomson Brooks/Cole, 2005. A text suitable for students new to meteorology. Comes with a CD-ROM to help explain concepts and demonstrate the atmosphere’s dynamic nature. -
Alexander, George. “Tiros 1 Shows Large Storms Have Vortex.” Aviation Week and Space Technology 74 (February 6, 1961): 74-75. Scientific discussion of early results from TIROS 1. Revelation of structure inside large cyclonic storms. -
Bilstein, Roger E. Orders of Magnitude: A History of the NACA and NASA, 1915-1990. Washington, D.C.: Government Printing Office, 1989. For general readers. Describes numerous experimental satellite programs, such as TIROS, in addition to human spaceflight activities of NASA. Places unpiloted probes, such as TIROS, in the overall setting of space achievement and improvement of life on Earth. -
Bird, John. The Upper Atmosphere: Threshold of Space. Washington, D.C.: Government Printing Office, 1988. Thorough explanation of atmospheric structure and phenomena. Describes for general readers what satellite technology can reveal about atmospheric conditions, weather, pollution, and the like. Contains many diagrams and photographs. -
Clark, Evert. “Tiros Exceeds Weather Bureau Hopes.” Aviation Week and Space Technology 72 (May 2, 1960): 30. Provides initial evaluation of preliminary TIROS 1 data. Quotes from project scientists express their optimism for future weather system understanding and prediction. -
Cortright, Edgar M. Space Exploration—Why and How. Washington, D.C.: Government Printing Office, 1965. General description of weather, communications, and interplanetary spacecraft. Provides several early TIROS weather photographs. -
Kolcum, Edward H. “Gamble on Tiros Satellites Is Paying Off.” Aviation Week and Space Technology 75 (October 2, 1961): 70-74. TIROS was an evolving series of weather satellites. This article, published eighteen months after the first TIROS launch, describes how much the TIROS program changed the nature of weather forecasting. -
Lewis, Craig. “NASA Tiros 1 Demonstrates Potential Satellite Reconnaissance Utility.” Aviation Week and Space Technology 72 (April 11, 1960): 28-30. Describes launch and early work of the TIROS satellite. Speculates on the prospects for operational weather reconnaissance from space. Photograph of launch and several early TIROS weather images. -
“Tiros Defines Weather Systems, Land Areas.” Aviation Week and Space Technology 72 (April 18, 1960): 34. Brief article provides a number of TIROS 1 images of large-scale atmospheric systems. -
“Tiros 1 Will Scan Cloud Cover, Earth Temperature.” Aviation Week and Space Technology 72 (March 14, 1960): 26-28. Describes TIROS spacecraft systems and mission profile. Explains how TIROS data was collected and transmitted to Earth for analysis.
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