Space Age (1957-1962):

The world's first communications satellite was Project SCORE (Signal Communication by Orbiting Relay Equipment), launched from Cape Canaveral using an Atlas B missile on Dec. 18, 1958. Among other firsts, it was the first successful trial of the Atlas as a space launch vehicle. At this early stage of the worlds space programs Sputniks 1 and 2 had been launched only a little over a year earlier, on Oct. 4 and Nov. 3, 1957 the primary objective of the mission was simply to place the body of the missile into low earth orbit, and AFBMDs primary role was to provide the missile and the launch. The communications package was built from modified commercial equipment by the Army Signal Research and Development Laboratory under the direction of the Advanced Research Projects Agency.

In late June 1958, the U.S. Army Signal Research and Development Laboratory (SRDL) at Fort Monmouth, New Jersey was directed to construct a communications satellite with a maximum weight of 150 pounds. The launch vehicle would be an Air Force Atlas ICBM. The entire rocket was to be placed into orbit and, therefore, it was decided that the communications equipment would be integrated into the fairing pods of the missile. The orbit was expected to be low, therefore life expectancy of the satellite was only 2 to 3 weeks. The low orbit and short life would limit opportunities for real-time relay between two ground stations, therefore, a store-and-forward mode was added by including a tape recorder. This would also give the satellite a worldwide broadcast capability. Since reliability was a concern, a second tape recorder was added to the communications package. The work progressed in strict secrecy.

By December 1958, the Army's SCORE (Signal Communications by Orbiting Relay Equipment) satellite was ready to be launched. A prerecorded message prepared by a member of the SRDL-SCORE team was loaded in the tape recorders. At the last minute, however, President Eisenhower was persuaded to record a Christmas message to the world. The President's tape was rushed to the Cape Canaveral launch site. The communications package was already sealed in the Atlas missile which was on the launch pad and fueled. On the morning of 18 December, the Signal Corps transmitted the President's message across Cape Canaveral to the communications payload on the waiting rocket. The SCORE payload dutifully recorded the new message onto both the primary and backup tape recorders.

At 1802 hours, 18 December 1958 the Atlas missile was launched into an orbit with a perigee of 114 miles, an apogee of 920 miles, an inclination of 32.3 degrees and a period of 101.5 minutes. On the first orbit, as the satellite passed over California, the primary payload did not respond properly. Finally on 19 December, the backup tape recorder responded to coded commands from the ground and transmitted the President's message on a short-wave frequency to the world below.


    "This is the President of the United States speaking. Through the marvels
     of scientific advance, my voice is coming to you from a satellite traveling
     in outer space. My message is a simple one: Through this unique means I 
     convey to you and all mankind, America's wish for peace on Earth and goodwill
     toward men everywhere."

The second SCORE package continued to work perfectly, responding to 78 real-time and store-and-forward voice and teletype transmissions between ground stations located in Georgia, Texas, Arizona and California. After 12 days the batteries failed. On 21 January 1959, the satellite reentered the Earth's atmosphere and burned up. The Air Force's 9,000 pound Atlas rocket body was the heaviest object to have been launched into orbit and the Army's SCORE satellite was the first communications satellite. The broader military significance of the experiment was it demonstrated the practical operation of a satellite radio-relay system with intercontinental capability.


Explorer Series:

Surprisingly, after the startling beginning make by the Soviet Union, after Sputnik 3 they never launched another major science mission for the next five years. Most of the other Soviet launches were dedicated to the development of manned space flight, the rest were failed lunar or planetary missions. During the 1957 to 1962 timeframe, the US made 101 successful satellite and space probe launches, including two planetary missions. In addition, there were 30 launch failures.

After Explorer 1, 14 other Explorer missions were launched by 1962. These included Explorer 6 with an 47 degree orbit of between 245 km and 42,400 km, the highest apogee to date. Explorer 6 also carried the first array of solar cells that allowed it to carry most number of science instruments to date. It was also the first attempt to image the Earth from orbit, but the resulting images were extremely blurry.

Other science goals of the Explorer missions were the first mapping of the radiation belts, detection of solar flare/winds, studies of gamma ray and counts of micrometeorites.


Discoverer/Corona :

The US Air Force gained its 'space wings' with this series of unmanned spacecraft launched into polar orbit from Vandenberg Air Force Base, California. Discoverer 1 was launched on Feb. 28, 1959. The program had the initial objective of developing a stabilized spacecraft from the orbiting stage of the Thor-Agena launch vehicle, capable of returning a re-entry capsule from orbit. However, the project is a cover for a series of spy satellites run jointly by the Air Force and CIA. Discoverer 1, the cover name for Corona rockets, lifts off from Vandenberg and disappears. No one knows what happened, but it is believed to have crashed somewhere near the South Pole.

The Corona, Argon, and Lanyard satellites were U.S. photographic surveillance satellites used from the late 50's through the early 70's. The satellites were designed to assess how rapidly the Soviet Union was producing long-range bombers and ballistic missiles, and where they were being deployed. The programs' worldwide photographic coverage was also used to produce maps and charts for the Department of Defense and other U.S. government mapping programs.

The satellites used film canisters that were returned to earth in capsules (a.k.a. "buckets") for evaluation. These capsules were designed to be recovered by a specially equipped C-130 aircraft during parachute descent, but were also designed to float to permit recovery from the ocean. All film was black-and-white, with the exception of some small samples of infrared and color film carried on some missions as experiments.

The first launches of the Corona program were announced by the USAF as satellites in the Discoverer series. This Discoverer program, then described as a satellite technology development effort, was in reality mainly a cover for the Corona photographic missions. However, the Discoverer program did not solely consist of surveillance missions, and included non-imaging test flights to verify technologies and fix recurring technical problems in the Corona series, as well as 2 flights to test sensors for the MIDAS early warning satellite system.

On April 13, 1959, Discoverer ll goes into orbit and successfully ejects a test capsule. But, because of a timing error, the capsule lands somewhere on the island of Spitsbergen, north of Norway, instead of hitting its target near Hawaii. The capsule is never found; CIA officials suspect it may have been snatched by the Soviets.

On June 3, Discoverer lll, carrying four mice, crashes in the Pacific Ocean shortly after takeoff. On June 25, Discoverer IV carries the first Corona camera, called KH-1, an abbreviation of the code name Keyhole. The rocket fails to reach orbit. Three more launches in August and November also are busts.

The KH- (KeyHole) designation is used to refer to all photographic reconnaissance satellites. The number following the KH- designation indicates what type camera system was used on the satellite. This designation system came into use during 1962 with the 4th camera system, with its predecessors retroactively identified as KH-1, KH-2, and KH-3.

Little information is available about the various satellite designs. However, some details about the various camera systems have been made available. Early systems (KH-1, KH-2, KH-3 and KH-6) carried a single panoramic camera, or a single frame camera (KH-5), while later systems (KH-4, KH-4A, and KH-4B) carried two panoramic cameras looking 30 degree apart (one looking forward, the other looking rear). The KH-6 camera was programmed to tilt between fore and aft to cover the same land area twice during a photographic pass and thus provide stereo coverage. Early systems operated with a single bucket, while later systems were configured with two buckets; the KH-4A was the first satellite with multiple film buckets. Additionally, the fore and aft camera's film were packaged separately for missions that carried twin panoramic cameras. Occasionally one of the pair of cameras malfunctioned or was programmed to halt, while its mate continued to operate.

Finally, on August 10, Discoverer Xlll is a partial success the satellite successfully reaches orbit and ejects a capsule. The capsule lands north of Hawaii the next day, 600 miles off target, and is recovered after floating in the ocean. Then, on August 19, with almost no public fanfare, Discoverer XIV is the first truly successful Corona mission. The returning capsule, containing 20 pounds of film and suspended from a parachute, is snatched from midair by an Air Force C-119 aircraft. The images, although fuzzier than U-2 photographs, cover areas of the Soviet Union never reached by the spy planes.

Corona reaches its prime from May 1966 through February 1971 where 32 launches in a row are either partially or completely successful. On May 25, 1972, the final Corona mission is launched, with the final capsule recovered on May 31. During the life of the program, Corona mapped 750 million square miles of the Earth's surface, mostly in the Soviet Union and China; the resolution of its cameras improved from initially distinguishing objects on the ground no smaller than 20 feet to picking out objects just five feet across.

Interestingly, the main purpose of Corona was to estimate the number of Soviet missiles, the so-called missile gap that dominated the 1960's Presidential election. However, Corona found far few missiles than thought, but the US government perpetuated the threat, promoting an arms build-up and an accelerated military program. By the end of Corona, satellites had imaged every Soviet missile base, imaged each Soviet submarine class, revealed the presence of Soviet missiles protecting the Suez Canal and identified Soviet nuclear assistance to China.

With the declassification of Corona images, comparison of images from the 1960's to the present day assist in several scientific programs. For example, comparison of Corona and Landsat image of the Aral Sea from August 1987 shows the extent of the environmental disaster that has occurred there. Excessive use of pesticides and unwise irrigation practices have poisoned and shrunk this once large and bountiful sea.


Transit

The Navy Navigation Satellite System, also known as TRANSIT, was the world's first operational satellite navigation system. Transit was originally conceived in the early 1960s to support the precise navigation requirements of the Navy's fleet ballistic missile submarines. Since 1962, when the first navigation sets were installed in ballistic missile submarines and aircraft carriers, many other types of Navy and scientific ships used the orbiting satellites for all-weather, global pinpoint navigation.

Transit is a space-based radiodetermination system consisting of satellites in approximately 600 mile polar orbits. The phasing of the satellites is deliberately staggered to minimize time between fixes for users. In addition, Transit has four ground-based monitors. The monitor stations track each satellite while in view and provide the tracking information necessary to update satellite orbital parameters every 12 hours.

Normally, a minimum of four operational TRANSIT satellites were needed to provide the required frequency of precise navigation fixes. The constellation consisted of two types of spacecraft -- Oscar and Nova. The final constellation consisted of six satellites in a polar orbit with a nominal 600 nautical mile altitude, three ground control stations, and receivers (i.e., the system's users). Of the six satellites, three provided navigation service while three others were "stored-in-orbit" spares. The last Transit satellite launch was in August 1988. The Transit Program terminated navigation service on December 31, 1996.

The satellites broadcast ephemeris information continuously on 150 and 400 MHz. One frequency is required to determine a position. However, by using the two frequencies, higher accuracy can be attained. A receiver measures successive Doppler, or apparent frequency shifts of the signal, as the satellite approaches or passes the user. The receiver then calculates the geographic position of the user based on knowledge of the satellite position that is transmitted from the satellite every two minutes, and knowledge of the doppler shift of the satellite signal.

Predictable positioning accuracy is 500 meters for a single frequency receiver and 25 meters for a dual frequency receiver. Repeatable positioning accuracy is 50 meters for a single frequency and 15 meters for a dual frequency receiver. Relative positioning accuracy of less than 10 meters has been measured through translocation techniques. Navigational accuracy is heavily dependent upon the accuracy to which vessel course, speed, and time are known. A one knot velocity input error can cause up to 0.2 nm fix error.

Availability is better than 99 percent when a Transit satellite is in view. It depends on user latitude, antenna mask angle, user maneuvers during a satellite pass, the number of operational satellites and satellite configuration. The reliability of the Transit satellites is greater than 99 percent. Coverage is worldwide but not continuous due to the relatively low altitude of the Transit satellites and the precession of satellite orbits.


Echo

During the late 1950s and early 1960s, researchers considered two possible technologies for space satellite communications. "Active" satellites would receive a signal, process it, and then transmit it back to earth. This technique became the basis for communications satellites prevalent today.

"Passive" satellites, such as Echo, were also briefly considered. This type of satellite only served as a reflective surface in which signals from the Earth were bounced back to the ground. After launch from Cape Canaveral on Aug. 12, 1960, Echo 1 was inflated to form a 100ft diameter balloon. The plastic surface was metal-covered so as to reflect radio waves from a ground-based transmitter to a receiving Earth station thousands of miles away. Many successful link-ups were made across the world before leakage of gas caused it to deform and lose its reflecting power. A spectacular sight, it was seen by many people and it re-entered the Earth's atmosphere on Apr. 24, 1968.

While Echo had the advantage of simplicity, active satellites quickly surpassed the limited range of communications possible from a reflective surface in space. By the time of the second Echo in 1964, active communications satellites had clearly demonstrated their much greater capabilities and it was used primarily for scientific experiments.


Cosmos

Large quantities of these satellites have been launched. Some are used for scientific research into the space environment, and others to test new spacecraft systems with civil and military applications. Cosmos 1, a non-recoverable scientific satellite, was launched on Mar. 16, 1962 from Kapustin Yar. Many of the larger spacecraft launched from Baikonur and Plesetsk apparently have reconnaissance duties; they eject capsules for recovery over Soviet territory usually within 8 to 12 days.

The Cosmos spacecraft had its origins before Sputnik. In 1956, the Soviet military identified a requirement for a photo-reconnaissance satellite. The Chief Designer, flushed after the success of Sputnik, instead advocated that manned spaceflight should have first priority. After bitter disputes, a compromise solution was reached. Soviet Space Agency was authorized to proceed with development of a spacecraft to achieve manned flights at the earliest possible date. However the design would be such that the same spacecraft could be used to fulfill the militaries unmanned photo reconnaissance satellite requirement. A series of 1K prototypes would prove the essential design; the 2K and 4K versions would be unmanned spy satellites, and the 3K the manned spaceship. The military resisted, but in November 1958 the Council of Chief designers approved the Vostok manned space program, in combination with Zenit spy satellite program.


Telstar

After the 1957 launch of Sputnik I, many considered the benefits, profits, and prestige associated with satellite communications. Because of Congressional fears of "duplication," NASA confined itself to experiments with "mirrors" or "passive" communications satellites (ECHO), while the Department of Defense was responsible for "repeater" or "active" satellites which amplify the received signal at the satellite--providing much higher quality communications. In 1960 AT&T filed with the Federal Communications Commission (FCC) for permission to launch an experimental communications satellite with a view to rapidly implementing an operational system. The U.S. government reacted with surprise-- there was no policy in place to help execute the many decisions related to the AT&T proposal. By the middle of 1961, NASA had awarded a competitive contract to RCA to build a medium-orbit (4,000 miles high) active communication satellite (RELAY); AT&T was building its own medium-orbit satellite (TELSTAR) which NASA would launch on a cost-reimbursable basis.

Telstar 1 was launched on July 10, 1962 into a 514 x 3051 mile. orbit by a Delta launch vehicle. The spacecraft weighed 171 pounds (the Delta capability was for a maximum payload of 180 pounds). The shape was a faceted sphere with a diameter of a little over 34 inches. Of six spacecraft built, two were launched. The solar cells provided just under 15 watts. The spacecraft was spin stabilized using the same rate as the third stage (typically 200 rpm) avoiding a despin mechanism. The receive and transmit antennas consisted of belts of small apertures (72 and 48 respectively) around the middle of the spacecraft resulting in a circularly polarized antenna with an isotropic pattern around the equator of the spacecraft. Frequencies used were 6,390 MHz uplink and 4,170 MHz downlink. Telstar was the first satellite to use a TWT amplifier since transistor technology at the time was not capable of the 3 W power output at the frequency required.

AT&T built a ground station in Andover, Maine (away from microwave repeaters to avoid interference) similar to, but larger than, the ground station used for Echo. A French station at Pleumeur-Bodou used a duplicate of the AT&T horn antenna while the British station at Goonhilly Downs used a parabolic dish. The satellite was in position for transatlantic relay for a maximum of 102 minutes per day. Telstar relayed the first live trans-Atlantic television transmission as well as picture facsimile, telephone, and data relay. On July 9, the day before the Telstar I launch, the U.S. conducted a high altitude nuclear test (Starfish). Telstar's orbit took it through the Earth's inner radiation belt as well as a small portion of the outer belt. The radiation exposure was increased by the Starfish nuclear explosion as well as by a Soviet test in October 1962. After four months of successful operation, some transistors in the command system succumbed to the radiation.


TIROS/Nimbus

TIROS (Television and Infra-Red Observation Satellite) was one of the first planned uses of the new technology of satellites was to observe and study the Earth's weather from space. At the beginning of the space age, in the late 1950s, the U.S. Army initiated development of the first weather satellite. When the National Aeronautics and Space Administration (NASA) was created in 1958, they took over the fledgling program (in cooperation with the U.S. Weather Bureau) and named it TIROS. Under a NASA contract, RCA designed and manufactured the satellite, intended as an experiment to test the feasibility of space-based weather observation.

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The TIROS I, launched in April 1960, was the world's first weather satellite. TIROS imaged large swaths of the Earth's surface, allowing forecasters and scientists to see directly for the first time the massive scale of our planet's weather systems. The satellite transmitted thousands of images of cloud patterns and other phenomena to ground stations during the three-month life of the satellite. TIROS I was followed by several other test satellites. Together these first TIROS satellites established the technical experience to start separate civilian and military space-based weather observation programs. By the mid 1960s, the civilian TIROS program launched a series of satellites to provide routine, daily weather observations. The program is still in operation today (with more sophisticated, more capable satellites) making space-based weather observations a commonplace part of television newscasts.

The objectives of TIROS was to test experimental television techniques designed to develop a worldwide meteorological satellite information system. To test Sun angle and horizon sensor systems for spacecraft orientation. The spacecraft was 42 inches in diameter, 19 inches high and weighed 270 pounds. The craft was made of aluminum alloy and stainless steel which was then covered by 9200 solar cells. The solar cells served to charge the on-board batteries. Three pairs of solid-propellant spin rockets were mounted on the base plate. Two television cameras were housed in the craft, one low-resolution and one high-resolution. A magnetic tape recorder for each camera was supplied for storing photographs while the satellite was out of range of the ground station network. The antennas consisted of four rods from the base plate to serve as transmitters and one vertical rod from the center of the top plate to serve as a receiver. The craft was spin-stabilized and space-oriented (not Earth-oriented). Therefore, the cameras were only operated while they were pointing at the Earth when that portion of the Earth was in sunlight. The video systems relayed thousands of pictures containing cloud-cover views of the Earth. Early photographs provided information concerning the structure of large-scale cloud regimes. TIROS-I was operational for only 78 days, but proved that satellites could be a useful tools for surveying global weather conditions from space.

The TIROS Program was NASA's first experimental step to determine if satellites could be useful in the study of the Earth. At that time, the effectiveness of satellite observations was still unproven. Since satellites were a new technology, the TIROS Program also tested various design issues for spacecraft: instruments, data and operational parameters. The goal was to improve satellite applications for Earth-bound decisions, such as "should we evacuate the coast because of the hurricane?". The TIROS Program's first priority was the development of a meteorological satellite information system. Weather forecasting was deemed the most promising application of space-based observations. TIROS proved extremely successful, providing the first accurate weather forecasts based on data gathered from space. TIROS began continuous coverage of the Earth's weather in 1962, and was used by meteorologists worldwide. The program's success with many instrument types and orbital configurations lead to the development of more sophisticated meteorological observation satellites.

TIROS initiated a remarkably successful program of weather observation. Nine TIROS were launched from 1960 to 1965, providing crucial background experience for developing work-a-day systems of satellites to monitor the Earth's weather and atmosphere. The first of these was the TIROS Operational System (TOS), launched over 1966-1969. The development of TIROS and these subsequent systems were closely connected to the separate weather satellite programs of the Department of Defense. Technological innovations and experience were traded back and forth (RCA was the primary contractor for both the civilian and military satellites). Beginning in the 1970s, this combined effort made possible highly-reliable systems of weather observation. The results have been striking. Today satellite imagery is part of our everyday lives, an expected and unremarkable part of television weather reports.

The follow-up program to TIROS was Nimbus 1, launched from Cape Kennedy on Aug. 28, 1964, and was the first of America's second-generation experimental weather satellites. Unlike the latter, which were spin-stabilized, Nimbus 1 was stabilized so that its experiments remained pointed at the Earth. It was placed in an elliptical, 263 by 579 mile path around the Earth instead of the circular 575 mile orbit planned. 27,000 pictures of excellent quality, covering the entire Earth, were synthesized at a large number of picture receiving stations during 26 days of active life before power failure terminated its career.

Inaugurated in early 1960s, the Nimbus weather satellite program was designed to complement the first series of meteorological spacecraft, TIROS. TIROS began the age of space-based meteorology in April 1960 with its first satellite. In this new field, Nimbus's purpose was to test advanced instruments for observing earth's weather and studying the atmosphere as well as to evaluate improved spacecraft designs. TIROS's purpose was to use proven technologies to provide an operational system of satellites for daily observation of the earth's weather.

Nimbus 1, launched in April 1964, failed after a month in orbit. Nimbus 2, launched in May 1966, provided a wealth of data over two and a half years. As a research and development satellite, it proved the scientific and observational value of an improved television camera system (the Advanced Vidicon Camera System) and of new infrared sensors (the High Resolution Infrared Radiometer and the Medium Resolution Infrared Radiometer). Of particular significance was a three-axis stabilized spacecraft design which allowed the satellite's instruments to point continuously at the earth's surface and gather data. At this time, all of the TIROS satellites were spin stabilized. As the spacecraft rotated the instruments rotated as well, periodically interrupting observations of the earth. This innovation in design was incorporated into the TIROS program in the late 1960s.

As research and development satellites, Nimbus series of craft served as a marker of the newness and uncertainties of space-based observation and scientific study in the 1960s. Specialized satellites were required to evaluate new ideas and advances in instrument and spacecraft design, which if successful, could be incorporated into the operational, work-a-day TIROS satellites. The Nimbus satellites had scientific value above and beyond proving new instruments. The HRIR and MRIR (High Resolution Infrared Radiometer and Medium Resolution Infrared Radiometer) on Nimbus 2, for example, provided crucial insight into the heat dynamics of the earth's atmosphere. Using data from these instruments scientists improved their understanding of temperature profiles of the earth's surface and atmosphere and the transmission of heat radiation in and out of the atmosphere.

Altogether seven Nimbus satellites were launched, the last in 1978. All spacecraft were designed and built by General Electric under contract to NASA. After launch, NASA turned control of the satellite (in the case of Nimbus 2) over to the Environmental Science Services Administration. In 1965 this organization supplanted the Weather Bureau and later would be reorganized as the present National Oceanic and Atmospheric Administration in 1970.

Current Weather Satellite Maps


Ocean Surveys (JASON)

Jason-1 is the first follow-on to the highly successful TOPEX/Poseidon mission that measured ocean surface topography to an accuracy of 4.2 cm, enabled scientists to forecast the 1997-1998 El Nio, and improved understanding of ocean circulation and its effect of global climate. The joint NASA-CNES program launched on a French spacecraft on an American Delta II from an American base. Like TOPEX/Poseidon, the payload will include both American and French instruments. Jason-1 altimeter data will be part of a suite of data provided by other JPL-managed ocean missions--the GRACE mission will use two satellites to accurately measure Earth's mass distribution, and the QuikSCAT scatterometer mission will measure ocean-surface winds.

For the first time, orbiting satellites have observed and measured a major tsunami event in open ocean, the Indian Ocean tsunami that resulted from the magnitude 9 earthquake southwest of Sumatra on December 26. The measurements are of tremendous value to researchers worldwide and will aid our understanding of these events. The main figure displays changes in sea surface height from previous observations made along the same ground track 20 to 30 days before the earthquake, showing the signals of the tsunami waves. The inset is a computer model of simulated changes in sea surface height created by Kenji Satake of the National Institute of Advanced Industrial Science and Technology, Japan. It provides a basin-wide perspective for interpreting the Jason and Topex/Poseidon satellite observations, which are in good agreement with the model.

The satellites recorded a maximum sea surface elevation gain (deviation from normal) of 50 centimeters (1.6 feet) on the open ocean about 1,200 kilometers (746 miles) south of Sri Lanka at the leading crest of a tsunami wave raging out of the Bay of Bengal. It was followed by a trough of sea surface depression of 40 centimeters (1.3 feet) below normal. The distance from one wave crest to the next was about 800 kilometers (500 miles). The first wave was followed by a second with a crest height of 40 centimeters (1.3 feet) above normal. Near the northern end of the Bay, two waves with crest heights of 40 centimeters (1.3 feet) and 20 centimeters (0.66 feet) above normal were approaching the coasts of Myanmar. Spreading across the Bay of Bengal from the earthquake zone offshore from Western Sumatra, these tsunami waves eventually reached shallow waters along the coasts of Sumatra, Sri Lanka, Thailand and Southern India. Their open ocean speeds reduced from that of a jet plane, 800 kilometers (500 miles) per hour, to about 32 kilometers (20 miles) per hour, building the open ocean wave heights of 0.5 meters (1.6 feet) or less to walls of water up to 10 meters (33 feet) high with great destructive power.


Questions:

  • Describe the early communication satellites (SCORE, Echo, Telestar).
  • What was the Corona program?
  • Describe the early weather satellite programs (TIROS, Nimbus).