(Lockheed Martin Missiles & Space)

Overview and History of the Defense Meteorological Satellite Program

Steven R. Strom and George Iwanaga

Aerospace support for the military's weather satellite program was initially limited—but increasing involvement over the years has helped the system achieve remarkable capability and reliability.

Shortly after the launch of Sputnik in 1957, the U.S. House Select Committee on Astronautics and Space Exploration asked several space experts for their forecasts of what the U.S. space program might achieve during the next decade. Their report, The Next Ten Years in Space: 1959–1969, predicted that "great improvements in weather forecasting will become possible with a satellite providing rapid overall data on cloud cover and atmospheric transmissions, albedo, and emission. This has tremendous implications, both civilian and military." There was consensus among several contributors that better weather coverage, particularly cloud-cover photography, could be immensely helpful to U.S. intelligence efforts.

These predictions proved quite accurate. In the ensuing years, meteorological satellites played a critical role in supporting military planning and reconnaissance operations around the globe. The Air Force's pathbreaking weather satellite program, which began in secrecy, vastly improved scientific knowledge of Earth's climate and environment, enabling more useful models and more accurate forecasts for diverse users and applications. Along the way, Aerospace made important but little-known contributions that helped the Air Force maintain its considerable capabilities in meteorological observation.

Conceptual drawing of the DMSP Block 1 satellite. The spacecraft rolled like a wheel in orbit, and its side-mounted camera took a picture once each revolution. NASA copied this design for the TIROS Operational System. (US Air Force)

An Auspicious Beginning

In 1958, the Department of Defense (DOD) began work on what would become the first meteorological satellite, TIROS (Television Infrared Observation Satellite). Within the year, the program was transferred to the newly formed National Aeronautics and Space Administration (NASA), with the U.S. Weather Bureau designated to provide satellite instrumentation, data reduction, and analysis of observations. TIROS was placed into orbit in April 1960, and TIROS-2 followed soon thereafter. Congress subsequently commissioned NASA to develop a national operational meteorological satellite system to serve both commercial and military users.

The TIROS spin-stabilized polar-orbiting satellites offered limited coverage of the globe. Air Force Undersecretary Joseph Charyk, who also headed the National Reconnaissance Office (NRO), recognized an immediate and increasing need for better coverage of Eurasia. Better knowledge of weather conditions—particularly cloud cover—would improve planning of photographic surveillance of the Soviet Union, China, and other nations of interest. In April 1961, Aerospace prepared a development plan for the Air Force's Space Study Committee that recommended using components of TIROS in a new satellite, launched by a Blue Scout rocket. The initial emphasis would be on cloud-cover photography with provisions for the later addition of more sophisticated equipment as development allowed. After Charyk determined that the planned NASA system could not meet military needs, he gave his conditional approval in August for the Air Force to begin its own program of satellite weather observation based at least in part on the Aerospace proposal. This program ultimately became known as the Defense Meteorological Satellite Program (DMSP; see sidebar, DMSP at a Glance).

The DMSP program office was located at Los Angeles Air Station (now Los Angeles Air Force Base) and overseen by the Space Systems Division, although personnel reported to NRO. Because Congress had already authorized and funded NASA to develop a national weather satellite system, knowledge of DMSP was limited to "need-to-know" personnel, and complete secrecy surrounded the program in its early years.

DMSP Block 4 satellite. The Air Force launched seven of these on Thor Burner II rockets between 1966 and 1969. Television resolution for Block 4 was approximately 1.5 kilometers at nadir, as opposed to only 5.5 kilometers for Block 3. (US Air Force)

As a result of certain DMSP constraints that differed from the usual Space Systems Division programs—including fixed-price, fixed-schedule contracting—Aerospace and the Air Force agreed that Aerospace would not assume general systems engineering/technical direction (GSE/TD) for the program. Nevertheless, Aerospace helped develop instrumentation and sensors for the early DMSP spacecraft. Ernst H. Rogers, David F. Nelson, and Robert L. Sempek, for example, performed work that led to the formulation of new concepts for the production of primary and secondary sensors and new methods of data processing and display. During the program's early years, the Space Sciences Laboratory also developed X-ray detectors to observe the aurora from DMSP orbits.

Setbacks and Successes

DMSP began operations with five attempted Block 1 satellite launches from Vandenberg Air Force Base in 1962 and 1963 using the Scout launch vehicle. All but one of them failed, but later attempts using the Thor Agena and Thor Burner I had greater success. The data transmitted from the DMSP satellites were received by two command/readout stations located near Loring Air Force Base in Maine and Fairchild Air Force Base in Washington. The data were then forwarded to Air Force Global Weather Central at Offutt Air Force Base in Nebraska and converted into photographs. By the time the Block 2 and Block 3 series went into operation in the mid-1960s, DMSP was becoming increasingly important in planning Vietnam War operations. The satellites supplied cloud-cover information to headquarters in Saigon and to aircraft carriers stationed in the Gulf of Tonkin, which allowed for more precise planning of tactical air missions.

As a result of the increased use of DMSP data by the military, the DMSP program office began reporting directly to the Space Systems Division in July 1965. From 1966 to 1969, a series of increasingly sophisticated satellites were launched as part of the Block 4 constellation. From 1970 to 1976, 11 satellites in the Block 5A, B, and C series were launched using the Thor Burner II as booster. After more than a decade of operations, DMSP was declassified in 1973, and civilians were allowed to share the program's data.

Aerospace researchers David Nelson and Ernst Rogers reviewing DMSP photos of an auroral display in July 1973, the year the program was declassified.

The Aerospace role in DMSP took on a new significance in 1976. That year, the Air Force began work on a new series of satellites that could provide higher-quality photographs both day and night. The satellites would be launched using Thor Delta rockets. That year, the Space and Missile Systems Organization (descendant of the Space Systems Division) requested Aerospace assistance with the review of a Thor launch vehicle failure, and James H. Elliott led the Aerospace effort. Elliott's team prepared an in-depth reconstruction of several past Thor flights and developed a performance model that revealed a critical fuel shortage. The model was accepted and subsequently employed on a series of successful DMSP launches. Later in 1976, the Air Force requested that Aerospace establish a program office and increase its assistance to DMSP, with full responsibility for general systems engineering and integration (GSE/I). The Aerospace DMSP program office, initially headed by Ernest LaPorte, began operation in early 1977.

A Last-Minute Save

In addition to helping improve launch vehicle reliability, Aerospace helped overcome problems with the satellites themselves. The first of the more sophisticated Block 5D satellites was launched in September 1976, only a few months before Aerospace assumed responsibility for GSE/I. Although the initial orbit insertion appeared successful, a telemetry signal soon revealed control problems, and the spacecraft began tumbling. The satellite's batteries were quickly depleted because the solar-cell array was not locked on the sun, and all systems were dead after 16 orbits. The Air Force formed a failure review team that included Aerospace members, including LaPorte and David L. Griep, director of the Control and Electromechanical Subdivision.

Aerospace president Ivan Getting and trustees review imagery from DMSP satellites with Aerospace researchers in June 1975. From left to right: David Nelson, Ernst Rogers, Ivan Getting, Gen. Bernard Schriever, and E. Hornsby Wasson.

The technical review determined that the cause of the failure was a high-pressure nitrogen leak from a B-nut connector. The expanding gas from the leak impinged on the solar panel, which produced an unforeseen torque. The identification of the leak, which interfered with the operation of a long boom supporting the solar panel, was made possible by Griep's development of a dynamic model using a digital-analog computer. During the next few weeks, tracking of the satellite continued. In early October, after the solar panel received enough sunlight to begin generating power again, the solar-array system was successfully switched to a battery-charging mode. As a result, it became possible, using environmental forces generated between the satellite and Earth's magnetic field, to control the spin vector. However, the spacecraft was still performing three revolutions per minute, which did not allow the satellite to fulfill its photographic mission.

During the next weeks, simulations were developed for the solar panel and spacecraft combination. They indicated that the solar panel could be pulled out to a stable position at the current rate of spin, but if the rate of spin quickly dropped, the panel could fall back to its previous position. Aerospace then developed a series of simulations of the entire satellite system, using a CDC 7600 computer (precursor to the Cray supercomputer). The satellite's Earth-sensor system was used to measure the spin rate and the spin angle. In December, a simulation by Aerospace scientists demonstrated that pulsing currents through magnetic coils in the satellite could produce small interactions with Earth's magnetic field—and if these were properly applied, it might slow the spin.

By late February 1977, Griep and his team were ready to apply their findings to the satellite itself, and they temporarily relocated to Offutt Air Force Base, the DMSP control center. The CDC 7600 computer was now linked to Offutt, which enabled the Aerospace team to conduct a series of simulations; however, the new simulations indicated that as the spin rate slowed to one-fifth of a revolution per minute, problems with the gyro suddenly developed, and rapidly grew worse. A defective gyro would limit the operational life of the craft after recovery, so a solution had to been found quickly. In the two weeks before the recovery effort (scheduled for the end of March), Draper Laboratory developed new computer software that would enable the spacecraft to function normally without the gyro by shifting the control to the satellite's Earth sensor. But questions remained about whether the software would work properly onboard the satellite. A series of rapid simulations was now required to verify the software modifications, and in one 8-hour period, Aerospace conducted 40 simulations, each one covering from 5 to 10 orbits of the satellite.

Aerospace researchers who worked on the recovery of a DMSP Block 5D-1 in April 1977, around the time that the Aerospace DMSP program office began operation. From left to right: William Russell, Ray Skrinska, W. L. Hayden, Jesse Lopez, Morey Gibbs, and David Griep.

On March 24, just one day before the problems with the gyro would have made recovery impossible, stabilization of the satellite was achieved. Aerospace corporate historian Everett Welmers wrote that after "six months of ingenuity, analyses, simulations, and hard work," the satellite was declared operational on April 1, 1977. Nonetheless, the Aerospace team was summoned again when another crisis with the same satellite occurred in mid May. This time, the satellite's yaw gyro had begun to drift. After a series of investigations, Aerospace corrected the drift and recommended the implementation of a control system that did not use gyros. Despite some continuing problems with yaw oscillation, stabilization of the satellite was ultimately achieved. As a result of the major Aerospace effort in helping the Air Force save its 5D-1 satellite, DMSP acquired, in Ivan Getting's words, "a new significance to The Aerospace Corporation." In the remainder of 1977, Aerospace also assisted with the reactivation of two more DMSP satellites that encountered on-orbit failures.

Convergence

Although the manner in which Aerospace joined the DMSP team was dramatic, the Aerospace program office continued to provide equally critical and timely support to DMSP operations, right up to the present. For example, Aerospace was integrally involved in the Block 5D-2 satellite missions, which were characterized by aggressive government oversight, intensive monthly program reviews, reduction of single-point failures, addition of critical redundant components, and implementation of lessons learned from previous launches. All of the Block 5D-2 missions were successful, beginning with the first in 1982 and proceeding through eight more from 1983 to 1997. In addition, Aerospace led an effort to replace the lubricant and bearings on the Operational Line Scan instrument (the primary cloud-imaging sensor on Block 5 satellites), which served to increase satellite life.

DMSP's Operational Line Scan instrument is sensitive enough in the visible spectrum to view clouds by moonlight and can generate nighttime imagery of Earth's surface. This picture shows the aurora borealis in October 2003. Areas of dense urbanization also appear as bright lights.

From the time that DMSP was declassified in 1973, proposals were periodically made to merge the program with the civilian meteorological satellite program managed by the National Oceanic and Atmospheric Administration (NOAA). Finally, in May 1994, President Clinton issued a directive merging the two polar-orbiting satellite programs. An integrated program office, comprising NASA, DOD, and NOAA personnel, assumed responsibility for major systems acquisition for the next-generation National Polar-orbiting Operational Environmental Satellite System (NPOESS) satellite. In 1998, DMSP satellite operations were transferred to NOAA, which jointly operates both military and civilian meteorological satellites, but the acquisition function for DMSP remains with DOD. The first phase of NPOESS is concerned with the development of critical sensors, and Aerospace is providing technical support for nine sensor contracts. Aerospace is also involved in planning the NPOESS Preparatory Project, which will provide global observations and scientific information as a follow-on to NASA's Earth Observing System. In addition, Aerospace provided important planning support to the convergence of ground operations when NOAA assumed authority over the program.

The present generation of DMSP satellites, Block 5D-3, became operational in November 2003. As DMSP enters its fifth decade of service, the program continues to provide valuable assistance in planning and protecting military operations around the world. The support that Aerospace provided has helped achieve Ivan Getting's goal of making Aerospace "the nation's technical repository for military satellite systems."

Acknowledgement

The authors thank Dave Nelson for his assistance in preparing this article.

References

1. The Aerospace Corporation Archives, President's Report to the Board of Trustees, Vol. II (1961–1980).
2. John S. Bohlson, Leslie O. Belsma, and Bruce H. Thomas, "Cloud Cover Over Kosovo," Crosslink, Vol. 1, No. 2 (Summer 2000).
3. Douglas Aircraft Company, Inc., Santa Monica Plant, Engineering Division, Preliminary Design of an Experimental World-Circling Spaceship (Santa Monica, CA, 1946).
4. History Office, Space and Missile Systems Center, Los Angeles Air Force Base, Historical Overview of the Space and Missile Systems Center, 1954–2003 (Air Force Pamphlet, 2003).
5. R. Cargill Hall, A History of the Military Polar Orbiting Meteorological Satellite Program, NRO History Office (2001).
6. The Next Ten Years in Space: 1959–1969, U. S. House Select Committee on Astronautics and Space Exploration (Washington, D.C., 1959).
7. Space and Missile Systems Center, Historical Archives, DMSP files.

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