The Promise of MIDAS: The First Experimental Early Warning Satellites

Today in the United States we almost take for granted the military’s ability to detect missile launches anywhere on the planet and quickly determine whether it poses a threat to us, our allies, or our interests around the globe. This capability helped to maintain the nation’s security for much of the Cold War and today provides an early warning against missile attacks by potential adversaries. This early warning capability is provided by a constellation of high flying SBIRS (Space Based InfraRed System) satellites which use state of the art infrared (IR) detector arrays to constantly scan the Earth’s surface.

An artist rendering of a SBIRS GEO satellite in Earth orbit. (Lockheed-Martin)

But this reliable early warning capability is a product of decades of effort by scientists and engineers across the country. At the dawn of the Space Age such a system was just a dream. Back then the country’s first line of defense against missile attack was a string of radar installations across the North American Arctic frontier, known as BMEWS (Ballistic Missile Early Warning System), supplemented by radar equipped aircraft. While a formidable line of defense, this system at best provided only 15 minutes of warning before a rocket-launched nuclear warhead would strike. With the memory of Pearl Harbor still fresh in the minds of the public and the military establishment, a better solution giving even more warning time was needed.

The Beginning

The beginning of the United States’ space-based early warning system can be traced back to studies performed during the early 1950s by Joseph J. Knopow. Working for the Operations Analysis Office in the Directorate of Operations at the USAF Headquarters, Knopow studied the ability of the then new generation of infrared (IR) sensors to detect turbojet powered bombers and transports as well as long range missiles. While this was found to be possible in principle, the detection of the bright plume generated by an ascending missile (potentially the most dangerous of these weapons) proved to be easiest with the technology available.

A portrait of Joseph J. Knopow who developed the concept of a satellite-based early warning system. (NRO)

In June of 1955, Knopow joined Lockheed’s new Missile and Space Division (now part of the aerospace giant, Lockheed Martin) that was setting up shop in Palo Alto, California. Among its early programs was the development of WS-117L (Weapon System 117L) and the Agena upper stage that it would use. At this time, WS-117L was a catch all for the varied USAF satellite proposals with direct military applications. On the top of the list was a reconnaissance satellite capable of returning detailed pictures from behind the Iron Curtain (see “The First Discoverer Missions: America’s Original (Secret) Satellite Program”). Also included under the WS-117L umbrella was an elint (electronic intelligence) capability designed to detect Soviet Bloc radars and intercept their communications. Knopow was able to convince his superiors about IR sensor’s ability to detect missile launches from orbit and in March of 1956, it was incorporated into the firm’s WS-117L proposal to the USAF as Subsystem G.

While Subsystem G was included in the WS-117L contract when the USAF selected Lockheed as the prime contractor in June of 1956, there were still a host of skeptics that needed convincing. Many believed that while in theory a missile plume could be detected by IR sensors, the complex natural background structure of the warm Earth and its atmosphere would overwhelm the system’s ability to differentiate a true threat from a false alarm. A system that generated an inordinate number of false alarms was essentially as useless as no system at all. Over the years that followed, Knopow (now appointed the subsystem manager and later would become the program manager) and others went out to convert most of the skeptics generating almost unbounded enthusiasm among some in the USAF in the process.

The Spacecraft

As broader support for the program was being sought, design work for the actual satellite moved forward. Like the reconnaissance satellite in WS-117L, this early warning payload would be integrated with the Agena upper stage being developed at Lockheed. Like the Agena used in the reconnaissance satellite, the Agena would provide the final impulse needed to achieve orbit after booster burnout as well as provide support functions for the payload once there. At the forward end of the Agena was mounted the W-17 IR detector payload subcontracted to Aerojet-General Corporation. IR scanners to test the concept and gather data on natural backgrounds from aircraft and balloons would be built by Baird-Atomic, Inc. based in Cambridge, Massachusetts. A few balloon flights were flown during the second half of 1959 to begin gathering the needed data on natural backgrounds.

The W-17 payload consisted of a turntable rotating at two RPM with a Bouwers-concentric telescope attached. The tilt of this telescope relative to the turntable could be changed on command and was equipped with 27 lead sulfide IR detectors using filters to scan different parts of the spectrum. With the satellite in a nose down attitude, the detectors would sweep out a large donut shaped region from just above the horizon downwards to the limits of the sensors’ field of view. The earlier DSP (Defense Support Program) early warning satellites used during the last century used a similar scanning technique although the whole spacecraft rotates, not just the sensor payload. Attitude control and orbital maintenance were provided by the Agena. Attached to its aft compartment were a pair of solar panels to provide power to the satellite and its payload.

A 1958 concept drawing of a USAF early warning satellite. (USAF)

While plans for an operational system based on this design were constantly in flux because of changing USAF requirements, generally it was planned to consist of around a dozen satellites in polar orbits at an altitude of 2,000 nautical miles (3,700 kilometers). Such a system could monitor virtually all of the Earth’s surface and provide up to 30 minutes warning of a missile launch – twice as much as the existing BMEWS radar system. While a Thor IRBM was briefly considered as a launch vehicle, only the Atlas ICBM was powerful enough to loft the 1,600-kilogram payload into the desired orbit. The mission also required the in-orbit engine restart capability of the Agena B, which was still under development. But for the initial pair of test flights, use of the smaller Atlas-Agena A to boost the payload into a low inclination, low altitude orbit from Cape Canaveral would suffice.

Concept art of the launch of the USAF early warning satellite. (USAF)

After the creation of ARPA (Advanced Research Projects Agency) in February of 1958, management of all military satellite programs including WS-117L were transferred to the new agency. Once again, a new group of doubters had to be convinced of the feasibility of this early warning system. By mid-1958 this had been largely accomplished and work proceeded to build the test satellites. On November 15, 1958 ARPA officials split up WS-117L into separate programs. The interim reconnaissance satellite was spun off as the highly secret Project Corona which would be launched under the cover of the Discoverer program. The development of a more advanced reconnaissance capability continued independently as SAMOS. Finally, Subsystem G gained its independence to become the Missile Defense Alarm System or MIDAS. At this point work on the program was accelerated with the goal of launching the first test payload in late 1959. By February of 1959, USAF plans called for an operational capability no later than 1962.

Because of problems with ARPA’s control of military satellite programs and widespread support for MIDAS, management of MIDAS along with some other projects was transferred back to the USAF Ballistic Missile Division on September 18, 1959. The new deployment plan called for four development flights (including the pair of Series I flights already in the works) for Phase I. Phase II included a half dozen research and development flights with an operational system coming as part of Phase III in the early 1960s. But this optimistic plan began to fall apart since the first two MIDAS test satellites were not even ready for flight until the beginning of 1960.

The Series I Missions

The first pair of MIDAS satellites, referred to as Series I, consisted of an Agena A stage with a battery-powered IR payload mounted on the forward end. These first two spacecraft would be launched into low-inclination orbits from Cape Canaveral, Florida to gather test data from low Earth orbit. The Atlas 29D booster for the first MIDAS mission was erected on the pad at Launch Complex 14 (LC-14) at Cape Canaveral on January 18, 1960 to start preparations for launch in earnest. Agena 1008 was assigned to support the payload with a total in orbit mass of 2,025 kilograms.

MIDAS 1 shown on the pad at LC-14 at Cape Canaveral prior to its launch on February 26, 1960. (Convair/SDASM)

MIDAS 1 lifted off from LC-14 at 12:25 PM EST on February 26, 1960 from LC-14 for the first flight of the new Atlas-Agena A launch vehicle. The Atlas 29D booster operated as expected through the shutdown of its sustainer engine and vernier engine cutoff to start the coast toward stage separation. Suddenly, all telemetry from Agena 1008 was lost and the pressure in the LOX tank of Atlas 29D dropped to zero. The missile went into a tumble and crashed downrange in the Atlantic. A subsequent investigation showed that the Inadvertent Separation Destruct System (ISDS) on Agena 1008 had accidentally detonated the stage’s destruct charges at stage separation. The ISDS required a redesign to prevent a similar malfunction in the future and would be entirely absent on the next MIDAS launch.

Agena 1007/MIDAS 2 being prepared for stacking on May 22, 1960. (Convair/SDASM)

Three months later, the second (and last) Series I payload, MIDAS 2 employing Agena 1007, was prepared for launch using Atlas 45D as its booster. Several experiments were planned during this mission to test the W-17 IR sensor package including the detection of flares on the ground and observing the test flight of an ICBM, Titan I serial number G-9, to be launched from Cape Canaveral. MIDAS 2 lifted off at 12:36 EST on May 24, 1960 from LC-14. A near-perfect performance by the Atlas-Agena A placed the 2,300-kilogram MIDAS 2 into a 484 by 511-kilometer orbit with an inclination of 33°. But once again, failure struck. The attitude control system on Agena 1007 failed after entering orbit sending MIDAS 2 into an uncontrolled tumble. A total of 30 minutes of data from the IR payload were recorded during the first two orbits resulting in some information on natural backgrounds and the detection of the IR-bright star, Betelgeuse. But the telemetry system finally failed after only 16 orbits. The now silent MIDAS 2 would remain aloft until its orbit finally decayed in 1974.

The launch of MIDAS 2 on May 24, 1960 from LC-14 at Cape Canaveral. (Convair/SDASM)

Efforts now turned towards building the Series II MIDAS. This new version carried an improved IR payload built by Baird-Atomic featuring 175 detectors capable of spotting an ICBM launch at a slant range of up to 7,800 kilometers. The turntable also had an increased spin rate of six RPM allowing the sensors to sweep across the Earth below every ten seconds. Instead of the Agena A, the Series II MIDAS used the larger and more capable Agena B to place the satellite in the 3,700-kilometer polar orbit intended for the operational system. The Atlas D along with the first burn of the Agena B would place the stage and its payload into a high-apogee transfer orbit with a second burn of the Agena circularizing the orbit at the desired altitude. The Series II spacecraft would also employ a pair of solar panels carried on the aft equipment rack of the Agena to recharge the spacecraft’s batteries. By March 1961, it was expected that over two dozen additional MIDAS test flights would be required to reach operational capability by January 1964.

But as work progressed on the new Series II satellite, other satellites would contribute data on natural backgrounds vital for the MIDAS program. On December 20, 1960, Discoverer 19 (codename “Tee Bird”) was launched on a Thor-Agena B from Launch Pad 75-3-5 at Vandenberg Air Force Base in California (today known as SLC-1E) entering a 178-by-324-kilometer orbit with an inclination of 89.6°. Instead of a high-resolution camera and film return vehicle like those carried by earlier Discoverer satellites as part of the Corona program, the Agena 1101 stage was equipped with a radiometry payload designated RM-1. While an attitude control gas leak on the Agena B made it difficult to stabilize the satellite, it did return valuable data that were described as “90% usable” before its orbit decayed on January 23, 1961.

The launch of Discoverer 19 on December 20, 1960. This mission acquired IR data of natural Earth backgrounds in support of MIDAS. (USAF)

A repeat of this mission using radiometry payload RM-2 was launched from Pad 75-3-5 as Discoverer 21 on February 18, 1961 under the codename “Bench Warrant”. In addition to performing its IR radiometry mission once reaching a 212-by-344-kilometer orbit with an inclination of 80.6°, Discoverer 21 also performed an important engineering test. During its first orbit, the engine of the Agena 1102 was restarted for 1.05 seconds adding about 11 meter per second to the satellite’s orbital velocity. This first test of the in-orbit restart capability was not only important to the MIDAS program but also to other programs as well including NASA’s new lunar program, Ranger, that would also use the Atlas-Agena B launch vehicle (see “The Prototype That Conquered the Solar System”). But once again, failure struck when the satellite’s power system failed on the ninth orbit bringing the mission to a premature end. The orbit of Discoverer 21 decayed on April 20, 1962. During this same time, more IR data of natural backgrounds were also secured using a high-flying U-2D aircraft during the first half of 1961. Over the next five years, a handful of smaller Department of Defense (DoD) scientific satellites along with a half dozen Corona reconnaissance satellites carrying smaller IR radiometry instruments as supplemental payloads would to gather yet more IR data in support of the MIDAS program.

The Series II Missions

After a 14-month standdown, forced in part by scheduling conflicts with the SAMOS reconnaissance satellite program which also used the Atlas-Agena B, the USAF was ready to launch the first of its improved Series II MIDAS satellites using the upgraded Atlas-Agena B. MIDAS 3 lifted off from SLC-3E at Vandenberg AFB (today, Vandenberg Space Force Base) at 8:11 AM PDT on July 12, 1961. Although the programmer on the Atlas 97D experienced a reset at booster engine cutoff, the Atlas D and the first burn of Agena 1201 successfully placed the 1,600-kilogram MIDAS 3 into an initial transfer orbit. A subsequent second burn of the Agena 1201 stage successfully nudged the stage and its payload into a 3,426-by-3,464-kilometer polar orbit with an inclination of 91.2°.

The launch of MIDAS 3 on July 12, 1961from SCL-3E at Vandenberg AFB. (Convair/SDASM)

But, as soon as MIDAS 3 achieved orbit, failure struck the program once again. One of the two solar panels failed to deploy properly and MIDAS 3 lost power after returning only a limited amount of data during the first five orbits. As an investigation into the failure started, the feasibility of the whole early warning concept was again called into question resulting in a lengthy series of reviews. Many felt that this system could not detect the launch of solid rocket propelled missiles which were now seen as the new and upcoming threat.

While scientists and engineers redoubled their efforts to convince government officials of the continued feasibility of their concept, Atlas 105D, Agena 1202 and its payload were prepared for the MIDAS 4 mission. MIDAS 4 was launched at 6:53 AM PDT on October 21, 1961 from SLC-3E at Vandenberg AFB. But failure reared its head once more when the ascending Atlas 105D lost roll control 186 seconds after launch eventually injecting the satellite into the wrong parking orbit. This malfunction was compounded by the Agena’s excessive use of attitude control gas during its pair of burns in an attempt to compensate for the trajectory errors. By the time MIDAS 4 completed its first 3496-by-3756-kilometer orbit inclined 95.9° to the equator, attitude control gas supply of Agena 1202 was depleted rendering the satellite uncontrollable. Then during the fourth orbit, one of the Agena’s solar panels failed starving the spacecraft of much needed power. During the brief time it had left, the IR payload on MIDAS 4 apparently did detect the night launch of a Titan ICBM, Titan I serial number AJ-21, 90 seconds after its 7:28 PM EDT liftoff from LC-19 at Cape Canaveral on October 24. MIDAS 4 was finally shut down after a week in orbit as its power reserves were finally depleted.

The launch of MIDAS 4 on October 21, 1961 from SLC-3E at Vandenberg AFB. (Convair/SDASM)

An investigation into the problems encountered during the MIDAS 4 mission was quickly started. The launch failure of SAMOS 4 on November 4 drew a new focus on the problems MIDAS 4 encountered during ascent. The common cause of the failures with Atlas 105D for the MIDAS 4 mission and Atlas 108D used for the SAMOS 4 launch was traced to the retrorocket package heat shields on both Atlas rockets which had broken off during launch exposing the gyroscope package to aerodynamic heating. A transistor used in the roll output channel was also suspected to be faulty. The transistor was replaced by a different type and the retrorocket heat shields were redesigned.

The MIDAS program was temporarily suspended at this point when a review committee headed by ARPA director Jack Ruina recommended that no attempt at an operational missile early warning system be made until the USAF demonstrated that it was a feasible concept. In addition to the issues with the detectability of solid rocket ICBMs, the committee found that program management of MIDAS was “awful” and at the current rate of success, “it would take ten years to develop an operational system”. In November 1961, the DoD issued a directive placing all of its space programs under strict secrecy, and so MIDAS was given the cover name “Program 461”. What little information which had been reaching the public about MIDAS was stopped and it would be 1998 before the program was declassified. The development time of the program was also lengthened to give more time to work out problems with the hardware.

After a six-month hiatus, the final Series II spacecraft using Agena 1203 and Atlas 110D as a booster was ready. MIDAS 5 was launched at 7:04 AM PST on April 9, 1962 from SLC-3E. The autopilot on Atlas 110D generated an insufficient pitch and roll program resulting in excessive altitude and insufficient velocity. This prevented the normal guidance system cutoff commands from being sent so sustainer engine cutoff was caused by propellant depletion while a backup command from the programmer performed vernier engine cutoff and Agena separation. As a result, MIDAS 5 ended up in an incorrect 2786-by-3408-kilometer orbit with an inclination of 86.7°. To compound the mission’s problems, a power failure struck the satellite during its sixth orbit prematurely ending yet another mission.

While theory and the limited orbital data indicated that the concept of an early warning satellite seemed basically sound, the MIDAS program was proving to be an abysmal failure. By the end of 1962, the status of MIDAS was downgraded to a research and development program as efforts were made to simplify the design of the MIDAS spacecraft and greatly improve its reliability. While work proceeded on the first Series III spacecraft, the development and deployment of an operational early warning satellite constellation seemed further away than ever.

General References

Sarah A. Grassley, Agena Flight History as of 31 December 1967 – Volume 1 (Declassified), Space and Missile Systems Organization – Air Force Systems Command, June 1969

R. Cargill Hall, “Missile Defense Alarm: The Genesis of the Space-based Infrared Early Warning”, Quest, Vol. 7, No. 1, pp. 5-17, Spring 1999

Robert E. McClellan, History of the Space Systems Division July – December 1965 (Declassified), SAMSO Office of Information Historical Division, October 1968

Curtis Peebles, The Corona Project: America’s First Spy Satellites, Naval Institute Press, 1997

Jeffrey T. Richelson, America’s Space Sentinels – DSP Satellites and National Security, University Press of Kansas, 1999

N. W. Watkins, “The MIDAS Project: Part I Strategic and Technical Origins and Political Evolution 1955-1963”, Journal of the British Interplanetary Society, Vol. 50, No. 6, pp. 215-224, June 1997