### Early Missile Warning

Surprisingly, the military space mission of early missile warning was not identified by any of the RAND studies of the late 1940s and early 1950s investigating the feasibility and usefulness of satellites. Therefore, it is amazing that by 1980 space based infrared systems were considered the fourth leg of our country's nuclear deterrent "Triad" of bombers, land based ballistic missiles and sea launched ballistic missiles helping to deter any nuclear attack against the United States. Infrared detection of missile launches for early warning was one of the three primary missions of the earliest USAF development for a reconnaissance satellites. The primary driver behind this early warning requirement, to prevent a nuclear Pear Harbor, was Strategic Air Command (SAC) commander General Curtis LeMay, who needed time to launch his strategic bombers in case of an attack on the Continental United States.

In 1956, when Lockheed won the contract to design, develop and build America's first military satellite, a young engineer named Joseph Knopow proposed, as part of the winning design, using a an infrared (IR) radiometer to detect hot exhaust gases of bombers and rockets. The project's objective was to put an IR sensor and telescope in a rotating turret into the nose of an Agena upper stage launch vehicle. The system was to launched by an Atlas-Agena rocket booster. The IR sensor was to be designed by Aerojet Corporation, and the overall satellite and system integration was to be accomplished by Lockheed. This system eventually became known as the Missile Detection Alarm System or MIDAS. MIDAS satellites were to be placed into 2000 miles polar orbits to detect missile launches from the Soviet Union. Unfortunately, MIDAS experienced problems from the beginning, the two worst being continuous budget cuts and requirements creep. The original mission of MIDAS in 1956 was strategic early warning, but by 1965, its missions included greater system reliability beyond several weeks operations, global coverage instead of just the Soviet Union, launch point determination, and real-time detection of nuclear detonations. MIDAS faced one major acquisition and three operational hurdles. The acquisition hurdle was how long should a program stay in the study and developmental stages before fielding it as an operational system, particularly when the system is a much needed but technologically challenging product.

The USAF desperately needed a warning system as advocated by General LeMay, but an IR sensor in space had never been tried, let alone used. The three major operational hurdles included detecting low radiance missiles such as solid rocket ICBMs besides large liquid ICBMs, discriminating rocket IR exhaust emissions from background emissions from clouds and reflections from the sun, and finally long-term system reliability. 1960 was a time when just getting a satellite into orbit was a minor miracle, let alone getting the systems to work for a long period of time. The program's earliest launches between 1960 to 1962 either didn't make it into orbit (MIDAS 1 and 6), or only lasted for a very short time without providing any useful or limited data (MIDAS 2, 3, 4 and 5). Again between 1960 and 1962, the Office of Secretary of Defense (OSD) and Secretary of the Air Force (SAF) directed three major reviews of the program to decide if it was going in the right direction or if this system was needed at all. But after each review, the operational Air Force forcefully backed the requirement for a space based early warning system. By 1962 MIDAS had become Air Force Program (AFP) 461. In 1963, the long years of work finally paid with two successful AFP 461 launches which demonstrated beyond a shadow of a doubt that early missile warning was indeed possible and obtainable. Finally in 1966, two our of three launches were highly successful and lasted over a year. The questionable reliability of the system had been resolved. This time, SAF would permit the USAF to start fielding an operational space based IR system.

In 1966, based on the successes of that year, the program was redirected again by OSD and SAF because of three factors. The first factor was the appearance of a new threat, the Fractional Orbital Bombardment System or FOBS that the Soviet Union had begun testing on, which could launch a nuclear attack against the US from the South Pole. The second factor was the addition of the nuclear detection mission as part of the new IR system. The VELA nuclear detection system was coming to the end of its operational life, and a new space platform was needed to continue this mission. The final factor was an idea proposed by two Aerojet engineers. The original MIDAS system had a spinning sensor inside the nose of a spacecraft at a medium polar orbit (2000 to 6000 miles). The two engineers, John Jamieson and Robert Richards, proposed using a spinning satellite at a geosynchronous orbit. At geosynchronous orbit, it would take only three satellites to provide total global coverage instead of the originally proposed eight to twelve satellites in polar orbit, and with a spinning satellite, the electronics needed for the system were greatly simplified. Also, the new system would be launched by the USAF's newest heavy lift booster, the Titan III-C. The new program, AFP 949, was initiated in August 1966, and the first launch occurred in November 1970. This first DSP satellite was the first military satellite to utilize a geosynchronous orbit to accomplish its mission.

This program eventually became know as the Defense Support Program or DSP. In 1971, the Overseas Ground Station (OGS), located in Woomera, Australia took over operational control of the satellite. In 1972, a Continental Ground Station (CGS), located at Buckley Air National Guard Base, near Denver, Colorado, joined the system. In 1972 and 1973, two additional satellites joined the constellation. During the 1970s, a total of eight DSP satellites were orbited each using 2000 short wave infrared (SWIR) detectors to accomplish their task. During this time period, DSP underwent three design changes including Phase I (Flights 1-4), Phase II (Flights 5-7), and Multi-Orbit Satellite/Product Improvement Modification (MOS/PIM) (Flight 8). Before DSP became operational, the US depended upon radar sites located across Canada and other sites to provide early warning to the National Command Authority. When DSP was first launched in 1970, it provided critical backup to these radar sites. By 1975, DSP was given was given co-equal status with the radar sites to provide early warning. By 1980, DSP had become so reliable, that the radar sites were abandoned. Space based infrared systems providing early missile warning had progressed and matured considerably from MIDAS to DSP. DSP had become the new space guardian overseeing and protecting our nation from any future strategic Pearl Harbors.

Nicholas M. Short, Sr. email: nmshort@ptd.net
Jim Rosalanka (jrosolanka@worldnet.att.net)