Defense Support Program (DSP)

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The origins and evolution of the Defense Support Program (part 1)
Infrared for missile warning
by Dwayne A. Day
Monday, August 22, 2022

In January 2020, American forces in the Middle East were on high alert, expecting an attack from Iran in response to an American attack that killed a senior Iranian general. Intelligence information indicated that a missile attack was likely, and so the United States Space Force used its Space Based Infrared Satellites (SBIRS) to monitor Iran’s missile launch sites. Staring sensors on the satellites in geosynchronous and highly elliptical orbits were focused on the launch locations, and when they spotted the infrared signatures of missiles, they were able to precisely track them and predict their targets, providing that information to American forces in Iraq with enough warning time for them to take cover.

SBIRS is just the latest in a long line of American missile warning satellites. It has been in operation for over a decade, taking over most of the space-based warning mission from the earlier Defense Support Program (DSP) satellites. The last DSP satellite was launched in 2007, but the program is still listed among operational systems by the US Space Force. If any DSP satellites remain in operation, they are likely serving in secondary roles or backup reserve to SBIRS.

The origins of DSP
Early warning of potential attack on the United States was one of the primary concerns of the fledgling American military space program. Early efforts concentrated on low orbit shortwave infrared satellites under the name Midas, for Missile Defense Alarm System. Midas evolved into Program 461 and test flights were conducted from 1963 to 1966.
The ultimate nightmare for US generals was that a Soviet FOBS could be launched over the South Pole and strike the United States totally undetected, destroying command and control centers before a response could be made. But even a FOBS launched to the east or west could present a major problem, since it might go undetected by radar until as little as five minutes from impact.

But although the latter tests of Program 461 satellites were successful, there were still questions as to the cost-effectiveness of satellites versus ground-based radars for the early warning mission. Space-based systems offered two advantages. The first was the ability to increase warning time of a Soviet attack. The Ballistic Missile Early Warning System (BMEWS), consisting of radars located at Clear, Alaska; Thule, Greenland; and Fylingdales, Great Britain, could provide approximately 15 minutes warning time of a ballistic missile attack on the United States. They were backed up by a series of coastal radars intended to warn of submarine-launched ballistic missile (SLBM) attack. A satellite-based system could increase the ICBM warning time from 15 to as much as 27 minutes, as well as double the warning time for many SLBM launches.

The Space Review: The origins and evolution of the Defense Support Program (part 1)

 

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The Space Review: The origins and evolution of the Defense Support Program (part 2)

The origins and evolution of the Defense Support Program (part 2)
DSP gets an upgrade
by Dwayne A. Day
Tuesday, September 6, 2022

The first Defense Support Program (DSP) satellite was launched in 1971, and by June 30, 1973, the four barrel-shaped spinning DSP satellites in orbit had detected a total of 1,014 missile launches as their large infrared telescopes swept the face of the Earth every ten seconds.[1] They had proven quite successful in their mission and had relieved some of the tension that was always present during the Cold War by dramatically reducing the chances of a Soviet surprise attack. (See “The origins and evolution of the Defense Support Program (part 1): Infrared for missile warning”, The Space Review, August 22, 2022.)

Although the early satellites had performed better than expected, they had some weaknesses that concerned Air Force leadership. A major issue was that the satellites were not well hardened against radiation. X-rays produced by nuclear tests created power transients in the satellites, making their main sensors temporarily useless. There was a very real danger that a nuclear detonation in orbit could render the satellites incapable of detecting missile launches. Several minor glitches in subsystems required attention as well.