Air Force Space Surveillance System

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Part of the master transmitter antenna at Lake Kickapoo, Texas c.2001.

The Air Force Space Surveillance System, colloquially known as the Space Fence, was a U.S. government multistatic radar system built to detect orbital objects passing over America. It is a component of the US space surveillance network, and according to the US Navy was able to detect basketball sized (29.5 inches (75 cm)) objects at heights up to 30,000 km (15,000 nautical miles.)[1]

The system ceased operation in September 2013.

The operation's headquarters were at Dahlgren, Virginia, and radar stations were spread out across the continental United States at roughly the level of the 33rd parallel north.

Description[edit]

There were three transmitter sites in the system:[2]

The master transmitter at Lake Kickapoo was said to be the most powerful continuous wave (CW) station in the world, at 768 kW radiated power on 216.97927 MHz.

When the system became operational in 1961, the original frequency was 108.50 MHz (just above the FM broadcast band). In 1965 the "Fence" system was modernized with the operating frequency doubled to 216.98 MHz (just above Channel 13 in the VHF TV broadcast band) to obtain higher resolution and to locate smaller objects. This frequency was used until the Fence was decommissioned in 2013. Fill-in transmitter sites at Gila River and Jordan Lake used offset frequencies listed above from the early 1990s to 2013 to help better detect which transmitter "illuminated" an object in space, as multiple transmitters could have illuminated the same object at the same time. Overhead imagery (see coordinates given above) of the Gila River and Jordan Lake sites shows the original design at the lower frequency.

There were six receiving stations:[2]

The following receiving stations were placed in cold storage in April 2013:

The receiving stations at Elephant Butte and Hawkinsville were considered to be "High Altitude" stations with longer and more complex antenna systems that are designed to see targets at higher altitudes than the other four receiving stations.

History[edit]

Author Curtis Peebles notes that the original Space Fence or Space Surveillance System began operations in 1959.[3] The system predated the formation of NORAD and was known as the U.S. Navy Space Surveillance System or SPASUR but also as NAVSPASUR (Naval Space Surveillance System).[4] From 1960 until the early 1990s the system was used in conjunction with a network of with Baker-Nunn cameras that could see "an object the size of a basketball at 25,000 miles."[3][5] Although formerly operated by the U.S. Navy for NORAD from 1961 until October 2004, command passed to the Air Force 20th Space Control Squadron on October 1, 2004.[1]

In 2009, the operations and maintenance contract for the day-to-day management and operation of the Fence was awarded to Five Rivers Services, LLC, based out of Colorado Springs, Colorado. On September 30, 2011, Five Rivers Services was awarded a $7,022,503 firm fixed price with cost reimbursable line items contract modification to manage, operate, maintain, and logistically support the nine Air Force Space Surveillance System field stations, presumably for Fiscal Year 2012.[6]

Plans for system upgrade: 2009-2012[edit]

The 850th Electronic Systems Group, Electronic Systems Center awarded 3 $30-million contracts to Lockheed Martin, Northrop Grumman and Raytheon on 11 June 2009.[7]

The Space Fence is envisaged to be a system of two or three S-band ground-based radars designed to perform uncued detection, tracking and accurate measurement of orbiting space objects. The Space Fence is intended to replace the Air Force Space Surveillance System, or VHF Fence, that was transferred from the Navy to the Air Force in 2004. The shorter wavelength of the S-band Space Fence allows for detection of much smaller satellites and debris.[7]

The February 10, 2009, collision of a U.S. Iridium communications satellite (Iridium 33) and a Russian Cosmos 2251 communications satellite, which added hundreds more pieces of debris to the atmosphere, highlighted the need for more precise tracking of space objects.[8]

Data collected from the Space Fence's sensors would potentially feed into the Joint Space Operations Center Mission System, which is used to track objects orbiting the Earth, monitor space weather and assess foreign launches. Used by operators at the 614th Air and Space Operations Center at Vandenberg Air Force Base, Calif., the 614 AOC's 24-hour-a-day, seven-day-a-week support provides vigilance of global and theater operations and equips the Joint Functional Component Command for space operations with the tools to conduct command and control of space forces.[7]

Plans to award the final contract have been stalled by U.S. budget sequestration in early 2013[9] and the AFSSS system is likely to be discontinued in October 2013 due to budget cuts.[10]

In 2014 Lockheed Martin won a contract to build a new S band space fence system.[11]

2013 Shutdown[edit]

On August 1, 2013, General William L. Shelton, commander of Air Force Space Command, directed that the Air Force Space Surveillance System be closed and all sites vacated effective October first.[12] The AFSSS was turned off September first.[13] "It appears they pulled the plug at 00:00 UT (6 am Local MDT) on September 1st," reports engineer Stan Nelson, who was monitoring the radar using an antenna in Roswell, New Mexico. The radar's final echoes came from a Russian satellite and a sporadic meteor."[14]

(Published August 13, 2013)

PETERSON AIR FORCE BASE, Colo. (AFNS) -- Due to resource constraints caused by sequestration, Air Force Space Command officials have directed the 21st Space Wing to prepare to discontinue operations at the Air Force Space Surveillance System by Oct. 1. Final decisions on all fiscal 2014 budget issues will be made over the next few weeks. By discontinuing operations, the AFSSS would not be maintained in operational status; however, equipment will not be removed until a final disposition determination is made. The AFSSS sites are operated under contract and the 21st SW has notified the vendor, Five Rivers Services in Colorado Springs, Colo., that it most likely will not exercise the next contract option beginning Oct. 1. By de-activating the AFSSS by Oct. 1, AFSPC would see a cost savings of approximately $14 million per year, beginning in fiscal 2014. AFSPC officials have devised modified operating modes for the Perimeter Acquisition Radar Characterization System at Cavalier Air Force Station, N.D., and for the space surveillance radar at Eglin Air Force Base, Fla., which allows the discontinuation of AFSSS operations while still maintaining solid space situational awareness. The AFSSS is a series of three transmitters and six receivers along the 33rd parallel stretching across the southern United States.The three transmitter sites are located at Jordan Lake, Ala.; Lake Kickapoo, Texas; and Gila River, Ariz. The six receivers are located at Tattnall, Ga.; Hawkinsville, Ga.; Silver Lake, Miss.; Red River, Ark.; Elephant Butte, N.M.; and San Diego, Calif. The two receiver sites at Tattnall and Silver Lake were deactivated in April of this year.The AFSSS, which has been operational since 1961, is just one part of AFSPC’s global Space Surveillance Network. The system is designed to transmit a “fence” of radar energy vertically into space to detect all objects intersecting that fence. The operational advantage of the AFSSS is its ability to detect objects in an un-cued fashion, rather than tracking objects based on previous information. The disadvantage is the inherent inaccuracy of the data, based on its dated design. The new operating modes at Cavalier AFS and Eglin AFB will provide more accuracy than the AFSSS and still collect un-cued observations.The AFSSS is typically referred to as the “space fence,” which has caused confusion with the new space fence being developed for the future. “The AFSSS is much less capable than the space fence radar planned for Kwajalein Island in the Republic of the Marshall Islands,” said General William L. Shelton, the commander of Air Force Space Command. “In fact, it’s apples and oranges in trying to compare the two systems.” Unlike the AFSSS, the new space fence will provide very precise positional data on orbiting objects and will be the most accurate radar in the Space Surveillance Network. It will provide enhanced space surveillance capabilities to detect and track orbiting objects such as commercial and military satellites, depleted space boosters and space debris. The new space fence will have much greater sensitivity, allowing it to detect, track and measure an object the size of a softball orbiting more than 1,200 miles in space. Because it is also an un-cued tracking system, it will provide evidence of satellite break-ups, collisions, or unexpected maneuvers of satellites. “When combined with the new Joint Space Operations Center’s high-performance computing environment, the new fence will truly represent a quantum leap forward in space situational awareness for the nation,” Shelton said. (Courtesy of Air Force Space Command Public Affairs)

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