20th Space Surveillance Squadron


The 20th Space Surveillance Squadron (20 SPSS), Site C‐6, Eglin Air Force Base (AFB), Fla., is a multiplatform operational unit. It maintains and operates the AN/FPS‐85 Eglin Phased Array Radar and operates the AN‐FSY‐3 Space Fence Phased Array Radar, located on Kwajalein Atoll in the Republic of the Marshall Islands. Combined, the two radars track more than 26,000 Near‐Earth and Deep‐Space objects. The 20 SPSS is a geographically separated unit (GSU) of Delta 2, Peterson Space Force Base, Colorado.


Execute multiplatform, tactical space domain characterization and responsiveness to achieve Space Delta 2 and USSPACECOM warfighting intent.


The 20 SPSS C‐6 operates and maintains the AN/FPS‐85 Phased Array Radar and operates the AN/FYS‐3 Phased Array Radar. These phased array radars are dedicated to tracking more than 26,000 near‐earth and deep‐space objects. The radars provide actionable space domain awareness for USSPACECOM's space surveillance mission area. It is part of the global Space Surveillance Network (SSN) and are the only two phased array radars dedicated to space domain awareness (SDA). They collect more than 63 million observations of satellites per year, accounting for 30 percent of the SSN's total workload. The unique aspect of this kind of radar is the phased array antenna technology. Unlike a mechanical radar, which must be physically aimed at an object in space to track and observe it, the phased array antenna is steered electronically by controlling the timing, or phase, of incoming and outgoing signals. This increases capabilities and decreases response time which allows near simultaneous tracking of multiple targets throughout the system's area of coverage.

The AN/FPS‐85 can detect, track and identify up to 200 satellites simultaneously. The maximum beam deflection is 60° on either side of the antenna center line which provides 120° azimuth of azimuth coverage. The antenna is inclined +45° for scan coverage of +3° to +105° elevation. Generating a combined output of 32 megawatts. The radar can track an object the size of a basketball at a range of more than 35,000 km.

The AN/FSY‐3 can detect, track and identify up to 500 satellites simultaneously. It is the dedicated southern hemisphere asset, capable of low inclination tracking. The unique structural design allows for 360° of azimuth coverage. The antenna coverage of +20° to +90° elevation. The radar can track an object the size of a beachball at a range of more than 36,000 km.


20 SPSS is located on Site C‐6, which is part of Eglin Air Force Base’s vast range complex. Additionally, it is located on the Gulf Coast in Florida's northwest panhandle and is located approximately 2 miles north of Highway 20 near Freeport, Florida. The Space Fence radar is at 20th SPSS Operating Location Alpha on Kwajalein Atoll in the Republic of the Marshall Islands located 2,100 nautical miles from Honolulu, Hawaii.


Construction of the AN/FPS‐85 radar began in October 1962 and testing was scheduled for May 1965; however, four months prior to completion, the building and all equipment were destroyed in a catastrophic fire caused by arcing electrical equipment. Construction of the new facility began in March of 1965. The Air Force took ownership of the site in September 1968 with the 20th Surveillance Squadron, or 20th SURS, as the primary operator. Space operations began in February 1969. Initially designed to track satellites, new software installed in 1975 enabled the unit to track submarine launched ballistic missiles, or SLBMs. This became the unit's primary mission, while space surveillance became secondary. From 1971 to 1984 the 20 SURS served as the Alternate Space Surveillance Center, providing computational support to the Space Surveillance Center at Cheyenne Mountain AS, Colorado.

If the need arose, the squadron could assume command and control of worldwide SSN. In 1979, the 20 SURS was renamed the 20th Missile Warning Squadron, or 20th MWS, and four years later the squadron was transferred to Air Force Space Command (AFSPC). During this time, the AN/FPS‐85 was the proving ground for development of phased array radars designed specifically for early warning of SLBM attacks.

These PAVE Phased Array Warning System (PAWS) radars assumed missile warning responsibilities from the 20th MWS and in 1987, the unit returned to its original mission of space surveillance with a corresponding name change to the 20th Space Surveillance Squadron.

In February 2003, the unit was again re‐designated, this time as the 20th Space Control Squadron, or 20 SPCS.

In April 2016, three GEO Deep Space Sensors (GEODSS) detachments were assigned under the 20 SPCS making this squadron the Department of Defense’s (DoD) premiere space surveillance unit, responsible for 45% of all Deep Space object observations.

In late 2020, 20 SPCS brought online the space surveillance radar site, Space Fence, as a fourth detachment, which helped in tracking commercial and military satellites, depleted rocket boosters, as well as space debris primarily across the low earth orbit.

In early 2022, operations of the space fence radar were transferred from Redstone Arsenal to Eglin Site C‐6, eliminating the fourth detachment. Additionally, the three GEODSS detachments were reassigned to the 15 SPSS in May 2022. On March 25, 2022, the 20 SPCS was renamed the 20th Space Surveillance Squadron. The 20 SPSS is now a dual‐platform operations center with plans to onboard three new Deep‐Space Advanced Radar Capability (DARC) radars in the new future.

(CAO December 2023)