Space Fence

Space Fence. It is a second-generation space surveillance radar system operated by the United States Space Force to track orbital debris and active satellites in low Earth orbit and medium Earth orbit. Developed to replace the aging VHF-band system first established on Kwajalein Atoll, the new S-band radar provides significantly enhanced sensitivity and tracking capacity. Its primary mission is to maintain the space domain awareness required for the safety of space operations and national security.

Overview

The system is a critical component of the broader Space Surveillance Network managed by the United States Space Command. Located on Kwajalein Atoll in the Republic of the Marshall Islands, its primary sensor is a ground-based, digitally-steered phased array radar operating in the S band. This technology allows it to detect and catalog objects as small as a marble in size, vastly improving upon the capabilities of its predecessor. Data from the radar is fused with information from other sensors like the Space-Based Space Surveillance system and the Ground-Based Electro-Optical Deep Space Surveillance network to create a comprehensive picture of the space environment.

Development and history

The original concept, known as the Air Force Space Surveillance System, was a Cold War-era network operational from 1961 until its decommissioning in 2013. The push for a modern replacement was driven by the increasing congestion of low Earth orbit and a series of major fragmentation events, such as the 2007 Chinese anti-satellite missile test and the 2009 satellite collision between Iridium 33 and Kosmos 2251. In 2009, the United States Air Force awarded a development contract to Lockheed Martin to build the new system. After overcoming budgetary challenges and a site selection process that also considered Western Australia, construction began on Kwajalein Atoll in 2015, with the site achieving initial operational capability in March 2020 under the Space and Missile Systems Center.

Technical specifications

The core of the system is a large, fixed-face phased array radar comprising thousands of transmit/receive modules. Operating in the higher-frequency S band (approximately 2-4 GHz) provides greater precision and resolution compared to the old VHF system. It uses a powerful, digitally-formed beam that can be electronically steered to track multiple objects almost instantaneously across a wide field of view. The site's location near the equator provides optimal coverage of populated orbital regimes, and its design emphasizes adaptive signal processing to distinguish small objects from background noise. The entire facility is supported by extensive power conditioning and cooling systems to manage the significant energy demands of the radar.

Operational capabilities

Once fully operational, the radar is designed to maintain a catalog of over 200,000 objects, dramatically increasing the number of items tracked from the previous catalog of about 23,000. It can detect objects with a radar cross-section as small as 1 centimeter in low Earth orbit, which includes potentially hazardous debris from old rocket bodies and satellite constellation fragments. The system's high update rate and precision tracking data are vital for predicting conjunctions to protect assets like the International Space Station and critical national security satellites operated by the National Reconnaissance Office. This data is shared with international partners and commercial entities through organizations like the Combined Space Operations Center and the 18th Space Defense Squadron.

Significance and impact

The deployment of this advanced sensor represents a major leap forward for global space traffic management and the security of the space domain. It enhances the ability of the United States Space Force to provide timely warnings to satellite operators worldwide, helping to prevent catastrophic collisions that could generate debilitating fields of orbital debris. This capability is foundational for the safety of multi-billion dollar commercial ventures, such as those by SpaceX and OneWeb, and supports the enforcement of norms for responsible behavior in space as advocated by the United Nations Committee on the Peaceful Uses of Outer Space. Furthermore, its tracking data is essential for supporting complex operations like on-orbit servicing and active debris removal missions being developed by agencies like DARPA and commercial entities.

Category:United States Space Force Category:Space surveillance Category:Radar