Pacific Command SBX-1

SBX-1 Genesis:
In January 2003, the United States government purchased a semi-submersible 50,000-ton seagoing platform from Moss Maritime, a Norwegian company specializing in special purpose offshore vessels and platforms, for use in the Missile Defense Agency’s (MDA’s) layered Ballistic Missile Defense System (BMDS).

MDA’s Ground-based Midcourse Defense Joint Program Office, a BMD component, oversaw platform modifications at the Keppel AMFELS shipyard in Brownsville, Texas; assembly and installation of the world’s largest X-band radar onto the platform at Kiewit Offshore Services in Ingleside, Texas; and additional modifications at Pearl Harbor Naval Shipyard in Honolulu, Hawaii.

The self-propelled vessel, in addition to the X-band radar, includes a bridge, control rooms, living quarters, workspaces, storage areas, a power generation area, and a helicopter landing pad. It also contains a command, control and communications system and an Inflight Interceptor Communication System Data Terminal. The platform maintains 60-days of supplies and fuel.

In July 2005, MDA officially named the vessel the “Sea-Based X-Band Radar-1,” or “SBX-1.” The SBX-1 underwent a wide range of sea trials and exercises in the Gulf of Mexico prior to beginning its journey around South America to its home port of Adak, Alaska. Moreover, the mobility of the SBX-1 allows its movement throughout ocean areas to support both missile defense advanced testing and defensive operations.

Design Overview:
As stated, the SBX-1 system is part of the Ground-Based Midcourse Defense (GMD) system being deployed by the MDA. Being sea-based allows the vessel to be moved to areas where it is needed for enhanced missile defense. Fixed radars provide coverage for a very limited area due to the curvature of the Earth. The primary mission of the SBX is the discrimination of actual enemy warheads from decoys, followed by precision tracking of the identified warheads.

The vessel has many small radomes for various communications tasks and a central, large dome that encloses and protects a phased-array, 1,800 tonne (4,000,000 pound) X band radar antenna. The small radomes are rigid, but the central dome is a non-rigid system where the cover is supported by positive air pressure. The amount of air pressure is variable depending on weather conditions.

AESA Radar:
The radar antenna itself is 4,130 sq ft. It has numerous solid-state transmit-receive modules mounted on an octagonal flat base which can move ±270 degrees in azimuth and 0 to 85 degrees elevation (although software currently limits the maximum physical elevation to 80 degrees). The maximum azimuth and elevation velocities are approximately 5-8 degrees per second. In addition to the physical motion of the base, the beam can be electronically steered off bore-sight.

There are over 22,000 modules installed on the base. Each module has one transmit-receive feed horn and one auxiliary receive feed horn for a second polarization, so there close to 45,000 feedhorns. The base is roughly 2/3 populated, with space for installation of additional modules. The current modules are concentrated towards the center, so as to minimize grating lobes. This configuration allows it to support the very-long-range target discrimination and tracking that GMD's midcourse segment requires. The array itself requires over a megawatt of power to operate.

This active electronically scanned array radar is derived from the radar used in the THAAD theater ballistic missile defense system, and is a part of the layered BMD program of the United States Missile Defense Agency . An important difference between SBX and the Aegis radar system used by the US NAvy is the use of X band radar. Aegis uses S band. For comparison, the Patriot land-based missile system uses the higher-frequency C band. The X band frequency is higher still, so its shorter wavelength enables finer resolution of tracked objects. The radar is designed and built by Raytheon Integrated Defense Systems for Boeing, the prime contractor on the project for MDA.

The radar has been described by the director of MDA as being able to track an object the size of a baseball over San Francisco in California from the Chesapeake Bay in Virginia, approximately 2,900 miles (4,700 km) away. The radar will guide land-based missiles from Alaska and California, as well as in-theatre assets.

CS-50 Vessel and Propulsion:
The CS-50 semi-submersible rig on which the radar is mounted was built as the "Moss Sirius" at the Vyborg Shipyard in Russia for Moss Maritime (now part of the Saipem offshore company). It was purchased for the Sea-based X-band Radar project by the Boeing company, outfitted with propulsion, power and living quarters at the AmFELS shipyard in Brownsville, Texas, and integrated with the radar at the Kiewit yard in Ingleside, Texas.

The thrusters which propel the vessel are electric and require substantial power. The maximum speed is 8-9 knots. To support this and the other electrical needs of the vessel, the SBX-1 has six 3.6-megawatt generators (12-cylinder Caterpillar diesels). The generators are in two compartments, one port and one starboard. The maximum power currently drawn is roughly 12 megawatts. There areplans to expand the number of generators to eight, four on each side, so that one entire compartment could be lost and the vessel would still continue to operate at full capability.

SBX-1 is home based at Adak Island, Alaska, part of the Aleutian Islands. From that location it can track missiles launched toward the US from both North Korea and China. Although her homeport is in Alaska, she will be tasked with moving throughout the Pacific Ocean to support her mission.

Key Facts/Features of SBX-1:

- The SBX-1 serves as the largest and most sophisticated phased array electro-mechanically steered X-band radar in the world. Steering electronically within its field of coverage and mechanically in azimuth and elevation allows the radar to track a full 360 degrees in azimuth and about 90 degrees in elevation from near the horizon to the zenith. As a result, the radar can track objects as they fly toward, over, and away from the vessel.

- Approximately 45,000 transmit/receive modules in the radar operate together to form the radar beam, which is capable of seeing an object the size of a baseball at a distance of 2,500 miles. Each module consists of the final transmit stage and initial receive stage from each antenna element. The radar also uses 69,632 multi-sectional circuits to transmit, receive, and amplify signals.

- The SBX-1, which is capable of traveling 9 knots under its own power, measures 240 feet wide, 390 feet long, and 280 feet high from its keel to the top of the radar dome (radome).

- Air pressure alone supports the radome that surrounds the radar. The radome weighs 18,000 pounds, stands more than 103 feet high, and measures 120 feet in diameter. Moreover, the high-tech synthetic fabric allows the radome to withstand winds in excess of 130 miles per hour.

- The SBX-1 crew includes approximately 86 officers, civilians, and contractor personnel to carry out its mission.

- In addition to the inherent stability of the vessel, the radar itself provides electronic stabilization of the radar beam to continue mission operations as the vessel responds to changing sea conditions.

- The marine diesel fuel capacity of the SBX-1 is 1.8 million gallons.

- As the principle midcourse sensor for the BMDS, the radar’s major functions are cued search, precision tracking, object discrimination, and providing a missile kill assessment. The In-flight Interceptor Communication System Data Terminal communicates instructions from the GMD Fire Control

Operational History:
The was 1st deployed in 2006. The ship has received upgrades and maintenance at Pearl Harbor, Hawaii several times since. This includes 170 days in 2006, 63 days in 2007, 63 days in 2008, 177 days in 2009, and 51 days in 2010.

When not at Hawaii, the SBX has been on operational deployments in the Pacific, including traveling to waters off Alaska. A $26 million, eight-point mooring chain system was completed for her in 2007 in Adak's Kuluk Bay.

On June 23, 2009, the SBX was moved to offshore Hawaii in response to a potential North Korean missile launch. Between 2009 and 2010, the vessel spent 396 continuous days at sea, which is a significant, long-term deployment for any military vessel.

On January 31, 2010, a terst intercept designated FTG-06 failed. The test was a simulation of a North Korean or Iranian missile launch ballistic missile launch. After analysis, it was determined that the test failure was based on t3wo issues. 1st, algorithms in the SBX radar software designed to filter out extraneous information from the target scene were unintentionally left disengaged and did not operate. 2nd, a mechanical failure in a thruster on the kill vehicle devleoped and the intercept could not occur in any case.

On December 15, 2010, after corrections and simulated tests, another test was conducted designated FTG-06a. In this test, the SBX-1 performed as expected and all of its algorithms operated without issue.

In May 2011, the SBX-1 entered Vigor Shipyard (formerly the Todd Pacific Shipyard) in Seattle for a $27 million upgrade and maintenance work by c Boeing. The work was completed in three months and in August 2011, SBX-1 departed Seattle for her next deployment.

In February 2012, the Missile Defense Agency requested only $9.7 million per year budget for 2013 through 2017. This was a reduced amount but would would allow the SBX to be maintained in a “limited test support” role, "while also retaining the ability to recall it to an active, operational status if and when it is needed.”

In April 2012, SBX-1 left Pearl Harbor to monitor North Korea's planned Unha-3 missile in the launch window of 12–16 April 2012. The vessel returned to Pearl Harbor on 21 May 2012. It redeployed to monitor the next North Korean launch attempt at the end of 2012.

In April 2013 SBX-1 was again deployed to monitor North Korea.