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Gray Star / COBRA GEMINI

Electronic Systems Center is developing a program that will result in what is believed to be the first dual-band, sea- and land-based radar system. The Cobra Gemini program will acquire three X- and S-band radar systems that can detect, acquire, track and collect both high-precision metric and signature data on targets of interest. CG is designed to be transportable and capable of operating anywhere in the world in either a land or sea-based mode. This program is included with other funding in Program Element 31315.

Properly deployed ship-based radars with ranges of about 2000 km can provide a forward-based radar missile defense interceptor commit function against many of the potential threats to the US. These radars can remain silent until cued by DSP or SBIRS-High. Because they would be difficult to target due to mobility and unknown location of ships, they would add robustness against defense suppression attacks, particularly before SBIRS-Low is available. Sea-based radars could be added to the NMD architecture to provide robustness against certain defense suppression attacks before SBIRS-Low is available, and in some scenarios, to provide an earlier interceptor commit. Two such radars could be procured, installed on existing ships, and integrated with NMD BM/C3 for a total cost of less than $0.5B. O&S costs for the ships would total about $0.03B/year.

The system, also known as STEEL TRAP, will use a two frequency dish-based radar that will serve a dual role. The primary mission of CG is to support the Central Measurement and Signatures Intelligence (MASINT) Office (CMO) requirement for ballistic missile data collection. CG will be capable of detecting, acquiring, tracking, and collecting both high precision metric and signature data on tactical ballistic missile launches, but it can also lend support to future military operations, since metric data can provide launch and impact point estimates as well as basic missile trajectory.

Although phased-array technology may provide better surveillance and track resolution, cost considerations dictated the use of a dish system in the Prototype.

Tracking is performed at S-band. The X-Band frequency, essential for signature data collection and for supporting the wide bandwidth imaging requirement, is not well-suited for initial target acquisition or tracking complexes which have significant spatial separation. At S-Band, the area of the beam is ten times greater than at X-Band and results in an excellent acquisition and tracking capability. X-band monopulse is not being considered due to cost and complications to feed and receiver design.

The maximum range window to be covered in bow-tie search mode is 1200 km. In the nominal mission scenario this window will extend from 300 km range to 1500 km range with 1 second dwell [1 second of noncoherent integration].

The original program concept called for one prototype system and two production radar systems. The first prototype system was designed and built by MIT/LL under contract to ESC, with the remaining two (2) systems to be built by industry via a competitive follow-on production contract. An option in the contract could fund up to 10 of the radar systems. Because of funding limitations, the original plan to have a follow-on production contract for two additional CG radar systems has been postponed indefinitely.

An acquisition team composed of Electronic Systems Center, MIT Lincoln Laboratory and the MITRE Corporation will develop and fabricate a prototype system. The MITRE Corporation will work closely with MIT/LL to accomplish technology transfer by capturing hardware and software information and code in industry-standard, commercially available electronic engineering environments to maximize the usefulness of the MIT/LL design to the industry follow-on system(s). The MIT/LL prototype contract commenced in Feb 96, and was a two year effort(followed by an extensive nine month testing period). The MIT/LL contract commenced in Feb 96, and will be a two year effort (followed by an extensive testing period). The major milestones are as follow: Feb 96, CG Development Effort Begins; Jul 97, MIT/LL moves radar to Westford, MA; Aug 97, MIT/LL starts testing at Westford, MA; Jan 98, Satellite Track Test at Westford, MA; Apr 98, Complete Ground-Based D/OT&E (Site TBD); Oct 98, Start Ship-Based D/OT&E; Jan 99, Ship-Based FOC.

After prototype development, a competitive production contract was to be awarded in 1998 to build two more systems and complete integration of a second U.S. Military Sealift Command modified oceanographic survey ship. The 224-foot-long T-AGOS ships were formerly used by the Navy in a sensor array mission. Testing of the ground-based prototype is expected to be complete by mid-1998 and aboard ship by early 1999. Total weight for the shipboard COBRA GEMINI system is approximately 50,000 kg.

The three radar systems in the initial contract were to each be sea- or shore-capable and air-transportable aboard U.S. military cargo planes. The system equipment is housed in environmentally controlled containers and can be mounted/dismounted from appropriately prepared and supported sea-going vessels. It can also be operated from appropriately prepared and supported land sites. The system is intended to be used to detect launches of 'rest of world' missiles in the Scud class. Cobra Gemini is not a replacement for Cobra Judy, ESC's other shipboard program. Cobra Judy looks for intercontinental ballistic missiles and Cobra Gemini will look for 'rest of world' missiles.

On 14 May 1999, Raytheon Support Services, Burlington, Mass., was awarded an $11,824,227 firm-fixed-price contract to provide for operation and maintenance from May 14, 1999, through May 13, 2000, of the Cobra Judy and Cobra Gemini radar systems deployed on the USNS Observation Island and the USNS Invincible (T-AGOS 10), respectively. There were four firms solicited and three proposals received. Expected contract completion date is May 13, 2000. Solicitation issue date was Oct. 20, 1998. Negotiation completion date was May 13, 1999. The 668th Logistics Squadron, Kelly AFB, Texas, is the contracting activity.


On 04 June 2002, it was announced that the Missile Defense Agency (MDA) intended to modify, on a sole source basis, Contract HQ0006-01-C-0001 with The Boeing Company, to develop a Sea-Based Test X-band Radar (XBR) capability in support of the Ground-Based Midcourse Defense (GMD) Program. This action will provide for the Sea-Based Test XBR capability design, development, acquisition of a sea-based platform, and modification of the platform and existing XBR to meet design requirements, integration and operational check-out, and radar test operations. Currently, Boeing is providing development of initial components of the GMD system (interceptor, XBR, and upgrades to the Early Warning Radars) under this contract. A sea-based platform for the Test XBR is required to support the expanded test operations of the GMD component of the Ballistic Missile Defense System Test Bed. The effort necessary to satisfy this Sea-Based Test XBR capability is highly specialized and tightly interwoven with the on-going GMD development efforts being provided by Boeing. No other source can meet this requirement without the intimate knowledge of, and the ability to provide the currently planned XBR element for installation on the sea-based platform and integration into the GMD system under this contract.

In 2002, Diversified Technologies, Inc. [DTI] won contracts to upgrade the X-band radar transmitters in both the Cobra Judy system on the USNS Observation Island, and the Gray Star system, located onboard the smaller USNS Invincible. A 45 kV,50 A solid state opening switch and fault sensing electronics replaced the vacuum tube crowbar that protected the X-band radar's TWT. Its sub-microsecond response means that fewer pulses are missed in case of an arc.The new system offers faster fault isolation, reduces fault energy delivered to the TWT,and reduces the size of fault currents and mechanical forces by orders of magnitude. In addition,two new DTI 150 kW switching power supplies replaced the original DC power supplies. These provide higher regulation and full redundancy for the transmitter system.




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