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SATCOM Availability Analyst Keeps Ships Well Connected on the High Seas June 2005
The Baltic Sea, June 2003: The USS Vella Gulf, a modern Ticonderoga-class cruiser, has just completed several days of joint training with a flotilla of NATO vessels. As the sleek 567-foot ship heels over, changing course to head for a picturesque Baltic port, the sailors prepare for liberty ashore. But the Electronics Maintenance Officer (EMO) isn't thinking about rest and relaxation. He can't see the forest of antennas on the decks above him, but he knows they are all pointing practically at the horizon. At these high northern latitudes, the communications satellites on which the Vella Gulf depends for everything from critical command and control information to quality-of-life services, such as email and TV broadcasts, hover just above the horizon. Some antennas continue to track as the ship levels again, settling into its new course, but other antennas now can no longer see their satellites, as their view is now blocked by other antennas, masts, and deckhouses. In the era of network-centric warfare, uninterrupted communications is crucial. "The consequences of SATCOM [satellite communications] blockage are ever more severe," says Gerald Fitzgerald, a principal information systems engineer with MITRE's Center for Integrated Intelligence Systems (CIIS). "A lot of the day-to-day command and control of the ship is now carried out by [the Department of Defense's Secret-level Command and Control data network] SIPRNet, email, and chat. When any of the high-bandwidth systems that carry SIPRNet to a ship are interrupted, the result can be chaos. The more the services rely on SATCOM traffic, the more serious the impacts are when, even for a few moments, the links are broken." A new software application known as SATCOM Availability Analyst (SA2) is helping ship commanders minimize the chances of that happening. With assistance from the Space and Naval Warfare Systems Command (SPAWAR) Systems Center in San Diego, California, MITRE developed SA2 for the Navy's Communications Program Office, to add a quantitative, analytic tool to the Navy's topside design process, and to help provide situational awareness for shipboard satellite communication terminal operators. Calculating Geometric Possibilities SA2 provides the SATCOM operator with a visual display showing where satellites are located relative to physical shipboard structures such as masts, cranes, deckhouses, and other shipboard antenna systems. The visibility of assigned communications satellites is determined by using blockage profiles for individual antennas in conjunction with real-time navigation and altitude data to continuously calculate unobstructed pointing angles to the satellites. Computer models summarizing blockage, ship motion, terrain masking, and satellite positions are combined to calculate when particular satellites are accessible. SA2 makes it possible for SATCOM operators and ship commanders to ensure satellite access wherever it is geometrically possible. By altering the ship's course a few degrees, they can often keep signals from being blocked. SA2 also aids in the planning of long voyages, where the goal is to keep the ship assigned to satellites with which it’s easy to maintain line of sight. Ship commanders can plan "cutovers" from one satellite to another in advance, taking into account not just how high the satellites appear in the sky (the traditional metric for choosing assignments), but also the exact location of interfering structures around their antennas. Where ships' missions permit, they can also plan courses that are most favorable for satellite reception. That's a big help for Navy and Coast Guard SATCOM operators, who traditionally have had to rely on their own memory for optimizing satellite access assignments and heading recommendations. "What you have now is a dynamic where you can plan," says Chief Warrant Officer Hector Castro, project officer for prototype testing with the U.S. Coast Guard's Maintenance and Logistics Command, Atlantic (MLCLANT) in Norfolk, Virginia. "If your mission takes you somewhere where you're not going to get communications, you can plan as such, and you can let somebody know. But if there is a way that you can accommodate communications and declare heading at that time, then you'll be able to do so. I think the important thing is awareness, and knowing ahead of time what systems will be available." More Antennas, Less Space
The only spot on a ship with an unbroken view of the sky is the top of the highest mast, but that location is usually reserved for aircraft navigation aids. The Navy topside design process tries to arrange antenna locations so that the most valuable antennas can see as much of the sky as possible. To get a more or less unbroken view of the sky, critical systems often employ two antennas in different places on the ship, but this only multiplies the problems for all the other systems, which now have even more equipment in their way. And to make matters worse, the Navy's plans to decrease the radar cross section of its ships adds pressures to keep the number of antennas to a minimum and complicates their placement. Determining the best locations for new antennas while minimizing the impact to existing systems was the challenge that originally inspired Fitzgerald to develop SA2. He already had a relevant model framework: a tool he built in 1998 for the Navy's Global Broadcast Service (GBS) office that helped determine where and when submarines could and couldn't access GBS. Although the issue was adverse weather conditions rather than satellite blockage, Fitzgerald thought the guiding principle behind the GBS tool—combining detailed models of SATCOM terminals with global geospatial models—could help both the Naval Sea Systems Command (which builds new ships) and SPAWAR (which, among other missions, installs new antennas) coordinate their plans to ensure the best satellite access possible.
Fitzgerald built a prototype of SA2 that was tested aboard the USS Coronado, the Third Fleet command ship, in July 2001. The initial test produced 13 requests for installation of the device. Meanwhile, Fitzgerald's SA2 concept came to the attention of James Hodge, a principal systems engineer at the MITRE site office in Colorado Springs, Colo. Hodge believed that SA2, with some modifications, could be used in a classified project he was leading. In early 2003, Fitzgerald and Hodge went to the Persian Gulf for a six-month deployment of SA2. The process of designing, developing, testing, and integrating SA2 took less than four months, culminating in its use in support of Operation Iraqi Freedom. "I decided to bring Gerry along with us on our deployment so that he could—in first person—understand exactly what we needed modified to make SA2 more operationally suitable for our military customer," says Hodge. "SA2 was brought to the level it was by having the developer right alongside the military user. And the results were phenomenal."
Meanwhile, Fitzgerald had co-authored a paper on SA2, published in the SPAWAR Systems Center 2001 Biennial Review, which discussed the problem of SATCOM blockage aboard ships and submarines. His paper caught the attention of the Coast Guard's MLCLANT, which was conducting its own research on SATCOM blockage. Representatives of the MLCLANT contacted MITRE to learn more. Within three months, the Coast Guard decided to give SA2 to a shipboard operator for a trial on the USCGC Confidence. A more formal system prototype was later tested on several other cutters. For Coast Guard ships, which tend to have single-antenna systems and much smaller aggregate bandwidth than those of the Navy, the consequences of SATCOM blockage can be even more severe. "We didn't have anything more than the knowledge of the operator that, at certain headings, his antenna was going to be blocked," says Castro. "There was no actual system to manage any of the blockages because it was understood that the phenomenon was there. There were not any tools that were developed to actually help manage this SATCOM blockage." "It's a very dynamic problem," says Fitzgerald. "But it's not rocket science. It's not vastly complicated in any of its pieces. What we succeeded in doing is tying these components all together—models of the antenna blockage; navigation handlers so we know where the ship is, which way it's heading, and how it's pitching and rolling; models of satellite motion; and also models for terrain blockage when ships are close to shore. This can make a huge difference in the number of hours per day in which ships have connectivity." "Our experience with MITRE was really good," says Castro. "The flexibility of Gerry's software engineering skills actually allows us to basically try this application on every conceivable flavor that we can come up with, and he's been great at accommodating the needs of the Coast Guard." SA2 continues to gain acceptance in both the Navy and the Coast Guard. The Coast Guard is using SA2 on three cutters and is considering deploying it on 40 of its largest cutters by the end of this year. On the Navy side, the story of the EMO aboard the Vella Gulf made its way to Carrier Strike Group Two (CSG2). In the spring of 2004, CSG2 contacted the Navy's Communications Program Office for help preparing the USS San Jacinto for the June 2004 Baltic exercise. MITRE installed SA2 aboard the San Jacinto, and the tool found immediate use diagnosing outages, planning outage-free courses, and even in determining which sides of piers would be best for mooring during in-port periods. It is still in use aboard the San Jacinto, and an enhanced version, which predicts both superstructure blockage and also electromagnetic interference problems between ship's systems, will be deployed on the San Jacinto and a helicopter assault carrier this summer. Plans are in process to incorporate SA2 into the Navy's standard shipboard communications and radar planning software early in 2006. Anticipating vast increases in the time their ships have connectivity, other Navy and Coast Guard commanders are looking into SA2. Among those recently expressing interest: the commanders of the USS Vella Gulf. —by W. Russell Woolard Related Information Websites |
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