By | May 8, 2006 | Uncategorized

The Missile Defense Agency (MDA) is pursuing several novel all- weather sensors that hold the promise of dramatically reducing the time it takes to detect the launch of a ballistic missile and classify it, two U.S. defense officials told Defense Daily earlier this week. "We would like to buy an additional 20 to 30 seconds," said one of these officials in describing the faster detection times that the MDA would like to achieve with these sensors compared to current U.S. overhead missile warning satellites like the Defense Support Program constellation.
Decreasing the time that it takes to detect ballistic missile launches, even if only by seconds, is crucial since every tick of the clock is precious when trying to shoot a missile down. This is especially important since some missiles are only in the air for several minutes between launch and impact.
"The sooner you know something about the target–where it is, what it is and where it’s coming from–the better you are in terms of the engagement," the same defense official said. Indeed reducing detection time, said the official, "equates to an increased battlespace." This would improve the chances of knocking down the missile in its boost phase and give the defense more shots overall at the missile throughout its entire trajectory, thereby increasing the chances of destroying it. These sensor technologies, of which there are currently three, are being developed under the MDA’s Early Launch Detection and Tracking (ELDT) initiative in cooperation with the Air Force Research Laboratory. Although they are early in their development, there is the potential that they could be fielded within the next decade as part of follow-on upgrades to existing U.S. sensor systems if they prove their worth in experiments over the next several years, the two officials said.
"We expect in the ’09 timeframe to have been able to carry the demonstration of these concepts to a point that then a decision could be made," said the one official during an interview on May 3. "There is no plan to build a separate constellation."
Two of the sensors are passive electro-optical devices envisioned for satellite constellations with global coverage, although they could be used on high-altitude airships or unmanned aerial vehicles, this same official said. The third is an active radar concept leveraging over-the-horizon (OTH) radar technologies that is eyed for ground-based roles in theaters of operation.
In the case of the latter, the MDA is exploring the possibility of conducting joint experiments with Australia, since the U.S. ally has extensive experience in operating OTH radar, the two officials said. This work would build upon the memorandum of understanding on ballistic missile defense cooperation that Australia signed with the United States in July 2004 (Defense Daily, June 22, 2004).
The MDA is currently involved in laboratory work, ground and airborne data-collection activities and some field experiments to advance the three sensors.
"There is still a lot of phenomenology that we are trying to understand," said the one official.
The first electro-optical concept is a narrowband sensor that is designed to discern missile plumes through clouds.
"We don’t look through [the clouds]," explained the one official. "We basically would be able to detect the signal on the top of any intervening cloud layer."
The challenge that engineers are trying to overcome with this sensor, the same official explained, is to be able to detect the plume’s signals despite the background "clutter" that the sensor sees. "Sunlit clouds are the big problem," the official said.
The second passive sensor is a hypertemporal infrared system that is designed to measure "how the plume signature varies as a function of time" in order to track the missile this official said.
The radar concept is a multistatic, high-frequency (HF) system. Program engineers are not building a new radar per se, but rather investigating whether existing HF transmitters and receivers have the range to detect the missiles to meet the mission, and, if so, how to fuse and link all of the data from the multistatic components, the same official said.
"Clearly the data fusion and datalinks are the key issues there," this official said.
The MDA is currently negotiating an agreement with the Australian Department of Defence to conduct joint experimentation of this concept. Australia operates the Jindalee OTH radar.
"We have been talking with the Australians and we would hope that an experiment might be included using their over-the-horizon radar to further this technology," stated the second defense official. The agency hopes to finalize the agreement before the end of this calendar year, this official said..
The MDA began the ELDT program in FY ’02 as part of its portfolio of advanced next-generation technologies. By the end of this fiscal year it will have spent $16 million on the ELDT initiative. It has earmarked an additional $19 million for it through FY ’10, according to the two defense officials.
The first official said the agency purposely chose to pursue three distinctly different types of sensors under the ELDT program. "The idea was that, if they all proved out, then you would be able to, if you chose to, implement a system that had robustness due to the different technologies," this official said.
Currently the ELDT technologies are not tied to any specific sensor acquisition program. Nor is the timeline for the potential insertion of them tied to any one of the MDA’s biennial fielding blocks of the Ballistic Missile Defense System, the official noted.
"Until we have shown, based on the data collections, what performance we expect to achieve, we are hesitant to be tied to any particular block," said this same official.
However, one potential candidate for the two passive sensors is the MDA’s Space Tracking and Surveillance System, which is being built by a team led by Northrop Grumman [NOC].

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