WASHINGTON — U.S. missile defense capabilities would stand to benefit from development and deployment of more forward-based sensors as well as a global constellation of missile tracking satellites, industry officials said.

During an Oct. 12 panel discussion here hosted by the George C. Marshall Institute, these officials said current missile defenses are limited by a lack of sensors able to track missiles from the early stages of flight. Such systems, operating in concert with existing sensors, would enable continuous or near continuous tracking of a missile during all phases of flight, improving the chances of a successful intercept, these officials said.

The U.S. Air Force operates satellites capable of detecting missile launches around the world, but detecting and early phase tracking are two different things. Typically, missile warheads are not continuously tracked until the latter stages of flight when they come within the range of ground-based cueing radars located near interceptor batteries.

“One of the concerns is that it’s not long before you’re overflown by the threat,” said F. Al Riley, director of strategy, strategic concepts and initiatives for Raytheon Integrated Defense Systems in Tewksbury, Mass. “I’d like to have a sensor looking ahead.”

But deploying forward-based sensors is easier said than done, the panelists agreed. Not only are they costly, but in the case of land-based radars they typically require host nation agreements, which have proved difficult to negotiate.

“Whether [forward-based sensors] will be useful is no question,” said David Zabalaoui, director of business development for Northrop Grumman Aerospace Systems in Redondo Beach, Calif. “Just how to implement it is.”

The panelists also agreed that money to develop any new capabilities is extremely difficult to come by in the current budget environment, particularly for longer-term projects such as advanced missile defense sensors.

The Missile Defense Agency (MDA) “has a huge dilemma,” said John Sandvig, director of advanced development for the airborne laser test bed program for Boeing Defense, Space and Security of St. Louis. “We need a system that can adapt to unknown situations today. It’s going to take 20 years or more to flush this system out. … But when the longer-term view is shorted, we never get investments to improve long-term capability.”

Among the projects the panelists said should be pushed forward is the Precision Tracking Space System (PTSS), a proposed constellation of satellites that would track missile bodies as they coast through space.

Northrop Grumman is among six companies working on the space-borne sensor program, and launch of the first two development satellites is planned for 2016.

Northrop Grumman built two experimental Space Tracking and Surveillance System satellites for the MDA. Those spacecraft recently demonstrated so-called cradle-to-grave tracking of a target missile.

Zabalaoui said it makes more sense in the long run to invest in a space-based tracking constellation than in ground-based sensors because the latter would have to be deployed in large numbers and at great expense to provide global coverage.

The MDA has for years been trying to secure funding from Congress for an operational constellation of missile tracking satellites, with little success to date. The cost of such a system would be in the billions of dollars.

The MDA requested $160 million for PTSS design and development work next year. The Senate defense appropriations bill for 2012 fully funds that request, while the House version of the legislation provides no funding. House and Senate appropriators are expected to decide a final funding figure for PTSS and other Pentagon programs during a conference to take place at an as-yet-undetermined date.