WASHINGTON – The U.S. Missile Defense Agency, which for years has failed to win funding for an operational constellation of missile tracking satellites, now envisions a partnership with the U.S. Air Force on a system that would also perform space surveillance, a top service priority, an MDA official said.

Richard Ritter, the MDA’s program executive for C4ISR — command, control, communications, computers, intelligence, surveillance and reconnaissance — also confirmed that the agency has awarded a contract to a satellite operator to host sensors that would help determine whether a missile has been successfully intercepted and destroyed. He declined to identify the operator — industry sources suspect it is Iridium Communications, which plans to begin launching a next-generation constellation of 72 low-orbiting satellites in 2016 — but said the MDA expects to spend about $100 million on the Spacebased Kill Assessment Project.

Ritter said the firm-fixed price contract was awarded on a sole-source basis and includes 20 to 22 hosted sensors.

Initial funding for the Spacebased Kill Assessment project was left over from the Precision Tracking Space System, a proposed constellation of missile tracking satellites that was cancelled as part of the MDA’s 2014 budget request to Congress. The Precision Tracking Space System was the MDA’s latest stab at a satellite constellation that would track missiles through all phases of flight, including — and most notably — after their propulsion systems have ceased firing.

Such a constellation would be used to cue the MDA’s other sensors as well as interceptors, but its likely multibillion-dollar price tag has kept it confined to the drawing boards. The MDA has, however, demonstrated the system’s potential worth using three experimental Space Tracking and Surveillance Satellites, one of them classified, all built by Northrop Grumman Aerospace of Redondo Beach, California.

The MDA is still in the midst of a congressionally directed study, known as an analysis of alternatives, to compare various missile tracking sensor architectures and help inform the agency’s future budget requests. The analysis, which agency officials expect to complete this spring, covers a full range of sensors based on land, at sea, in the air and in space, and is expected to give the agency a sense of how many satellites it needs.

Speaking July 28 here at a panel discussion hosted by the Missile Defense Advocacy Alliance, Ritter said “there is a desire” from several Defense Department mission areas to be part of a low Earth orbit constellation that would offer multiple capabilities, chiefly space surveillance.

Defense Department officials have placed a major emphasis on space situational awareness over the past year or two, citing what they see as emerging Russian and Chinese threats to satellites. Senior U.S. government officials have touted $5 billion to $7 billion in planned investment over the next five years — industry sources have put the figure closer to $8 billion — in what they characterize as “space protection” activities, most of them classified.

The MDA and Air Force already rely on many of the same assets for missile warning and tracking and space surveillance. These include ground-based radars originally developed for missile early warning, as well as the MDA’s experimental STSS satellites.

Ritter said one possibility for a possible multi-mission constellation would feature several variations of the same basic satellite design, each with different capabilities. He said the launch of such a constellation is probably 10 years away.