It was a big relief to U.S. defense officials in May when the first geosynchronous satellite in the Space Based Infrared System (SBIRS) successfully reached orbit. The new spacecraft is equipped with sensors that will provide the first indication of hostile missile launches, nuclear explosions and other heat-generating events around the globe relevant to national security.

Such information is essential to nuclear deterrence, which as currently practiced requires the nation’s strategic arsenal to be capable of surviving an attack and then retaliating in a controlled and proportionate manner. If news of enemy missile launches is not received quickly, the ability of U.S. forces to respond effectively might be so uncertain as to impair the entire structure of deterrence.

There isn’t much doubt that the SBIRS constellation will be a big improvement over existing Defense Support Program satellites. Each of the four geosynchronous satellites positioned about 36,000 kilometers above the equator will carry a scanning sensor with three times the sensitivity and twice the revisit rate of legacy sensors, plus a staring sensor that can provide persistent, higher-resolution coverage of specific areas (like Iran or North Korea).

The sensitivity and timeliness of information generated by the new satellites will also enable the SBIRS constellation to provide valuable reconnaissance for the nation’s ballistic missile defense system, conventional warfighters and intelligence analysts. But the core mission, the one that matters most, is assuring sufficient warning of hostile missile launches so that the nation’s nuclear arsenal can credibly deter aggression.

What many observers don’t grasp is how tenuous the existing missile warning system has become.

The first and most vital line of defense in that system since 1970 has been the legacy satellites that SBIRS will replace. Prime contractor Northrop Grumman has introduced numerous upgrades to the Defense Support Program satellites that have improved their reliability, sensitivity and survivability. However, a review of the program’s launch history indicates that the Air Force has managed to successfully launch only one of the satellites in the last 10 years — which is very worrisome when you consider that the nominal design life for the latest versions of Defense Support Program satellites is only five years. Fortunately, the satellites typically exceed their design life by 250 percent, and some have lasted even longer. But there’s a reason engineers specify conservative design lives, so the fact that the last successful launch of a legacy satellite occurred in 2004 means that America’s missile warning network is living on borrowed time.

Under the original SBIRS development plan, there was little danger of a gap in missile warning. The new spacecraft were supposed to begin reaching orbit in 2002, providing plenty of time to transition from the legacy constellation to the new one. But a variety of hardware and software problems delayed the program by many years, and then in 2008 the last (and most recently launched) Defense Support Program spacecraft mysteriously failed in orbit.

It was the unforeseen combination of SBIRS delays and a legacy satellite failure that got policymakers scrambling to identify options for filling a potential gap in missile warning. What they learned to their dismay is that there weren’t any viable alternatives to stretching out the performance of the Defense Support Program and straining to get SBIRS into orbit as soon as possible.

There are a number of possibilities for squeezing more life out of the Defense Support Program satellites, from reducing the fuel margins required for boosting them into retirement orbits to working around the failure of specific components in an architecture designed for redundancy. But at this point some of the satellites in use must be “single string” spacecraft, meaning there are no backups for key functions, because the most recent Defense Support Program satellites still believed to be functioning were launched in 2000, 2001 and 2004. That’s a long time to be operating continuously in space without any repairs.

The launch of SBIRS sensors on two National Reconnaissance Office (NRO) satellites in highly elliptical polar orbits beginning in 2006 has somewhat diminished the danger while bolstering confidence in the sensors to be carried on the more capable geosynchronous birds. But the sensors hosted by NRO can’t provide the coverage afforded by near-circular equatorial orbits at geosynchronous distances, so there’s no alternative to fielding the full SBIRS architecture.

Policymakers appear to believe that the legacy constellation will be viable through 2013, after which SBIRS will have to assume most of the missile warning mission. Thus, a lot is riding on the success of the GEO-1 satellite that reached orbit in May. With solar panels and antennas deployed, operators are testing the twin sensors and other on-board equipment to make sure they meet performance specifications.

SBIRS has been an uncommonly controversial program that began during a period of turmoil in space acquisition and was saddled with more requirements than any satellite should have to meet (three times too many, the Defense Science Board said in 2003). But the most capable part of the system has now reached orbit with all of its “key performance parameters” intact, which is a major achievement for prime contractor Lockheed Martin and payload integrator Northrop Grumman.

It is also a big victory for the U.S. Air Force, which stuck with the SBIRS architecture despite years of criticism. Its leaders understood the urgency of replacing legacy missile warning satellites before they failed. However, it will still be some time before the constellation is fully deployed, so the danger has not passed.

The bottom line on nuclear deterrence is that it isn’t likely to work unless U.S. leaders have reliable information about what other nuclear powers are doing, and right now SBIRS is the only solution that can meet that need in a timely fashion.


Loren Thompson is chief operating officer of the Lexington Institute.