In the years since the Cold War ended, the U.S. military has become heavily dependent upon satellite communications to maintain its global connectivity. Without such links, it would be difficult for the military to operate in a coordinated fashion or exchange information critical to situational awareness.
Defense experts have repeatedly warned that the availability of space-based communications could be compromised in future conflicts by the fact that 80-90% of all military traffic is transmitted on vulnerable commercial satcom channels. However, there is a related problem that far fewer military observers have noticed: only about 1% of defense communications today are protected against even the most modest jamming threats.
Jamming means overloading key frequencies with so much electronic "noise" that communications cannot get through to intended destinations. It's a simple process in the case of unprotected satellite links, because signals are relatively weak after traveling 22,000 miles from transponders in geosynchronous orbit -- the orbit that communications satellites must maintain in order to serve as "stationary" links above particular points on the Earth's surface (they aren't really stationary, but they appear to be because their rotation matches that of the Earth).
If the satellites were any closer to Earth they would zoom across the surface at a speed of several miles per second, making them unavailable as communications nodes most of the time. So they must sit 22,000 miles above sea level, which makes their signals easy to overwhelm with modest amounts of electromagnetic interference, especially if the jammer is near communications receivers.
The only satellite constellation the military is currently building that can provide protection against the full array of potential communications threats is the Advanced Extremely High Frequency (AEHF) system. AEHF is designed to cope with everything from jammers to hackers to scintillation from thermonuclear explosions. However, although it will provide ten times as much capacity as the legacy MilStar constellation, it can only carry a small portion of the military communications traffic passing through space portals.
As a result, the amount of that traffic that is well protected against jamming will peak at 6-7% in fiscal year 2012, leaving over 90% of joint-force transmissions vulnerable to degradation. That's not a serious problem if the biggest threats we face are rag-tag adversaries such as the Taliban, but in a war with China there's a high likelihood that America's military would lose the use of most of its satcom links in places like the Western Pacific.
The Bush Administration had an initiative for addressing this problem called the Transformational Communications Satellite program, or TSAT. TSAT would have provided internet-like access to U.S. warfighters all over the world, including troops on the move, from a constellation of five very capable satellites. However, TSAT was canceled last year due to astronomical (no pun intended) costs, and now the military space community has no real plan for assuring that a reasonable portion of joint-force communications traffic will be protected against jamming in the future.
The feasible, affordable answer is not to begin a new program, but to start incrementally evolving AEHF towards a more robust capability. I argued in Space News several years ago that such an approach was more likely to work out than trying to implement the complex TSAT initiative, but at the time everybody in the business was still chasing the TSAT opportunity. Now that it's gone, military planners need to start thinking about how the government can leverage its investment in AEHF through incremental improvements to each new satellite.
If that move is not made soon, our warfighters may one day face an adversary who knows how to isolate them from the rest of the joint force and then kill them.