Why Military Satellites Matter
At issue is the next generation of the Navy’s Mobile User Objective System (MUOS), a narrowband tactical satellite communications system that is designed to improve secure voice, video and data services communications for U.S. forces on the move. MUOS provides a tenfold increase in transmission throughput over the current ultra high frequency (UHF) military satellite system. Manufacturer Lockheed Martin Corp. has built five satellites so far.
In November 1999, a MUOS concept study was initiated and a number of architectures were evaluated. The one that appeared most practical to Navy acquisition officials was something akin to having the Defense Department become an anchor tenant on one of the commercial L-band systems, principally INMARSAT, Iridium or Globalstar.
But the program manager of the UHF Follow On (UFO) project, which was heading the study, thought differently. He argued that the risk of command-and-control communications interruptions — when forces might be under fire in dense foliage or in heavy rainstorms — demanded the use of the lowest possible satellite frequency. That frequency would have a larger corresponding wavelength, and the larger wavelength would be inhibited less by rain or by tree leaves.
The program manager proposed that the Navy build a satellite in the same frequency range as the UFO satellite system that was then being used. A vigorous debate ensued. With military UHF, the Navy would own the system and therefore be obligated to program the money up front. With L-band leases, the services could have a pay-as-you-go approach to mobile communications and avoid upfront costs. The decision was made to use military UHF.
A similar discussion is now unfolding with regard to a MUOS follow-on system. One aspect of the discussion has changed to include not only where the money is spent but the question of whether the money be made available at all. In an environment of tight budgets, is a military satellite program simply too expensive?
These are decisions that have real-world implications for forces in the field that depend on timely and reliable communications. The realities of war are not functions of abstract considerations.
From the standpoint of physics, military UHF must be the preferred option to connect war fighters to each other and to their support systems. This is based on three major considerations: frequency, mobility and resilience.
Military UHF is not technically in the UHF band. It actually includes the upper range of the very high frequency band. The effect of that location in the spectrum means that the wavelength of military UHF is 3 to 3.5 times larger than the wavelength of L-band. The result is that tree leaves and rain block a much larger proportion of an L-band wavelength than a military UHF wavelength, leading to more interference.
A practical demonstration can be made by trying to communicate over a cellular satellite phone in a rainstorm or under heavy foliage. The reality is that in some rainstorms, in some forests and even in some sandstorms, military UHF will enable a war fighter to reliably communicate.
The second consideration is mobility. Military UHF can use antennas to provide nearly omnidirectional command-and-control communications without a significant perturbation to an aircraft fuselage or other combat vehicle structure. Consider the possibility of having to fly in a certain pattern to maintain command connectivity, or to have to significantly perturb the fuselage of fighter and bomber aircraft to include a tracking antenna. That may be an acceptable option for tankers and heavy bombers, but definitely not for any aircraft or any vehicle that must make quick direction changes.
Resilience is the third major consideration that favors military UHF, but it has received little attention. Military communications face two substantial threats: jamming and hacking. Some countries have demonstrated an ability and willingness to jam opponents. It was reported in 2013 that China may have the capability of jamming the Joint Tactical Information Distribution System, which allows military commanders and operators to share information on position, tracking, monitoring and targeting data. It has also been reported that China is the principal supplier of satellite jamming equipment to Iran.
UHF, if its use is extended, will in all probability retain the spectrum construct established by MUOS. That enables forces in the field to use 20 MHz (four contiguous 5 MHz channels) for frequency hopping protection against jamming. Reducing communications messages to a very low data rate and hopping data rate over range of frequency could give mobile forces a significant ability to get through in all but the most powerful and sophisticated producers of interference. And for that, other options such as switching satellites could be employed.
Another issue is protection against hacking. A nation’s intelligence service can be as limited and inexpensive as one team of hackers. Cyber-attacks from around the world are continuing to penetrate the U.S. government. Waves of computer intrusions into sensitive government information systems have confounded efforts to identify their sources.
The most explosive example of this penetration is the apparent capture, although disputed, of the U.S. RQ-170 Sentinel drone by Iran. Iranian electronic warfare specialists were able to cut off communications links to the Sentinel. Using knowledge gleaned from previously downed drones and a technique proudly claimed by Iranian commanders, the Iranian specialists then reconfigured the drone’s GPS coordinates to make it land in Iran at what the drone thought was its actual home base in Afghanistan.
The easy solution to all of this, in theory, is to get away from packet communications and go back to circuit switching. That isn’t happening. It costs too much. But the bandwidth available on a MUOS-like follow-on provides spectrum for variable coordinates to be used in protecting against hacking.
The Defense Department today must have unique modems to employ cyberprotections as well as anti-jam techniques. No commercial L-band system provides anything similar, nor can it. It just costs too much.
Frequency control should also be a consideration. The Joint Staff and the services can control the use of military UHF, albeit as a secondary user, far more effectively than L-band, especially given the competitive commercial environment that exists around the world. Going to any commercial L-band system fundamentally relinquishes that option.
These considerations should make military ownership of satellite systems operating at military UHF frequencies a staple of command-and-control communications. It is a matter of life and death.
James Mazzei is a satellite communications systems engineer and a former adjunct professor at the Johns Hopkins, University of Maryland and George Mason University graduate schools.