April 7, 2016: The U.S. Army has developed a new training program for soldiers operating and maintaining systems (usually communications) that depend on space satellites. Once soldiers are given the basic “how to recognize a satellite hack” instruction they will receive updates as the army acquires additional information on new methods for hacking satellites. What this training does is make it easier for troops to tell if their satellites have been hacked or jammed or if the problem is simply some equipment malfunction. Being able to sort this out rapidly makes it possible to get the satellite capabilities restored more quickly.

The jammer threat to GPS devices is nothing new and requires constant attention because so many weapons, vehicles and individual troops depend on satellite navigation. The increasing frequency of attacks on satellite control systems, especially communications satellites threatens long range communications as well as GPA. This is more important now than in years past because more military units in a combat zone depend on constant communications with data and facilities back in the United States or elsewhere on the planet.

Since 2001 there has been a growing number of space satellites being "hacked." In part this is largely the result of an increase in the number of satellites up there, and the number of ground stations broadcasting information up into the sky. Many of these early "hacks" turned out to be satellite signals interfering with one another. Same with cases where people believe their GPS or satellite communications signals are being jammed. On further investigation, the real reasons tend to be less interesting, and a lot more technical. All this usually has a large element of human error mixed in. But some of the disruptions were deliberate. The new U.S. Army training tries to reduce the confusion these equipment problems produce.

All of the accidental jamming demonstrated to hackers how easy it was to do it on purpose. There were a growing number of examples of that. In response the U.S. Air Force has long (decades) been developing electronic tools for attacking and defending satellite communications and the satellites themselves was already training people to attack and defend space satellites. This effort involved figuring out new or improved ways to jam satellites. Then you keep that stuff secret, in case potential enemies have not figured this out themselves. Next, you work on ways to defeat the weapons developed. Most of this is playing around with the signals themselves. You can unjam a jamming signal with another signal. However, a lot of trial and error is required, and you want to get that done way in advance of any actual war. When you do have to use this stuff for real, you have to expect that the enemy may well have come up with some angle you missed. Thus there will be some rapid improvisation, and you will have more time and resources for this if you have worked out, ahead of time, the details of disasters you have already anticipated. No one releases much information about this, for obvious reasons. There isn't much discussion from any government, unless there was a terrorist attack using these techniques. Now that has happened in a very public fashion and it was done using clever and determined hacking of the ground based networks that control the programming and the satellites.

The U.S. Department of Defense has already bought over 200,000 anti-jamming systems for JDAM and other weapons that use GPS guidance. It’s been known since the 1990s that GPS signals are easy to jam and there have already been attempts by some nations to use such jammers when facing GPS guided weapons. In addition to developing more jam resistant GPS guidance systems money is also going to more accurate, non-GPS, backup systems. The best candidate is an improved INS (Internal Navigation System). INS have existed for nearly a century but have gotten smaller, cheaper, and more reliable as electronic components did the same over the last half century. Basically INS uses three gyroscopes and three accelerometers to constantly measure changes in direction and changes in velocity. With that the INS will always know where it is in relation to its initial starting point (which can be obtained initially via unjammed GPS or older means). Miniature INS devices have long served as a backup for GPS guided weapons. But while GPS guidance can land a bomb or missile within 10 meters (32 feet) of a target, INS can only achieve 30 meter accuracy. GPS also has the advantage of not needing to have its exact position entered after the INS is turned on. On the upside, that means INS cannot be jammed or spoofed.

But now American researchers believe they have new concepts and technologies that will greatly improve current INS accuracy and cost. Prototypes have been nearly as accurate as GPS and almost as small. Cost is still a factor, with the new INS still costing more than 10 times what GPS does. But this is all a big improvement over what has been available before. The new INS can now be used to monitor GPS and alert the operator that their GPS has either developed a problem or is being jammed. The new INS is also useful for some fast missiles that often lose their GPS signal as they maneuver. Another urgent chore for INS is to alert users that their GPS is being spoofed (sent a false signal that is luring the user away). Thus, even with the ability of anti-jamming tech to keep up with jammer technology, there is still a demand for a new INS.

Many Department of Defense navigation and electronics experts believe current anti-jamming efforts are sufficient to keep GPS viable, but the new INS technology has attracted a lot of attention because in the military a backup is something that is always appreciated because when equipment fails in combat it’s literally a matter of life or death. Meanwhile, the U.S. is building and testing more compact GPS anti-jamming systems for smaller (as small as 200 kg/440 pounds) UAVs. This is part of a program to equip all American UAVs, even the smallest ones, with more secure GPS. While all UAVs can be “flown” by the operator, the GPS makes it a lot easier for the operator to keep track of exactly where his UAV is at all times and sometimes the UAV is programmed to simply patrol between a series of GPS coordinates. If the GPS jams or fails the operator can usually use the video feed to find landmarks on the ground and bring the UAV back to where it can be seen and landed.

Another new approach to dealing with jammers is adding HOG-J (Home On GPS Jam) capability to GPS guided weapons so that, if the jamming is too effective, the weapon will just go after the jammer. HOG-J has already been tested and it works. Now this tech has to be made reliable and able to function effectively in combat. Meanwhile GPS detection gear on JDAMs and other smart bombs are equipped with more and more jam-resistant versions and other forms of guidance for back up (like laser, heat imaging or radar) and simply to provide more options. As time goes on the tech gets more capable and reliable as well as cheaper to build.

While American troops have not yet encountered much (if any) battlefield GPS jamming, the threat exists. The most tangible evidence of this comes from North Korea, which has long made, sold, and itself used GPS jammers. In 2012 North Korea attacked South Korea with a massive GPS jamming campaign and have done it periodically ever since. The jamming began in early 2012 and continued for over two weeks. It took less than a day to confirm that the signal was coming from North Korea and was mainly aimed at the South Korean capital (Seoul). The jamming had little impact inside the city itself (the ground based jamming signal was blocked by buildings and hills) and was only noted by several hundred aircraft landing or taking off from local airports and over a hundred ships operating off the coast. In all these cases the ships and aircraft had backup navigation systems, which were switched on when GPS became unreliable. This is how navigation systems, especially those that rely on an external (satellite) signal are designed. This was the third time North Korea has used GPS jamming against South Korea. For most of March, 2011, North Korea directed a GPS jamming signal across the border towards Seoul. A separate jammer has been directed at cell phone traffic. The GPS jamming signal could be detected up to a hundred kilometers south of the DMZ.

Meanwhile, this is old news for the U.S. Department of Defense, which has spent most of the last two decades developing anti-GPS jamming technology. For years military aircraft have been equipped with complex and expensive GPS receivers that will usually continue to work even if they are being jammed. There are several ways you can defeat attempts to jam GPS signals. While some of the methods are well known, others are classified. No one has successfully used GPS jammers in combat yet but the potential is there. Now the North Koreans are giving large scale demonstration of GPS jamming. Anti-jamming technology is increasingly complex. None of the major players (the U.S., Russia, China, Israel, and several other industrialized countries) are talking, and for good reason. If you don't know what techniques the other guys are using you can't deal with them.

China and Russia are both selling GPS jammers. Some of the latest Russian GPS jammers have recently been used in eastern Ukraine. In 2007, China brought to market a powerful truck mounted GPS jamming system. These "GPS jamming vans" are meant to create a protective "bubble" over an area the van is in the middle of. Sales have been slow. A year before the 2003 invasion of Iraq it was believed that Saddam had bought many GPS jammers, to deal with U.S. JDAM GPS smart bombs. The JDAM has a backup INS, which was no secret, and the Iraqi GPS jamming efforts had no significant effect on the 2003 campaign.

There are several approaches to defeating GPS jamming, and knowing which one each American GPS guided weapon uses makes it easy to develop a way to jam the "jam-proof" GPS. So the U.S. Air Force is understandably reluctant to discuss what they are doing. Given the cost of jam proofing all existing GPS weapons, it's more likely that jam-proof GPS weapons will only be used against targets where the GPS accuracy is vital. Against most targets the accuracy provided by the inertial guidance system will do. Also note that you can bomb GPS jammers with a bomb equipped with a guidance system that homes in on a GPS jamming signal. For that reason it's thought that any use of GPS jammers will involve dozens of jammers in each area so protected. The GPS jamming has no effect on the even more accurate laser guided bombs, and some countries buy smart bombs with both laser and GPS/INS systems. Most countries are working on anti-jamming tech in anticipation of encountering more jamming if war comes.