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that are not monitored by enemies or are more effective for current environmental conditions. As Figure 17 illustrates, only a small part of the entire frequency spectrum is technically and legally available for U.S. forces to use in peacetime. Limiting U.S. sensors and communications to these parts of the spectrum can give an edge to enemy EMS forces searching for them. Future U.S. systems that can maneuver across a larger part of the EMS would increase the time needed for enemies to find, jam, decoy, or otherwise counter them.
FIGURE 17. SPECTRAL AGILITY
Spectral agility is similarly important for U.S. countermeasure capabilities that must chase increasingly agile enemy sensor or communication systems. The need for increased agility in the IR region of the EMS is of particular concern. Most contemporary IR countermeasures are focused on countering short-range seekers on IR-based missiles. Future IR countermeasure systems will need to be effective against long-range sensors in the lower frequencies of the IR spectrum, especially as new focal plane sensor technologies and greater computer processing power improve the precision and detection range of passive IR sensors. Agility can also reduce the probability that enemy passive sensors will detect U.S. active sensors, communications, and countermeasures. DoD is beginning to incorporate features that enable EMS warfare systems to change the size, shape, and direction of their beams as shown in Figure 18. U.S. sensor and communication systems should also have the ability to change their operating patterns to deny opponents opportunities to intercept, classify, and exploit a predictable series of signals. Sensors or communication systems that are able to adjust their power to the minimum needed for an operation can reduce their risk of being exploited by the enemy.