OBJECTIVE: Exploit the relative sparseness and randomness of typical signal intelligence (SIGINT) signal spaces with sampling techniques that can sample a signal space at lower sampling rates without losing any information, or conversely, obtain more information from the signal space from without increasing sample rate. DESCRIPTION: Typical SIGINT collection platforms attempt to collect signal information over a wide RF spectrum for extended periods of time, resulting in large amounts of data that need to be transported off the platform through sometimes limited-bandwidth communications links. With new communications services and radar systems being developed over an ever-expanding RF spectrum, the job of covering all signals of interest, and handling the large amount of associated data, is becoming more of a challenge for data collection platforms such as the E-2 Hawkeye and Broad Area Maritime Surveillance (BAMS). This is especially true in the case of communications intelligence (COMINT), in which it may be desirable to send samples of signals off-board for analysis. Although the typical signal space is in fact busy, it is also commonly the case that the signals in the space are randomly spaced within the spectrum, and that there are substantial portions of the spectrum that are empty. These empty spaces are not necessarily known a priori, thus, when conventional Nyquist-type sampling is used, it is necessary to sample the space at sufficiently high speeds to cover the entire space, even the unknown blank regions. It is desirable to exploit the relative sparseness and randomness of typical SIGINT signal spaces with sampling techniques that can sample a signal space at lower sampling rates without losing any information, or conversely, obtain more information from the signal space from without increasing sample rate. This would, for example, reduce the demands on air-to-ground links that would be used to transport samples of COMINT signals to ground-station analysis centers. PHASE I: Identify methods of improving high efficiency SIGINT data collection and assess their feasibiilty in use on Navy aircraft. Select one or more critical hypotheses for small scale experimentation if necessary to support prototyping algorithms and approaches. PHASE II: Develop and prototype the approach on one or more aircraft and/or one or more frequency band of interest. May pilot the approach with proof of concept for ground use on an aircraft with a frequency band of interest. PHASE III: Apply lessons learned to develop and produce high efficiency SIGINT collection for Navy aircraft. PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: This approach can be used to design high performance communications for commercial aircraft.