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EXECUTIVE SUMMARY 7 TASK 2 What augmentations and technical improvements to the GPS itself are feasible and could enhance military, civilian, and commercial use of the system? Today GPS is a true dual-use system. Although it was originally designed to provide a military advantage for U.S. forces, the number of civilian users now exceeds the number of military users. During the course of the study, the NRC committee examined various technologies and augmentations applicable to GPS. It determined that several improvements could be made to the system that would enhance its use for civilian, commercial, and military users without compromising national security. Some of the improvements could be made immediately; others could be incorporated on some of the Block IIR spacecraft that are currently being built and included in the specification requirements for the next generation Block IIF spacecraft. The committee's recommendations are listed below and a detailed discussion of each is provided in Chapter 3. Although the approximate cost of each improvement is given when available, potential funding mechanisms for each improvement are not discussed. In general, the issue of GPS funding is addressed by the National Academy of Public Administration. Recommendations that Enhance GPS Performance for Civil and Commercial Users The NRC committee found that the most prominent need for commercial and civil users is greater stand- alone accuracy, availability, and integrity. With improved performance of the basic GPS signal, many users would no longer require augmentations to obtain the data they require. Any additional system enhancements and modifications to improve standalone positioning accuracy for civilian users are relatively ineffective in the presence of SA. However, if the recommendation to deactivate SA is implemented, the committee has identified several enhancements that could provide significant improvement for both civilian and military users. With SA removed, the major enhancement that would greatly increase accuracy for civilian users is the addition of a new, unencrypted signal that allows for corrections of errors introduced by the ionosphere.10 While very important for civil users, this feature will provide minimal additional capability to military users because they already have this capability through use of their encrypted signals. Immediate steps should be taken to obtain authorization to use an L-band frequency for an additional GPS signal, and the new signal should be added to GPS Block IIR satellites at the earliest opportunity. 10 A preliminary analysis of the L-band spectrum allocation that was conducted by Mr. Melvin Barmat, Jansky/Barmat Telecommunications Inc., Washington D.C., January 1994, is shown in Appendix I.
