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Codeless and Semi-Codeless Access to the Global Positioning System

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Office of Space Commercialization, National Oceanic and Atmospheric Administration, Department of Commerce.


Notice and request for comments.


The Office of Space Commercialization seeks comments on a plan to transition the installed base of codeless and semi-codeless Global Positioning System (GPS) user equipment to next-generation equipment utilizing the modernized civil GPS signals known as L2C and L5. The plan was developed under the auspices of the National Executive Committee for Space-Based Positioning, Navigation, and Timing (PNT). Under the plan, the Department of Defense, as the operator of GPS, will continue Start Printed Page 28434enabling codeless/semi-codeless GPS access until December 31, 2020, by which time the L2C and L5 signals will be available on 24 or more modernized GPS satellites. Users should re-equip to use the modernized signals, since codeless/semi-codeless GPS access cannot be assured beyond 2020.


Submit comments on or before June 16, 2008.


You may submit comments by any of the following methods: E-mail: Fax: (202) 482-4429 (Attn.: Jason Kim). Mail/Courier: Jason Kim, Office of Space Commercialization, U.S. Department of Commerce, 6818 Herbert C. Hoover Building, 14th St. & Pennsylvania Ave., NW., Washington, DC 20230. Due to ongoing delays in mail delivery, respondents are encouraged to submit comments by mail early, or to transmit them electronically. Office hours for courier delivery are 9 a.m. to 5 p.m., Monday through Friday, except Federal holidays.

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Jason Kim, Senior Policy Analyst, Office of Space Commercialization, U.S. Department of Commerce, (202) 482-5827.

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The Global Positioning System (GPS) is a U.S. Government constellation of 24 or more satellites providing precise positioning, navigation, and timing (PNT) capabilities, free of direct user fees, on a continuous, worldwide basis. GPS currently transmits PNT information on two radio frequencies known as L1 (1575 MHz) and L2 (1227 MHz). In the future, GPS will also transmit information on a third frequency known as L5 (1176 MHz).

GPS transmits encrypted signals known as Y-code or P(Y)-code at the L1 and L2 frequencies. Y-code is intended primarily for U.S. and allied military use, but the civilian community has developed techniques that exploit Y-code at L1 and L2 to achieve significant accuracy gains. Such techniques, collectively known as codeless or semi-codeless GPS access, have been integrated into a range of GPS receivers sold commercially around the world.

The Y-code signal was never designed or intended for codeless/semi-codeless access. However, the Department of Defense, as the GPS operator, has historically supported codeless and semi-codeless users by documenting a time-limited commitment to the Y-code signal in the GPS Standard Positioning Service (SPS) Performance Standard and the Federal Radionavigation Plan. For example, the current GPS SPS Performance Standard (dated October 2001) includes the statement that, “Until such time as a second coded civil GPS signal is operational, the U.S. Government has agreed to not intentionally reduce the current received minimum Radio Frequency signal strength of the P(Y)-coded signal on the L2 link, as specified in ICD-GPS-200C or to intentionally alter the P(Y)-coded signal on the L2 link.” As a result, manufacturers have continued to develop codeless/semi-codeless GPS equipment.

The U.S. Government acknowledges the global use of GPS codeless and semi-codeless techniques and plans to maintain the existing GPS L1 Y-code and L2 Y-code signal characteristics until such time that an alternative capability exists to replace it. Since 1999, the Department of Defense has worked closely with the civilian agencies on the National Executive Committee for Space-Based PNT (and its predecessor, the Interagency GPS Executive Board) to add new capabilities to GPS that supplant the need for codeless/semi-codeless access. In 2005, the U.S. Air Force began launching modernized GPS satellites featuring a new civil signal at L2 called L2C. L2C is designed to work in combination with the legacy civil signal (called C/A) at L1 to enable high accuracy without codeless/semi-codeless techniques. In 2009, the Air Force will begin adding a third civil signal called L5 to all new GPS satellites. L5 will also work in combination with L1 C/A and/or L2C to enable high accuracy without codeless/semi-codeless techniques.

The National Executive Committee for Space-Based PNT seeks to encourage the development and adoption of next-generation GPS receivers that achieve high accuracy via use of L2C and/or L5 instead of codeless/semi-codeless techniques. To facilitate business decisions and stable planning for equipment developers and end users, the National Executive Committee intends to set a fixed target date for the equipment transition.

The National Executive Committee proposes December 31, 2020, as the target date for transitioning the installed base of codeless/semi-codeless GPS equipment to next-generation capabilities utilizing the modernized civil GPS signals. This date is based upon the current launch schedule for the GPS program, which will have 24 GPS satellites transmitting the L2C signal to users by 2016, and 24 GPS satellites transmitting L5 by 2018. The date is also based on preliminary discussions the Office of Space Commercialization has held with GPS equipment manufacturers. The manufacturers indicated that a transition period of approximately ten years should be sufficient to allow the installed base of codeless/semi-codeless GPS users to re-equip with next-generation receivers as part of their normal equipment amortization, obsolescence, and upgrade cycle.

Should there be unforeseen delays in the GPS modernization program, the National Executive Committee will reassess the target date for the transition.

After the transition date, the characteristics of the Y-code signals transmitted by modernized GPS satellites may change without further notice and may preclude codeless/semi-codeless use of the Y-code signals. However, for those legacy satellites that have no modernized capabilities, codeless/semi-codeless access to Y-code at L1 and L2 will continue until those satellites are decommissioned.

The Office of Space Commercialization encourages the GPS user community and manufacturing industry to provide feedback on this proposed plan within the next 30 days. Both domestic and international comments are welcome due to the global nature of GPS use. The National Executive Committee will take the public comments into account as it prepares a final announcement on the date for the codeless/semi-codeless GPS transition. The Department of Defense will publish the final announcement in the Federal Register.

Concurrent with the final transition plan announcement, the Department of Defense intends to release an update to the SPS Performance Standard that no longer includes a reference to Y-code stability in support of codeless/semi-codeless access. The final announcement would serve to document the government's continued commitment to protect codeless/semi-codeless GPS access through the end of the transition period. Specifically, the final announcement would commit the Department of Defense to maintaining the existing GPS L1 Y-code and L2 Y-code signal characteristics until December 31, 2020. The announcement would also state that should there be unforeseen delays in the GPS modernization program, the date will be reassessed.

Instructions for the submission of comments.

Page Limit—Submissions should be limited to a maximum length of four pages.

Identification and Cover Sheet—Mark each page of the submission with the docket number, submitter's name (and Start Printed Page 28435organization, if applicable), date of submission, and contact information (if the submitter chooses to provide it).

Additional information—The Office of Space Commercialization encourages interested persons who wish to comment to do so at the earliest possible time. The Office will consider all comments received before the close of the comment period on June 16, 2008. Consideration of comments received after the end of the comment period cannot be assured. The Office will not accept comments accompanied by a request that part or all of the material be treated confidentially because of its business proprietary nature or for any other reason. All comments submitted in response to this notice will be a matter of public record and will be available for public inspection and copying at

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Authority: NSPD-39; 10 USC Sec 2281(b)(5).

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Dated: May 14, 2008.

Ed Morris,

Director, Office of Space Commercialization.

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[FR Doc. E8-11148 Filed 5-15-08; 8:45 am]