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Invitation for Public Comment on Mitigation Options for Global Positioning System Satellite Vehicle Number 49

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Research and Innovative Technology Administration, DOT.


Notice, request for public comments.


The U.S. Government is providing notice that it is actively considering several mitigation options prior to changing the health status of Global Positioning System (GPS) satellite IIR-20M (satellite vehicle number 49—SVN 49) from unhealthy to healthy. The potential mitigations are each designed to reduce the impact of the unique nature of the SVN 49 signal to a portion of the user segment. The mitigations are described in an Appendix posted in the public docket. The mitigations are intended only for use with the SVN 49 satellite and will not be implemented for any other GPS satellite. Responses from this public comment period will be considered during the final decision to choose which mitigation(s) to implement.

After successful implementation of the selected mitigation(s), U.S. Government leaders will determine the conditions necessary to set SVN 49 healthy. It is anticipated this timeline will occur over the next one to three years. Please review the posted Appendix and submit concerns or adverse impacts that may affect your user equipment to the Docket.

Two teleconferences will be hosted by the U.S. Air Force GPS Wing to discuss the mitigation options. These will be held on March 26, 2010 and April 30, 2010 at 4 PM EDT. The teleconference number is 1-800-366-7242 passcode: 6530000#. Please note that if you want a specific comment made during either telephone conference included in the docket, you must submit a public comment to the docket as outlined below.


Comment Period: Written comments should be submitted by May 28, 2010.


You may submit comments identified by RITA Docket ID Number RITA 2010-0002 by any of the following methods: Federal eRulemaking Portal: Go to Follow the online instructions for submitting comments.

Mail: Docket Management Facility: U.S. Department of Transportation, 1200 New Jersey Avenue, SE., West Building Ground Floor, Room W12-140, Washington, DC 20590-0001.

Hand Delivery or Courier: West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC, between 9 a.m. and 5 p.m. ET, Monday through Friday, except Federal holidays.

Fax: 202-493-2251.

Instructions: Identify docket number, RITA 2010-0002, at the beginning of your comments. To receive confirmation that DOT received your comments, include a self-addressed stamped postcard containing the Docket number.

All comments received by DOT will be posted at

All comments/questions will be posted electronically without change or edits, including any personal information provided.

Privacy Act: Anyone is able to search the electronic form of all comments/questions filed in our dockets by the name of the individual submitting the comment or question (or signing the comment, if submitted on behalf of an Start Printed Page 14659association, corporation, business entity, labor union, etc.). You may review DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78) or you may visit

Confidential Business Information: If you wish to submit any information under a claim of confidentiality, you should submit three copies of your complete submission, including the information you claim to be confidential business information, to the address given below under FOR FURTHER INFORMATION CONTACT. In addition, you should submit a copy from which you have deleted the claimed confidential business information to the docket. When you send a comment containing information identified as confidential business information, you should include a cover letter setting forth the reasons you believe the information qualifies as “confidential business information”. (49 CFR 7.17)

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Ms. Karen Van Dyke, DOT/RITA, 1200 New Jersey Ave., SE., Washington, DC 20590, 202-366-3180, or Lt. Col. James Lake, 310-653-3613,

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The GPS satellite SVN 49 has a unique signal that may result in degraded performance for some GPS user equipment. This satellite currently operates with the navigational message set in an unhealthy state to prevent any adverse impact to users. To minimize the adverse impacts, several mitigations are under consideration. Each mitigation is intended for a specific user group and can be used with or without the other mitigations. All mitigations are intended for use with SVN 49 only and no changes will be made regarding other GPS satellites. The mitigations are briefly described as:

  • Set SVN 49 healthy with current 152m Antenna Phase Center (APC) and associated clock offsets.
  • Set SVN 49 healthy with factory default APC and clock offset.
  • Users switch to multipath-resistant receivers to minimize adverse impact from SVN 49 signal.
  • Modify receiver software to use look-up table corrections to account for unique SVN 49 signal.
  • Increase SVN 49 User Range Accuracy (URA) minimum value to 3 by changing bits in the GPS data message that allow user equipment to de-weight or exclude SVN-49 signals.
  • Remove data modulation from L2 P(Y)-code to mitigate impact to high precision users.
  • Change L2C PRN code to a “unique sequence” to prevent L2C users from including SVN 49 in their solutions.
  • Change SVN-49 from PRN-01 to PRN-32 to prevent updates to WAGE users.
  • Use spare health code so future users could use SVN 49 despite unhealthy setting.

More information is presented in the Appendix posted in the public docket. Implementation of each mitigation is contingent upon several factors including cost, number of users impacted, schedule, and the needs of the U.S. Government. If you would like to submit a public comment concerning these proposed actions, please follow the instructions listed above.

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Issued in Washington, DC, on March 22, 2010.

Robert L. Bertini,

Deputy Administrator.

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[FR Doc. 2010-6814 Filed 3-25-10; 8:45 am]