GPS IIR-20 (SVN-49)Information.ppt

* GPSW SVN-49 Information_25Jan2010 * GPSW SVN-49 Information_25Jan2010 GPSW SVN-49 Information_25Jan2010 GPS IIR-20 (SVN-49)Information 25 January 2010 Col David Goldstein Chief Engineer, GPS Wing Global Positioning Systems Wing GPSW SVN-49 Information_25Jan2010 Purpose for this briefing Discuss SVN-49 signal problem with GPS community Provide information on potential mitigations Present way forward for SVN-49 SVN-49 (PRN-01) Background SVN-49 unlike other GPS IIR Satellites had L5 RD Demonstration Payload Demo payload made use of Auxiliary Payload port No impact on L1 and L2 signals was intended or expected “Out of family” elevation angle dependent Pseudo Range Residuals (PRR) seen at monitor stations and by other GNSS users world-wide Root cause studied and established Signals reflecting off L5 filter and transmitted through satellite antenna Result is permanent, static multipath signal within satellite Signal distortion is user elevation angle dependent Little or no distortion at low elevation angle Signal distortion impacts receivers differently depending on unique designs Non IS-GPS-200 compliant receivers greatly complicate the issue Varying impacts prevent a single solution for all forms of user equipment SVN-49 (PRN-01) Continued Current Status SVN-49 set unhealthy but still operated as part of GPS constellation Control segment parameters temporarily adjusted to allow 2SOPS to continue to include SVN-49 in operational constellation (152 meter antenna phase center offset) Will permanently modify Kalman Filter to accommodate SVN-49 without impacting users GPSW and 50 SW exploring additional mitigation steps and eliciting user feedback Potential mitigation steps include Increase SVN-49 User Range Accuracy (URA) – change bits in GPS data message that allow user equipment to de-weight or exclude SVN-49 signals Change SVN-49 PRN code to one outside range used by current user equipment Modify SVN-49 signal configurations to mitigate impact to hig