Global Navigation Satellite Systems for Positioning and Time Transfer

1. Global Navigation Satellite Systems for Positioning and Time Transfer T. Schildknecht, A. Jäggi R. Dach, G. Beutler Astronomical Institute, University of Bern OPERA Seminar, Jan 26, 2012, LNF - INFN, Frascati, Italy Astronomisches Institut der Universität Bern

2. Observation Equations • Code observation(on one or two carrier frequencies) • Simplified time transfer Astronomisches Institut der Universität Bern

3. "traditional method" quasi-simultaneous observations of one satellite by two receivers (simultaneous in s/c time scale) broadcast ephemeris dual frequency  ionosphere correction receiver i computes its clock offset using satellite j 1PPS output/input synchronized to receiver clock off-line processing of measurements at CERN/LNGS 1PPS 1PPS Common View Time Transfer Astronomisches Institut der Universität Bern

4. "standalone mode" Receiver computes its clock offset from GPS time using all satellites in view receiver internal clock synchronized to GPS time 1PPS output synchronized to receiver clock broadcast ephemeris dual frequency  ionosphere correction (on-line) mode of PolaRx receivers at CERN and LNGS 1PPS All in View Timing Receivers Astronomisches Institut der Universität Bern

5. "Precise Point Positioning"(off-line processing) receiver stores "pseudorange" and "phase" observations 1PPS output synchronized to receiver clock Off-line computation of receiver clock offset (and station coordinates) using high-precision IGS satellite orbits and satellite clock corrections scientific processing software  1PPS All in View PPP Astronomisches Institut der Universität Bern

6. receivers store "pseudorange" and "phase" observations 1PPS outputs synchronized to receiver clocks Off-line computation of receiver clock offsets (and station coordinates) using high-precision IGS satellite orbits and satellite clock corrections scientific processing software  1PPS 1PPS Geodetic Time Transfer Astronomisches Institut der Universität Bern

7. antenna cable delay (frequency independent) "internal" delay (frequency dependent "receiver" clock determined from processing is referenced to antenna phase center both delays take into account by timing receivers only relevant for absolute timing! delays calibrated by METAS for CERN and LNGS receivers 1PPS Receiver-Internal Delays Astronomisches Institut der Universität Bern

8. determine offset between traveling receiver and receiver #1  123456789 1PPS 1PPS 1PPS Calibration with Traveling Receiver Astronomisches Institut der Universität Bern

9. determine offset between traveling receiver and receiver #2   123456789 1PPS 1PPS 1PPS Calibration with Traveling Receiver Astronomisches Institut der Universität Bern

10. Setup at CERN and LNGS Astronomisches Institut der Universität Bern

11. PTB Calibration Results PPP results P3 results (common view) Astronomisches Institut der Universität Bern

12. Traveling Receiver Closure <0.04ns Astronomisches Institut der Universität Bern

13. PTB Calibration Results Astronomisches Institut der Universität Bern

14. Summary • PTB performed a state of the art relative time transfer calibration between CERN and LNGS. • A mobile time transfer receiver and two different data processing methods were used (P3 CV and PPP). • CLNGS – CCERN = 2.31 ± 0.90 ns • Remember: this refers to the 1PPS reference points NOT to the actual measurement points in the labs! • An independent “geodetic time transfer” should be performed (requires receiver RINEX data files); in this case the internal delays must be taken from the METAS calibration. monitoring (a posteriori) of Astronomisches Institut der Universität Bern