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GNSS Tracking Strategy - 2019

The ILRS has been working with the IGS and other interested parties to settle on a GNSS tracking strategy that would satisfy both mission and user requirements. For some applications, users want denser tracking on a few satellites. For other applications, users want some tracking on the full complex of GNSS satellites, even if that tracking is sparse. In addition, there are also requests for focused campaigns, in particular, for tracking GNSS satellites while going through Earth shadow to study the effects of radiation pressure. We presently have over 60 GNSS satellites (GLONASS, Galileo, BeiDou) on the ILRS roster. More will be added in the near future. The total could reach nearly 100 when GPS is added in the 2024 timeframe.

The strategy that the ILRS has agreed to implement is the following:

  • GNSS tracking will continue to be prioritized with the other ILRS satellites by the standard ILRS priority scheme (by altitude and inclination);
  • Four GNSS satellites will be identified by each constellation (Galileo, GLONASS, and BeiDou) for intensive tracking, with three sectors (at least 2 normal points each) spaced widely apart over the pass. If stations cannot obtain three sectors they should try to get two sectors. These four satellites per constellation would be selected by the constellation and would have the highest priority among the GNSS satellites.
  • All of the remaining GNSS satellites would be tracked by the stations on an as time available basis; selection of targets should be determined by the stations for data yield, but stations are asked to try to diversify among all three constellations because we need some data on all three.
  • There may be some special tracking periods (e.g. satellite eclipses, etc.) that may need other scheduling.

The agreed high priority GNSS satellites are:

  • BeiDou3-M2, 3-M3, 3-M9, and 3-M10
  • Galileo-102, -202, -209, -210
  • GLONASS-131, -134, -138, and -139

The ILRS asks that you implement this new priority strategy in your tracking operation, by August 15, 2019. Please contact the ILRS CB if you have any questions.