Dear Station Colleagues,

At the moment the ILRS network is faced with severe limitations in its tracking capacity. A number of stations have been closed and others have reductions in their operation periods. We need to make some changes in our tracking priorities to best accommodate the situation. Above all, however, is thesafety of our personnel.

Considerations:

1. We need to stress theimportance of the geodetic satellites since their data are the basis of the reference frame and since they are passive (no alternative tracking systems), we want to maintain continuity oftheir orbits (so we don't lose them);

2. Altimeter satellites can get by with a couple of passes each week from each station;

We ask the stations to adjust their operating schedules as possible using the following priorities:

Priority 1. Geodetic 1: LAGEOS 1 and 2, and LARES (Reference Frame)

Priority 2. Geodetic 2: Starlette, Stella, Larets, BE-C, Ajisai, Etalon 1 and 2 (avoid loss of contact)

Priority 3. Altimeter: Jason-3, ICESat (a couple of passes per week on each is sufficient)

Priority 4. Other LEO satellites: within the availabletrackingschedule; (one pass per satellite per shift is sufficient)

Priority 5. GNSS satelliteswithin the available tracking schedule (try to sample each constellation)

Current high priority GNSS satellites:

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

If time permits tracking of any additional GNSS satellites, selection of targets should be determined at the convenience of the station.

Hopefully the need for this abbreviated schedule will not be required for very long.

If you have any questions, please contact me.

Mike Pearlman

ILRS Central Bureau