1. NSGF prediction service
ILRS2005 Eastbourne 6th October Graham Appleby

2. Background
For about 10 years, IRVs generated by SGF for a large sub-set of the ILRS targets;
Originally long time-span (30 – 60 days)
Need/motivation:
as backup for daily ‘official’ ILRS predicts;
Long time-span predicts feed the SGF hourly rapid QC
Changed with other ILRS providers to daily production.

3. Multi-day IRV-based predicts as rapid QC

4. IRVs and satellites IRV tuning process:
Provided tuning is fully applied, restituted orbit should represent the underlying precise prediction ‘quite well’:
for MEO and HEO, IRV-orbits follow prediction at m level;
For LEO, more difficult to force errors due to simple on-site force model into x and xdot;
So may be several m errors on top of how the predictions will noticeably degrade.

5. IRVs and satellites (2)
Predictions generated for:
Larets, Starlette, Stella, Envisat, Ajisai,Topex/P, Jason-1, Lageos (1+2), Etalon (1+2).
GPS 35+36, GLONASS (ILRS targets) – via predicted orbits from CODE.

6. cpf Invited by Randy Ricklefs to test out new procedure;
Currently generate 3-day predictions (body-fixed xyz) on daily basis as part of continuing IRV production;
Off-line tests of their use, for Lageos, in collaboration with Werner Gurtner, show good agreement with predicted alt, az, range from IRVs;
Currently distributed by to McDonald and Zimmerwald;
Will be implemented at Hx as time permits:
Motivation:
Better predictions, important for kHz;
Access to IceSat for instance.