3. Best practices for operators to publicly share satellite positions and trajectories
SATCON1 Recommendation 9 states we must “Determine the cadence and quality of updated positional information or processed telemetry, distribution, and predictive modeling required” to minimize impacts to astronomy. SATCON1 Recommendation 10 calls for “a new standard format for publicly available ephemerides beyond [TLEs]” in order to incorporate uncertainties and other useful information.
In general, the position of a satellite at a future time is forecast with a propagator algorithm that uses an orbital solution from the recent past. Orbital solutions may be in the form of either general perturbations, i.e., time-averaged Keplerian elements that include atmospheric drag computations (commonly represented in TLE format), or ephemerides, i.e., state vectors of position and velocity data (sometimes referred to as an orbit ephemeris message or OEM).
Orbital solution information is typically shared in the form of TLEs from radar observations and improved by ephemerides and supplemental TLEs from satellite operators. This is then used to forecast the ephemeris of the satellites and provide precise date, time, and sky position (Right Ascension and Declination) of each visible satellite from a particular observer’s longitude and latitude. We note that in the future, the US Commerce Department’s Open Architecture Data Repository may be responsible for sharing space situational awareness data[1]. We encourage this to be fully public and coordinated with the SatHub initiative.
To implement SATCON1 Recommendations 9 and 10, we propose the following: Detailed in Section 3.1:
- All operator-provided orbital solutions must include reasonable estimates of uncertainties, so observers with a variety of instrumentation can properly plan observations.
- Operators must publicly provide orbital solutions at a frequent and regular cadence for the benefit of observation planning and image masking.
