For many years the space community has used orbital elements at epoch to define orbits. Yes, it does allow you to easily visualize the orbits; however, these are only valid for Earth orbits that have no perturbations due to lunar and solar gravity, Earth bulge, or atmospheric drag.
To solve this problem, we have proposed that TLEs (Two-line Elements) also include state vectors. State vectors are spacecraft position and velocity in 3 dimensions at epoch. These are valid for any orbit that uses the ECI (Earth-centered Inertial) coordinate frame, including cislular orbits.
The objection used by leaders in the space community is that mean values cannot be assigned to state vectors but can be applied to all orbital elements except True Anomaly. Our response to this is that “estimates” can be calculated for state vectors based on current and past observations using the following process that is similar to a Kalman filter state estimator:
1) Take an observation (radar and/or telescope) to establish a state vector at the current epoch.
2) Propagate past observed state vectors, using the equation of motion method used by SOS, to the current epoch.
3) Combine the past and present state vectors with weighting based on the age of the observed state vectors.
We believe that our suggestion is based on common technical sense and will make TLEs more useful in the future.
Andrew Motes