The availability of accurate and timely state
predictions for objects in near-Earth orbits is becoming
increasingly important due to the growing congestion in
key orbital regimes. The Two-line Element Set (TLE)
catalogue remains, to this day, one of the few publicly-
available, comprehensive sources of near-Earth object
ephemerides. At the same time, TLEs are limited by their
corresponding low-fidelity physical models, introducing
errors and uncertainty into state predictions. Previous
literature has shown that filtering TLEs with batch least
squares methods can yield significant improvements in
long-term state prediction accuracy. However, this pro-
cess can be highly sensitive to TLE quality which can
vary throughout the year. It will be shown that remov-
ing systematic biases in along-track position prior to state
estimation can reduce post-fit position errors by an order
of magnitude for selected satellites in the Medium Earth
Orbit (MEO) regime.