Evaluation of high-accuracy catalogs during the Gannon storm

As we move towards solar maximum in 2025, there has been an increased level of space weather activity in the form of frequent solar and geomagnetic storms. During May 10-12, 2024, Earth was hit by the biggest geomagnetic storm since the 2003 Halloween storm.

The energy influx during these storm conditions causes an increased atmospheric drag acting on low Earth orbit (LEO) satellites. This leads to an increased orbital decay that may not have been accounted for during the mission design, thus shortening the mission life. In extreme cases, satellites in very low Earth orbits may reenter as demonstrated by the 2022 Starlink reentry event.

In addition to the increased satellite decay and the subsequent orbit maintenance and attitude maneuvers required to take shelter from storms, there can be significant operational consequences on satellite orbit determination and prediction. Different operators use different thermospheric density models for operations and some of them tend to be outdated versions. Even so, the state-of-the-art semi-empirical thermospheric models are not able to capture the increased thermospheric density variations or able to get the phase of the storm-induced density rise and decay correct. Moreover, the forecasting of storm conditions, specifically the geomagnetic indices, can be quite poor and often limited to a latency of just a few hours. Therefore, on an individual operator level, there are significant errors introduced in the orbit determination and prediction of their assets during these perturbed space weather conditions.

The consequences are more severe for maintenance of high-accuracy space catalogs (HACs). Prediction ephemerides from HACs are instrumental to conjunction analyses (CA) and collision avoidance (COLA) services. Any loss of tracked space objects or degradation of prediction accuracy has a direct effect on the subsequent CA/COLA services. During the 2003 Halloween storm, the majority of the LEO satellites in the space object catalog maintained by the US Air Force are said to have been lost temporarily and required days of analyst time for the re-cataloging. Since 2003, there have been a significantly large number of objects added to the space catalog.

For this presentation, we will analyze the variation in the orbit prediction accuracy and the cadence of state and ephemeris updates through the period encompassing the Gannon storm. We will look at prediction and definitive ephemerides from various sources such as Precise Orbit Determination (POD) ephemerides, and HACs maintained by commercial and government entities. A statistical analysis of orbit prediction errors and “loss” of orbital state solutions will provide insights into the steps that are required to be taken to ensure that CA/COLA services are not hindered. This is very relevant as the space population continues to grow during this period of heightened space weather activity. We will also outline some of the issues encountered in tuning an orbit determination process to arrive at a converged solution during perturbed space weather events that are partly responsible for the degradation in catalog accuracy.