Austin Beer, Kratos; Kameron Simon, Kratos
Keywords: Passive RF, Maneuver Detection, Pattern of Life
Abstract:
In todays contested and congested space environment, it is becoming more important to identify and characterize satellite maneuvers in order to maintain Space Domain Awareness (SDA). In the geosynchronous (GEO) belt, legacy satellites have used chemical thrusters to perform maneuvers. Whether it is a slot changing maneuver, station keeping maneuver, or a trim burn, these maneuvers are caused by a large amount of delta-v provided by the thrusters over a short duration of time. This makes them easy to identify in a relatively small amount of time. However, newer GEO satellites are being equipped with more cost-effective electric propulsion thrusters. This technology makes it more difficult to detect maneuvers in near-real time, due to the low delta-v applied to the satellite over long durations. The acceleration being applied by the electric propulsion system is so small that it is difficult to notice the satellite is no longer following natural motion. This is significant as it can result in erroneous orbit determinations. Since electric propulsion is more cost-effective and provides a lower delta-v, owner-operators will also maneuver these satellites more frequently compared to satellites with chemical thrusters.
Optical and radar phenomenologies can easily observe chemical thruster GEO burns in their observations since the change in the satellites position is large and nearly instantaneous and can be seen in the association residuals. Another phenomenology, passive RF, is also able to detect these maneuvers using different techniques. The first uses the changes in the Doppler shift of the satellite signal. The second uses the changes in the time difference of arrival (TDOA) and frequency difference of arrival (FDOA) data from the passive RF system.
Electrically propelled satellite maneuvers are not as easy to detect due to the small amount of a delta-v applied over a long duration. This is a concern for SDA because it is easy to miss maneuvers in near real time, causing the understanding of where the satellite is to be incorrect. Since passive RF techniques require the use of the satellites own transmitted signal, it can be used to determine in near-real time when an electrically propelled satellite is maneuvering and provide indications and warnings (I&W) of the maneuver. This is because when the thrusters are turned on the satellites emitted signal moves with the satellite.
Passive RF ranging techniques are able detect these maneuvers using the TDOA/FDOA data in its orbit determination process in near-real time. Once the maneuver is identified, the satellite must be monitored through the end of the maneuver, which can take several hours. Once the maneuver is complete, passive RF ranging can provide the new position of the satellite. This new position can then be used for conjunction assessment and to help begin characterizing the maneuver. Identifying when a maneuver occurs and characterizing it allows a pattern of life to be built for satellites maneuvering in the GEO belt. This construct helps with maintaining custody of satellites and accurate ephemeris for satellites and identifying when satellites are not following standard pattern of life maneuvers.
This paper will show that passive RF can be used to identify and characterize maneuvers of satellites in the GEO belt in near-real time and build a pattern of life. It will cover satellites that are propelled by both chemical and electric thrusters and talk to the differences in identifying and characterizing them and processing the data. Real world commercial data will be used from the Kratos Global Sensor Network (KGSN) to highlight this capability, along with a discussion of the analytics.
Date of Conference: September 14-17, 2021
Track: SSA/SDA