Kameron Simon, Kratos
Keywords: passive RF, orbit determination, ephemeris
Abstract:
In the Space Domain Awareness (SDA) mission area, particularly in regard to geosynchronous orbits, there are primarily two phenomenologies in the existing Space Surveillance Network (SSN) and commercial market used to observe, measure, and characterize Closely Spaced Objects (CSO): ground-based radar and electro-optical sensors. These phenomenologies and capabilities are well known in the SDA community. This paper presents and highlights the unique abilities of an upcoming phenomenology in SDA, passive RF sensing.
Satellites often fly in CSO scenarios in today’s space environment. This presents a need to know exactly how close satellites are to each other. However, identification of each unique satellite during a CSO scenario at GEO is complicated because the primary means of doing so is from ground-based radars or optical telescopes. Oftentimes, these resource’s cross tag measurements are unavailable during solar exclusions, are expensive to operate, or are not geographically located where they can apply their capabilities. The result is that measurements used during the orbit determination process to create ephemeris do not accurately represent where each satellite is truly located. This results in incorrect ephemeris.
Not knowing exact locations of satellites with respect to each other and detecting maneuvers after the maneuvers have already occurred leads to a higher probability of collision or losing awareness of the vehicles. Each active satellite uses an RF signal to communicate with the ground. These signals are unique and allow Passive RF sensors to track active satellites without cross tagging. Because of this, passive RF sensors provide a cost effective way to receive highly accurate correctly tagged measurements to be used in orbit determination to create correct ephemeris. Passive RF is not impacted by weather or solar exclusions, is available 24/7, and is able to monitor multiple satellites simultaneously.
Maintaining custody of both satellites during a CSO scenario is crucial and very possible with passive RF antennas by using a single or multiple apertures. Multiple apertures can be used to passively range the satellites to create highly accurate correctly tagged measurements used in orbit determination. These measurements produce highly accurate ephemeris, allowing operators and users to know exactly where the satellites are with respect to each other. Passive RF ranging also provides Indications and Warning (I&W) in real time when one of the satellites maneuver. A single aperture can be used to maintain custody of the satellites by monitoring the satellite’s RF Doppler shift to provide I&W of maneuvers in real time. The maneuver I&W from either Doppler monitoring or passive RF ranging can cue the passive RF ranging system to generate highly accurate ephemeris to determine where each satellite currently is and where it will be at a future time.
This paper will propose that passive RF antennas can be used in support of CSO scenarios for the purpose of unique satellite identification and ephemeris generation with maneuver detection. It will cover the unique highly accurate correctly tagged measurements used for orbit determination and maneuver detection by observing each satellite’s own RF transmissions. Real world commercial examples will be used to highlight this capability, along with a discussion of the analytics.
Date of Conference: September 15-18, 2020
Track: Astrodynamics