Matt Prechtel, Kratos RT Logic
Keywords: Sensors, RF, Maneuver Detection, Anomalies, SSA, Ranging, Patterns of Life
Abstract:
In the Space Situational Awareness mission area, and in particular, with Geosynchronous orbits, there are primarily two technologies in surveillance architectures used to observe, measure and characterize Resident Space Objects (RSOs); ground based radar and optical telescopes. Both of these technologies are well known to the AMOS community and have commercial operators. This abstract proposes that a third technology, Commercial Passive RF sensing can add an additional sensor dimension to the SSA domain and is worthy of architectural inclusion as a fundamental sensor type.
Commercial Passive RF sensing systems provide a key capability in the timely identification of SSA activities and can support the following types of events:
Capability
Description
SSA Need
Maneuver Detection
Monitoring for subtle or large frequency shifts to observe changes orbital parameters conducive with application of delta-V.
Proximity operations support
Safety of flight
Maneuver planning / conjunction assessment
Anomaly Detection / Patterns of Life
Monitoring for sudden unexpected changes in satellite behaviors by observing payload, beacon, and telemetry signals.
Anomaly resolution support
Safety of flight
Satellite Health and Safety
Passive Ranging
Time Difference of Arrival, Frequency Difference of Arrival multi-aperture range estimation
Catalog maintenance
Maneuver planning / conjunction assessment
Ephemeris generation
Regarding maneuvers, Satellites often maneuver for small adjustments in station keeping or larger adjustments when changing orbital characteristics. In the SSA domain today, detection of a maneuvering satellite is complicated as the primary means of doing so is from ground based radars or optical telescopes. Often these resources are not available to support persistent monitoring, are unavailable during daytime, or are not geographically located where they can apply their capabilities. Passive RF sensors provide an excellent, augmentation capability in that they are 24/7 capable and not affected by adverse weather. Furthermore, in addition to detection of a maneuver event, with multiple RF sensors the direction of the maneuver can be determined and ephemeris for the spacecraft post maneuver can be generated.
Next, characterization through RF sensing of SATCOM transponder, payload and telemetry signals can be used to determine nominal behavior of an RSO, and provide an indication when the satellite has deviated from its defined norm. This characterization can be collected over extended periods, stored and then used as a reference for comparison purposes. This collection of RF information becomes the satellites established pattern of life. An example of where RF sensing detected an anomaly based upon a deviation from expected behavior was clearly observed with the AMC-9 anomaly that happened in June 2017.
Finally, passive ranging and ephemeris generation can be accomplished by collecting and cross correlating RF signals at multiple ground antenna locations. The process is similar to the method GPS receivers utilize but in reverse. With each collection system calculating delay times from the transmitter, and using surveyed collection sites, the range and angles to the satellite can be determined thus providing the ability to generate state vectors on the RSO.
Date of Conference: September 11-14, 2018
Track: Poster