Daniel Finch, Silentium Defence; James Palmer, Silentium Defence; James Cooper, COMSPOC; Daniel Oltrogge, COMSPOC; Thomas Johnson, Exa Research, LLC
Keywords: Silentium Defence, Passive Radar, MAVERICK, validation
Abstract:
Passive radar, unlike traditional radar, utilises radio frequency (RF) energy already in the environment to obtain radar detections in lieu of a dedicated transmitter. With an abundance of existing energy available from geographically diverse sources, passive radar offers wide field of view coverage and long observation times. Further, without the need to operate the transmit infrastructure, and the authorisations and associated timelines that accompany radiating high energy into space, lower operational costs can be achieved. Passive radar can also operate continuously, regardless of the time of day or weather conditions, to enable observations to be conducted uninterrupted. This technology is also markedly different from passive RF, as it provides direct observations of debris or other non-active resident space objects (RSOs).
Passive radar has made significant inroads as a disruptive technology across multiple markets and surveillance applications over the last decade. The adaptation of passive radar to the surveillance of space has been reported, however Silentium Defences MAVERICK S-series system is the first purpose-built Space Situational Awareness (SSA) sensor utilising this technology.
Silentium Defence has recently opened its first observatory hosting the MAVERICK sensor. Developed with the support of the Australian Space Agency, and called Oculus, the observatory is positioned within a 180-ha parcel of land located in a rural area north of the city of Adelaide in South Australia. Offering a near unimpeded horizon-to-horizon view and located on the outer edge of a dark-sky reserve, this site is also well positioned to host complementary SSA sensors.
The MAVERICK S-series sensor exploits FM radio broadcasts transmitted from multiple sites across south-eastern Australia. Located up to 400 km from the observatory, these broadcast sites collectively transmit several megawatts of continuously radiated power across the field of regard. A 64-element surveillance array at the observatory, constructed of folded dipole antennas and arranged in two perpendicular arms, is used to collect the RF energy reflected off the RSOs. The signal from each channel is conditioned and digitised independently, allowing simultaneous receive beams to be formed during the processing stage. A set of high-gain antennas are used at the observatory to obtain a reference copy of the broadcast signals, and a single high-performance computer is then utilised to perform the processing to produce the radar metric observations.
MAVERICK natively measures time difference of arrival (relative to each of the broadcast signal also known as bistatic delay), frequency difference of arrival (Doppler), and angle in two dimensions. Further motion derivatives are also able to be inferred from these measurements. Taking advantage of the long observation durations that are possible with this technology (due to the ultra-wide field of view in both angular dimensions and the continuous signal transmission) enables an accurate orbit to be determined within a single pass. The ability to form multiple receive beams also allows numerous RSOs to be tracked simultaneously across the entire field of regard.
Silentium Defences observation analysis dashboard enables a detailed assessment of the data and comparison to ephemeris data for validation purposes. Data from the Oculus observatory is currently being assessed in collaboration with COMSPOC to verify the accuracy and calibration of the system.
In this presentation, we will provide a brief overview of the passive radar concept before covering capabilities and opportunities for low Earth orbit SSA. Using a unique selection of data obtained from the MAVERICK radar, this work will demonstrate the benefits that passive radar offers for SSA and how it may form part of a complementary suite of SSA sensors.
Date of Conference: September 27-20, 2022
Track: SSA/SDA