Matthew Stevenson, LeoLabs; Michael Nicolls, LeoLabs; Inkwan Park, LeoLabs; Chris Rosner, LeoLabs Inc.;
Keywords: radar, LEO, RCS, orbit tracking, SSA, debris
Abstract:
We present an overview of the capabilities of LeoLabs’ Kiwi Space Radar (KSR) and a quantitative analysis of its measurement accuracy and precision. KSR is a recently-completed S-band radar in New Zealand. It is designed for the dual purposes of tracking catalogued low-Earth resident space objects (RSOs) and searching for RSOs smaller than the nominal 10-cm limit of current catalogues. KSR is the first of planned world-wide network of S-band radars being built by LeoLabs.
KSR is designed to be sensitive to targets with radar cross sections as small as -34 dBsm through LEO, corresponding to an approximate physical size of 2 cm. It is estimated that there are several hundred thousand such RSOs in LEO, the vast majority of which have yet to be catalogued. Collisions with RSOs this small are predicted to be catastrophic for active satellites. Therefore, there is a clear need for the cataloguing and tracking of these objects in order to allow the long-term, sustainable use of Low Earth Orbit.
KSR is capable of making high-fidelity, independent measurements of the range, doppler velocity, and angular positions of RSOs. The angular position measurements are achieved via interferometric correlation, which allows the instrument to pinpoint the target’s angular location within the radar beam. KSR is also designed with twin fields-of-view separated by 180 degrees in azimuth. This configuration provides an effective means for KSR to acquire widely time-separated measurements on a single target during a single transit. Such widely-separated measurements allow for full 6-parameter orbit fits during a single target transit, which is critical for gaining custody of previously uncatalogued targets.
KSR incorporates a novel data processing architecture which enables it to search a radar beam across all plausible range and doppler velocity values for Low Earth Orbit. This gives KSR the ability to conduct simultaneous tracking and searching operations: it can be scheduled to acquire measurements for orbit updates on catalogued targets, while simultaneously searching the very same data set for any uncatalogued pieces of small debris. These additional detections are possible even if the serendipitous targets have vastly different range and doppler velocity values than the intended target.
We demonstrate KSR’s performance through a quantitative analysis of its range and doppler velocity accuracy and precision. We do so via comparisons of KSR measurements with our own orbital solutions, as well as available high-precision third-party orbits. We show the improvement of orbital fit quality through the inclusion of KSR data.
We also show a quantitative analysis of KSR’s angular measurements. The accuracy and precision of these measurements is demonstrated via comparison to orbital predictions and self-consistency analysis. As part of this discussion, the importance of angular measurements for scheduling measurements in the KSR twin field-of-view is emphasized.
KSR’s radar cross section measurements are also presented. KSR’s radar cross section measurements give us a method for categorizing radar cross sections via approximate size. This, in turn, allows for more accurate orbital force modeling of atmospheric drag and solar radiation pressure, as well as conjunction analysis via hardbody radius. We also show how the radar cross section measurement precision allows for the extension of LeoLabs’ attitude stability index.
Finally, we present several case-studies using KSR data that illustrate the unique capabilities of this instrument and demonstrate the potential of the full LeoLabs network of radars when it is fully completed.
Date of Conference: September 15-18, 2020
Track: Optical Systems Instrumentation