Kathleen Minear, Specialized Arrays Inc; G. Patrick Martin, Specialized Arrays Inc
Keywords: Space situational awareness, orbital debris, orbit determination, widely-spaced coherent transmit arraying, large reflector uplink arraying, complex envelope phase/time transfer, radar, LILO, AOA
Abstract:
A comprehensive solution for detection and one-pass accurate characterization of all Earth-propagating objects that incorporates widely-spaced coherent transmit arraying has been developed, modeled, and simulated. Performance characteristics, enabling technologies, how it works and future direction will be presented.
On a two-year government contract ending on September 29, 2010, we led a team of engineers in a successful demonstration of widely-spaced large reflector coherent transmit arraying at X-band to the DSCS B13 satellite. The system consisted of three 12m reflectors set more than 60m apart (>2000 wavelengths). This break-through capability is one of the enabling technologies in the Equatorial Space Situational Awareness (SSA) radar array presented here.
In this demonstration modulated signals from the three 12m antennas were combined at 8GHz with nearly theoretical results. During a Florida tropical depression less than 0.5 dB combining loss was achieved. Critical advances from this demonstration included (1) the instant availability of the array (no system calibration is required), (2) phase transfer synchronization (vs. time), (3) complex envelope beamforming at baseband and (4) real-time atmospheric compensation. Because of these features it was recognized by NASA to be the first operationally feasible solution for widely-spaced, large reflector, coherent transmit arraying.
Over the last six years we have developed a method and system for SSA using a radar array of widely-spaced ground reflectors. The enabling technologies are: (1) widely-spaced coherent transmit arraying (providing exceptional EIRP, G/T and AOA), (2) location near or on the Equator and orientation pointing towards the horizon, (3) very high accuracy AOA (4) specialized hardware for time differentials and Doppler and (5) specialized algorithms for target location and velocity determination. From these measurements we calculate orbit parameters. Importantly, this method mitigates the too short arc (TSA) problem, (object time in the beam) due to the high precision Angle of Arrival, AOA resulting from the array diameter orientation and advanced algorithms.
The proposed system works on the principal that ALL propagating (non-station-kept) Earth-orbiting objects will pass through a strategically placed array beam and with advanced hardware and algorithms those objects can be characterized with unprecedented accuracy immediately. The objects orbit parameters are determined within a single pass coincident with its detection. The array is expandable for smaller objects and longer distances. With only a three reflector minimal configuration, ?40dBsm (marble sized) objects can be detected up to 1000km. Orbit errors of a few meters position and a few cm/sec velocity are predicted for -40dBsm LILO objects. Importantly the array can immediately transition to an ISAR imaging mode while the system tracks the object.
Date of Conference: September 11-14, 2018
Track: Poster