A device is described for generating true-time delays optically for microwave signals used in beam steering and beam shaping in phased-array antennas. The device can be adapted to provide delays from picoseconds to nanoseconds. A single, compact unit should provide parallel delays for more than 64 independent antenna elements with a greater than 6-bit resolution. The time delays are produced by multiple reflections in a mirror configuration with continuous refocusing. A single spatial light modulator selects independent optical path lengths for each of the parallel antenna elements. Amplitude control for beam shaping can be integrated into the device. The unit can be made rugged for harsh environments by use of solid-block construction. The operation of the true-time delay device is described, along with the overall system configuration. Preliminary experimental data are given.
Practical stellar interferometry for space domain awareness is
challenged by the relative motions of orbital objects and telescope
arrays that require array phasing using guide stars. An orbital
object’s image sensitivity to the location and brightness of the guide
star is problematic, possibly resulting in a degraded resolution or
loss of image content when both objects fall within the
interferometer’s field of view. We characterized an orbital object’s
visibility using visibility contrast to noise ratios (
C
N
R
Δ
v
) as a performance metric for orbital
object image quality. Experimental validations included orbital object
visibility measurements for dual binary pinholes that were scaled in
size and brightness individually to match expected interferometer data
collection scenarios. We show agreement in
C
N
R
Δ
v
results, indicating resolvable
orbital object signals during periods of collection when signal
contributions from both the orbital object and guide star are present.
Expanding presented results to imaging interferometers, we discuss how
dual object imaging could degrade performance under the scenarios
examined.
What is believed to be a novel holographic optical encoding scheme has been developed to enhance the performance of laser sensors designed for the measurement of wavelength and angular trajectory. A prototype holographic imaging diffractometer has been created to reconstruct holographic cueing patterns superimposed in the focal plane of wide-angle scene imagery. Based on experimental pattern metric measurements at the focal plane, a theoretical model is used to compute the laser source wavelength and its apparent propagation direction within the sensor's field of view. The benefits of incorporating holographic enhancements within an imager-based sensor architecture are discussed.
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