Recognition of objects in orbit and their intentions with space‐borne sub‐THz Inverse Synthetic Aperture Radar

An important aspect of Space Situational Awareness is to estimate the intent of objects in space. This paper discusses how discriminating features can be obtained from Inverse Synthetic Aperture Radar images of such objects and how these discriminators can be used to recognise the objects or to estimate their intent. If the object is, for example, a satellite of a known type, the scheme proposed is able to recognise it. The ability of the scheme to detect damage to the object is also discussed. The focus is on imagery obtained in the sub-terahertz band (typically 300 GHz) because of the greater imaging capability given by the diffuse scattering which is observed at these frequencies. The paper also discusses the importance of being able to use images obtained by electromagnetic simulation to be able to train the subsystem which recognises features of the objects and describes a practical scheme for creating these simulations for large objects at these very short wavelengths

Plasma Biomarkers of Brain Atrophy in Alzheimer's Disease

Peripheral biomarkers of Alzheimer's disease (AD) reflecting early neuropathological change are critical to the development of treatments for this condition. The most widely used indicator of AD pathology in life at present is neuroimaging evidence of brain atrophy. We therefore performed a proteomic analysis of plasma to derive biomarkers associated with brain atrophy in AD. Using gel based proteomics we previously identified seven plasma proteins that were significantly associated with hippocampal volume in a combined cohort of subjects with AD (N = 27) and MCI (N = 17). In the current report, we validated this finding in a large independent cohort of AD (N = 79), MCI (N = 88) and control (N = 95) subjects using alternative complementary methods—quantitative immunoassays for protein concentrations and estimation of pathology by whole brain volume. We confirmed that plasma concentrations of five proteins, together with age and sex, explained more than 35% of variance in whole brain volume in AD patients. These proteins are complement components C3 and C3a, complement factor-I, γ-fibrinogen and alpha-1-microglobulin. Our findings suggest that these plasma proteins are strong predictors of in vivo AD pathology. Moreover, these proteins are involved in complement activation and coagulation, providing further evidence for an intrinsic role of these pathways in AD pathogenesis

Simple generic ways to estimate radar performance and tolerable interference levels

A generic way of estimating the radar cross section of radar targets is introduced, which can be used to make simple estimates of radar performance. This approach is complemented by simple ways of approximating the detection performance of a well-designed radar and estimates of the resolution to which an operator can detect changes in the performance of a radar.</p

Amplitude distribution of low grazing angle G-band littoral sea clutter

G-band radar sensing of the marine environment is of interest for maritime autonomy, however at present, no phenomenological data of low grazing angle sea clutter at this frequency is available in the literature. Future sensor design is contingent on the modeling of empirical data, with polarization expected to be a key parameter. This paper presents the results of an analysis of data of radar returns from the water’s surface gathered in 2022 at Coniston Water, UK. The difference in amplitude distribution and normalized radar cross section (NRCS) between HH (horizontal-horizontal) and VV (vertical-vertical) polarization is shown for two 0.5° wide grazing angle swaths centered at 2° and 4°. HH is seen to produce longer-tailed distributions than VV for both swaths, with a mean NRCS for thresholded data (i.e. for wave signal peaks) of -33.3 dB (HH) and -35.2 dB (VV) for the swath centered at 2°, and -38.6 dB (HH) and -41.6 dB (VV) for the swath centered at 4°

Amplitude distribution of low grazing angle G-band littoral sea clutter

G-band radar sensing of the marine environment is of interest for maritime autonomy, however at present, no phenomenological data of low grazing angle sea clutter at this frequency is available in the literature. Future sensor design is contingent on the modeling of empirical data, with polarization expected to be a key parameter. This paper presents the results of an analysis of data of radar returns from the water’s surface gathered in 2022 at Coniston Water, UK. The difference in amplitude distribution and normalized radar cross section (NRCS) between HH (horizontal-horizontal) and VV (vertical-vertical) polarization is shown for two 0.5° wide grazing angle swaths centered at 2° and 4°. HH is seen to produce longer-tailed distributions than VV for both swaths, with a mean NRCS for thresholded data (i.e. for wave signal peaks) of -33.3 dB (HH) and -35.2 dB (VV) for the swath centered at 2°, and -38.6 dB (HH) and -41.6 dB (VV) for the swath centered at 4°

Space-Based Sub-THz ISAR for Space Situational Awareness-Laboratory Validation

The advantages of sub-Terahertz technology (sub-THz, 200a700 GHz) have already been advanced for imaging and recognition of a space object's state from a space-based sensor using inverse synthetic aperture radar (ISAR). The technology benefits from wide absolute signal bandwidths, giving high range resolution and from enhanced sensitivity to surface texture. An experimental validation of such a system in controlled laboratory conditions is presented. Possible image formation methods are proposed and evaluated experimentally. Images of real parts of satellites have been produced at sub-THz frequencies and compared to lower frequency images. Other results include sub-THz bistatic ISAR, and sub-THz cross-polarized images which highlight the scattering from rough surfaces while attenuating the very bright scatterers seen from conventional monostatic images.</p