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32 pages, 6124 KiB

Open AccessArticle

Range-Doppler-Time Tensor Processing for Deep-Space Satellite Characterization Using Narrowband Radar

by Alexander Serrano, Jack Capper, Robert L. Morrison, Jr. and Mohamed D. Abouzahra

Remote Sens. 2024, 16(8), 1374; https://doi.org/10.3390/rs16081374 - 13 Apr 2024

Viewed by 553

Abstract

There is growing demand for the high-fidelity characterization of satellites in Geosynchronous Earth Orbit (GEO) to support Space Domain Awareness (SDA). This is particularly true for newly launched satellites, where it is necessary for satellite providers to ascertain whether components have deployed properly. [...] Read more.

There is growing demand for the high-fidelity characterization of satellites in Geosynchronous Earth Orbit (GEO) to support Space Domain Awareness (SDA). This is particularly true for newly launched satellites, where it is necessary for satellite providers to ascertain whether components have deployed properly. Conventional wideband radar systems are capable of imaging satellites provided that (i) they have sufficient power aperture and bandwidth, and (ii) they observe enough target aspect change to generate a resolved image. While wideband radars are used routinely for characterizing satellites in Low-Earth Orbit (LEO), powerful radars with sensitivity sufficient for large GEO ranges (36,000 km or greater) are lacking. Thus, researchers often rely on more widely available high-power narrowband tracking radars for GEO characterization. In this paper, we present a novel range-Doppler-time (RDT) tensor processing technique for GEO characterization with narrowband radar. This technique encapsulates the strengths of previously proposed methods for narrowband-radar characterization at GEO, providing a generalized approach that can be applied in a variety of settings. The technique generates fully resolved 2D images of rotating GEO satellites in low-bandwidth scenarios. In cases where aspect change is limited, the technique provides detailed Doppler information for enhanced satellite status monitoring. This work presents a comprehensive quantitative analysis of the technique that considers the impact of key parameters on characterization performance. Simulated radar data, and radar data collected in a compact range on a scaled satellite model, are used to evaluate the technique. Full article

(This article belongs to the Special Issue Radar for Space Observation: Systems, Methods and Applications)

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24 pages, 7230 KiB

Open AccessArticle

Space Domain Awareness Observations Using the Buckland Park VHF Radar

by David A. Holdsworth, Andrew J. Spargo, Iain M. Reid and Christian L. Adami

Remote Sens. 2024, 16(7), 1252; https://doi.org/10.3390/rs16071252 - 1 Apr 2024

Viewed by 646

Abstract

There is increasing interest in space domain awareness worldwide, motivating investigation of the use of non-traditional sensors for space surveillance. One such class of sensor is VHF wind profiling radars, which have a low cost relative to other radars typically applied to this [...] Read more.

There is increasing interest in space domain awareness worldwide, motivating investigation of the use of non-traditional sensors for space surveillance. One such class of sensor is VHF wind profiling radars, which have a low cost relative to other radars typically applied to this task. These radars are ubiquitous throughout the world and may potentially offer complementary space surveillance capabilities to the Space Surveillance Network. This paper updates an initial investigation on the use of Buckland Park VHF wind profiling radars for observing resident space objects in low Earth orbit to further investigate the space surveillance capabilities of the sensor class. The radar was operated during the Australian Defence “SpaceFest” 2019 activity, incorporating new beam scheduling and signal processing functionality that extend upon the capabilities described in the initial investigation. The beam scheduling capability used two-line element propagations to determine the appropriate beam direction to use to observe transiting satellites. The signal processing capabilities used a technique based on the Keystone transform to correct for range migration, allowing the development of new signal processing modes that allow the coherent integration time to be increased to improve the SNR of the observed targets, thereby increasing the detection rate. The results reveal that 5874 objects were detected over 10 days, with 2202 unique objects detected, representing a three-fold increase in detection rate over previous single-beam direction observations. The maximum detection height was 2975.4 km, indicating a capability to detect objects in medium Earth orbit. A minimum detectable RCS at 1000 km of −10.97 dBm² (0.09 m²) was observed. The effects of Faraday rotation resulting from the use of linearly polarised antennae are demonstrated. The radar’s utility for providing total electron content (TEC) measurements is investigated using a high-range resolution mode and high-precision ephemeris data. The short-term Fourier transform is applied to demonstrate the radar’s ability to investigate satellite rotation characteristics and monitor ionospheric plasma waves and instabilities. Full article

(This article belongs to the Special Issue Radar for Space Observation: Systems, Methods and Applications)

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30 pages, 1835 KiB

Open AccessArticle

Numerical Evaluation of Planetary Radar Backscatter Models for Self-Affine Fractal Surfaces

by Anne Virkki

Remote Sens. 2024, 16(5), 890; https://doi.org/10.3390/rs16050890 - 2 Mar 2024

Viewed by 636

Abstract

Numerous analytical radar-scattering laws have been published through the past decades to interpret planetary radar observations, such as Hagfors’ law, which has been commonly used for the Moon, and the cosine law, which is commonly used in the shape modeling of asteroids. Many [...] Read more.

Numerous analytical radar-scattering laws have been published through the past decades to interpret planetary radar observations, such as Hagfors’ law, which has been commonly used for the Moon, and the cosine law, which is commonly used in the shape modeling of asteroids. Many of the laws have not been numerically validated in terms of their interpretation and limitations. This paper evaluates radar-scattering laws for self-affine fractal surfaces using a numerical approach. Traditionally, the autocorrelation function and, more recently, the Hurst exponent, which describes the self-affinity, have been used to quantify the height correlation. Here, hundreds of three-dimensional synthetic surfaces parameterized using a root-mean-square (rms) height and a Hurst exponent were generated, and their backscattering coefficient functions were computed to evaluate their consistency with selected analytical models. The numerical results were also compared to empirical models for roughness and radar-scattering measurements of Hawaii lava flows and found consistent. The Gaussian law performed best at predicting the rms slope regardless of the Hurst exponent. Consistent with the literature, it was found to be the most reliable radar-scattering law for the inverse modeling of the rms slopes and the Fresnel reflection coefficient from the quasi-specular backscattering peak, when homogeneous statistical properties and a ray-optics approach can be assumed. The contribution of multiple scattering in the backscattered power increases as a function of rms slope up to about 20% of the backscattered power at normal incidence when the rms slope angle is 46°. Full article

(This article belongs to the Special Issue Radar for Space Observation: Systems, Methods and Applications)

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17 pages, 17331 KiB

Open AccessArticle

ATLAS: Latest Advancements and First Observations

by João Pandeirada, Miguel Bergano, Paulo Marques, Bruno Coelho, Domingos Barbosa and Mário Figueiredo

Remote Sens. 2024, 16(4), 704; https://doi.org/10.3390/rs16040704 - 17 Feb 2024

Viewed by 883

Abstract

The increasing amount of space debris poses a significant threat to operational satellites and space-based services. This article updates the community on the current status of the development of ATLAS, a tracking radar that is part of the EUSST network and aims to [...] Read more.

The increasing amount of space debris poses a significant threat to operational satellites and space-based services. This article updates the community on the current status of the development of ATLAS, a tracking radar that is part of the EUSST network and aims to detect space objects in low Earth orbits. This article focuses on the latest activities performed: calibration of the pointing system and initial observations of space objects. The calibration procedure consisted of cross-scanning the Solar disk and yielded great results, obtaining an offset of 5.3° in azimuth and 0.10° in elevation. The first observation campaign resulted in 33 range detections of the International Space Station (ISS) with a probability of false alarm of

10^{- 9}

. The observations were then used to readjust the radar equation to assess the real-world performance of the system. Full article

(This article belongs to the Special Issue Radar for Space Observation: Systems, Methods and Applications)

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24 pages, 10663 KiB

Open AccessArticle

Space Target Tracking with the HRRP Characteristic-Aided Filter via Space-Based Radar

by Shuyu Zheng, Libing Jiang, Qingwei Yang, Yingjian Zhao and Zhuang Wang

Remote Sens. 2023, 15(19), 4808; https://doi.org/10.3390/rs15194808 - 3 Oct 2023

Cited by 1 | Viewed by 1084

Abstract

Approaching space target tracking is a typical and challenging mission in the space situational awareness (SSA) field. As the space-based radar is able to monitor the space targets of interest full-weather all-time, the space-based radar system is utilized in this paper. However, most [...] Read more.

Approaching space target tracking is a typical and challenging mission in the space situational awareness (SSA) field. As the space-based radar is able to monitor the space targets of interest full-weather all-time, the space-based radar system is utilized in this paper. However, most multi-target tracking (MTT) filters in target tracking studies merely utilize the location or narrow measurements, and many potentially valuable electromagnetic scattering characteristics are missed, which leads to space target false tracking problems. The space-based radar transmits a wide-band signal, and the measured high-resolution range profile (HRRP) information is an effective characteristic for different target discrimination. Therefore, the HRRP characteristics of space targets are implemented into the update recursion of the MTT filter, which can be utilized to improve the tracking performance. Then, to predict the target HRRP sequence, the geometrical theory of diffraction (GTD) model is utilized. Additionally, a modified spatial spectrum method with a novel covariance matrix is designed to improve the scattering parameter estimation accuracy. Finally, an adapting threshold is devised for merging the Gaussian mixture (GM) components weights. The proposed threshold is on the basis of the proposed HRRP characteristic-aided probability hypothesis density (PHD) filter, and it can tackle the problem of space target discrimination. Simulation results validate the effectiveness and robustness of the proposed probability hypothesis density (HGI-PHD) filter aided by HRRP information and improved with GM weights. Full article

(This article belongs to the Special Issue Radar for Space Observation: Systems, Methods and Applications)

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22 pages, 43024 KiB

Open AccessArticle

Joint Power and Bandwidth Allocation with RCS Fluctuation Characteristic for Space Target Tracking

by Qingwei Yang, Libing Jiang, Shuyu Zheng, Yingjian Zhao and Zhuang Wang

Remote Sens. 2023, 15(16), 3971; https://doi.org/10.3390/rs15163971 - 10 Aug 2023

Viewed by 839

Abstract

Reasonable allocation of space-based radar resources is a crucial aspect of improving the accuracy of space multi-target tracking and enhancing spatial awareness. The conventional resource allocation algorithm fails to exploit the high dynamic radar cross-section (RCS) characteristics, resulting in poor tracking robustness, tracking [...] Read more.

Reasonable allocation of space-based radar resources is a crucial aspect of improving the accuracy of space multi-target tracking and enhancing spatial awareness. The conventional resource allocation algorithm fails to exploit the high dynamic radar cross-section (RCS) characteristics, resulting in poor tracking robustness, tracking divergence, or even loss of tracking. However, the RCS of space targets fluctuates considerably in actual tracking scenarios, which cannot be disregarded for space target tracking tasks. To address this issue, we propose an adaptive allocation method that considers the dynamic RCS fluctuation characteristic for space-based radar tracking assignments. The proposed method exploits the predictable orbital information of space target to calculate the real-time observation angle of radar, and then obtains the multi-target dynamic RCS through the target RCS dataset. By combining the obtained RCS sequence, radar power, and bandwidth, an optimal model for radar tracking accuracy is established based on the multi-target posterior Cramér–Rao lower bound (PCRLB) to evaluate the tracking performance. By resolving the aforementioned multivariance optimization problem, we eventually acquire the results of power and bandwidth pre-allocation for tracking multiple space targets. Simulation results validate that, compared with the traditional methods, the proposed joint dynamic RCS power and bandwidth allocation (JRPBA) method can achieve superior tracking accuracy and minimize instances of missed tracking. Full article

(This article belongs to the Special Issue Radar for Space Observation: Systems, Methods and Applications)

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21 pages, 6098 KiB

Open AccessArticle

The Radar Signal Processor of the First Romanian Space Surveillance Radar

by Călin Bîră, Liviu Ionescu and Alexandru Rusu-Casandra

Remote Sens. 2023, 15(14), 3630; https://doi.org/10.3390/rs15143630 - 21 Jul 2023

Viewed by 1352

Abstract

This paper describes the work for the radar signal processor, the core of the Cheia space surveillance radar. It presents the basic operation, the requirements and the achieved processing performance together with a description of optimizations both in terms of signal-to-noise ratio and [...] Read more.

This paper describes the work for the radar signal processor, the core of the Cheia space surveillance radar. It presents the basic operation, the requirements and the achieved processing performance together with a description of optimizations both in terms of signal-to-noise ratio and in terms of software processing. The Cheia Radar is financed by the European Space Agency and will be used for the tracking of low Earth orbit objects and for refining the international catalogs of space objects. Full article

(This article belongs to the Special Issue Radar for Space Observation: Systems, Methods and Applications)

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Review

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24 pages, 24671 KiB

Open AccessReview

Overview of High-Power and Wideband Radar Technology Development at MIT Lincoln Laboratory

by Michael MacDonald, Mohamed Abouzahra and Justin Stambaugh

Remote Sens. 2024, 16(9), 1530; https://doi.org/10.3390/rs16091530 - 26 Apr 2024

Viewed by 465

Abstract

This paper summarizes over 60 years of radar system development at MIT Lincoln Laboratory, from early research on satellite tracking and planetary radar to the present ability to perform the centimeter-resolution imaging of resident space objects and future plans to extend this capability [...] Read more.

This paper summarizes over 60 years of radar system development at MIT Lincoln Laboratory, from early research on satellite tracking and planetary radar to the present ability to perform the centimeter-resolution imaging of resident space objects and future plans to extend this capability to geosynchronous range. Full article

(This article belongs to the Special Issue Radar for Space Observation: Systems, Methods and Applications)

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Other

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16 pages, 16925 KiB

Open AccessTechnical Note

Micro-Doppler Signature Analysis for Space Domain Awareness Using VHF Radar

by Emma Heading, Si Tran Nguyen, David Holdsworth and Iain M. Reid

Remote Sens. 2024, 16(8), 1354; https://doi.org/10.3390/rs16081354 - 12 Apr 2024

Viewed by 498

Abstract

The large quantity of resident space objects orbiting Earth poses a threat to safety and efficient operations in space. Radar sensors are well suited to detecting objects in space including decommissioned satellites and debris, whereas the more commonly used optical sensors are limited [...] Read more.

The large quantity of resident space objects orbiting Earth poses a threat to safety and efficient operations in space. Radar sensors are well suited to detecting objects in space including decommissioned satellites and debris, whereas the more commonly used optical sensors are limited by daylight and weather conditions. Observations of three non-operational satellites using a VHF radar system are presented in this paper in the form of micro Doppler signatures associated with rotational motion. Micro Doppler signatures are particularly useful for characterising resident space objects at VHF given the limited bandwidth resulting in poor range resolution. Electromagnetic simulations of the micro Doppler signatures of the defunct satellites are also presented using simple computer-aided design (CAD) models to assist with interpretation of the radar observations. The simulated micro Doppler results are verified using the VHF radar data and provide insight into the attitude and spin axis of the three resident space objects. As future work, this approach will be extended to a larger number of resident space objects which requires a automated processing. Full article

(This article belongs to the Special Issue Radar for Space Observation: Systems, Methods and Applications)

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