Space Debris Tracking Research Articles

Using superconducting single photon detector to improve the coupling efficiency of multimode fibers in the telescope ranging system

The receiving system adopts the coupling manner of space beam and the multimode fiber among some space target laser ranging system. The fiber coupling efficiency can affect the number of echo photons and ranging accuracy, especially in lunar laser ranging, high orbit satellite laser ranging and space debris tracking. This article proposes a method utilizing the telescope pointing technique and a four-pixel superconducting nanowire single photon detector (SNSPDs) to measure coupling efficiency of multimode fiber. SNSPDs has the excellent performance with high detection efficiency, low dark count rate, and low recovery time. In the experiment, SNSPDs receives the changing signals caused by adjusting the offset angle of the telescope. The root mean square of deviation between measured results and theoretical calculations is 4.48%. The method is based on existing laser ranging systems and is suitable for scientific engineering verification of optical fibers already installed in the system and monitoring of system status.

A hybrid grey wolf optimizer using opposition-based learning, sine cosine algorithm and reinforcement learning for reliable scheduling and resource allocation

As the number of space debris in geosynchronous Earth orbits continues to grow, the threat posed by space debris to satellites surveillance is increasing, and the available orbital resources are also decreasing. Thus, reasonably scheduling and allocating the resources for space object tracking has become vital. This paper establishes an optimization model for the resource allocation and scheduling problem for space debris tracking. A fusion algorithm that combines the grey wolf optimizer, opposition-based learning, sine cosine search strategy, and reinforcement learning was proposed and used to solve the problem. Six groups of realistic data were selected based on the relevant background information of space debris tracking to test the validity and effectiveness of the proposed algorithm. The performance of the state-of-the-art optimization algorithms was compared with that of the proposed algorithms. The result of the experiment indicates that the proposed algorithm effectively solves the resource allocation and scheduling problem for space debris tracking.

Observation Strategy Optimization for Distributed Telescope Arrays with Deep Reinforcement Learning

Time-domain astronomy is an active research area now, which requires frequent observations of the whole sky to capture celestial objects with temporal variations. In the optical band, several telescopes in different locations could form a distributed telescope array to capture images of celestial objects continuously. However, there are millions of celestial objects to observe each night, and only limited telescopes could be used for observation. Besides, the observation capacity of these telescopes would be affected by different effects, such as the sky background or the seeing condition. It would be necessary to develop an algorithm to optimize the observation strategy of telescope arrays according to scientific requirements. In this paper, we propose a novel framework that includes a digital simulation environment and a deep reinforcement learning algorithm to optimize observation strategy of telescope arrays. Our framework could obtain effective observation strategies given predefined observation requirements and observation environment information. To test the performance of our algorithm, we simulate a scenario that uses distributed telescope arrays to observe space debris. Results show that our algorithm could obtain better results in both discovery and tracking of space debris. The framework proposed in this paper could be used as an effective strategy optimization framework for distributed telescope arrays, such as the Sitian project or the TIDO project.

Nonlinear attitude maneuvering of a flexible spacecraft for space debris tracking and collision avoidance

This work addresses the problem of attitude maneuvering of a spacecraft equipped with two flexible solar panels, in response to an alert in two distinct operational scenarios: (a) detection of an approaching debris, and (b) collision avoidance of an impacting debris. In scenario (a) the approaching debris is assumed to be off a collision course with the satellite. As a result, the latter can track the debris, to provide supplementary observations (in addition to those given by ground stations) that allow improving the estimation of its trajectory. Instead, in scenario (b) an impact is predicted, therefore the satellite shall perform a collision avoidance maneuver. This is designed with the objective of minimizing propellant consumption, while ensuring a miss distance greater than a specified threshold value. This research considers the overall dynamics by modeling the spacecraft as a multibody structure, with the use of the Kane's method, which simplifies the process of deriving all the governing equations, while identifying their minimum number. Flexibility is introduced using a modal decomposition technique, under the assumption of small amplitude oscillations. In the two scenarios of interest, efficient strategies are introduced to rotate the solar panels, for the purpose of either maximizing their irradiation or minimizing their oscillations. A new nonlinear reduced-attitude control law, which enjoys global stability properties, is proposed, and is shown to improve the performance of attitude maneuvers when only a single axis must be driven toward a desired direction. Actuation is modeled as well, by assuming the use of a pyramidal array of four single-gimbal control momentum gyroscopes. Their steering law includes singularity avoidance, based on the singular value decomposition of the actuation matrix. Numerical simulations demonstrate that the agile attitude maneuvering strategies proposed in this study allow achieving the operational objectives in the two scenarios of interest, with limited elastic oscillations.

Research on the Efficient Space Debris Observation Method Based on Optical Satellite Constellations

The increasing amount of space debris poses a major threat to the security of space assets. The timely acquisition of space debris orbital data through observations is essential. We established a mathematical model of optical satellite constellations for space debris observation, designed a high-quality constellation configuration, and designed a space debris tracking observation scheduling algorithm. These tools can realize the efficient networking of space debris from a large number of optical satellite observation facilities. We designed a constellation consisting of more than 20 low-Earth orbit (LEO) satellites, mainly dedicated to the observation of LEO space objects. According to the observation scheduling method, the satellite constellation can track and observe more than 93% of the targets every day, increase the frequency of orbital data updates, and provide support for the realization of orbital space debris cataloguing. Designing optical satellite constellations to observe space debris can help realize the advance perception of dangerous collisions, timely detect dangerous space events, make key observations about high-risk targets, greatly reduce the false alarm rate of collisions, and provide observational data support for space collisions.

Autonomous Trajectory Generation Comparison for De-Orbiting with Multiple Collision Avoidance.

Over the past four decades, space debris has been identified as a growing hazard for near-Earth space systems. With limited access to space debris tracking databases and only recent policy advancements made to secure a sustainable space environment and mission architecture, this manuscript aims to establish an autonomous trajectory maneuver to de-orbit spacecrafts back to Earth using collision avoidance techniques for the purpose of decommissioning or re-purposing spacecrafts. To mitigate the risk of colliding with another object, the spacecraft attitude slew maneuver requires high levels of precision. Thus, the manuscript compares two autonomous trajectory generations, sinusoidal and Pontragin’s method. In order to determine the Euler angles (roll, pitch, and yaw) necessary for the spacecraft to safely maneuver around space debris, the manuscript incorporates way-point guidance as a collision avoidance approach. When the simulation compiled with both sinusoidal and Pontryagin trajectories, there were differences within the Euler angle spacecraft tracking that could be attributed to the increased fuel efficiency by over five orders of magnitude and lower computation time by over 15 min for that of Pontryagin’s trajectory compared with that of the sinusoidal trajectory. Overall, Pontryagin’s method produced an autonomous trajectory that is more optimal by conserving 37.9% more fuel and saving 40.5% more time than the sinusoidal autonomous trajectory.

Matched template analysis of continuous wave laser for space debris ranging application

The growth of human-made space debris, sharing the same Earth’s orbital space as active satellites, is a worrying environmental condition. Precise tracking and orbital modelling of space debris are vital to predict potential future collisions with active satellites. This paper investigates a continuous-wave laser ranging method where a bench-top experiment models the reflected amplitude modulated optical signal from a space debris target. The optical signal is digitised and stored to undergo post-digital signal processing using a parameter estimation matched filter approach to estimate the time-varying delay between the target debris and the observing telescope. The experiment investigated two different detection methods, the direct detection of the optical signal and the coherent detection where the optical signal is amplified with a bright local oscillator before signal detection. The experimental results show that the coherent detection method can provide a more precise time-varying delay estimate than the direct detection method due to the improved signal-to-noise ratio. The experimental results also show improved precision in the parameter estimation when using larger portions of the acquired signal’s time series. The experimental results were used to model for a potential space debris application. For example, assuming the received signal power from the target debris is approximately 3.5fW, the time-varying delay of the target debris using the coherent detection method can be estimated with a precision of 1m/s using 2.5s of the acquired signal time series. This is well within the expected minimum time series that can be collected from a space debris target from a single flyover at the telescope site.

Active Control Loop of the BOROWIEC SLR Space Debris Tracking System.

The task of tracking cooperative satellites equipped with laser retroreflectors, by means of Satellite Laser Ranging (SLR), is an issue well described in the literature. The follow-up movement of the ground-based transceiver telescope behind an orbital object is based on the positional ephemeris data. The problem of controlling the follow-up motion of the telescope’s mount mostly in the configuration in this case boils down to the interpolation of the positional ephemeris data of the orbital object, which is the information input vector for the motion control system of the orthogonal and non-coupled axes of the propulsion system. In the case of tracking and determining the position of uncooperative objects (not equipped with retroreflectors), for which we can include rocket bodies and fragmentary elements, the task of keeping track of them becomes complex. The positional uncertainty of the ephemeris of uncooperative objects obtained mainly by means of survey radar acquisition requires the use of innovative solutions and complex control systems that enable the effective implementation of the tracking process. This paper presents innovative methods for the active control loop used in the SLR technique, consisting of dynamic motion corrections based on the passive optical acquisition with object recognition and analysis of the photon trace scattered from an orbital object.

Radarski sistem za praćenje ciljeva velikih brzina zasnovan na upotrebi BPSK signala i digitalnoj kompenzaciji doplerovog pomaka

Introduction/purpose: This paper presents a model of a high speed target radar tracking system that is much simpler than the existing ones. The Doppler shift is compensated before signal compression, simultaneously with the modification of the clock signal in the compression filter. This is possible thanks to the development of FPGA technology. The most important for this application are very fast clock control units which enable operation with different frequency references up to 1 GHz with an accuracy far below 1 Hz. Methods: In this paper, the methodology of mathematical modeling and simulation is used. Results: The results of the analysis of the most important effects in radars caused by high-speed targets are presented and discussed - target migration through resolution cells and compression filter response distortion due to high target acceleration. Conclusion: Thanks to flexible RF and signal processing hardware, complex radar processing procedures are not required. The sensitivity of the BPSK signal to the Doppler shift (which is usually considered a disadvantage) can be used to reject targets at a slightly different rate. This system can be used in space debris tracking, airspace target tracking, car driving, etc.

A Modern Space Situational Awareness System

We, Tuparev AstroTech in partnership with Astro Syteme Austria, present a next-generation Space Situational Awareness (SSA) system currently being created for the tracking and characterisation of satellites and space debris in the age of big-data astronomy. Our SSA system will be based on the image processing of white-light images to detect streaks produced by satellites and space debris. These images will be obtained by a network of 20-30 custom and in-house built SSA observatory stations, which will be made operational worldwide over the coming decade. The system will use machine learning algorithms to choose the optimal part of the sky to observe at any given moment, analyse the incoming data on-site and in real-time, and deliver various standardised data packages and science-quality images to be stored on a bespoke central archive capable of storing petabytes of data. With this system, we aim to cover a greater geographical and celestial area than any previous SSA system, to create a scalable system that is both fast and efficient, and to enable access to orders of magnitude more storage capacity and information than any other system currently available, commercial or governmental.

Measurements to Space Debris in 2016–2020 by Laser Sensor at Borowiec Poland

Abstract In 2014, a significant upgrade was made to the Borowiec (BORL 7811) laser-ranging system, which is the part of Space Research Centre of the Polish Academy of Sciences (SRC PAS). Two high-energy lasers modules were installed. First is the EKSPLA PL-2250, used for tracking objects equipped with retroreflectors. Second is the Continuum Surelite III, dedicated to the tracking of space debris without retroreflectors. In 2016, the BORL station joined the space debris tracking laser group and, since then, is tracking systematically inactive/defunct satellites and typical rocket bodies from LEO regime. Today, the BORL is tracking regularly about 80 different space debris objects. The paper presents the activity of the BORL laser station in observations of space debris. The results presented are from years 2016 to 2020. The sum of all passes from this period is almost 2 000, giving over 23 000 normal points. Average root mean square error (RMS) of objects with satellite laser ranging-dedicated (SLR-dedicated) retroreflectors ranges 1.5 cm–14 cm and of objects without SLR-dedicated retroreflectors ranges 8 cm–222 cm.

Astrobotics: Swarm Robotics for Astrophysical Studies

This paper introduces the emerging field of astrobotics, that is, a recently-established branch of robotics to be of service to astrophysics and observational astronomy. We first describe a modern requirement of dark matter studies, i.e., the generation of the map of the observable universe, using astrobots. Astrobots differ from conventional two-degree-of-freedom robotic manipulators in two respects. First, the dense formation of astrobots give rise to the extremely overlapping dynamics of neighboring astrobots which make them severely subject to collisions. Second, the structure of astrobots and their mechanical specifications are specialized due to the embedded optical fibers passed through them. We focus on the coordination problem of astrobots whose solutions shall be collision-free, fast execution, and complete in terms of the astrobots' convergence rates. We also illustrate the significant impact of astrobots assignments to observational targets on the quality of coordination solutions To present the current state of the field, we elaborate the open problems including next-generation astrophysical projects including 20,000 astrobots, and other fields, such as space debris tracking, in which astrobots may be potentially used

Advanced volume holographic filter to improve the SNR of polychromatic sources in a noisy environment.

We present a new type of filter that improves the SNR of systems where polychromatic signal and noise are located at different distances within the same line of sight. The filter is based on holographic technology that allows for the discrimination of wavefronts by range. In using a combination of two holographic elements, a pre-disperser and a thick volume hologram, we were able to significantly increase the spectral bandwidth of the filter, from 9nm without the pre-disperser to 70nm with both holographic elements. Laboratory proof of concept demonstrated that such a filter is capable of an SNR improvement of 15 dB for a monochromatic source, and up to 7.6 dB for a polychromatic source. This filter can find applications in astronomic observation, satellite or space debris tracking, and free-space optical communication.

Correcting TLEs at epoch: Application to the GPS constellation

Two-Line Elements (TLEs) issued by the space-track catalog are still the most extensive public data source for space debris tracking to date. However, TLEs accuracy at epoch is typically larger than 1 km in Low Earth Orbit (LEO) and 3 km in Medium Earth Orbit (MEO). Therefore, TLEs are too coarse to enable collision avoidance maneuvers. The present work aims at correcting TLEs orbits at epoch to enable operational conjunction assessment and help satellite operators better protect their assets at moderate cost.Using only Moon-Earth and Sun-Earth distance time series, as well as 2018 TLE data for 14 GPS satellites and SGP4 propagation over a short period, we were able to correct the TLEs of the 29 operational GPS satellites by 65% on average for year 2019, reducing the 3D RMS error at epoch from 2.2 km to 680 m. In other words, we improved TLEs accuracy from 5 km to 1.5 km with a 95% confidence level.

거창 레이저 추적 시스템의 광 경로 전환을 위한 회전 디스크의 우주쓰레기 레이저 추적 성능 분석

한국천문연구원은 인공위성 레이저 추적, 적응광학, 우주쓰레기 레이저 추적 등 과학 연구 및 국가적 미션을 수행하기 위해 다목적 레이저 추적 시스템 개발을 추진해 오고 있다. 지상에서 고출력 펄스 레이저를 발진하여 우주쓰레기로부터 반사된 신호를 바탕으로 거리를 측정하는 우주쓰레기 레이저 추적 시스템은 광 경로 전환을 위해 회전 디스크 방식을 이용한다. 이러한 방식은 수신검출기로 반사시킬 수 없는 충돌 영역이 발생하여 우주쓰레기 추적 성능에 영향을 미친다. 본 논문에서는 회전 디스크가 추적 성능에 영향을 미치는 홀 크기, 홀 개수, 회전 속도, 레이저와 홀의 중첩 비율, 레이저 빔 반경을 고려하여 추적 성능 분석 모델을 제시하였다. 제시된 성능 분석 모델을 이용하여 추적 범위 및 충돌 영역을 분석하고 거창 레이저 추적 시스템의 요구 조건을 만족하는 회전 디스크 사양을 제시하였다.

Sapienza Space debris Observatory Network (SSON): A high coverage infrastructure for space debris monitoring

Optical observations represent a passive method for space debris tracking and monitoring. Although being constrained to limited time intervals, e.g. when the target is in sunlight and the observatory is in darkness, a debris observatory network distributed over multiple locations can improve the observational interval and favor the data integration for more consistent and significant results. The Sapienza Space Systems and Space Surveillance Laboratory (S5Lab) At Sapienza University of Rome has established Sapienza Space debris Observatory Network (SSON), an international network of optical observatories addressed at debris surveillance. The network is composed of six observatories owned and controlled by Sapienza, plus five observational sites controlled by collaborators (mainly University of Michigan and the University of Bern). The network operations have been carried out during several observations campaign, including the Tiangong-1 space station re-entry campaign performed in support of the Inter-Agency space Debris Committee (IADC). The heterogeneous capabilities of the different observatories represent an advantage for acquiring a wider set of debris monitoring data with different techniques. A strong synergy between our institution and the Italian specialized industry has also revealed to be very productive in the context of the network establishment.The present paper will describe the SSON infrastructure and the opportunities, improvements and future perspectives for research institutions or space industry of this wide observatories network will be discussed.

Highly compact nanosecond laser for space debris tracking

This study demonstrated the use of a highly compact nanosecond laser system operating at 532 nm and producing a maximum output power of 70 W with a pulse width of 5 ns at 0.5 kHz, for space debris tracking. To improve the ranging accuracy while minimizing the influence of the pulse noise, a bidirectional Q-switch was adopted in the oscillator to generate a short pulse width with less tailing. The laser was applied for low-Earth-orbit space debris tracking, and space debris with the farthest distance of 1701.9 km at the minimum radar cross-section of 1 m2 could be detected with a ranging precision of up to 26.90 cm.

The ILRS: approaching 20 years and planning for the future

The International Laser Ranging Service (ILRS) was established by the International Association of Geodesy (IAG) in 1998 to support programs in geodesy, geophysics, fundamental constants and lunar research, and to provide the International Earth Rotation Service with data products that are essential to the maintenance and improvement in the International Terrestrial Reference Frame (ITRF), the basis for metric measurements of changes in the Earth and Earth–Moon system. Other scientific products derived from laser ranging include precise geocentric positions and motions of ground stations, satellite orbits, components of Earth’s gravity field and their temporal variations, Earth Orientation Parameters, precise lunar ephemerides and information about the internal structure of the Moon. Laser ranging systems are already measuring the one-way distance to remote optical receivers in space and are performing very accurate time transfer between remote sites in the Earth and in Space. The ILRS works closely with the IAG’s Global Geodetic Observing System. The ILRS develops (1) the standards and specifications necessary for product consistency, and (2) the priorities and tracking strategies required to maximize network efficiency. The service collects, merges, analyzes, archives and distributes satellite and lunar laser ranging data to satisfy a variety of scientific, engineering, and operational needs and encourages the application of new technologies to enhance the quality, quantity, and cost effectiveness of its data products. The ILRS works with (1) new satellite missions in the design and building of retroreflector targets to maximize data quality and quantity, and (2) science programs to optimize scientific data yield. Since its inception, the ILRS has grown to include forty laser ranging stations distributed around the world. The ILRS stations track more than ninety satellites from low Earth orbit (LEO) to the geosynchronous orbit altitude as well as retroreflector arrays on the surface of the Moon. Applications have been expanded to include time transfer, asynchronous ranging for targets at extended ranges, free space quantum telecommunications, and the tracking of space debris. Laser ranging technology is moving to lower energy, higher repetition rates (kHz), single-photon-sensitive detectors, shorter pulse widths, shorter normal point intervals for faster data acquisition, and increased pass interleaving, automated to autonomous operation with remote access, and embedded software for real-time updates and decision making. An example of pass interleaving is presented for the Yarragadee station (see Fig. 4); tracking of LEO satellites is often accommodated during break in LEO and GNSS passes. New satellites arrays provide more compact targets and work continues on the development of lighter less expensive arrays for satellites and the moon. The service now provides operational ITRF products including daily/weekly station positions and daily resolution Earth orientation products; the flow of weekly combination of satellite orbit files for LAGEOS/Etalon-1 and -2 has recently been established. New products are under testing through a pilot project on systematic error monitoring currently underway. The article will give an overview of activities underway within the service, paths forward presently envisioned, and current issues and challenges.

Ground Experiment Development for Acquiring, Tracking and Pointing of Small Space Debris

Space debris is increasingly threatening, especially small space debris on the order of centimeters because of the difficulties in detecting and cleaning. Various detection and active cleaning approaches have been reported. Among these approaches, the laser cleaning approach exhibits advantages of pollution free and high benefit-cost ratio. Compared with theoretical investigations of laser cleaning, experimental studies are not sufficient. To validate the detecting and cleaning methods of small space debris, the experimental setup for acquisition, tracking and pointing system is developed. Dual CCD cameras with filters are proposed to detect space debris. Additionally, a two degree-of-freedom laser pointing mirror using neural network control is presented. Finally, the proposed acquisition, tracking and pointing of small space debris is demonstrated in the experimental study.

Multi-Sensor Space Debris Tracking for Space Situational Awareness With Labeled Random Finite Sets

As a result of the dependence worldwide on satellite technology, it is now necessary to use advanced multi-target tracking algorithms for space debris tracking systems to maintain custody of space objects around the earth. One principal challenge is the correct association of observations with objects. This paper presents a multi-sensor, space-debris tracking algorithm using δ-generalized labeled multi-Bernoulli (δ-GLMB) filtering. The algorithm provides a solution to the key challenges (e.g., detection uncertainty, data association uncertainty, and clutter) in multiple object tracking. An efficient implementation of the multi-sensor δ-GLMB filter is proposed. In order to avoid exhaustively computing all the terms, we propose to use the ranked assignment algorithm with an extended assignment matrix for multiple sensors to determine the most significant terms. A measurement-based birth model is used to identify the previously unknown space objects. Sensors can have the same or different observation volumes. The expectation-maximization (EM) algorithm is used to approximate densities across observation volumes. The performance is demonstrated using the simulation results.