Debris Laser Research Articles

Study on Echo Characteristics of Debris Laser Ranging Based on Multi-Elevation Method

Study on Echo Characteristics of Debris Laser Ranging Based on Multi-Elevation Method

Analysis of the Ranging Capability of a Space Debris Laser Ranging System Based on the Maximum Detection Distance Model

Based on the radar equation and system noise characteristics, the maximum detection range model of a space debris laser ranging system at a 1064 nm wavelength is established, taking into account the factors of atmospheric transmission and sky background radiance. Through theoretical analysis and simulation experiments, the influencing factors of atmospheric transmission and sky background radiance are studied, and the influencing factors are normalized into the maximum detection range model by polynomial fitting. The results indicate that a high atmospheric transmission comes from a high altitude and low target zenith angle; a low sky background radiance comes from a small target zenith angle and low solar altitude angle, while the angular distance has no obvious influence on the sky background radiance. The experimental results indicate that the comprehensive accuracy of the maximum detection range model of the system is 86%, and the effectiveness of the model is verified by using a 1064 nm wavelength laser ranging for the debris target with a distance of 700–1100 km and a cross section area of 4–10 m2. The model can be used to evaluate the ability of the space debris laser ranging system at a 1064 nm wavelength.

The factors influencing the success probability of near-infrared space debris laser ranging detection

The factors influencing the success probability of near-infrared space debris laser ranging detection

Space Debris Laser Ranging with range-gate-free Superconducting Nanowire Single-Photon Detector

Space Debris Laser Ranging (DLR) is a technique to measure range to defunct satellites, rocket bodies or other space targets in orbits around Earth. The analysis shows that one of the reasons for the low success probability of DLR is the inaccurate orbital prediction of targets. Then it is proposed to use the Superconducting Nanowire Single-Photon Detector (SNSPD) running in automatic-recoverable range-gate-free mode, in which case, the effect of the accuracy of the target’s orbital prediction on the success probability of DLR is greatly reduced. In this way, 249 space debris were successfully detected and 532 passes of data were obtained. The smallest target detected was the space-debris (902) with an orbital altitude of about 1000 km and a Radar Cross Section (RCS) of 0.0446 m2. The farthest target detected was the space-debris (12,445) with a large elliptical orbit and an RCS of 18.2505 m2, of which the range of the normal point (NPT) of the measured arc-segment on January 27, 2019 was 6260.805 km.

Range Prediction Deviation Real-time Correction Algorithm for Space Debris Laser Ranging

Range Prediction Deviation Real-time Correction Algorithm for Space Debris Laser Ranging

Real time recognition method of weak signal in space debris laser ranging

Real time recognition method of weak signal in space debris laser ranging

Developments of Space Debris Laser Ranging Technology Including the Applications of Picosecond Lasers

Debris laser ranging (DLR) is receiving considerable attention as an accurate and effective method of determining and predicting the orbits of space debris. This paper reports some technologies of DLR, such as the high pulse repetition frequency (PRF) laser pulse, large-aperture telescope, telescope array, multi-static stations receiving signals. DLR with a picosecond laser at the Shanghai Astronomical Observatory is also presented. A few hundred laps of space debris laser-ranging measurements have been made. A double-pulse picosecond laser with an average power of 4.2 W, a PRF of 1 kHz, and a wavelength of 532 nm has been implemented successfully in DLR, it’s the first time that DLR technology has reached a ranging precision at the sub-decimeter level. In addition, the characteristics of the picosecond-pulse-width laser transmission with the advantages of transmission in laser ranging were analyzed. With a mode of the pulse-burst picosecond laser having high average power, the DLR system has tracked small debris with a radar cross-section (RCS) of 0.91 m2 at a ranging distance up to 1726.8 km, corresponding to an RCS of 0.1 m2 at a distance of 1000 km. These works are expected to provide new technologies to further improve the performance of DLR.

1 kHz重复频率多脉冲皮秒激光器研制及其空间碎片激光测距应用

1 kHz重复频率多脉冲皮秒激光器研制及其空间碎片激光测距应用

Daylight space debris laser ranging

Satellite laser ranging allows to measure distances to satellites equipped with retroreflectors in orbits up to 36000 km. Utilizing a higher powered laser, space debris laser ranging detects diffuse reflections from defunct satellites or rocket bodies up to a distance of 3000 km. So far space debris laser ranging was only possible within a few hours around twilight while it is dark at the satellite laser ranging station and space debris is illuminated by the sun. Here we present space debris laser ranging results during daylight. Space debris objects are visualized against the blue sky background and biases corrected in real-time. The results are a starting point for all space debris laser ranging stations to drastically increase their output in the near future. A network of a few stations worldwide will be able to improve orbital predictions significantly as necessary for removal missions, conjunction warnings, avoidance maneuvers or attitude determination.

Tracking the space debris from the Changchun Observatory

Changchun Observatory tracked Space Debris since Feb. 2014. This paper presents the technologies and results of Changchun station for space debris laser ranging (DLR) system. The system operates with a laser of 60 mJ/10 ns/500 Hz@532 nm laser and an optical camera for closed-loop tracking. Target selection assistant was introduced to DLR system. To represent the probability of return, the rebound index was calculated. Data identification was implemented in tracking control software and data processing. To improve the return rate, Range Bias/Time Bias is auto-corrected in the tracking software. The aim of this paper is to show the results and the analysis of the space debris observed during the period from the year 2014 to the year 2016. There are 491 passes observed for 232 different space debris targets were obtained during 35 terminator sessions. The observed targets are ranging between 460 km to 1800 km, with Radar Cross Sections (RCS) from $>15~\mbox{m}^{2}$ to $<1.0~\mbox{m}^{2}$ . The Root Mean Square (RMS) value of the range is measured to be less than 1 m for small targets, due to the 10 ns laser pulse length while for large objects it can reach up to 3.5 meters.

The progress of laser ranging technology at Shanghai Astronomical Observatory

As an important station of International Laser Ranging Service (ILRS), Shanghai Astronomical Observatory (SHAO) has upgraded Satellite Laser Ranging (SLR) system with high repetition rate and achieved some technological progress. There are a lot of improvements for overall system performance, such as annual observation passes, measurement precision and quality of observation data. SLR technology with repetition rate of 10 kHz is accomplished firstly in China, and space debris laser ranging technology with 200 Hz laser is promoted and proved to be more detective for weak echo, which lead to successful measurement for 40,000 km satellites and space debris within 3000 km. At the same time, SLR based on multi-telescopes and 1064 nm wavelength are planned to make a breakthrough of detection capabilities, and also to expand its application fields. These progresses will be introduced in this paper in detail.

Space debris laser ranging with a 60 W single-frequency slab nanosecond green laser at 200 Hz

Space debris laser ranging was achieved with a 60 W, 200 Hz, 532 nm nanosecond slab, single-frequency green laser at the Shanghai Astronomical Observatory’s 60 cm satellite laser ranging system. There were 174 passes of space debris measured in 2017, with the minimum radar cross section (RCS) being 0.25 m2 and the highest ranging precision up to 13.6 cm. The RCS of space debris measured with the farthest distances in 174 passes was analyzed. The results show that the farthest measurement distance (R) and RCS (S) were fitted to R = 1388.159S0.24312, indicating that this laser can measure the distance of 1388.159 km at an RCS of 1 m2, which is very helpful to surveillance and research on low-Earth-orbit space debris.

Satellite Laser Ranging System at Geochang Station

Korea Astronomy and Space Science Institute (KASI) has been developing the space optical and laser tracking (SOLT) system for space geodesy, space situational awareness, and Korean space missions. The SOLT system comprises satellite laser ranging (SLR), adaptive optics (AO), and debris laser tracking (DLT) systems, which share numerous subsystems, such as an optical telescope and tracking mount. It is designed to be capable of laser ranging up to geosynchronous Earth orbit satellites with a laser retro-reflector array, space objects imaging brighter than magnitude 10, and laser tracking low Earth orbit space debris of uncooperative targets. For the realization of multiple functions in a novel configuration, the SOLT system employs a switching mirror that is installed inside the telescope pedestal and feeds the beam path to each system. The SLR and AO systems have already been established at the Geochang station, whereas the DLT system is currently under development and the AO system is being prepared for testing. In this study, the design and development of the SOLT system are addressed and the SLR data quality is evaluated compared to the International Laser Ranging Service (ILRS) tracking stations in terms of single-shot ranging precision. The analysis results indicate that the SLR system has a good ranging performance, to a few millimeters precision. Therefore, it is expected that the SLR system will not only play an important role as a member of the ILRS tracking network, but also contribute to future Korean space missions.

High precision space debris laser ranging with 4.2 W double-pulse picosecond laser at 1 kHz in 532nm

Space debris laser ranging with a 4.2 W double-pulse 532 nm picosecond laser at a pulse repetition frequency of 1 kHz was achieved at the Shanghai satellite laser ranging (SLR) station, which receiving telescope was 60 cm. Space debris’ radar cross sections were from 2 m2 to 12 m2, and ranging precision was up to centimeters. A compound regenerative amplifier was used to realize double pulses output with pulse space of 4.1 ns. Double pulses would have the same detection ability as the equal energy single pulse. A 500 μm diameter avalanche photo-diode detector with less than 10 kHz dark noise and a quantum efficiency of 40% at 532 nm was developed to improve the measurement capability. And also a spectral filter with high efficiency and narrow bandwidth were applied. Basing on the Shanghai SLR system, the laser ranging to space debris with picosecond laser at 1 kHz was successfully implemented for the first time among the global SLR stations. The results showed that the ranging precision root-mean-square can be achieved about 5 cm. It will be very useful to monitor and study the space debris.

First laser measurements to space debris in Poland

The Borowiec Satellite Laser Ranging station (BORL 7811, Borowiec) being a part of the Space Research Centre of the Polish Academy of Sciences (SRC PAS) went through modernization in 2014–2015. One of the main tasks of the modernization was the installation of a high-energy laser module dedicated to space debris tracking. Surelite III by Continuum is a Nd:YAG pulse laser with 10 Hz repetition rate, a pulse width of 3–5 ns and a pulse energy of 450 mJ for green (532 nm). This new laser unit was integrated with the SLR system at Borowiec performing standard satellite tracking. In 2016 BORL 7811 participated actively to the observational campaigns related to the space debris targets from LEO region managed by the Space Debris Study Group (SDSG) of the International Laser Ranging Service (ILRS).Currently, Borowiec station regularly tracks 36 space debris from the LEO regime, including typical rocket bodies (Russian/Chinese) and cooperative targets like the inactive TOPEX/Poseidon, ENVISAT, OICETS and others. In this paper the first results of space debris laser measurements obtained by the Borowiec station in period August 2016 – January 2017 are presented. The results gained by the SRC PAS Borowiec station confirm the rotation of the defunct TOPEX/Poseidon satellite which spins with a period of approximately 10 s. The novelty of this work is the presentation of the sample results of the Chinese CZ-2C R/B target (NORAD catalogue number 31114) which is equipped (probably) with retroreflectors. Laser measurements to space debris is a very desirable topic for the next years, especially in the context of the Space Surveillance and Tracking (SST) activity. Some targets are very easy to track like defunct ENVISAT or TOPEX/Poseidon. On the other hand, there is a big population of different LEO targets with different orbital and physical parameters, which are challenging for laser ranging like small irregular debris and rocket boosters.

Stare and chase of space debris targets using real-time derived pointing data

We successfully demonstrate Stare & Chase: Space debris laser ranging to uncooperative targets has been achieved without a priori knowledge of any orbital information. An analog astronomy CCD with a standard objective, piggyback mounted on our 50cm Graz SLR receive telescope, ‘stares’ into the sky in a fixed direction. The CCD records the stellar background within a field of view of approx. 7°. From the stellar X/Y positions on the sensor a plate solving algorithm determines the pointing data of the image center with an accuracy of approx. 15 arc seconds. If a sunlit target passes through this field of view, its equatorial coordinates are calculated, stored and a Consolidated Prediction Format (CPF) file is created in near real time. The derived CPF data is used to start laser ranging (‘chase’ the object) within the same pass to retrieve highly accurate distance information. A comparison of Stare & Chase CPFs with standard TLE predictions shows the possibilities and limits of this method.

Analysis on the experiment of satellite laser ranging of defunct Tiangong-1 spacecraft

Tiangong-1, which was launched on 29 September 2011, is the first prototype space station of China. During the past two years in its lifetime, Tiangong-1 has been visited by a series of Shenzhou spacecraft. On 21 March 2016, it had formally ended its service and now is replaced by Tiangong-2. The orbit of Tiangong-1 is about 400 km above the ground where Tiangong-2, the international space station and other satellites are located as well. The space debris is now posing great collision risk to these space assets. The satellite laser ranging (SLR) is a space tracking technique with the highest precision. Its precise data lay a solid foundation for reliable conjunction assessment. On October 2002, Greene, Mount Stromlo SLR station of Australia, announced that it was possible to track a piece of space debris of a size of 15 cm at a distance of 1250 km using the SLR technology. In 2011, both Graz SLR station of Austrian and Grasse LLR station of France succeeded in debris laser ranging data. In China, Shanghai Astronomical Observatory obtained debris laser ranging data in 2008, Yunnan Observatory in 2010 and Changchun Observatory in 2014 also obtained debris data using SLR. In 2014, Changchun Observatory observed a total of 244 space debris in altitude about 400 to 1800 km. Tiangong-1 spacecraft was equipped with corner cube reflectors (CCRs), which were designed mainly for orbital rendezvous with Shenzhou spacecraft and now provide convenience for SLR. From March to May of 2016, a coordinated laser ranging experiment on Tiangong-1 was made by Changchun Observatory (ILRS site ID: 7237) of National Astronomical Observatories, Sheshan station (ILRS site ID: 7821) of Shanghai Astronomical Observatory and Purple Mountain Observatory. Tiangong-1 has not been tracked by international laser ranging service (ILRS) and the orbit prediction of consolidated prediction format (CPF) cannot be obtained from ILRS. In general, the two line elements (TLE) of space objects can be downloaded from internet ( https://www.space- track.org) which is released by north American air defense command (NORAD). However, the TLE prediction error of Tiangong-1 (NORAD ID: 37820) is about several kilometers that is not precise enough for SLR. During the experiment, the actual prediction is provided by Purple Mountain Observatory. By the end of the experiment, data of 23 passes was obtained. Precise orbit determination is made by using the SLR data and the root mean squares (RMS) of the SLR observation residuals is about 10 cm. For one pass of scattered data, the orbit determination program is not convergent. Then combined orbit determination is made using one pass of SLR data and optical celestial position data. The relative weight of SLR data to optical data is 100:1 and the RMS of the SLR observation residuals is about 6.9 cm. The new orbit prediction is propagated from the orbit determination of SLR data and its precision is about 200–300 m. The radial precision is better than 100 m that is accurate enough for later laser ranging. In general, the experiment of satellite laser ranging to defunct Tiangong-1 spacecraft will have positive effects on precise orbit determination of both Tiangong-2 and other low earth orbit space objects.

53 cm双筒望远镜高重频空间碎片激光测距系统

53 cm双筒望远镜高重频空间碎片激光测距系统

Randomized Hough transform filter for echo extraction in DLR

The signal-to-noise ratio (SNR) of debris laser ranging (DLR) data is extremely low, and the valid returns in the DLR range residuals are distributed on a curve in a long observation time. Therefore, it is hard to extract the signals from noise in the Observed-minus-Calculated (O-C) residuals with low SNR. In order to autonomously extract the valid returns, we propose a new algorithm based on randomized Hough transform (RHT). We firstly pre-process the data using histogram method to find the zonal area that contains all the possible signals to reduce large amount of noise. Then the data is processed with RHT algorithm to find the curve that the signal points are distributed on. A new parameter update strategy is introduced in the RHT to get the best parameters. We also analyze the values of the parameters in the algorithm.We test our algorithm on the 10Hz repetition rate DLR data from Yunnan Observatory and 100Hz repetition rate DLR data from Graz SLR station. For 10Hz DLR data with relative larger and similar range gate, we can process it in real time and extract all the signals autonomously with a few false readings. For 100Hz DLR data with longer observation time, we autonomously post-process DLR data of 0.9%, 2.7%, 8% and 33% return rate with high reliability. The extracted points contain almost all signals and a low percentage of noise. Additional noise is added to 10Hz DLR data to get lower return rate data. The valid returns can also be well extracted for DLR data with 0.18% and 0.1% return rate.

A Real-Time Orbit Determination Method for Smooth Transition from Optical Tracking to Laser Ranging of Debris.

A critical requirement to achieve high efficiency of debris laser tracking is to have sufficiently accurate orbit predictions (OP) in both the pointing direction (better than 20 arc seconds) and distance from the tracking station to the debris objects, with the former more important than the latter because of the narrow laser beam. When the two line element (TLE) is used to provide the orbit predictions, the resultant pointing errors are usually on the order of tens to hundreds of arc seconds. In practice, therefore, angular observations of debris objects are first collected using an optical tracking sensor, and then used to guide the laser beam pointing to the objects. The manual guidance may cause interrupts to the laser tracking, and consequently loss of valuable laser tracking data. This paper presents a real-time orbit determination (OD) and prediction method to realize smooth and efficient debris laser tracking. The method uses TLE-computed positions and angles over a short-arc of less than 2 min as observations in an OD process where simplified force models are considered. After the OD convergence, the OP is performed from the last observation epoch to the end of the tracking pass. Simulation and real tracking data processing results show that the pointing prediction errors are usually less than 10″, and the distance errors less than 100 m, therefore, the prediction accuracy is sufficient for the blind laser tracking.