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Sixteen-Pixel NbN Nanowire Single Photon Detector Coupled With 300-??m Fiber
摘要： Niobium nitride (NbN) nanowires have a high repetition rate and efficiency, making them ideal for superconducting nanowire single photon detectors (SNSPDs). However, it is difficult to fabricate NbN arrays over large areas, which is critical for various applications. This paper describes a 4 × 4 NbN SNSPD array (16 pixels) and optical coupling with a 300-μm-diameter multimode fiber using beam compression technology. This is the first NbN SNSPD coupled with such large-diameter fibers. The designed pixels are positioned as closely as possible (pixel filling factor about 98.5%), almost without dead area between them. This results in a system efficiency of 46% and a quantum efficiency of 94.5% for photons (λ = 1064 nm) coupled from multimode fibers. An intrinsic time resolution of less than 69 ps can be obtained. The proposed high-performance single photon detector is suitable for satellite laser ranging. Furthermore, the proposed system is feasible for large SNSPD arrays with NbN, paving the way for the development of efficient photon cameras with NbN nanowires.
关键词： single-photon detector,Multimode fiber,satellite laser ranging,niobium nitride
更新于2025-09-16 10:30:52
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Replacing GRACE/GRACEa??FO C30 with satellite laser ranging: Impacts on Antarctic Ice Sheet mass change
摘要： Satellite laser ranging (SLR) observations have long been relied upon for measuring changes in Earth’s dynamic oblateness, C20. This major component of Earth’s time-variable gravity field is not well-observed by the GRACE and GRACE-FO missions, leading to the common practice of replacing their values with those obtained by SLR. The C30 coefficient, which has a large impact on the recovered Antarctic Ice Sheet mass changes, is shown here to be poorly observed by GRACE/GRACE-FO when either mission is operating without two fully functional accelerometers. The GRACE spacecraft pair operated nominally until October 2016 when one accelerometer was powered off due to battery limitations, while GRACE-FO is currently excluding one accelerometer from the data processing due to elevated noise levels. Beginning with the launch of LARES in 2012, SLR-derived C30 values are suitable for replacing any problematic GRACE/GRACE-FO estimates, enabling the accurate recovery of Antarctic Ice Sheet mass changes, among others.
关键词： mass change,Antarctic Ice Sheet,C30,GRACE-FO,satellite laser ranging,GRACE
更新于2025-09-16 10:30:52
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The progress of laser ranging technology at Shanghai Astronomical Observatory
摘要： 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 ?rstly 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 ?elds. These progresses will be introduced in this paper in detail.
关键词： Detection capability,Satellite laser ranging,Space debris,Data quality
更新于2025-09-12 10:27:22
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Thermal Influence of the Screw Axial Load on a 1-mm Accuracy Laser Ranged Satellite
摘要： This work explores the role of the screw axial load on the temperature experienced by the mounting set of a Cube Corner Retroreflector (CCR) in a spherical satellite, designed to achieve 1-mm accuracy in satellite laser ranging. Since thermal gradients inside CCRs induce refractive index gradients, changing the optical behaviour, thermal analysis and simulation are needed to ensure the best performances. The screw axial load influences the thermal interface resistances between the rings of the mounting set, changing their thermal behaviour. It is important to study the temperature, not only for the thermal gradients inside a CCR, but also to check that the Kel-F mounting rings do not overcome their maximum operative temperature. Two models have been realized in the commercial software C&R Thermal Desktop?: a model to simulate the entire satellite behaviour and a detailed model to represent the cavity which includes the CCR and its mounting set. Different on-orbit scenarios are analyzed, focusing on the influence of the screw axial load in each of them.
关键词： Satellite laser ranging,Thermal analysis,Cube corner retroreflector,Thermal modelling
更新于2025-09-11 14:15:04
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Satellite Laser-Ranging as a Probe of Fundamental Physics
摘要： Satellite laser-ranging is successfully used in space geodesy, geodynamics and earth sciences; and to test fundamental physics and specific features of General Relativity. We present a confirmation to approximately one part in a billion of the fundamental weak equivalence principle (“uniqueness of free fall”) in the Earth’s gravitational field, obtained with three laser-ranged satellites, at previously untested range and with previously untested materials. the weak equivalence principle is at the foundation of General Relativity and of most gravitational theories.
关键词： geodynamics,weak equivalence principle,space geodesy,Satellite laser-ranging,General Relativity
更新于2025-09-11 14:15:04
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Determination of Global Geodetic Parameters Using Satellite Laser Ranging Measurements to Sentinel-3 Satellites
摘要： Sentinel-3A/3B (S3A/B) satellites are equipped with a number of precise instruments dedicated to the measurement of surface topography, sea and land surface temperatures and ocean and land surface color. The high-precision orbit is guaranteed by three instruments: Global Positioning System (GPS) receiver, laser retroreflector dedicated to Satellite Laser Ranging (SLR) and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) antenna. In this article, we check the possibility of using SLR observations and GPS-based reduced-dynamic orbits of active S3A/B satellites for the determination of global geodetic parameters, such as geocenter motion, Earth rotation parameters (ERPs) and the realization of the terrestrial reference frame, based on data from 2016-2018. The calculation process was preceded with the estimation of SLR site range biases, different network constraining tests and a different number of orbital arcs in the analyzed solutions. The repeatability of SLR station coordinates based solely on SLR observations to S3A/B is at the level of 8-16 mm by means of interquartile ranges even without network constraining in 7-day solutions. The combined S3A/B and LAGEOS solutions show a consistency of estimated station coordinates better than 13 mm, geocenter coordinates with a RMS of 6 mm, pole coordinates with a RMS of 0.19 mas and Length-of-day with a RMS of 0.07 ms/day when referred to the IERS-14-C04 series. The altimetry observations have to be corrected by the geocenter motion to obtain unbiased estimates of the mean sea level rise. The geocenter motion is typically derived from SLR measurements to passive LAGEOS cannonball-like satellites. We found, however, that SLR observations to active Sentinel satellites are well suited for the determination of global geodetic parameters, such as Earth rotation parameters and geocenter motion, which even further increases the potential applications of Sentinel missions for deriving geophysical parameters.
关键词： reference frame realization,UT1-UTC,geocenter coordinates,low Earth orbiters,polar motion,Satellite Laser Ranging (SLR)
更新于2025-09-11 14:15:04
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Orbit Determination of Korean GEO Satellite Using Single SLR Sensor
摘要： Geostationary Earth Orbit (GEO)-Korea Multi-Purpose Satellite (KOMPSAT)-2B (GK-2B) is a Korean geostationary Earth orbit (GEO) satellite that is scheduled to be launched in 2020 for meteorological and ocean monitoring. While the primary orbit determination (OD) for GK-2B is by ground-based radar observations and the expected orbit precision is less than 1 km, a satellite laser ranging (SLR) technique has been selected as a subsidiary OD method to verify/complement/enhance primary OD results. In general, the available time and equipment for observing GEO satellites with SLR are limited. Furthermore, because the optical sensors mounted on GK-2B may be defected by laser, only a domestic single SLR station would obtain the tracking data. This research presents the mitigation of these drawbacks to improve orbit precision. Observation data generation and the associated OD of GK-2B are performed by considering numerical SLR data analysis on Compass-G1, a Chinese GEO navigation satellite, and Chinese SLR station at Changchun. With the OD performed for two scenarios with the varying number of observations, the 3D position error is 24.01 m when 13 observations per day are obtained, while the error becomes 43.46 m when 9 observations per day are obtained. To verify these results, the OD of Compass-G1 using actual SLR data from Changchun station is performed to yield 31.89 m for 3D error, which is favorable compared with the external precise ephemeris by GeoForschungsZentrum (GFZ) analysis center. Therefore, the OD based on single SLR station is applicable to estimating the orbit within less than 100 m.
关键词： orbit determination (OD),satellite laser ranging (SLR),GK-2B,Compass-G1,geostationary Earth orbit (GEO)
更新于2025-09-10 09:29:36