Richard J. Cartwright, Chloe B. Beddingfield, Tom Nordheim, Catherine Elder, Will Grundy, Ali Bramson, Michael Sori, Robert Pappalardo, Marc Neveu, Devon Burr, Anton Ermakov, Joe Roser, Julie Castillo-Rogez, Mark Showalter, Ian Cohen, Zibi Turtle, Mark Hofstadter
The five classical Uranian moons are possible ocean worlds that exhibit bizarre geologic landforms, hinting at recent surface-interior communication. However, Uranus' classical moons, as well as its ring moons and irregular satellites, remain poorly understood. We assert that a Flagship-class orbiter is needed to explore the Uranian satellites.
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The 27 satellites of Uranus are enigmatic, with dark surfaces coated by material that could be rich in organics. Voyager 2 imaged the southern hemispheres of Uranus' five largest 'classical' moons Miranda, Ariel, Umbriel, Titania, and Oberon, as well as the largest ring moon Puck, but their northern hemispheres were largely unobservable at the time of the flyby and were not imaged. Additionally, no spatially resolved datasets exist for the other 21 known moons, and their surface properties are essentially unknown. Because Voyager 2 was not equipped with a near-infrared mapping spectrometer, ou…
Feasibility of Passive Sounding of Uranian Moons using Uranian Kilometric Radiation
本研究评估利用天王星千米辐射被动探测天王星冰卫星的可行性，发现其可直接探测冷海洋并约束内部结构，但受源尺寸和照明几何限制。
We present the astrometry of the five largest satellites of Uranus from observations spread over almost three decades with photographic plates and CCDs (mainly), taken at the Pico dos Dias Observatory - Brazil. All positions presented here are obtained from the reanalysis of measurements and images used in previous publications. Reference stars are those from the Gaia Early Data Release 3 (Gaia EDR3) allowing, in addition to a higher accuracy, a larger number of positions of the largest satellites as compared to our previous works. From 1982 to 1987, positions were obtained from photographic p…
Spacecraft VLBI tracking to enhance stellar occultations astrometry of planetary satellites
本文提出利用航天器VLBI跟踪在时间上接近恒星掩星时局部精化行星位置，并以Juno任务为测试案例，将木星角位置不确定性降至250-400米，从而提升卫星星历精度并惠及行星探测任务。
The modulation of high-energy transients' (or steadily emitting sources') light curves due to the imperfect alignment of the detector's view axis with the spin axis in a spin-stabilized satellite is derived. It is shown how the orientation of the detector's view axis with respect to the satellite's spin axis may be estimated using observed light curves. The effects of statistical fluctuations are considered. Conversely, it is shown how the attitude of a spin-axis stabilized satellite as well as the unknown position of a celestial source of high-energy photons may be determined using a detector…
The precise knowledge of the positions of space debris objects and in particular of defunct satellites is fundamental for satellite operations. Several studies showed that it is possible to improve the accuracy of the orbit determination results by fusing different types of observables, i.e. classical astrometric positions and range measurements. Particularly promising in the space debris field are the ranges provided by a satellite laser ranging system. The factors that limit the applicability of the satellite laser ranging (SLR) techniques are the altitude of the target, the accuracy of the …
Modelling of spacecraft apparent brightness: a study on OneWeb constellation satellites
本研究针对人造卫星光污染影响天文观测的问题，基于经典光度学理论开发可适配任意形状航天器的视亮度数学模型，并利用GAL Hassin天文台的OneWeb卫星观测数据完成验证，可用于低光污染航天器研发。
The use of astronomical data for satellite tracking
本研究利用天文观测数据识别和跟踪人造卫星，通过分析天文图像中的航天器 streak，评估其对航天器监控和轨道参数推导的有用性，并与现有卫星数据库进行比较。
Earth is constantly being bombarded with material from space. Most of the natural material end up being dust grains that litter the surface of Earth, but larger bodies are known to impact every few decades. The most recent large impact was Chelyabinsk which set off a 500-kiloton explosion which was 40 times that of the Hiroshima nuclear explosion. Apart from meteors, there is a growing threat of space assets deorbiting. With these impending space threats, it is critical to have a constellation of satellites to autonomously lookout for meteors and reentering space debris. By using multiple spac…
Prospects for localising Planet 9 with a future Uranus mission
本研究针对第九行星定位问题，提出利用未来天王星任务巡航期测距数据，通过蒙特卡洛-马尔可夫链方法评估其定位能力，证实该任务可实现高精度定位，兼具非天王星科学研究潜力。
Starlink Generation 2 Mini Satellites: Photometric Characterization
本研究对Starlink第二代迷你卫星开展光度表征，发现其虽尺寸更大但比第一代更暗，测得亮度抑制模式下的视星等及距离修正后数值，明确该模式可将距离修正后的卫星光度降低12倍。
The purpose of this document is to discuss the scientific case of a space mission to the ice giants Uranus and Neptune and their satellite systems and its relevance to advance our understanding of the ancient past of the Solar System and, more generally, of how planetary systems form and evolve. As a consequence, the leading theme of this proposal will be the first scientific theme of the Cosmic Vision 2015-2025 program: What are the conditions for planetary formation and the emergence of life? In pursuing its goals, the present proposal will also address the second and third scientific theme …
Satellite tracking involves sending electromagnetic signals to Earth. Both the orbit of the spacecraft and the electromagnetic signals themselves are affected by the curvature of spacetime. The arrival time of the pulses is compared to the ticks of local clocks to reconstruct the orbital path of the satellite to high accuracy, and to implicitly measure general relativistic effects. In particular, Schwarzschild space curvature (static) and frame-dragging (stationary) due to the planet's spin affect the satellite's orbit. The dominant relativistic effect on the path of the signal photons is Shap…
Brightness Characterization and Modeling for Amazon Leo Satellites
研究亚马逊莱奥卫星的亮度特性，发现其大部分超过IAU推荐亮度限制，影响科学研究和夜空审美。
One of the primary objectives of small satellites is to reduce the costs associated with spacecraft development and operations as compared to traditional spacecraft missions. Small satellite missions are generally able to reduce mission planning, hardware, integration, and operational costs; however, small satellite missions struggle with reducing software development and testing costs. This paper presents the case study of the NASA Operational Simulator for Small Satellites (NOS3), a software-only simulation framework that was developed for the Simulation-to-Flight 1 (STF-1) 3U CubeSat missio…
The Langton Ultimate Cosmic ray Intensity Detector (LUCID) is a payload onboard the satellite TechDemoSat-1, used to study the radiation environment in Low Earth Orbit ($\sim$635km). LUCID operated from 2014 to 2017, collecting over 2.1 million frames of radiation data from its five Timepix detectors on board. LUCID is one of the first uses of the Timepix detector technology in open space, with the data providing useful insight into the performance of this technology in new environments. It provides high-sensitivity imaging measurements of the mixed radiation field, with a wide dynamic range i…
Asteroid modelling by starlight diffraction: The shape of Dimorphos, the satellite of (65803) Didymos
通过分析星光掩星事件中的衍射特征，研究迪莫罗斯的形状和大小，首次利用多条 chords 的衍射数据约束其投影形状，结果与后续研究一致，表明其呈赤道扁平的撞击后形状。
CubeSats and small satellites are emerging as low-cost tools to perform astronomy, exoplanet searches and earth observation. These satellites can be dedicated to pointing at targets for weeks or months at a time. This is typically not possible on larger missions where usage is shared. Current satellites use reaction wheels and where possible magneto-torquers to control attitude. However, these actuators can induce jitter due to various sources. In this work, we introduce a new class of actuators that exploit radiometric forces induced by gasses on surface with a thermal gradient. Our work show…
Predicted Brightness of Starlink Internet Satellites at 350 km
针对SpaceX提议将19440颗Starlink卫星部署在350 km低轨道的方案，研究模拟其天空分布与视星等，验证了该轨道在曙暮光期对天文观测影响更严重、夜间影响更小的结论，与SpaceX的定性陈述一致。
A moon or natural satellite is a celestial body that orbits a planetary body such as a planet, dwarf planet, or an asteroid. Scientists seek understanding the origin and evolution of our solar system by studying moons of these bodies. Additionally, searches for satellites of planetary bodies can be important to protect the safety of a spacecraft as it approaches or orbits a planetary body. If a satellite of a celestial body is found, the mass of that body can also be calculated once its orbit is determined. Ensuring the Dawn spacecraft's safety on its mission to the asteroid (4) Vesta primaril…
Observations of BlueWalker 3 (BW3) beginning on December 8 of this year indicate that its apparent brightness had decreased. We postulate that the orbital beta angle and resultant solar power considerations required an adjustment to the satellite attitude around that time. So, the nominally zenith facing side of the flat-panel shaped spacecraft, which supports the solar array, was tilted toward the Sun. Consequently, the nadir side, which is seen by observers on the ground, was mostly dark. Thus, BW3 has generally appeared faint and on some occasions was not seen at all. The amount of fading w…
The Brightness of Starlink Mini Satellites During Orbit-Raising
本研究观测Starlink V2 Mini卫星升轨亮度，发现SpaceX在357km高度启动的亮度消减措施有效率达93%，低轨升轨卫星对天文观测影响较小但引发公众与飞行员关注。
Initial Observations of the First BlueBird Spacecraft and a Model of Their Brightness
本文基于大量目视观测首次给出 BlueBird 卫星的平均视星等与归算星等，并建立亮度模型，揭示其设计变更对亮度行为的影响。
High power Earth and orbital-based directed energy (DE) systems pose a potential hazard to Earth orbiting spacecraft. The use of very high power, large aperture DE systems to propel spacecraft is being pursued as the only known, feasible method to achieve relativistic flight in our NASA Starlight and Breakthrough Starshot programs. In addition, other beamed power mission scenarios, such as orbital debris removal and our NASA program using DE for powering high performance ion engine missions, pose similar concerns. It is critical to quantify the probability and rates of interception of the DE b…
BlueWalker 3 Satellite Brightness Characterized and Modeled
本研究针对BlueWalker 3卫星展开，观测其发射后不同阶段的亮度变化，分析变暗原因与异常明亮的几何条件，构建基于形状、朝向及含朗伯、伪镜面分量反射函数的亮度模型，明确其典型与天顶附近的视星等范围。
At present, there is a great worldwide interest in the development of technologies that allow information about the X-ray emission from pulsating cosmic sources to be used to obtain navigation solutions for deep-space spacecraft. In this paper, we illustrate the technique for determining the spatial position of a spacecraft based on the already existing data from the RXTE X-ray space observatory. We show that the spacecraft position toward the Crab pulsar can be determined using an X-ray detector with an effective area of about 0.6 sq.m in the energy range 3-15 keV with an accuracy up to 730 m…
During the On-Station Thermal Test campaign of the LISA Pathfinder the data and diagnostics subsystem was tested in nearly space conditions for the first time after integration in the satellite. The results showed the compliance of the temperature measurement system, obtaining temperature noise around $10^{-4}\,{\rm K}\, {\rm Hz}^{-1/2}$ in the frequency band of $1-30\;{\rm mHz}$. In addition, controlled injection of heat signals to the suspension struts anchoring the LISA Technology Package (LTP) Core Assembly to the satellite structure allowed to experimentally estimate for the first time th…
Brightness of the Qianfan Satellites
本文通过观测和朗伯反射模型分析千帆卫星的亮度，指出其星等范围为4至8等，并警示若不降低亮度将对天文研究造成影响。
The rapid advancement and miniaturization of spacecraft electronics, sensors, actuators, and power systems have resulted in growing proliferation of small-spacecraft. Coupled with this is the growing number of rocket launches, with left-over debris marking their trail. The space debris problem has also been compounded by test of several satellite killer missiles that have left large remnant debris fields. In this paper, we assume a future in which the Kessler Effect has taken hold and analyze the implications on the design of small-satellites and CubeSats. We use a multiprong approach of surve…
BlueBird 6 is Fainter than Block 1 Satellites
该研究对比 BlueBird 星座 Block 2 卫星 BlueBird 6 与 Block 1 卫星的视星等，发现 BlueBird 6 亮度低 0.55 个星等，单位表面积亮度仅为 Block 1 的 17%，虽亮度超 IAU 限制但数量更少。
CubeSats are small satellites used for scientific experiments because they cost less than full sized satellites. Each CubeSat uses an on-board computer. The on-board computer performs sensor measurements, data processing, and CubeSat control. The challenges of designing an on-board computer are costs, radiation, thermal stresses, and vibrations. An on-board computer was designed and implemented to solve these challenges. The on-board computer used special components to mitigate radiation effects. Software was also used to provide redundancies in cases of faults. This paper may aid future space…
Spacecraft inertial parameters estimation using time series clustering and reinforcement learning
本文提出结合时间序列聚类与强化学习优化驱动序列的机器学习方法，用于估计运行中惯性参数变化的航天器，并在多卫星部署场景中验证其对常见扰动的鲁棒性。
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