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You Y.,National University of Defense Technology | You Y.,Ecole Polytechnique Federale de Lausanne | Wang H.,National University of Defense Technology | Paccolat C.,Ecole Polytechnique Federale de Lausanne | Li J.-R.,China Manned Space Engineering Office
Yuhang Xuebao/Journal of Astronautics | Year: 2016

A square root unscented Kalman filter (SRUKF)-based angles-only navigation (AON) method is proposed for spacecraft rendezvous using single optical/infrared camera as relative navigation sensors both in far/middle and close-in range. To address the well-documented range observability problem of AON, a decimeter scale camera installation offset from the mass center of the chaser is intentionally set. A camera measure model is constructed by the range scope and the observation sensitivity matrices are furtherly derived. We theoretically prove the component in cross-track or radial generates range observability for v-bar relative station keeping. Small error and zero mean Gaussian distribution hypotheses are not essential any more using SRUKF. Through numerical simulation, in far/middle range, the estimation error of the SRUKF-based AON is just half of the traditional extended Kalman filter (EKF)-based AON. In close-in range, the range observability problem is solved when the camera offset is considered. SRUKF and EKF have the same order computational burden for the state estimation, but SRUKF is about 10% faster than the EKF due to using the two powerful linear algebra techniques, QR decomposition, Cholesky factor updating. Last but not least, even with the non-Gaussian initial estimation error, the unbiased estimation of the relative range is still achieved. © 2016, Editorial Dept. of JA. All right reserved.

News Article | October 26, 2016
Site: www.newscientist.com

China launched its second space station today, with a two-member crew to follow next month, according to China space agency officials. The launch of Tiangong-2 is another step towards China’s goal of a self-sustaining space station by 2022, and a reminder of the nation’s space prowess. A Long March 2F rocket launched Tiangong-2 from China’s Gobi Desert at 22:04 local time, coinciding with the lunar Mid-Autumn Festival, Chinese officials announced. It will manoeuvre itself into orbit about 380 kilometres above Earth, then raise its orbit to 393 kilometres when a Shenzhou-11 capsule arrives in October carrying two astronauts, who will live on the station for 30 days. The station is designed for a two-year lifetime, and will dock with China’s first cargo ship, Tianzhou-1, in April 2017. The station is 18.4 metres wide and weighs 8.6 tons, said Wu Ping, deputy director of the China Manned Space Engineering Office, in a press conference broadcast on state-run media. Despite its small size and short lifespan, Tiangong-2 is an important precursor to China’s larger space station, which it aims to launch on a Long March 5 rocket in the next six years, says Dean Cheng, a Chinese space policy expert at the Heritage Foundation in Washington DC. Next year will bring China’s 19th Communist Party Congress, in which prime minister Xi Jinping is expected to win a second term, and a new space station is a sign of the party’s prowess, Cheng adds. “It’s a reminder that China has a manned space programme, including the ability to put its own astronauts into space, something the Americans cannot do,” he says – US astronauts are currently flown by Russia. “It’s about national pride, but it’s also, as the Chinese would put it, ‘very dense in high technology’. And it has military implications, and they are very upfront about this. All of these are elemental to why are they doing this.” It’s not all for political posturing, though. Tiangong-2 carries 14 experiments, including atmospheric sensing instruments that can detect air pollution. It is equipped with a precise atomic clock, which is accurate to one second every 30 million years. The clock will help measure fluctuations in microgravity with greater precision, according to the space agency. The station will also contain cardiovascular health experiments, a quantum communications experiment, a plant cultivation study and a gamma-ray burst instrument called POLAR, which is a collaboration between Chinese, Swiss and Polish scientists. That experiment reflects China’s interest in joining forces with smaller nations and developing countries, which lack their own robust space programmes, says Scott Pace, director of the Space Policy Institute at George Washington University in Washington DC. Earlier this year, the China Manned Space Agency and the UN announced a partnership to allow UN member states to conduct experiments and send astronauts to the Chinese space station. Pace says this benefits China’s image as well as its economy. “In the 60s, during the moon race, the measure of international leadership was showing what you could do by yourself,” he says. “Today, the measure of international leadership is what you can get other people to do with you.” Wu says Tiangong-2 has several upgrades compared with Tiangong-1, which launched in 2011. These will include a new mechanical arm; new equipment to perform medical experiments; and better living quarters with new exercise and recreation facilities. The changes will make astronauts’ 30-day stay in space “more comfortable, more convenient and more colourful”, Wu says. Tiangong-1 lost communication with Earth in March, but is still in orbit roughly 370 kilometres above us. It is losing about 110 metres of altitude every day, and is expected to re-enter the atmosphere sometime late next year, though scientists are unsure where or when this will happen. Wu acknowledged recent launch failures, but did not directly address the suspected failure of a Long March 4C on 31 August. Cheng says development of the Long March 5 is behind schedule, so another successful Tiangong launch is a point of pride. “I would say they are quite self-sufficient, and happily so. We sort of assume a lot of the time that they are just hankering to join up with [the US], and I would suggest that no, the evidence is not at all clear,” Cheng says. “They would like international recognition, of course. But they are not going to play second fiddle to anyone.”

Zhong Z.-Y.,China Manned Space Engineering Office | Zhou J.-P.,China Manned Space Engineering Office | Zhang H.-L.,China Manned Space Engineering Office | Zhang W.-M.,Shanghai JiaoTong University | Meng G.,Shanghai JiaoTong University
International Journal of Heat and Mass Transfer | Year: 2016

As an inherent energy dissipation mechanism, the thermoelastic damping (TED) imposes an upper limit on the quality factors of microresonators. On the basis of Hamilton principle, the governing equation of solid-liquid-thermal coupling vibration of fluid-conveying microresonator is deduced. For different thermal boundary conditions, the analytical expressions of TED are separately derived by solving the heat diffusion equation of the thermal flow across the fluid-conveying microbeam. The results show that the liquid in the hollow microbeam has significant impact on TED. The natural frequency decreases with the increase of the flow velocity or axial pressure. However, both for the two proposed fluid-conveying models, TED increase with the increase of the flow velocity or axial pressure. The peak value of TED of the proposed models is larger than the hollow beam, but smaller than the solid beam. As a function of channel geometry, beam properties and flow velocity, the second peak is about to occur for the fluid-conveying beam. In addition, different from the results of the hollow beam and the low flow velocity models, the peak value of TED in the high flow velocity model increases monotonously with the increasing ratio of channel width to channel height due to the great area of heat convection between the inner channel and the fluid. © 2015 Elsevier Ltd.

Zhong Z.-Y.,China Manned Space Engineering Office | Zhang H.-L.,China Manned Space Engineering Office | Zhang W.-M.,Shanghai JiaoTong University | Liu Y.,Shanghai JiaoTong University
Optical Engineering | Year: 2016

As a unique type of driving force, the transverse optical gradient force has been extensively studied and applied in the nanowaveguides resonator. Recently, it is demonstrated that the optical forces in slot waveguides of hyperbolic metamaterials can be over two orders of magnitude stronger than that in conventional dielectric slot waveguides. To investigate the nonlinear dynamic characteristic of hyperbolic waveguide resonator driven by optical gradient force, a continuum elastic model of the optoresonator is presented and analytically solved using the methods of Rayleigh-Ritz and multiple scales. The results show that the optical force is strengthened with the increase of the filling ratio of silver in the hyperbolic waveguide. The resonance frequency becomes greater with the increase of the filling ratio of silver no matter what the geometric parameters and physical property parameters are. However, the steady maximum vibration amplitude becomes smaller, and the degree of system stiffness softening also reduces. © 2016 Society of Photo-Optical Instrumentation Engineers (SPIE).

Li G.-F.,Beihang University | Li G.-F.,China Aerospace Science and Technology Corporation | Chen L.-D.,China Aerospace Science and Technology Corporation | Tang G.-S.,China Aerospace Science and Technology Corporation | Zhang L.-Y.,China Manned Space Engineering Office
Yuhang Xuebao/Journal of Astronautics | Year: 2011

A mathematical model for the rendezvous launch window based on the rendezvous multi-constraints including orbit sunlight constraint, sunlight incidence constraint for optics navigation measurement devices and coplanar constraint is established in this paper. The method and the scheme of the rendezvous launch window were presented and the effects of every constraint on the rendezvous launch window are analyzed. The sets of annual rendezvous launch windows of both target and chaser under sunlight constraint are constructed. According to two mission programming modes, methods for determining the annual coplanar launch time sets for both target and chaser are also proposed. The day window and the time window of the annual rendezvous launch window sets with multi-constraints are plainly presented for analysis and programming of the rendezvous launch windows. Simulation computations indicate that the set of annual rendezvous launch windows is correct and valid. The model, the method and the result for the rendezvous launch window are benefit to analysis and programming of the rendezvous mission.

Zheng A.,Science and Technology on Aerospace Flight Dynamics Laboratory | Zheng A.,China Aerospace Science and Technology Corporation | Sun J.,Science and Technology on Aerospace Flight Dynamics Laboratory | Sun J.,China Aerospace Science and Technology Corporation | And 3 more authors.
Zhongguo Kongjian Kexue Jishu/Chinese Space Science and Technology | Year: 2014

The Unified S-band System (USB) is the main TT&C (Telemetry, Tracking and Command) network used in space missions including manned spacecraft and lunar exploration programs of China. Firstly, all kinds of errors existed in the USB range and range-rate measurements were analyzed, and the error correction models of tropospheric refraction delay, ionospheric delay, time tag bias, phase center error, channel delay and satellite ephemeris error were presented. Secondly, the accuracy of the USB measurements was evaluated and obtained based on the residual analysis of the USB range and range-rate measurements of a real space mission. Finally, according to the current actuality of disposal and application of USB measurements, some advices that should be noted in data processing were put forward. The conclusions have important reference value to improve the accuracy of orbit determination based on the USB system of China.

Zhong Z.-Y.,China Manned Space Engineering Office | Zhou J.-P.,China Manned Space Engineering Office | Zhang H.-L.,China Manned Space Engineering Office | Zhang T.,Shanghai University of Engineering Science
Computers and Structures | Year: 2016

Small deflections and moments exist on the boundaries of the flexible supports of MEMS cantilever-based sensors. The qualitative dynamical behavior is significantly affected by the non-ideal boundary conditions. Based on the Boussinesq's and Cerruti's displacement equations and the principle of energy equivalence, rigorous theoretical solutions of the normal, tangential and rotational equivalent stiffness are presented in this paper. The proposed model is validated by the fact that the theoretical results remained a good situation consistency with the reported experimental data. The variations of the equivalent stiffness with the geometric dimensions of the cross section of the flexible supports are investigated. It is observed that when the "Hard material" is used as the supports' materials, e.g. Silicon carbide, the equivalent stiffness is large. Yet the equivalent stiffness is small for the "Soft material", e.g. Silicon and Poly-silicon. In addition, by employing the method of multiple time scales, the non-dimensional differential partial equation of the motion as well as coupled boundary conditions are analytically solved. The results indicate that the resonance frequencies decrease with the flexible supports, however, increase due to the nonlinearity mechanical spring. © 2016 Elsevier Ltd. All rights reserved.

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