Charge exchange interactions on near-Earth proton radiation for orbit perturbation of high area-to-mass ratio objects

This novel concept expels neutral gas in the presence of geomagnetically-trapped protons in near-Earth orbit. The expelled neutral gas acts to induce charge exchange collisions with the geomagnetically-trapped protons and induce drag on objects which pass through it. The charge exchange collisions between the neutral gas and the geomagnetically-trapped protons create neutrals with similar kinetic energy that are not confined by the geomagnetic field. The charge exchange neutrals are able to collide with orbital objects and perturb their orbits. The delta-v applied by the charge exchange neutral flux is greatest on high area-to-mass objects. Numerical simulation shows charge exchange neutral impacts produce a delta-v on objects on the order of 3.8 x 10⁻¹¹ m/s at a distance of 1 km from the center of the expelled gas in a 1,000 km orbit. The impulse imparted by charge exchange neutral impacts is at least six orders of magnitude smaller than that provided by the induced drag caused by gas expulsion. The localized drag increase can force a majority of small objects into the orbit of the expelled gas cloud, even if that orbit is retrograde to the initial orbit of the objects. This new technique can be applied to the remediation of space debris.     

First astrometric observations of space debris with the MéO telescope

The MéO (for Métrologie Optique) telescope is the Satellite and Lunar Laser Ranging (SLR) dedicated telescope of Observatoire de la Côte d’Azur (France) located at plateau de Calern. The telescope uses an altazimuth mount. The motorization of the mount has a capability of 6 deg/s allowing the follow up of Low Earth Orbits (LEO) satellites, as well as Medium Earth Orbits (MEO) and geostationary (GEO) satellites, and the Moon. The telescope has a primary mirror of 1.54 m. It uses a Nasmyth focus equipped with an EMCCD camera. The telescope field of view, defined by the equivalent focal length and the size of the camera, is currently 3.4 arcmin × 3.4 arcmin.     

Debris swarms seen by SMEI

The large 3° × 60° fields-of-view of the Solar Mass Ejection Imager (SMEI) instruments are oriented on the stabilized Coriolis satellite to image most of the sky each Sun-synchronous orbit. Besides observing coronal mass ejections, the SMEI mission objective, SMEI also has detected a plethora of Earth-orbiting satellites (resident space objects or RSOs) brighter than ∼8th magnitude at a rate of about 1 per minute. Occasionally, SMEI sees an RSO swarm: a sudden onset of a large number of RSOs, many more than the nominal rate, upto dozens detected in a 4-s frame. These swarms usually last for a few minutes. A sample of six such RSO ensembles is analyzed in this paper in which the distance and the direction of the velocity vector for individual objects are estimated. We present the observational evidence indicating that the swarms must be near-field objects traveling in orbits near that of Coriolis, and that the relatively speeds between the objects and Coriolis are low. Further, analyses indicate that the RSOs are quite close (<20 m) and are generally moving radially away from the satellite. The predicted encounter geometries for Coriolis passing through or near a small debris cloud is, generally, quite inconsistent with the observations. The most likely explanation consistent with the observations is that SMEI is seeing debris being ejected from the Coriolis spacecraft itself. An analysis of distance and brightness for a subset of the RSOs indicates that the median diameter of the debris particles is ∼80 μm.     

Nostoc sphaeroides Kützing,an excellent candidate producer for CELSS

Some phytoplankton can be regarded as possible candidates in the establishment of Controlled Ecological Life Support System (CELSS) for some intrinsic characteristics, the first characteristic is that they should grow rapidly, secondly, they should be able to endure some stress factors and develop some corresponding adaptive strategies; also it is very important that they could provide food rich in nutritious protein and vitamins for the crew; the last but not the least is they can also fulfill the other main functions of CELSS, including supplying oxygen, removing carbon dioxide and recycling the metabolic waste. According to these characteristics, Nostoc sphaeroides, a potential healthy food in China, was selected as the potential producer in CELSS. It was found that the oxygen average evolution rate of this algae is about 150 μmol O₂ mg⁻¹ h⁻¹, and the size of them are ranged from 2 to 20 mm. Also it can be cultured with high population density, which indicated that the potential productivity of Nostoc sphaeroides is higher than other algae in limited volume. We measured the nutrient contents of the cyanobacterium and concluded it was a good food for the crew. Based on above advantages, Nostoc sphaeroides was assumed to a suitable phytoplankton for the establishment of Controlled Ecological Life Support System. We plan to develop suitable bioreactor with the cyanobacterium for supplying oxygen and food in future space missions.     

An overview of RADOM results for earth and moon radiation environment on Chandrayaan-1 satellite

The RADiatiOn Monitor (RADOM) is a miniature dosimeter-spectrometer that flew onboard the Chandrayaan-1 lunar mission in order to monitor the local radiation environment. Primary objective of the RADOM experiment was to measure the total absorbed dose, flux of surrounding energetic particles and spectrum of the deposited energy from high energy particles both en-route and in lunar orbit. RADOM was the first experiment to be switched on after the launch of Chandrayaan-1 and was operational until the end of the mission. This paper summarizes the observations carried out by RADOM during the entire life time (22 October 2008–31 August 2009) of the Chandrayaan-1 mission and compares the measurement by RADOM with the radiation belt models such as AP-8, AE-8 and CRRESS.     

Towards a scientific understanding of the risk from extreme space weather

Like all natural hazards, space weather exhibits occasional extreme events over timescales of decades to centuries. Historical events provoked much interest, and sometimes alarm, because bright aurora becomes visible at mid-latitudes. However, they had little economic impact because the major technologies of those eras were not sensitive to space weather. This is no longer true. The widespread adoption of advanced technological infrastructures over the past 40 years has created significant sensitivity. So these events now have the potential to disrupt those infrastructures – and thus have profound economic and societal impact. However, like all extreme hazards, such events are rare, so we have limited data on which to build our understanding of the events. This limitation is uniquely serious for space weather since it is a global phenomenon. Many other natural hazards (e.g. flash floods) are highly localised, so statistically significant datasets can be assembled by combining data from independent instances of the hazard recorded over a few decades. Such datasets are the foundation on which reliable risk assessment methodologies are built. But we have a single instance of space weather so we would have to make observations for many centuries in order to build a statistically significant dataset. We show that it is not practicable to assess the risk from extreme events using simple statistical methods. Instead we must exploit our knowledge of solar-terrestrial physics to find other ways to assess these risks. We discuss three alternative approaches: (a) use of proxy data, (b) studies of other solar systems, and (c) use of physics-based modelling. We note that the proxy data approach is already well-established as a technique for assessing the long-term risk from radiation storms, but does not yet provide any means to assess the risk from severe geomagnetic storms. This latter risk is more suited to the other approaches, but significant research is needed to make progress. We need to develop and expand techniques to monitoring key space weather features in other solar systems (stellar flares, radio emissions from planetary aurorae). And to make progress in modelling severe space weather, we need to focus on the physics that controls severe geomagnetic storms, e.g. how can dayside and tail reconnection be modulated to expand the region of open flux to envelop mid-latitudes?     

CCSDS空间网络互联协议发展及启示

空间互联网将是由各种区域网构成的复杂异构网络,为了使其能够逐步实现自动化运行,网络效益得到最大程度的发挥,须做好网络互联的顶层规划与设计,并开发具体的标准技术.根据近年CCSDS (Consultative Committee for Space Data Systems,空间数据系统咨询委员会)发布的建议书,以及相关工作组的项目规划情况,介绍了SSI(Solar System Internetwork,太阳系互联网)体系结构、IPoC(IP over CCSDS space links,在CCSDS空间链路之上承载IP),以及DTN(Delay Tolerant Networking,容延迟网络)等标准项目.从CCSDS空间网络互联技术的发展历程不难得出结论:我国未来空间网络互联应注重区域网之间互联的顶层设计;区域网内部各子网之间的互联技术应选择以航天任务需求牵引为主;DTN将在区域网之间互联以及区域网从简单到复杂发展中都发挥重要作用.     

航天器空间环境干扰力矩分析与仿真研究

针对航天器在轨运行时所受到的空间环境干扰力矩进行建模分析,并通过实时解算和矢量叠加的方式进行仿真研究,尤其对太阳光压力矩与大气阻力力矩的建模与仿真提出了新的方法,该方法通过建立光照面与迎风面的判断准则,准确地对太阳光压力矩与大气阻力力矩进行了估计。对各种空间环境干扰力矩的精确建模与仿真为航天器精确姿态控制设计及系统姿态控制方案和控制执行机构的选取提供了依据,文中提出的方法简单易用,工程实现性强,为未来的工程应用提供了一定的理论依据。     

Specification of the Earth’s plasmasphere with data assimilation

In this paper we report on initial work toward data assimilative modeling of the Earth’s plasmasphere. As the medium of propagation for waves which are responsible for acceleration and decay of the radiation belts, an accurate assimilative model of the plasmasphere is crucial for optimizing the accurate prediction of the radiation environments encountered by satellites. On longer time-scales the plasmasphere exhibits significant dynamics. Although these dynamics are modeled well by existing models, they require detailed global knowledge of magnetospheric configuration which is not always readily available. For that reason data assimilation can be expected to be an effective tool in improving the modeling accuracy of the plasmasphere. In this paper we demonstrate that a relatively modest number of measurements, combined with a simple data assimilation scheme, inspired by the ensemble Kalman filtering data assimilation technique does a good job of reproducing the overall structure of the plasmasphere including plume development. This raises hopes that data assimilation will be an effective method for accurately representing the configuration of the plasmasphere for space weather applications.     

A high order method for orbital conjunctions analysis: Sensitivity to initial uncertainties

A high order method to quickly assess the effect that uncertainties produce on orbital conjunctions through a numerical high-fidelity propagator is presented. In particular, the dependency of time and distance of closest approach to initial uncertainties on position and velocity of both objects involved in a conjunction is studied. The approach relies on a numerical integration based on differential algebraic techniques and a high-order algorithm that expands the time and distance of closest approach in Taylor series with respect to relevant uncertainties. The modeled perturbations are atmospheric drag, using NRLMSISE-00 air density model, solar radiation pressure with shadow, third body perturbation using JPL’s DE405 ephemeris, and EGM2008 gravity model. The polynomial approximation of the final position is used as an input to compute analytically the expansion of time and distance of closest approach. As a result, the analysis of a close encounter can be performed through fast, multiple evaluations of Taylor polynomials. Test cases with objects ranging from LEO to GEO regimes are considered to assess the performances and the accuracy of the proposed method.