2011年世界空间探测与科学观测活动回顾

2011年,美国、中国和俄罗斯等国都开展了多项空间探测与科学观测活动,发射了月球探测器、木星探测器等,尤其是由于2011年有火星探测器发射窗口,所以进行了两次重要的火星探测器发射,但有喜有悲：携带了世界最先进火星车“好奇号”的美国“火星科学实验室”顺利升空,并奔向火星;而携带了中国首个火星探测器“萤火-1”的俄罗斯的“火卫一-土壤”探测器虽然发射成功,但由于探测器本身故障而无法进入地火转移轨道,导致该任务失败。     

“火卫- -土壤”设计周全出师未捷令人遗憾

2011年11月9日零点16分,北京时间凌晨4点16分,中国首颗火星探测器“萤火一号”搭载俄罗斯“火卫-- -土壤”探测器,在位于哈萨克斯坦境内的拜科努尔发射场发射升空。仅仅7个小时后,北京时间9号中午11点左右,俄联邦航天署发布消息。“火卫-- -土壤”探测器及其所搭载的中国“萤火一号”火星探测器在飞行过程中出现意外,它们未能按计划实现变轨,结果导致此次火星卫星探测失败。     

“萤火一号”“搭错车”火星憾失中国客

2011年11月9日北京时间4点16分。搭载有我国首颗火星探测器——萤火一号的俄罗斯“火卫-- -土壤”探测器由俄罗斯火箭发射升空。升空后由于“火卫-- -土壤”在飞行过程中出现意外。未能按计划实现变轨,萤火一号也无法奔向火星。真可谓出师捷接身先死。那么,“火卫—— -土壤”和萤火一号原定科学目标和主要性能如何呢？     

探索火星的新征程

新的征程由美国宇航局(NASA)研制的“勇气”号探测器(MER-A),于今年6月10日从佛罗里达州的卡纳维拉尔角成功地发射升空。第二个探测器“机遇”号(MER-B)原定于6月25日随后发射,由于天气和技术原因,发射推迟到7月7日。另一方面,欧洲的“火星快车”也已于6月2日发射。3艘飞船将历时7个月,飞越近5亿千米的距离,预定于2004年1月降落在火星南纬15度的古谢夫环形山。之所以集中选择在6月份发射,是因为这段时间火星离地球距离较近,这样的机会每26     

现代天文学历史大事记

1971年12月2日前苏联“火星-3号”探测器首次在火星表面软着陆成功。 1973年12月3日。“先驱者10号”探测器飞临木星。 美国发射的“先驱者10号”探测器经过1年零9个月的艰难跋涉,穿过危险的小行星带,越过木星周围的强辐射区,与木星相会。它飞临木星时,沿木星赤道平面从木星右侧绕过,在距木星13万千米的地方穿过木星云层,拍摄了第一张木星照片。     

火星重力场模型发展回顾及对萤火一号的展望

首先回顾了火星重力场探测的历史、各有关探测器的轨道特征和获取的资料情况,特别对最成功的MGS项目的情况作了详细介绍。然后对确定火星重力场模型过程中的有关问题作了介绍,包括动力学模型、三体摄动问题、太阳光压和大气阻力模型等。重点介绍了其中的先验条件和求解重力场的算法,后者主要介绍GSFC采用的最小二乘法和先验约束方法及其数据定权和误差校准的经验。文中还对火星重力场与地形学进行了比较分析,并对火星重力场时变性的探测与研究作了重点讨论。最后对火星重力场探测中存在的主要问题作了详细讨论,并展望了我国第一颗火星探测器"萤火一号"对火星重力场研究的可能贡献。     

2008年着陆火星探险的“不死鸟”——“凤凰”号火星探测器

在太阳系九大行星中,没有一颗如火星这样让地球人着迷。这颗远在上亿千米之外的红色行星一次次点燃起人类探索的激情。目前正在考察火星的探测器有美国的“火星环球勘测者”、“奥德赛”探测器以及欧洲的“火星快车”探测器,火星地面有“勇气”号、“机遇”号两辆火星车,还有目前的“火星勘测轨道飞行器(MRO)”,据喷气推进实验室的学者称,这是最新一代火星探测器,其探测的能力超过上述探测器的总和。更引人瞩目的是,2005年6月美国宇航局又批准了“凤凰”计划(Phoenix),它将于2007年发射升空,2008年在火星北极地区着陆。与此前的火星探测计划相比,“凤凰”计划更为经济实用。     

首次在火星极区着陆的凤凰号

2007年8月4日美国宇航局成功发射的凤凰号火星探测器,于今年5月25日成功在火星极区着陆。由于近年来科学家发现火星北极地区覆盖有大量的冰,所以美国制定了以寻找水为核心的火星探测战略,凤凰号就是这个战略的执行者。凤凰号有三大任务：采集土壤样本进行分析,寻找水、致力探索火星生命,日后监控火星天气状况。     

火星全球勘测者和探路者

火星全球勘测者和探路者陈丹１９９６年１１月和１２月美国相继发射了两艘火星探测器一一火星全球勘测者和火星探路者，前者于１９９７年９月，后者于１９９７年７月抵达火星。由此开始了新一轮的火星探测。自１９７６年美国的海盗１号和２号成功探测过火星之后，就再没有...     

未来的“火星快车”探测器

火星一直是公众非常感兴趣和关心的焦点,它是目前太阳系中最有可能找到生命（过去存在过或现在的）的地方,它将成为人类未来探索的主要星球,人类甚至有可能向火星移民。下世纪初,国际上将有多个探测器要探索火星,欧洲自己发射探测器考察火星的梦想终要成为现实,欧空...     

火星电离层无线电掩星探测仿真研究

对中俄联合火星星-星电离层掩星技术体制进行了分析和介绍,采用三维射线追踪方法对电离层掩星事件的电波观测值进行了模拟计算,并利用模拟的掩星观测数据进行了电子密度廓线反演,结果说明仿真算法可靠.利用仿真的方法,分别对掩星电波相位观测误差和卫星轨道误差等带来的反演误差进行了个例计算和分析,结果得到:5%周的相位测量误差对白天电离层掩星探测结果的影响可以忽略,而夜间电子密度测量的绝对误差小于4×108 m-3;卫星轨道误差对掩星的主要影响是导致电离层高度抬升或下降.结果表明,中俄联合火星电离层掩星探测技术体制先进,可望获得高精度的电子密度廓线;其技术体制也可以用于月球电离层环境的探测.     

Revealing Mars’ deep interior: Future geodesy missions using radio links between landers, orbiters, and the Earth

In the frame of a comparison between Earth, Venus, and Mars, a vision on future geodesy missions to Mars is discussed with particular focus on furthering our understanding of the interior, rotation, and orientation of this terrestrial planet. We explain how radioscience instruments can be used to observe the rotation and orientation and therewith to study the deep interior of Mars and its global atmosphere dynamics. Transponders in X-band and Ka-band are proposed with radio links between a lander or a rover and an orbiter around Mars and/or directly to the Earth. The radio budget links are studied in the frame of possible mission constraints and simulations are performed, which show that important information on the interior of Mars can be obtained from the radioscience data. From the observation of Mars’ orientation in space and of tidal effects on a spacecraft orbiting around Mars we show that it is possible for instance to constrain the dimension and composition of the core, the percentage of light element within the core, and to determine the presence of a pressure-induced mineral-phase transition at the bottom of the mantle.     

The New Wuqing 70 m Radio Telescope and Measurements of Main Electronic Properties in the X-band

The new Wuqing 70 m radio telescope is first used for the downlink data reception in the first Mars exploration mission of China,and will be used for the other ...     

Mars and Jupiter: Radio emission at 1.35 cm

We report observations of the radio disk temperatures of Mars and Jupiter made during October 1971, at a wavelength of 1.35 cm. The mean disk temperature of Jupiter is 136 ± 5°K, in good agreement with the value 139 ± 6°K obtained by Wrixon et al. (1971) with the same instrument three years earlier. The disk temperature of Mars is 181 ± 11°K, consistent with an essentially wavelength independent disk temperature for Mars at radio wavelengths. The ratio of the two disk temperatures, 1.33 ± .07, is largely free of the systematic uncertainties: antenna gain, pointing, and atmospheric extinction.     

Lander radioscience for obtaining the rotation and orientation of Mars

The paper presents the concept, the objectives, the approach used, and the expected performances and accuracies of a radioscience experiment based on a radio link between the Earth and the surface of Mars. This experiment involves radioscience equipment installed on a lander at the surface of Mars. The experiment with the generic name lander radioscience (LaRa) consists of an X-band transponder that has been designed to obtain, over at least one Martian year, two-way Doppler measurements from the radio link between the ExoMars lander and the Earth (ExoMars is an ESA mission to Mars due to launch in 2013). These Doppler measurements will be used to obtain Mars’ orientation in space and rotation (precession and nutations, and length-of-day variations). More specifically, the relative position of the lander on the surface of Mars with respect to the Earth ground stations allows reconstructing Mars’ time varying orientation and rotation in space.Precession will be determined with an accuracy better by a factor of 4 (better than the 0.1% level) with respect to the present-day accuracy after only a few months at the Martian surface. This precession determination will, in turn, improve the determination of the moment of inertia of the whole planet (mantle plus core) and the radius of the core: for a specific interior composition or even for a range of possible compositions, the core radius is expected to be determined with a precision decreasing to a few tens of kilometers.A fairly precise measurement of variations in the orientation of Mars’ spin axis will enable, in addition to the determination of the moment of inertia of the core, an even better determination of the size of the core via the core resonance in the nutation amplitudes. When the core is liquid, the free core nutation (FCN) resonance induces a change in the nutation amplitudes, with respect to their values for a solid planet, at the percent level in the large semi-annual prograde nutation amplitude and even more (a few percent, a few tens of percent or more, depending on the FCN period) for the retrograde ter-annual nutation amplitude. The resonance amplification depends on the size, moment of inertia, and flattening of the core. For a large core, the amplification can be very large, ensuring the detection of the FCN, and determination of the core moment of inertia.The measurement of variations in Mars’ rotation also determines variations of the angular momentum due to seasonal mass transfer between the atmosphere and ice caps. Observations even for a short period of 180 days at the surface of Mars will decrease the uncertainty by a factor of two with respect to the present knowledge of these quantities (at the 10% level).The ultimate objectives of the proposed experiment are to obtain information on Mars’ interior and on the sublimation/condensation of CO₂ in Mars’ atmosphere. Improved knowledge of the interior will help us to better understand the formation and evolution of Mars. Improved knowledge of the CO₂ sublimation/condensation cycle will enable better understanding of the circulation and dynamics of Mars’ atmosphere.     

Radio occultation measurements and MGCM simulations of Kelvin waves on Mars

We have derived new results concerning thermal tides on Mars from a combination of radio occultation measurements and numerical simulations by a Mars General Circulation Model (MGCM). This investigation exploits a set of concurrent observations by Mars Express (MEX) and Mars Global Surveyor (MGS) in mid-2004, when the season on Mars was midspring in the northern hemisphere. The MEX occultations sampled the atmosphere near the evening terminator at latitudes ranging from 54° N to 15° S. The MGS occultations provided complementary coverage near the morning terminator at latitudes of 35° N and 71° S. The geopotential field derived from these measurements contains distinctive modulation caused by solar-asynchronous thermal tides. Through careful analysis of the combined observations, we characterized two prominent wave modes, obtaining direct solutions for some properties, such as the amplitude and phase, as well as constraints on others, such as the period, zonal wave number, and meridional structure. We supplemented these observations with MGCM simulations. After evaluating the performance of the MGCM against the measurements, we used the validated simulation to deduce the identity of the two tidal modes and to explore their behavior. One mode is a semidiurnal Kelvin wave with a zonal wave number of 2 (SK2), while the other is a diurnal Kelvin wave with a zonal wave number of 1 (DK1). Both modes are known to be close to resonance in the martian atmosphere. Our observations of the SK2 are more complete and less ambiguous than any previous measurement. The well-known DK1 is the dominant solar-asynchronous tide in the martian atmosphere, and our results confirm and extend previous observations by diverse instruments.     

Solar EUV and Electron-Proton-Hydrogen Atom-Produced Ionosphere on Mars: Comparative Studies of Particle Fluxes and Ion Production Rates Due to Different Processes

The total photoelectron and secondary electron fluxes are calculated at different times and altitudes along the trajectory of Mars Global Surveyor passing through the nightside and dayside martian ionosphere. These results are compared with the electron reflectometer experiment on board Mars Global Surveyor. The calculated electron spectra are in good agreement with this measurement. However, the combined fluxes of proton and hydrogen atom as calculated by E. Kallio and P. Janhunen (2001, J. Geophys. Res.106, 5617-5634) were found to be 1-2 orders of magnitude smaller than the measured spectra. We have also calculated ionization rates and ion and electron densities due to solar EUV, X-ray, and electron-proton-hydrogen atom impacting with atmospheric gases of Mars at solar zenith angles of 75°, 105°, and 127°. In the vicinity of the dayside ionization peak, it is found that the ion production rate caused by the precipitation of proton-hydrogen atom is larger than the X-ray impact ionization rate while at all altitudes, the photoionization rate is always greater than either of the two. Moreover, X-rays contribute greatly to the photoelectron impact ionization rate as compared to the photoion production rate. The calculated electron densities are compared with radio occultation measurements made by Mars Global Surveyor, Viking 1, and Mars 5 spacecraft at these solar zenith angles. The dayside ionosphere produced by proton-hydrogen atom is smaller by an order of magnitude than that produced by solar EUV radiation. X-rays play a significant role in the dayside ionosphere of Mars at the altitude range 100-120 km. Solar wind electrons and protons provide a substantial source for the nightside ionosphere. These calculations are carried out for a solar minimum period using solar wind electron flux, photon flux, neutral densities, and temperatures under nearly the same areophysical conditions as the measurements.     

The early thermal evolution of Mars

Hf‐W isotopic systematics of Martian meteorites have provided evidence for the early accretion and rapid core formation of Mars. We present the results of numerical simulations performed to study the early thermal evolution and planetary scale differentiation of Mars. The simulations are confined to the initial 50 Myr (Ma) of the formation of solar system. The accretion energy produced during the growth of Mars and the decay energy due to the short‐lived radio‐nuclides ²⁶Al, ⁶⁰Fe, and the long‐lived nuclides, ⁴⁰K, ²³⁵U, ²³⁸U, and ²³²Th are incorporated as the heat sources for the thermal evolution of Mars. During the core‐mantle differentiation of Mars, the molten metallic blobs were numerically moved using Stoke's law toward the center with descent velocity that depends on the local acceleration due to gravity. Apart from the accretion and the radioactive heat energies, the gravitational energy produced during the differentiation of Mars and the associated heat transfer is also parametrically incorporated in the present work to make an assessment of its contribution to the early thermal evolution of Mars. We conclude that the accretion energy alone cannot produce widespread melting and differentiation of Mars even with an efficient consumption of the accretion energy. This makes ²⁶Al the prime source for the heating and planetary scale differentiation of Mars. We demonstrate a rapid accretion and core‐mantle differentiation of Mars within the initial ~1.5 Myr. This is consistent with the chronological records of Martian meteorites.     

Propagation of tropospheric gravity waves into the upper atmosphere of Mars

We study the propagation of gravity waves in the martian atmosphere using a linearized one-dimensional full-wave model. Calculations are carried out for atmospheric parameters characteristic of Mars Orbiter Laser Altimeter (on Mars Global Surveyor MGS) observations of apparent gravity waves in high latitude clouds and MGS radio occultation measurements of temperature variations with height suggestive of gravity wave activity. Waves that reach the thermosphere produce fluctuations in density comparable in amplitude with the density variations detected in Mars Odyssey aerobraking data. Gravity waves of modest amplitude are found to deposit momentum and generate significant heating and cooling in the martian atmosphere. The largest heating and cooling effects occur in the thermosphere, at altitudes between about 130 and 150 km, with heating occurring at the lower altitudes and cooling taking place above.     

Argon in the Martian atmosphere: Do the results of Mars 6 agree with the optical and radio occultation measurements?

Mars 6 discovered an inert gas (probably argon) in the Martian atmosphere. An analysis is carried out for the available spectroscopic observations, radio occultation results, and other data with the aim of determining the maximum argon content with which they are consistent. Possible seasonal variations of pressure are taken into account. It is shown that 25–30% of argon is consistent with all these data. The presence of argon slightly increases the mean pressure estimates; 25% argon increases pressures derived from radio occultation data by 0.5 mbar.