排序方式: 共有24条查询结果,搜索用时 15 毫秒
21.
Karl-Heinz Glassmeier Hermann Boehnhardt Detlef Koschny Ekkehard Kührt Ingo Richter 《Space Science Reviews》2007,128(1-4):1-21
The ROSETTA Mission, the Planetary Cornerstone Mission in the European Space Agency’s long-term programme Horizon 2000, will
rendezvous in 2014 with comet 67P/Churyumov-Gerasimenko close to its aphelion and will study the physical and chemical properties
of the nucleus, the evolution of the coma during the comet’s approach to the Sun, and the development of the interaction region
of the solar wind and the comet, for more than one year until it reaches perihelion. In addition to the investigations performed
by the scientific instruments on board the orbiter, the ROSETTA lander PHILAE will be deployed onto the surface of the nucleus.
On its way to comet 67P/Churyumov-Gerasimenko, ROSETTA will fly by and study the two asteroids 2867 Steins and 21 Lutetia. 相似文献
22.
Kyoung-Min Roh Hermann Luehr Markus Rothacher Sang-Young Park 《Aerospace Science and Technology》2009,13(1):49-58
This paper proposes a suitable orbit design for the lower pair of ESA's Swarm constellation mission, flying side-by-side in near-polar and circular orbits with a separation of only 1.4° at ascending node. Both orbits are suggested to be frozen orbits to minimize the evolution, and an along-track separation strategy is applied to avoid collision risk. The characteristics of the proposed orbit type are examined through numerical techniques including high-fidelity perturbation models. The prime change from the initial configuration is an along-track separation. The perturbations causing the along-track drift are analyzed by switching on/off certain perturbations. The results indicate that the tesseral harmonics and the atmospheric drag yield dominant effects. The atmospheric drag effect shows a dependence on the local time of the ascending node. From two months of orbit propagation for the altitude 300 km the maximum along-track drift we obtain is about 80 km, which is still within the measurement requirement range. Several maneuver strategies for maintaining the proposed orbit design are suggested. The results analyzed for the proposed orbit design show that collision risk can be avoided by along-track separation within the frozen orbit design. Consequently, this combination is considered as a suitable approach for Swarm's lower pair. 相似文献
23.
H. Steinle H. Bloemen W. Collmar R. Diehl W. Hermsen G. Lichti M. McConnell J. Ryan V. Schnfelder G. Stacy A. W. Strong B. N. Swanenburg M. Varendorff O. R. Williams 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1993,13(12):731-734
During the first part of the COMPTON Gamma Ray Observatory sky survey, COMPTEL has detected the quasars 3C273 and 3C279 and the radio galaxy Centaurus A. This paper summarizes the preliminary findings and gives an upper limit on the MeV flux of the Seyfert galaxy NGC4151. 相似文献
24.
Electric and thermal power have to be available at the base site on the lunar surface before the first lunar crew arrives. Unlimited solar energy is available during the lunar day, but this must be stored for use during the lunar night unless nuclear energy systems are available. State-of-the-art candidate systems are reviewed and the production of solar cells on the moon is discussed. Various options for developing a lunar power plant are proposed. These must be simulated and optimized in a real lifecycle systems scenario to provide operations and cost data essential for choosing a strategy. 相似文献