Abstract The Venus Climate Orbiter mission (PLANET-C), one of the future planetary missions of Japan, aims at understanding the atmospheric circulation of Venus. Meteorological information will be obtained by globally mapping clouds and minor constituents successively with four cameras at ultraviolet and infrared wavelengths, detecting lightning with a high-speed imager, and observing the vertical structure of the atmosphere with radio science technique. The equatorial elongated orbit with westward revolution fits the observation of the movement and temporal variation of the atmosphere which as a whole rotates westward. The systematic, continuous imaging observations will provide us with an unprecedented large data set of the Venusian atmospheric dynamics. Additional targets of the mission are the exploration of the ground surface and the observation of zodiacal light. The mission will complement the ESA's Venus Express, which also explores the Venusian environment with different approaches.

Abstract The ISAS (Institute of Space and Astronautical Science) working group is currently studying the feasibility of a Venus orbiter mission [Proposal Report of feasibility study of Venus Climate Orbiter (in Japanese), ISAS working group, 2001], called PLANET-C project, in which a 3 axis stabilized spacecraft will be launched in early 2008, and it will arrive at Venus in 2009. Primary purpose of the mission is to observe Venus climate so as to understand mechanism of the global circulation and three-dimensional motion of the Venus atmosphere in the lower stratum. In order to achieve the above scientific objectives, the spacecraft will carry several types of optical cameras mainly with near-infrared wavelengths. An accurate orientation for the attitude control is required in the spacecraft design. Furthermore, thermal control of the cameras is critical, because of large heat input from camera hoods and strict requirement of low temperature of detecting head. This paper describes characteristics of the PLANET-C spacecraft. And also depicted are the mission outline and the operation plan of the attitude orientation.

Li-ion batteries, which have the advantage of high discharge voltage and high energy-to-weight ratios, have been studied energetically in recent years aiming at space applications in many countries such as Japan, the U.S. and France. Japan's asteroid explorer Hayabusa (MUSES-C: Asteroid Sample-return Spacecraft), which was launched in May 2003 and is on its way to the Earth hopefully with some samples collected at the asteroid ITOKAWA, is the world's first spacecraft powered by a Li-ion battery, from The Furukawa Battery Corp. The battery consists of 11 prismatic 13.2 Ah battery cells connected in series and has a specific energy of more than 85 Wh/kg. The bus voltage varies from 32.5 to 47.5 V during the battery mode according to the state of charge of the battery. On the basis of the battery technology for 'Hayabusa', we started developing the Li-ion battery for the Venus Climate Orbiter 'PLANET-C' in 2002. Since a further improvement in the mass advantage was requested for the mission, the enlargement of the capacity and the increase of the energy density were examined through the surface modification of an anode active material and the improvement of the separator. As a result, a 23.5 Ah class prismatic Li-ion battery of high energy density was made for trial purposes by 2004. We performed a life test keeping the battery fully charged under the float charge condition, and found that their aged deterioration was reduced by half from the battery for 'Hayabusa'. This aged de

Abstract The Longwave Infrared Camera (LIR) onboard the first Japanese Venus mission, PLANET-C, or the Venus Climate Orbiter, operates in the middle infrared region with a single bandpass filter of 8–12 μm, measuring thermal radiation emitted from the cloud tops of the Venusian atmosphere. A horizontal wind vector field at the cloud-top height will be retrieved by means of a cloud tracking method. In addition, absolute temperature will be determined with an accuracy of 3 K. Since solar irradiation scattered by the atmosphere is much weaker than the atmospheric thermal radiation, LIR can continuously monitor a hemispheric wind field independent of the local time of the apocenter throughout the mission life. Wind and temperature fields obtained by LIR will provide key parameters to solve climatological issues related to the Venusian atmosphere. The use of an uncooled micro-bolometer array (UMBA), which requires no cryogenic apparatus, as an image sensor contributes to the reduction of power consumption and the weight of the LIR imager. An instrumental field-of-view of 12° is equal to the angle subtended by Venus when observed from a height of 9.5 Rv. The pixel field-of-view corresponds to a spatial resolution of 70 km viewed from the apocenter. A mechanical shutter functions not only as an optical shutter but also as a reference blackbody. The temperature stability of the sensor is especially important, because fluctuation of thermal radiation from the internal environment of t

現在、金星探査機(PLANET-C: Venus Climate Orbiter)は2010年打上げを前提に、ミッション解析が進められている。軌道計画の実現性を確認する目的で、打上げ直後の第1可視運用性、金星周回軌道中の日陰時間、探査機に要求される燃料重量などを算出し、探査機システムとの整合性を確認した。本稿では、これら2010年打上げ軌道の特徴と現状における打上げウィンドウを示す。 In the present study, the launch windows in May and June, 2010 are applied to the PLANET-C (Venus Climate Orbiter) Venus exploring mission. So as to verify the system compatibility between the orbital design and the spacecraft capability, antenna elevation in the first visible pass from UDSC (Usuda Deep Space Center) and shadow duration of the elliptic orbit about Venus are evaluated in this paper. Required velocity amount for orbit and attitude correction is also estimated for the 2010 launch orbit. Currently, three weeks in total of launch possibilities, one week in May and two weeks in June 2010, are ensured for the PLANET-C mission. 資料番号: AA0063480014