The fairing of the launcher selected for the Space Infrared telescope for Cosmology and Astrophysics (SPICA) mission is not compatible with a primary mirror of 3.5m in diameter. Thus three alternative optical designs of the SPICA Telescope Assembly (STA) with a primary mirror of reduced size were defined and their theoretical optical performances assessed. The impact of the size reduction on the STA optical performances was then quantified. Based on the results of the study, we defined a STA optical design optimum in terms of optical performances and of accommodation of instruments in the STA focal surface.
ESA and JAXA plan to launch a satellite called
EarthCARE (Earth Clouds, Aerosols and Radiation
Explorer). The Cloud Profiling Radar (CPR), which will
be the first millimeter-wave Doppler radar in space, is
installed on this satellite as one of main sensors to observe
clouds. This paper describes the design results and PFM
performance of EarthCARE CPR.
SPICA is a next generation infrared astronomy mission to reveal the origin of planets and galaxies. The mission is led by
Japan Aerospace Exploration Agency (JAXA) in collaboration with the European Space Agency (ESA) and international
consortiums in Japan, Europe, USA, and the Republic of Korea. SPICA is an "observatory" based on the heritage of
AKARI's "all sky survey". ESA provides a 3-m class telescope using technology heritage of Herschel. The SPICA will
achieve superior sensitivity in the mid- to far- infrared astronomy to be launched into space. SPICA has a completely
new cooling system, which utilizes efficient mechanical coolers. This system enables a large, cryogenically cooled
telescope in space. SPICA system concept and requirements are clear, but it is not easy to design. SPICA spacecraft
consists of the Payload Module (PLM) and the Bus Module (BM). The PLM includes mechanical coolers and passive
thermal shields, which enable to cool down the telescope and scientific instruments below 6K. The PLM is connected to
the BM with low thermal conductivity truss structure to keep the PLM cool and the BM warm. This paper describes how
to meet the system requirements to establish the feasible design of SPICA spacecraft.
The altitude of the Tropical Rainfall Measuring Mission (TRMM) satellite was raised from 350km to 402.5km in August 2001 in order to extend its lifetime. The minimum detectable value of Z-factor after the boost is 1.2dB higher. We compared the actual PR products before and after the altitude increase using statistical methods in order to verify the algorithms and the Precipitation Radar (PR) rain products after the orbit was raised, and to confirm the influence of raising the orbit on PR rain products. The reflectivity factor histograms do not exhibit any significant changes after the raising of the satellite, except for a 1.2dB increase of the minimum detectable value. The results are consistent with the estimation before the raising. The monthly global average of the conditional rain rate in 3A25 product increased 0.2 mm/h after the orbit raising. This result corresponded to the simulated rainfall average estimated from the 1C21 product before the raising. Changes in monthly global rainfall average of unconditional rain, height of rainfall and height of bright band due to the orbit raising were not significant. This result shows that the orbit change had little influence on the PR estimation.
KEYWORDS: Satellites, Telecommunications, Acquisition tracking and pointing, Laser communications, Satellite communications, Sensors, Laser systems engineering, Data communications, Control systems, Communication engineering
Free-space laser communication systems offer many advantages such as high data rate, small sized equipment, low consumption electric power and others. There are, however, many development factors to construct a realistic laser communication system in space. Precise Acquisition, Tracking, and Pointing (ATP) functions are key issue to establish the laser communication system in space. OICETS (Optical Inter-orbit Communications Engineering Test Satellite) has been developed by National Space Development Agency of Japan (NASDA) to verify an optical data link technology in space. ATP functions of the OICETS satellite for a laser inter-orbit link system must be controlled with an angular accuracy better than a few micro radian under vibrational disturbances of the host satellite. The microvibrational disturbances continually come from the satellite subsystem operations such as reaction wheels, solar paddle motors, scan sensors and so on. NASDA performed an on-ground microvibration test to evaluate vibration characteristics of the OICETS satellite and to verify laser tracking performances of the ATP system. The test was carried out by using a simulated OICETS satellite that consists of a mechanical structure model and an engineering model of the laser communication terminal. The mechanical structure model is equipped with some flight components and mass dummy components. The satellite is suspended from a lifting tackle by four straps and the free-free configuration was simulated using a suspension device. As a result, the incremental residual tracking error of 0.19 micro radians was measured due to the microvibration of the disturbing sources from the satellite platform.