Development of a High Precision Deployable Modular Antenna for the Next Space VLBI Mission
- Paper number
IAC-05-C2.1.B.01
- Author
Dr. M.C. Natori, Japan Aerospace Exploration Agency (JAXA)/ISAS, Japan
- Coauthor
Dr. H. Hirabayashi, Japan Aerospace Exploration Agency (JAXA)/ISAS, Japan
- Coauthor
Mr. S. Iikura, NEC TOSHIBA Space Systems (NTS), Japan
- Coauthor
Dr. Yasuhiro Murata, Japan Aerospace Exploration Agency (JAXA)/ISAS, Japan
- Coauthor
Dr. N. Okuizumi, Japan Aerospace Exploration Agency (JAXA)/ISAS, Japan
- Year
2005
- Abstract
We are developing the satellite for the next space VLBI mission called VSOP2 (VLBI space observation program-2, [1]). It is planned to be launched in 2011 (in the earliest case), and follows the first space VLBI mission, VSOP. The VSOP2 satellite orbit will have an apogee height of 25,000km, a perigee height of 1,000km, and an inclination of 31 degrees. The satellite will coobserve astronomical objects with 5-15 ground radio telescopes in the 8, 22 and 43GHz bands. VSOP2 will realize a resolution of 40micro arcsecond at a wavelength of 7mm. The scientific objectives include the study of jets and accretion disks around the super massive black holes of active galactic nuclei (AGN), and young stellar objects. To obtain the highest possible sensitivity we wish to make the antenna as large as possible, however the satellite must be small enough to fit inside the nose fairing of the launch vehicle, the M-V rocket developed by ISAS/JAXA. For the VSOP mission we realized an antenna with an effective diameter of 8m, the surface of which was shaped by geodesic tension cables. The VSOP satellite antenna was successfully deployed and used for the first space VLBI mission for more than 7 years [2]. The antenna for the VSOP2 satellite will have an off-axis design, based on that of JAXA's forthcoming telecommunication mission, ETS-8, with the antenna surface consisting of seven hexagonal modules supported by deployable trusses. In addition, a new radial rib structure [3] is employed for the VSOP2 antenna modules to obtain surface accuracy as high as 0.3mm rms. We developed a full-scale test module for checking the concept of the radial rib surface. Adjustment procedure of the surface, actual adjustment of the module, detailed design of the deployment mechanism, and the mechanical interface while the module is folded for the launch are presented. A new way to apply the zerogravity correction to the high precision antenna surface instead of regular conventional cup up/cup down measurements is introduced. The surface of the module is a mesh of goldcoated molybdenum wire. We have measured the reflectivity and transparency of the mesh between 18GHz and 110GHz, and confirmed that the mesh can be used at the VSOP2 observing frequencies. We continue to work to find a mesh with a lower reflection loss for the use up to 43GHz. We will discuss the overall antenna system including the dynamic performance, and the concept for adjusting the antenna after the deployment in orbit, using two adjustment mechanisms at the main- and sub-reflector supports. References [1] H. Hirabayashi et al., Proceedings of the 7th EVN Symposium, (eds. R. Bachiller, F. Colomer, J.F. Desmurs, P. de Vicente, p.285-288 (astroph/0501020). [2] M.C. Natori, H. Hirosawa, T. Takano, K. Miyoshi and H. Yanai, "Ground Adjustment and In-Orbit Deployment of a Deployable Antenna onboard HALCA," IAF-98-I.4.08, 49th Int'l. Astronautical Congress, Sept.-Oct. 1998, Melbourne. [3] M.C. Natori, H. Hirabayashi, N. Okuizumi, S. Iikura and K. Nakamura, "A Structure Concept of High Precision Mesh Antenna for Space VLBI Observation," AIAA-2002-1359, 43rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials (SDM) Conf., April 2002, Denver.
- Abstract document