Comments concerning the work and plans in Japan related to satellite gravity missions

Yoichi Fukuda
fukuda@kugi.kyoto-u.ac.jp

We were working on a project for investigating future satellite missions from 2002 to 2004. Since then we have not achieved remarkable progresses, in particular for planning full missions like GRACE-FO.

However a small satellite mission (DPF:DECIGO Pathfinder), which is aiming at the detection of the gravity wave, has been proposed as a candidate of JAXA's small satellite series. JAXA ISAS announced that they will launched at least 3 satellites in 5 years (2012-) with a standard bus and M-V follow-on rocket. Although the first and the second missions have already been selected, DPF has stayed in the next most possible candidate. Dr. Araya of ERI, Univ. Tokyo is involved in DPF for developing an on-board accelerometer or a drag free system, and we expect that DPF will work as a gravity field satellite as CHAMP perhaps with a slightly better performance. On the other hands, DPF needs some practical outcomes to explain its mission necessity to JAXA. So DPF guys welcome the supports from the gravity communities. They are now working for the next selection of the launch timing around 2015.

Another movement is also regarding the JAXA's small satellite series. Prof. Tsuda of RISH, Kyoto Univ. is also planing to propose a small satellite which mainly aims GPS occultation measurements. But he also want to include an accelerometer for gravity field measurements. This will be a successive potent candidate as well.

I think these missions should contribute as a milestone for the future Japanese gravity missions, also multi-satellite should be an important point to improve spatial and temporal resolutions.