Astro-G (also known as VSOP-2, and very rarely called VSOP-B) was a planned radio telescope satellite by JAXA. It was expected to be launched into elliptic orbit around Earth (apogee height 25,000 km, perigee height 1,000 km).
Astro-G was selected in February 2006 against the competition of a proposed new X-Ray astronomy mission (NeXT) and a proposed solar sail mission to Jupiter. Funding started from FY 2007 with a budget of 12 billion yen, around 100 million US dollars. It was planned to be launched in 2012 but a technical difficulty of dish antenna as well as the budget constraint lead to put the development on hold for fiscal year 2010. Eventually the project was canceled in 2011 for the increased cost and the difficulty of achieving science goals.
It was planned to feature a 9 m diameter dish antenna to observe in 8, 22 and 43 GHz bands, it will be used in a combination of ground radio telescopes to create Very Long Baseline Interferometry. It was expected to achieve ten times higher resolution and ten times higher sensitivity than its predecessor HALCA.
Science targets 
Key science :
- Jet structure, collimation and acceleration regions
- Structure of accretion disks around AGN
- Structure of magnetic fields in protostars
Other science targets:
- Galactic masers in star-forming region
- Extragalactic Megamasers
- Radio quiet quasars
- X-ray binaries, SNR, gravitational lenses etc.
- [dead link]
- "事業番号3-34" (in Japanese). Retrieved March 9, 2010.
- "10-1．平成22年度予算案の概要" (in Japanese). Retrieved March 9, 2010.
- "電波天文衛星（ASTRO‐G）の状況について（報告資料）" (in Japanese). JAXA. August 24, 2011. Retrieved February 5, 2012.
- "平成23年宇宙開発委員会（第35回） 配付資料" (in Japanese). Ministry of Education, Culture, Sports, Science and Technology. November 30, 2011. Retrieved February 5, 2012.
- VSOP-2 Project - National Astronomical Observatory of Japan
- http://www.vsop.isas.jaxa.jp/vsop2/ (Japanese)