An upcoming report from the U.S.-China Economic and Security Review Commission says that in 2007 and 2008 hackers were able to mess with American satellites in orbit. They were apparently able to access them from a remote station in Norway and the Commission thinks it's likely that the attacks originated in China.

From Bloomberg:

A Landsat-7 earth observation satellite system experienced 12 or more minutes of interference in October 2007 and July 2008, according to the report.
Hackers interfered with a Terra AM-1 earth observation satellite twice, for two minutes in June 2008 and nine minutes in October that year, the draft says, citing a closed-door U.S. Air Force briefing.