Space telescope: Focus on priorities

The concerns and frustration of the planetary community over the uncertainty of the 2016 ExoMars mission are understandable (see go.nature.com/zimumq). Several budgetary factors are to blame, and these precede and are unrelated to the recently increased costs of launching the James Webb Space Telescope.

The US President's 2012 budget proposal for NASA's Planetary Science Division, released in February 2011, dropped from the previous year's figure by roughly US$1 billion over the next five years.

In addition, the cost of the Mars Science Laboratory, initially estimated at $650 million in 2003 (at a time when all major mission costs were underestimates), has risen to around $2.5 billion.

The cost of the missions in NASA's Science Mission Directorate budget for 2008 was also found to be understated by billions of dollars.

The scientific community needs to support the decadal priorities of each of the science divisions at NASA and avoid firing inwards, which will threaten funding for science overall.