If you've been following our calls for NASA to explore Europa (or even better, if you haven't), and have questions like, "why haven't we explored Europa already?" and "I thought NASA was working on the Europa Clipper mission?," Jeff Foust of the Space Review wrote up an excellent piece reviewing the recent history of humanity's effort to explore this compelling, watery moon:
NASA has been working on reducing a cost of a Europa orbiter mission, in large part by no longer making it an orbiter. The concept now favored within the space agency is something called “Europa Clipper.” Instead of going into orbit around Europa, the spacecraft would instead go into orbit around Jupiter and make repeated close flybys of the moon. The most recent mission designs involve 45 flybys of Europa over three and a half years, with the vast majority of them coming within 100 kilometers of the moon’s surface. That approach minimizes the spacecraft’s exposure to radiation as well as propellant needed for entering orbit around Europa.
That work on Europa Clipper has largely been done at the insistence of Congress, rather than by NASA’s own initiative. In the final fiscal year 2013 budget, Congress set aside $75 million of NASA’s planetary sciences budget specifically for Europa mission studies, and followed that up with $80 million in the fiscal year 2014 budget, even though NASA requested no money in either year’s budget request for Europa. The text of the final 2014 appropriations bill noted that the $80 million “shall be for pre-formulation and/or formulation activities for a mission that meets the science goals outlined for the Jupiter Europa mission in the most recent planetary science decadal survey.”
Read the full piece on the Space Review, where he also delves into the potential role of the Space Launch System to launch a Europa mission and how the recently-discovered plumes impact mission design.