Details of the next NASA Discovery Program Mission Announcement of Opportunity have been released by NASA. The draft of the AO will be released next month, but a few of the key elements of the document are now available. Discovery missions are low-cost, Principal Investigator-led projects. For this AO, any solar system target is acceptable, excluding the Earth and the Sun. So Mars missions would be acceptable.
For an Io mission like IVO, there are a few key details to consider. First, Advanced Stirling Radioisotope Generators (ASRGs) can be used as power sources for a proposed mission. If a proposer wishes to use them, NASA will provide two of them at no cost to the project's cost cap. This decision will allow the missions developed under the DSMCE concept study program to be proposed for this AO. However, there is one problem for the Io Volcano Observer. The cost cap for the next Discovery mission is currently set at $425 million (FY10). This is $25 million less than planned for in the DSMCE program, and the IVO team already needed to find a way to cut $21 million from the cost estimate provided by JPL's Team X. So the current cost cap would make it difficult to do a mission like IVO even with the power sources provided by NASA. One point I should make though is that I am not sure if the $471 million cost estimate for IVO by Team X included the launch vehicle as that will be provided by NASA at no cost to the mission's cost cap.
According the announcement by NASA, 2-3 missions will be approved to continue to Phase A, allowing for a refinement of the mission concepts. After the completion of Phase A, one mission will be selected to go to Phase B and then on to mission completion. This setup is probably intended to prevent some of the cost overruns that have plagued many of the recent Discovery program missions like MESSENGER and Dawn. Downselection to Phase A should occur in July 2010 and then to the single mission in November 2011.
Tip of the plutonium to Van Kane.
EDIT 07/14/2009: Since this post seems to be pretty popular for people looking for info on the Discovery AO, I should point out that launch vehicle costs (along with ASRGs) are excluded from the cost cap, which should make it was easier for proposals like IVO to meet the $425 million (FY10) limit.
Link: NASA intends to release a Discovery Program Draft AO [nspires.nasaprs.com]