In recent exoplanet meeting "The Next 40 Years of Exoplanets", there was much discussion of the inablity of the community to agree on whether to support coronagraph missions or interferometer missions, with white papers for the decadal survey contradicting each other, saying only their preferred method would work and the other method wouldn't work, with the result that both SIM and TPF have been cancelled. Geoff Marcy said he was unhappy about the last ten years and unhappy about the next ten years and said the title of the Astro2010: The Astronomy and Astrophysics Decadal Survey which is "New Worlds, New Horizons in Astronomy and Astrophysics" is disingenuous in the use of "New Worlds" because SIM and TPF were cancelled.

Has the community since then reached a consensus as to which method is preferable and what are the deciding factors ?


We don't really know what method is better yet because there are too many factors we don't know. Sensitivity and throughput are the most important aspects of such a mission but the details of both are highly variable and dependent on operational issues on spacecraft designs we haven't explored yet.

The cancellation of SIM and TPF is probably as much due to budget pressure due to overruns from JWST and other big missions as it is due to any lack of consensus within the exoplanet community.

However, the good news is that it doesn't matter as much as it may seem. Space based science is going to undergo a sea change in the next few decades due to the revolution in orbital launch prices that is just now underway (spurred largely by SpaceX). This revolution will fundamentally change the nature of unmanned spaceflight because it will dramatically lower the cost and dramatically increase access to orbital launch. Ultimately this means that unmanned spaceflight will be unmoored from the traditional gatekeepers of NASA, ESA, JAXA, etc. It will become more decentralized, much like the way large telescopes are built and run today.

In a few years it'll be possible for a collection of Universities to decide to build and launch a space telescope, without the approval or interference of NASA. But it won't be just one, it'll be several. It'll be possible to launch telescope prototypes for experimenting and developing different technologies such as coronagraphy or interferometry. In the long term this is a much better outcome. Instead of one big mission and then maybe another big mission a decade later we'll see an explosion of independently organized missions.

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  • $\begingroup$ I think the cancellation (indefinite delay?) of SIM and TPF is due to their poor showing in the decadal. WFIRST, LISA and IXO, the top three large missions, are all being indefinitely delayed due to JWST over-runs. I am also optimistic about the future of affordable launches, but remember the major costs of JWST are not in the launch, but in the integration and testing of such a huge instrument. $\endgroup$ – Jeremy Jul 5 '11 at 20:30
  • $\begingroup$ @Jeremy launch costs are multiplicative. If it costs x mil to launch, then a mission is only justified if the payload costs at least y > x mil. Which tends to end up being big percentages of total available funding, so you spend z mil to ensure that the mission has the highest chance of success. It snowballs. Lowering costs allows launching missions that cost far less in total and have only a high rather than extraordinarily high chance of success. You can launch prototypes and improve designs (and remove defects) iteratively. Ultimately resulting in more successful missions overall. $\endgroup$ – Wedge Jul 6 '11 at 2:56

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