The Missing Discovery Mission

by Paul Gilster on October 31, 2006

Having championed Webster Cash’s New Worlds Imager in earlier posts, Centauri Dreams was nonplussed yesterday to see NASA’s list of concept study selections for Discovery-class missions. Chosen for further work and 1.2 million in funding each were an asteroid sample return mission, a Venus orbiter, and a mission to produce a gravity field map of the Moon. New Worlds Imager was nowhere in sight.

NASA also chose three ‘missions of opportunity,’ meaning missions that can use existing spacecraft to produce new work. Out of these, the idea with most relevance to extrasolar work is Drake Deming’s Extrasolar Planet Observations and Characterization (EPOCh), which would use the high-resolution camera on the Deep Impact spacecraft to look for Earth-sized worlds around other stars.

Deming is a formidable player in the world of exoplanet detection (he was involved, for example, in the recent work on Upsilon Andromedae b) and we’ll be keeping an eye on EPOCh. But we’re also going to keep advocating Cash’s New Worlds Imager. The premise is to fly a starshade and separate telescope that would work in tandem (though separated by 15,000 miles) to detect planetary systems down to the terrestrial planet level. The daisy-shaped starshade could be a mere 50 meters in diameter yet capable of groundbreaking imaging, especially if the telescope using it were the James Webb Space Telescope, scheduled for launch in 2013.

That capability of double-duty for the Webb telescope should tempt NASA mission planners, who like to use existing equipment stretched into new applications. The current Discovery announcement includes another study that would use the Deep Impact spacecraft to perform a second cometary flyby, and a proposal for a flyby of comet Tempel 1 using the existing Stardust spacecraft to see what has changed since the Deep Impact mission’s visit in 2005. So Cash’s mission fits the budgetary bill (it’s a $400 million proposal) and is worthy of future consideration.

A recent Cash paper on the starshade is “Detection of Earth-like planets around nearby stars using a petal-shaped occulter,” Nature 442 (6 July 2006), pp. 51-53, with abstract available. As for the Discovery concept studies announced yesterday, one or more could be selected to move into a development stage after review; those decisions are expected next year. The budgetary benchmark for a completed mission is $425 million.

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