How 'Starshades' Could Aid Search for Alien Life (space.com)

Nineteen different subscale versions of a light-blocking "starshade" were tested recently in the Nevada desert.

The next step in the exoplanet revolution may be an in-space "starshade" that lets alien worlds step out of a blinding glare.
Researchers are testing designs for a starshade, which would fly in formation with a future space-based telescope. The starshade, also known as an "external occulter," would block the light from a star while allowing the scope to spot emissions from much dimmer orbiting planets.
Scientists are conducting desert tests of the technology on Earth. They're using the McMath-Pierce Solar Telescope at Kitt Peak National Observatory in Arizona to model a starshade's ability to help future instruments find and characterize rocky, Earth-like alien worlds.
A starshade may be used on NASA's potential Wide-Field Infrared Survey Telescope (WFIRST), a space-based instrument that would feature a primary mirror 8 feet (2.4 meters) wide, the same size as that of the agency's iconic Hubble Space Telescope.
Several years ago, the U.S. National Reconnaissance Office (NRO) donated two space telescopes to NASA. In 2013, the space agency announced it hoped to use one of these scopes for WFIRST. That move spurred anticipation in the U.S. astronomical community for Hubble-quality imaging over an area of sky 100 times larger than that viewed by Hubble. This version of the mission is called WFIRST-AFTA (for "Astrophysics-Focused Telescope Assets").
The WFIRST-AFTA mission would carry out exoplanet exploration, dark energy research, and galactic and extragalactic surveys.
Small-scale versions of starshades have undergone nighttime desert testing in Nevada and California and, more recently, at the McMath-Pierce Solar Telescope site.
The sites selected for evaluating starshade designs each have pros and cons, but collectively the evaluations are complementary and help to validate optical modeling of the idea, said Steve Warwick, Starshade program manager at Northrop Grumman Aerospace Systems.
"We can't do everything we can do in space on the ground in terms of optics, but the tests add a lot of confidence to how the starshade will work on orbit," Warwick told Space.com.
McMath operators said testing sharshades with the telescope, which was dedicated in 1962, was the craziest way that anyone had used the facility to date, Warwick said.
"They were extremely helpful and excited to see what we could do with their facility," Warwick said of the McMath team. Starshade testing at the Arizona site has been done twice so far, in late March and then in June.
The hope is to return to that location in the November-December time period; the exact timing will depend partly on other McMath users' schedules, Warwick said.
A mix of NASA funding and Northrop Grumman funding has enabled the starshade test program to move forward.


http://www.space.com/30429-starshade-alien-life-search-wfirst-tech.html?cmpid=NL_SP_weekly_2015-09-02