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Exoplanet-hunting TESS returns first images

18 Sep 2018

'First light' for satellite telescope launched earlier this year as multi-camera payload captures view of the Large Magellanic Cloud.

NASA has released the first full-frame image captured by all four cameras on board the exoplanet-hunting Transiting Exoplanet Survey Satellite (TESS).

Launched in April this year, TESS began science operations in July and captured the released imagery in early August. The results represent “first light” for the new space telescope, and indicate that it is ready to begin looking for exoplanets by monitoring almost the entire night sky to look for regular dips in the brightness of relatively nearby stars.

The “first light” imagery, captured in just half an hour, includes broad-swath views of the Large and Small Magellanic Cloud, among what NASA described as a wealth of stars and other celestial objects including clusters that are known to harbor exoplanets.

Designed and built by the Massachusetts Institute of Technology’s (MIT) Lincoln Laboratory in Lexington, Massachusetts, and the MIT Kavli Institute, the cameras on board TESS are based around 16.8 megapixel CCD sensors. Each of the four identical cameras features seven lenses to provide a wide (24x24°) field of view.

George Ricker, TESS’ principal investigator at MIT Kavli, said of the initial imagery captured: “This swath of the sky’s southern hemisphere includes more than a dozen stars we know have transiting planets based on previous studies from ground observatories.”

TESS is scheduled to take two years to survey 26 sectors of the sky, spending nearly a month on each sector – equivalent to some 85 per cent of the entire sky in total. During the first year of operations it will monitor the southern sky, before switching its attention to the northern sky for the second part of the survey.

By the end of its survey, of around 200,000 target stars, TESS ought to have captured around 5000 transit-like signals for direct imaging. From that data a short-list of 50 transiting exoplanets thought to be no more than four times the size (diameter) of Earth should result.

Spectroscopic search for ‘another Earth’
TESS represents something of a follow-up to the Kepler mission, which used similar methods to locate upwards of 2600 exoplanets. However, the TESS cameras are looking at stars much closer to home than Kepler, concentrating on targets between 30 and 300 light years away, and up to 100 times brighter.

That brightness is expected to make the target stars ideal candidates for follow-up spectroscopic studies of exoplanet atmospheres – something that will be possible following the launch of the James Webb Space Telescope (JWST), now expected sometime in 2020. The coming generation of extremely large telescopes currently under construction could also be used to perform that kind of analysis.

Spectroscopy of exoplanet atmospheres raises the prospect of searching for gases like oxygen and water vapor, which could indicate the presence of life on distant worlds.

Following the “first light” imagery release, NASA’s astrophysics division director Paul Hertz said: “In a sea of stars brimming with new worlds, TESS is casting a wide net and will haul in a bounty of promising planets for further study.

“This first light science image shows the capabilities of TESS’ cameras, and shows that the mission will realize its incredible potential in our search for another Earth.”

To schedule science observations, the MIT team working on TESS coordinates with Northrop Grumman in Falls Church, Virginia. TESS transmits images every two weeks, each time the satellite’s unusual cis-lunar orbit returns it closest to Earth.

NASA’s Deep Space Network receives that data and forwards it to the TESS Payload Operations Center at MIT for initial evaluation and analysis, before full data processing and analysis at NASA’s Ames Research Center in California generates calibrated images and refined light curves that can then be used to identify promising exoplanet transit candidates.

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