The Transiting Exoplanet Survey Satellite
At last September’s School of Science Breakfast, Jacqueline Hewitt Ph.D. ’86 (VIII), the Director of the MIT Kavli Institute, introduced the audience to an exciting MIT-led NASA mission: the Transiting Exoplanet Survey Satellite (TESS).
Hewitt outlined the long history of the TESS project, which began as a small private mission at the MIT Kavli Institute for Astrophysics and Space Research (MKI), supported by the Kavli Foundation, Google seed funding, and MIT donors. After being restructured and proposed as a Small Explorer Class Mission in 2008 and again as an Explorer Class Mission in 2010, it was greenlighted for development in 2013. TESS has grown into a $200 million mission with a team that includes the NASA Goddard Space Flight Center, the NASA Ames Research Center, the Harvard-Smithsonian Center for Astrophysics, the Space Telescope Science Institute, and several universities and observatories. George Ricker, a senior research scientist at MKI, is the mission’s Principal Investigator.
When TESS launches in 2017, it will monitor over 200,000 stars in search of exoplanets capable of supporting life. One of the leaders of MIT’s science effort and Class of 1941 Professor of Planetary Science and Physics, Sara Seager, outlined the conditions needed for a habitable planet in a paper published in Science in 2013. These conditions included having an orbit within a habitable zone around a “quiet” star that doesn’t produce a lot of radiation, and a greenhouse effect that increases the likelihood of water.
In order to find habitable exoplanet candidates, TESS will use the same method of detecting exoplanets as the Kepler mission, looking for the minute but measureable dips in a star’s light intensity caused by a planet passing in front of – or “transiting” – the star.
The Kepler mission not only found 1,000 exoplanets, but revealed that Earth-sized and “Super Earth” planets of up to twice Earth’s radius were far more common than previously thought. While these results were encouraging, most of the exoplanets Kepler found orbit stars that are too faint and distant to allow scientists to determine whether relatively small Earths and Super Earths possess characteristics necessary for life.
In contrast, TESS will focus on the bright stars in Earth’s more immediate neighborhood. The mission is expected to identify 3,000 new planets ranging from small rock and ice planets to gas giants, including 500 Earth-sized and Super Earth exoplanets to be targeted for detailed study by the James Webb Space Telescope after it launches in 2018.
TESS will employ a number of innovations developed at MIT, including a unique high-Earth orbit that is both close enough for high data-downlink rates and far enough away to avoid Earth’s harmful radiation belts. The orbit is highly stable and keeps TESS’s sensitive instrumentation within a steady temperature range during long periods of observation. Once TESS is in orbit, the all-sky survey will be carried out by cameras designed at the Lincoln Laboratory, containing novel CCD detectors with high signal-handling capacity and photometric accuracy and speed, also developed and fabricated at the Lincoln Laboratory.
Hewitt believes that the TESS mission will provide extraordinary opportunities for MIT to raise its international profile, expand its educational and research mission, and make MIT a credible center for space exploration missions to a risk-averse NASA. Because the mission’s Science Operations Center will be based in Building 37, MKI will have an opportunity to rebuild its infrastructure and to pave the way for future space exploration projects. MIT students will also have more mission-building training available to them: Kerry Cahoy, an Assistant Professor in the AeroAstro and EAPS Departments, is already using TESS as a test case in a graduate course in satellite engineering. TESS is helping MKI and MIT to attract some of the best scholars in planetary science: When the first MIT Torres Postdoctoral Fellowship for Research on Exoplanets was offered at MKI, 160 applications were submitted. The four postdoctorates that fellowship currently supports helped to tip the balance toward MIT in the NASA selection process.