In February 2016, NASA selected the proposal from the Pennsylvania State University led by Principal Investigator Dr. Suvrath for an Extreme Precision Doppler Spectrometer (EPDS). Details of the NASA Research Announcement (NRA) can be found at the solicitation website. Six teams originally submitted proposals in response to NASA’s invitation and, of those, two were down-selected in January 2015 for further study before the final selection was made.

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Pennsylvania State University led by Principal Investigator Dr. Suvrath

The EPDS instrument will employ a standard method to capture evidence of exoplanets: detecting subtle Doppler shifts in starlight. As planets orbit, they tug their host stars this way and that, alternately squeezing and stretching the waves of starlight that reach our telescopes. The size of the star’s wobble reveals the mass of the orbiting planet, whether a massive gas giant like Jupiter or a small, rocky world like Earth. Combined with data from NASA space telescopes such as Kepler (operating since 2009) and TESS (to be launched in 2017), the new EPDS instrument will confirm planetary candidates discovered by those missions and improve our understanding of their properties. When operational in October 2018 on the WIYN telescope, the new spectrometer will have the precision to measure a star’s line-of-sight velocity (its “wobble”) to better than 0.5 meters per second (1 mile per hour). For context, the average human walking speed is about 3 miles per hour. Such extreme precision is needed to measure the mass of an Earth-sized planet orbiting a sun-like star.

Stellar Wobble
Very high velocity precision is needed to measure the mass of low mass planets through the subtle motion, the “wobble”, that a planet induces in its host star. The Extreme Precision Doppler Spectrometer (EPDS) destined for Kitt Peak will measure stellar motions with a precision of 0.1 - 0.5 m/s (or 0.2 - 1 mph), velocities comparable to the running speed of a desert tortoise or gila monster. With such high precision, the spectrometer will be able to detect and characterize Jupiter- and Neptune-sized gas giant planets as well as super-Earth and Earth-sized rocky planets. (Credit: NOAO)