Characterizing the Evolving PSF of the EXPRES Spectrometer
Abstract
The EXtreme PREcision Spectrometer (EXPRES) is an R~150,000 spectrometer stationed at the 4.3- meter Lowell Observatory Discovery Channel Telescope (DCT). EXPRES is designed to detect the ultra-small shifts in the motions of stars hosting small exoplanets - measuring radial velocities on the orders of centimeters to meters per second. In order to measure these minute redshifts and blueshifts with adequate precision, EXPRES must employ robust wavelength calibration techniques. Currently, night-by-night wavelength calibrations are made with multiple calibration light sources, including a Thorium Argon lamp (ThAr) and a stabilized Laser Frequency Comb (LFC). Combined, these sources have yielded wavelength solutions with low scatter; however, without a time- and wavelength- dependent model of the Point Spread Function (PSF), systematic errors of order 10 cm s-1 could be degrading this data. In order to increase the precision of EXPRES' wavelength fits, (and thus increase the precision of the instrument's measured radial velocities,) we measure the evolution of EXPRES' PSF and attempt to deconvolve out dependencies such as focus, wavelength, and temperature from the nightly wavelength solutions.
- Publication:
-
American Astronomical Society Meeting Abstracts #235
- Pub Date:
- January 2020
- Bibcode:
- 2020AAS...23517512K