Quantifying solar spectral contamination as a function of moon distance for EXPRES
By: Carissa Avina-Beltran
Department: Astrophysics
Faculty Advisor: Dr. John Michael Brewer
In the age of extreme precision radial velocities (EPRV), new spectrographs are reaching towards 10 cm/s precision of observations in an effort to identify low mass and possibly Earth-size planets around Sun-like stars. One of the challenges for state of the art RV instruments like EXPRES, ESPRESSO, and NEID is to distinguish doppler velocities from stellar photospheric noise. As EXPRES looks at bright stars it takes ~10 minute observations as frequently as possible to look at targets no closer than 30 degrees from the Moon. It is common practice to avoid targets within 60 degrees and prevent reflected sunlight from the moon contaminating the stellar spectra and reducing the precision of RV measurements. Avoiding such a large area of the sky limits the cadence that we may observe many targets of interest. We are analyzing two years of science spectra for targets at various lunar separations in an effort to discover at what distance this contamination reduces precision.