PHASES: Opto-mechanical solutions to perform absolute spectrophotometry from space

¹ Instituto Nacional de Astrofísica, Óptica y Electrónica, Aptdo. Postal 51 y 216, 72000 Puebla, Pue., Mexico
² Dublin Institute of Technology (DIT), Bolton Street, Dublin 1, Ireland

^a e-mail: cburgo@inaoep.mx
^b e-mail: dinesh.vather@dit.ie
^c e-mail: Niall.Murphy@dit.ie

Abstract

This work provides an update of the current status of PHASES, which is a project aimed at developing a space-borne telescope to perform absolute flux calibrated spectroscopy of bright stars. PHASES will make it possible to measure micromagnitude photometric variations due to, e.g., exo-planet/moon transits. It is designed to obtain 1% RMS flux calibrated low resolution spectra in the wavelength range 370–960 nm with signal-to-noise ratios >100 for stars with V<10 in short integration times of ∼1 minute. The strategy to calibrate the system using A-type stars is outlined. PHASES will make possible a complete characterization of stars, some of them hosting planets. From the comparison of observed spectra with accurate model atmospheres stellar angular diameters will be determined with precisions of ∼0.5%. The light curves of transiting systems will be then used to extract the radius of the planet with similar precision. The demanding scientific requirements to be achieved under extreme observing conditions have shaped the optomechanical design. A computational model and a high-precision interferometric system have been developed to test the performance of the instrument.