Peter Plavchan (George Mason University): "The NASA Landolt Mission"

The NASA Landolt mission is a timely PIONEERS program that will provide significant improvement in the accuracy of photometric measurements of absolute stellar fluxes. This will be accomplished with a high accuracy National Institute of Standards and Technology (NIST) calibrated suite of single-mode fiber-fed laser beacons which will be observable from selected ground-based observatory stations. Landolt will improve the photometric accuracy to <0.5% at visible (VIS) and near-infrared (NIR) wavelengths for >60 target stars – improving upon the half-century old techniques that use ground-based blackbodies and calibrated lamps along with model stellar atmospheres and sounding rocket measurements. The Landolt mission will allow us to re-calibrate the brightnesses of millions of stars. Such measurements can only be achieved by a space-based orbiting artificial star, where the physical photon flux is accurately known. Accuracy of absolute flux zero points is now the leading error budget term in the characterization of stars, be they standard stars or exoplanet hosts. Similarly, the accuracy of the ratio of the VIS/NIR absolute flux calibration zero point is the limiting error budget term in the Supernovae (SNe) Ia cosmological constraints on dark energy, a key science goal of the Nancy Grace Roman Space Telescope (Roman) and Vera C. Rubin Observatory (Rubin). Consequently, Landolt will enable the refinement of dark energy parameters, improve our ability to assess the habitability of terrestrial worlds, and advance fundamental constraints on stellar evolution.