Calibrating the Universe with a CANDLE

To obtain the precision necessary to meaningfully test dark energy models, or predict the habitability of exoplanets, modern astrophysical experiments have stringent requirements on the control of systematic uncertainties.  Dark energy probes that rely on optical and near infrared surveys of Type Ia supernovae (SNe Ia) require calibrations that support accurate measurements of SNe Ia absolute relative calibration (color calibration) with uncertainties < 0.4%.  Similarly, the characterization of exoplanet environments need absolute flux calibration of their host stars with uncertainties up to 10 times smaller than achieved to date, i.e. < 0.5%.

A solution to calibration that supports ASTRO2020 science objectives is CANDLE (Calibration using an Artificial star with NIST-traceable Distribution of Luminous Energy), a light source that behaves as an artificial star and is accessible to space-based observatories like JWST, Roman Space Telescope, future IR/VIS/UV telescopes or ground- based systems like Rubin Observatory, and next generation extremely large telescopes.  This points to a calibration payload that could piggy-back on a star shade or be deployed as an independent payload in a suitable orbit for space-based observatories or placed in an Earth-orbiting satellite and be accessible to ground-based telescopes.

I will describe the design of a precision SI-traceable, artificial star engineering demonstration unit: CANDLE, that provides calibrated light between 0.3 µm and 2.5 µm.  CANDLE consists of 3 complementary modes: single mode fiber lasers, a solar reflector and a programmable spectrum mode.  CANDLE is designed to fit in a volume of  approximately 24 U (1U=1000 cc).

I will also discuss a mission concept that deploys a CANDLE to enable cross-checks and mitigate systematic effects.  By calibrating the output beam profiles, rigorously demonstrating the uncertainty budget, and establishing performance parameters for different orbits, we aim to establish the path toward a flight-ready payload, that both supports the ASTRO2020 key science and ensures that the vast data archives from NASA’s astrophysics missions can maximize science well into the future.