The Japan-United States Infrared Interferometry Experiment (JUStIInE): balloon-borne pathfinder for a space-based far-IR interferometer

The balloon-borne Japan-United States Infrared Interferometry Experiment (JUStIInE) is a pathfinder for the first space-based far-IR interferometer. JUStIInE will mature the system-level technology readiness of spatio-spectral far-IR interferometry and demonstrate this technique with scientific observations. Operating at wavelengths from 30 to 90 mu m, JUStIInE will provide unprecedented sub-arcsecond angular resolution and spectroscopic data. Our plan is to develop a cryogenic Michelson beam combiner and integrate it with an existing and tested telescope optical system and gondola from the Japanese Far-infrared Interferometric Telescope Experiment (FITE). With two JUStIInE balloon flights we plan to collect, calibrate, analyze, and publish scientific results based on the first far-IR spatio-spectral observations of young stellar objects, evolved stars, and the active galactic nucleus of NGC 1068. The NASA Astrophysics Roadmap envisages a future in which interferometry is applied across the electromagnetic spectrum, starting in the far-infrared. The Far-IR Probe recommended in the 2021 Decadal Survey presents an opportunity to take that important step. A Far-IR Probe mission based on this concept will enable us to understand terrestrial planet formation and spectroscopically study individual distant galaxies to understand the astrophysical processes that govern their evolution.