BEGINS: The Balloon Experiment For Galactic INfrared Science

BEGINS is a proposed long-duration, suborbital balloon payload designed to measure dust properties and environments in the vicinities of massive stars. BEGINS will make spectral energy distribution (SED) maps of various environments in the Vela molecular cloud and other sources to probe the environments and to test dust models. It will do this with two pioneering advances: spectrophotometric imaging in the understudied mid- and far-infrared regime and high sensitivity using a cryogenically cooled telescope coupled to a focal plane array of kinetic inductance detectors. Several square degrees will be mapped from 25 to 400 microns with spectral resolving power R = 10 from 25 to 64 microns and R = 3.5 from 64 to 400 microns. Dust absorbs most light from newly formed stars and reprocesses it into infrared emission, making the infrared a crucial waveband for characterizing the environments of star formation. The emergent infrared spectrum is expected to depend upon the radiation field temperature, proximity to the sources of radiation, and size and composition of the dust grains. With new capabilities in SED mapping, particularly from 30 to 50 microns, BEGINS will resolve how the spectral energy distribution of dust serves both as a diagnostic of star-formation environment and a diagnostic of interstellar dust evolution. BEGINS’ payload is comprised of a gondola responsible for structure, power, pointing, and telemetry, a 0.5 meter all-aluminum Cassegrain telescope and support structure, an instrument with a 200 mK focal plane array of kinetic inductance detectors and the associated readout electronics. It will have stored cryogens to cool the telescope from ambient to liquid helium temperature for an experiment to improve sensitivity an order of magnitude by eliminating thermal emission from the telescope. The science instrument is extremely simple and compact, coupling kinetic inductance detectors to continuously linear-variable filters in the focal plane. BEGINS builds on heritage of previous balloon payloads for the gondola, detector readout electronics, and cryogenics. If successful, the cooled telescope will enable unprecedented sensitivity for suborbital infrared observations.