SPIDER

SPIDER (SPIDER is the official name, but previously was considered an acronym for Suborbital Polarimeter for Inflation Dust and the Epoch Of Reionization) is a balloon-borne observatory with six 26-cm aperture microwave, cryogenically-cooled refracting telescopes, each dedicated to a polarimeter with TES sensors. It is part of the effort to find large-scale patterns (primordial B-modes) in CMB polarization. SPIDER flew its initial mission over Antarctica in January 2015, successfully yielding data, though damaged on landing, not unusual for such balloon-based missions (but still far less expensive than equivalent space-based observatories). A second Antarctica flight took place December 2022 to January 2023, covering more frequencies.