(Suborbital Polarimeter for Inflation Dust and the Epoch of Reionization)
(2015 balloon-borne observatory to observe CMB polarization)
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 aperturemicrowave, 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.