We evaluate the ability of Spider, a balloon-borne polarimeter, to detect a divergence-free polarization pattern (B-modes) in the cosmic microwave background (CMB). In the inflationary scenario, the amplitude of this signal is proportional to that of the primordial scalar perturbations through the tensor-to-scalar ratio r. We show that the expected level of systematic error in the Spider instrument is significantly below the amplitude of an interesting cosmological signal with r = 0.03. We present a scanning strategy that enables us to minimize uncertainty in the reconstruction of the Stokes parameters used to characterize the CMB, while accessing a relatively wide range of angular scales. Evaluating the amplitude of the polarized Galactic emission in the Spider field, we conclude that the polarized emission from interstellar dust is as bright or brighter than the cosmological signal at all Spider frequencies (90 GHz, 150 GHz, and 280 GHz), a situation similar to that found in the "Southern Hole." We show that two ∼ 20-day flights of the Spider instrument can constrain the amplitude of the B-mode signal to r < 0.03 (99% CL) even when foreground contamination is taken into account. In the absence of foregrounds, the same limit can be reached after one 20-day flight.

We present a new upper limit on cosmic microwave background (CMB) circular polarization from the 2015 flight of SPIDER, a balloon-borne telescope designed to search for B-mode linear polarization from cosmic inflation. Although the level of circular polarization in the CMB is predicted to be very small, experimental limits provide a valuable test of the underlying models. By exploiting the nonzero circular-to-linear polarization coupling of the half-wave plate polarization modulators, data from SPIDERʼs 2015 Antarctic flight provide a constraint on Stokes V at 95 and 150 GHz in the range ℓ 33 307 < <. No other limits exist over this full range of angular scales, and SPIDER improves on the previous limit by several orders of magnitude, providing 95% C.L. constraints on ℓ ℓ C 1 2 ℓ VV p + ( ) ( ) ranging from 141 to 255 μK 2 at 150 GHz for a thermal CMB spectrum. As linear CMB polarization experiments become increasingly sensitive, the techniques described in this paper can be applied to obtain even stronger constraints on circular polarization.

We describe Spider, a balloon-borne instrument to map the polarization of the millimeter-wave sky with degree angular resolution. Spider consists of six monochromatic refracting telescopes, each illuminating a focal plane of large-format antenna-coupled bolometer arrays. A total of 2,624 superconducting transition-edge sensors are distributed among three observing bands centered at 90, 150, and 280 GHz. A cold half-wave plate at the aperture of each telescope modulates the polarization of incoming light to control systematics. Spider's first flight will be a 20-30-day Antarctic balloon campaign in December 2011. This flight will map ∼8% of the sky to achieve unprecedented sensitivity to the polarization signature of the gravitational wave background predicted by inflationary cosmology. The Spider mission will also serve as a proving ground for these detector technologies in preparation for a future satellite mission.

SPIDER is a balloon-borne instrument designed to map the polarization of the millimeter-wave sky at large angular scales. SPIDER targets the B-mode signature of primordial gravitational waves in the cosmic microwave background (CMB), with a focus on mapping a large sky area with high fidelity at multiple frequencies. SPIDER's first longduration balloon (LDB) flight in January 2015 deployed a total of 2400 antenna-coupled Transition Edge Sensors (TESs) at 90 GHz and 150 GHz. In this work we review the design and in-flight performance of the SPIDER instrument, with a particular focus on the measured performance of the detectors and instrument in a space-like loading and radiation environment. SPIDER's second flight in December 2018 will incorporate payload upgrades and new receivers to map the sky at 285 GHz, providing valuable information for cleaning polarized dust emission from CMB maps.

We have developed antenna-coupled transition-edge sensor (TES) bolometers for a wide range of cosmic microwave background (CMB) polarimetry experiments, including BICEP2, Keck Array, and the balloon borne SPIDER. These detectors have reached maturity and this paper reports on their design principles, overall performance, and key challenges associated with design and production. Our detector arrays repeatedly produce spectral bands with 20%-30% bandwidth at 95, 150, or 220 GHz. The integrated antenna arrays synthesize symmetric co-aligned beams with controlled side-lobe levels. Cross-polarized response on boresight is typically ∼ 0.5%, consistent with cross-talk in our multiplexed readout system. End-to-end optical efficiencies in our cameras are routinely 35% or higher, with per detector sensitivities of NET∼300 µK CMB √ s. Thanks to the scalability of this design, we have deployed 2560 detectors as 1280 matched pairs in Keck Array with a combined instantaneous sensitivity of ∼ 9 µK CMB √ s, as measured directly from CMB maps in the 2013 season. Similar arrays have recently flown in the SPIDER instrument, and development of this technology is ongoing.