Spider (polarimeter)

Spider is a balloon-borne experiment designed to search for primordial gravitational waves imprinted on the cosmic microwave background (CMB). Measuring the strength of this signal puts limits on inflationary theory.

Spider

Altitude	36 km (118,000 ft)
Wavelength	3, 2, 1.1 mm (100, 150, 273 GHz)
First light	1 January 2015
Telescope style	balloon-borne telescope cosmic microwave background experiment radio telescope
Number of telescopes	6
Mass	3.5 t (3,500 kg)
Website	spider.princeton.edu

The Spider instrument consists of six degree-resolution telescopes cooled to liquid Helium temperature (4 K) which observe at frequencies of 100 GHz, 150 GHz, and 280 GHz (corresponding to wavelengths of 3 mm, 2 mm, and 1.1 mm). Each telescope is coupled to a polarisation-sensitive transition-edge bolometer array cooled to 300 mK.

The first balloon flight of the experiment launched in January 2015 from McMurdo Station, Antarctica, with support from NASA's Columbia Scientific Balloon Facility. This Long Duration Balloon flight lasted for about 17 days, mapping about 10% of the full sky. Further flights planned for successive seasons enable upgrades and changes to the modular telescope, and ever-improving frequency coverage and depth.

The primary science goals include:

1. characterization of the curl-free component of the CMB polarization on the largest scales
2. searching for the signature of inflationary gravitational waves in the CMB polarization
3. characterization of the polarization properties of the emission from our own Milky Way Galaxy