The E and B Experiment (EBEX) was an experiment that measured the cosmic microwave background radiation of a part of the sky during two sub-orbital (high-altitude) balloon flights and took large, high-fidelity images of the CMB polarization anisotropies using a telescope which flew at over 42,000 metres (138,000 ft) high.

[2][3] It circled around the South Pole using the polar vortex winds before landing on 24 January 2013 about 400 miles (640 km) from McMurdo.

Polarimetry is achieved with a continuously-rotating achromatic half-wave plate supported by a superconducting magnetic bearing and a fixed wire grid polarizer.

The wire grid is mounted at 45 degrees to the incoming light beam and transmits one polarization state while reflecting the other.

The EBEX telescope was reported missing in May 2012, while in transit from the University of Minnesota to the NASA Columbia Scientific Balloon Facility in Palestine, Texas.