WALOPNorth

PASIPHAE (the Polar-Areas Stellar Imaging in Polarization High-Accuracy Experiment) is an optopolarimetric survey aiming to measure the linear polarization from millions of stars, and use these to create a three-dimensional tomographic map of the magnetic field threading dust clouds within the Milky Way.

This map will provide invaluable information for future CMB B-mode experiments searching for inflationary gravitational waves, providing unique information regarding line-of-sight integration effects. Optical polarization observations of many stars at known distances, tracing the same dust that emits polarized microwaves, can map the magnetic field between them.

The Gaia mission is measuring distances to a billion stars, providing an opportunity to produce a tomographic map of Galactic magnetic field directions, using optical polarization of starlight. Such a map will not only boost CMB polarization foreground removal, but it will also have a profound impact in a wide range of astrophysical research, including interstellar medium physics, high-energy astrophysics, and evolution of the Galaxy.

To accomplish this, 2 Wide-Area Linear Optical Polarimeters (WALOPs) were constructed at IUCAA, India and installed in the SAAO’s 1m telescope (Southern hemisphere) and Skinakas’1.3m telescope (Northern hemisphere). They will conduct a survey of both northern and southern Galactic polar regions targeted by CMB experiments, covering over 10000 square degrees, which will measure linear optical polarization of over 360 stars per square degree (over 3.5 million stars, a 1000-fold increase over the state of the art).

My job was to design the instrument for the Skinakas Observatory (WALOPNorth). This is how it will look like, when construction is complete.