The Deep Space project is based on scientific collaboration between the Niels Bohr Institute, Copenhagen University and University California (Santa Barbara), USA under supervision of Prof. P.Naselsky and Prof.P.Lubin.

The UCSB extensive technology and deployment of instrument to Summit station (Greenland) is supported and coordinated by US National Science Foundation in conjunction with C2HM Hill Polar service.

The financial support is given by  Villum Fonden (Denmark) and partially, by Discovery Center of Excellence (Denmark).

Measurements of the B-mode of polarisation of the Cosmic Microwave Background (CMB) provide an excellent probe of the inflationary era of the early Universe. This type of polarisation is very sensitive to the appearance of the cosmological gravitational waves produced during inflation (CGW).

When CMB sky maps are absolutely clean of foregrounds, the B-mode vanishes, while existence of CGW can lead to nonzero B-polarisation signals. 

It has become clear recently that galactic foreground emission will be the fundamental limit to studies of CMB polarisation. After the Planck mission this issue is in the primary focus of modern observational cosmology, especially after the BICEP II experiment. The lack of information about synchrotron and dust emission from our Galaxy can easily be misinterpreted as a CGW signal. It is therefore necessary to investigate foregrounds at lower frequencies (below 20 GHz) as well in order to be confident in any measurement of the tensor modes.

The Deep Space project is based on scientific collaboration between the Niels Bohr Institute, Copenhagen University and University California (Santa Barbara), USA under supervision of Prof. P.Naselsky and Prof.P.Lubin. The financial support is given by Villum Fonden (Denmark) and partially, by Discovery Center of Excellence (Denmark). The UCSB extensive technology and deployment of instrument to Summit station (Greenland) is supported and coordinated by US National Science Foundation in conjunction with C2HM Hill Polar service.

The project is devoted to map the low frequency galactic polarisation emission at the Summit Station in Greenland at 10 GHz for 50\% of the sky at various elevation angles. This summer (2019) we have deployed the GreenPol telescope to Greenland to map the sky at 10 GHz using a 2.2 meter off-axis Gregorian telescope with a reflection half wave plate at its focus, with plans for higher frequency measurements in the future. The data of this measurement is now under investigation and the preliminary results will be presented within next two years .

In parallel with the Deep Space project we have investigated the Planck low frequency foregrounds and have developed new methods for testing the properties of E and B-modes. All these methods are part of the Deep Space data analysis pipeline. Namely, we have developed the so-called "vector decomposition" of the Stokes parameters  into E-and B-families of polarisation, and we have identified different zones of the sky that have strong excess of the E-mode over B-mode, and vice versa. Some of these zones lie in the Deep Space field of view, where the polarised signal mainly consists of the B-mode. In addition, working with partially covered sky data, it was necessary to improve the data analysis to minimise the leakage from E-mode to the B-mode. This Work has been completed.

In general, our activity in the B-mode domain will lead to better understanding of the polarised foregrounds joining low frequency data from the Deep Space and Planck experiments. It is already a step forward in CMB science devoted to detection of the cosmological gravitational waves from inflation.

Pavel Nasselski, Professor
Email: naselsky@nbi.ku.dk
Phone: +45 24 94 25 99