theme description

Signal processing for radio telescope arrays

Contact: Alle-Jan van der Veen

Future radio telescopes will have many thousands of receiving elements. Already LOFAR has around 50,000 antennas. How can such systems be calibrated? What is needed to make an accurate image?
The trend in radio astronomy is to construct large arrays of small antennas. An example is the LOFAR system, where 50,000 antennas are distributed over 50 stations in The Netherlands and neighboring countries. In the future, we will have SKA (square kilometer array, consisting of 1 million antennas) and OLFAR, a distributed radio telescope in space. Central issues for us are array calibration, interference cancellation, and image formation using array processing techniques.

Array calibration should correct for electronic gains and phases, but also for the turbulent ionosphere. It consists of several stages: station calibration (after which we can form accurate beams on the sky), and central calibration (that should correct for small changes in the station beamshapes, as well as ionospheric calibration). Calibration is tightly coupled to image formation: at high-level, the image is supposed to consist of point sources, and calibration parameters are adjusted to get these in focus. However, stations see a large portion of the sky, including the galactic plane, which doesn't show up as a point source and should be suppressed. We use extensions of factor analysis for this.

Our aim in this theme is to provide a firm array signal processing foundation that will enable these new instruments to reach their potential.

Projects under this theme

PIPP OLFAR: Breakthrough technologies for Interferometry in Space

Combine multiple satellites into one single scientific instrument: a radio telescope in space

History

Data reduction and image formation for future radio telescopes

The future SKA telescope will produce large amounts of correlation data that cannot be stored and needs to be processed quasi real-time. Image formation is the main bottleneck--can compressive sampling and advanced algebraic techniques help?

Radio astronomical calibration and imaging techniques

New, larger and more complex radio telescopes bring new challenges. Foremost among these is the calibration of the data in order to remove atmospheric and instrumental effects which corrupt the exceedingly faint signals from cosmic sources.

Low-frequency distributed radio telescope in space

Below 15 MHz, the ionosphere blocks EM signals from the sky. Therefore, can we design a radio telescope in space, using a swarm of inexpensive nano-satellites? Accurate localization and clock recovery is important.