| As explained in an earlier AJDI, the Symbionos project investigates the possible symbiosis of LOFAR and GNSS observations, for mutual benefit in terms of the ionosphere. It is a joint project with the Dutch aerospace lab NLR, under ESA contract EGEP ID 89.08.
The picture shows (part of) the special test observations that were done recently. LOFAR was pointed towards a sequence of bright(ish) radio sources close to the the positions of two different GPS satellites, as they moved across the sky. The signals of the latter were recorded by an advanced dual-frequency GNSS receiver in the concentrator node of the LOFAR core.
Since the signals received by both instruments propagate through the same part of the ionosphere, they should be affected by (almost) the same Total Electron Content (TEC). So any differences between them tell us how well LOFAR and GNSS can complement each other in practice.
The LOFAR HBA fields have a diameter of about 5 degrees. They are centered on bright sources from the recently completed MSSS sky survey. Indicated are the brightness of the central source, and the total number of MSSS sources in that field (which will be used for calibration). In this early stage, we steer clear of the complications caused by the Milky Way (yellow) or very bright radio sources like Taurus A.
The Symbionos team was very pleased with the generous help of the LOFAR science support group, especially Luciano Cerrigone, in preparing and executing these rather unusual observations. We are also grateful to George Heald for mining the MSSS survey for suitable calibration sources and Local Sky Models.
|Madroon Community Consultants (MCC)