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Demonstrating array bootstrapping using EMBRACE

Submitter: Dion Kant and Erik van der Wal
Description: It is known that an aperture array implementation as a radio telescope can lead to a large number of cables. During assembly of the array all cables need to be connected carefully to the right input channels of the array station back-end processing. However, within the EMBRACE project, we developed a method for which a correct administration of the cables, connecting tiles to the station back-end processing, is not required anymore. Obviously, this can save money during installation and commissioning of such systems.

A correct array configuration is generated from scratch without any required a-priori knowledge of the array cabling. The method involves a sequence of measurements with an uncalibrated array on known sources to generate a sufficient number of independent equations to solve for the tile positions.

The animated figure shows a demonstration of the method using GPS satellites as sources. The picture series starts with the lmn coordinate system local to EMBRACE in which all visible GPS satellites are marked. The background of the figure shows the tile beams being pointed in sequence onto three satellites with the highest (temporal) elevation. Note that only the phase information of the source signals is used to determine the relative tile positions and not the GPS data itself!

Next the phase information of the captured data is used to calculate the tile positions and the results are shown in the last diagram. Shown are dots at the tile positions and from the diagram the 4x4 and the 6x7 tile configurations including their orientation in the LMN coordinate system follow. Note that one tile is missing in the 6x7 array.

By using an integration time of 1 second per measurement, our current method utilises 6 measurements to obtain a position accuracy less than 15 cm. This is more than enough for our application however, accuracy can be increased by trading measurement speed.
Copyright: Copyright EMBRACE team (C) 2012
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