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EMBRACE Demonstrates Stability

Submitter: The EMBRACE Team
Description: Being a "new kid on the block", aperture array systems still have to demonstrate their technological merit when it comes to astronomical observations. Even something seemingly simple like pointing/tracking requires proper verification when the beam is synthesized from many stationary elements.

To demonstrate EMBRACE's multi-hour stability and tracking cabilities, we observed the pulsar B0329+54 for 9 hours (from an elevation of 50 degrees, through transit, and then back down to 50 degrees elevation). The array was calibrated only once before the start of the observation, using GPS satellites to determine the phase calibration coefficients necessary to phase the array into a single beam on the sky.

As can be seen, the pulsar was visible throughout the 9-hr observation, though the signal strength varied on on timecales of typically 15-30 minutes. It is quite possible that this variation is simply due to scintillation of the source in the small, 12-MHz band we recorded. In order to confirm this, we are currently planning a second experiment using 48MHz of bandwidth. In any case, this 9-hr observation is a major step forward compared with previous attempts to track a source continuously over multiple hours.

The successful tracking of such a weak astronomical signal places high demands on the re-pointing precision of the beam and the dynamical behavior of the EMBRACE array at the WSRT. Such observations are part of a general push to demonstrate the usefulness of aperture array technologies for radio astronomy. Stay tuned for more EMBRACE news.
Copyright: ASTRON
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