Daily Image

31-08-2010
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Hartebeesthoek's successful return to EVN observations

Submitter: Bob Campbell
Description: The 26-meter antenna at the Hartebeesthoek Radio Astronomy Observatory in South Africa is the only EVN-member antenna in the southern hemisphere. HartRAO is also a fundamental geodesy station, having GPS and satellite laser ranging in addition to the VLBI antenna (from bottom to top in the picture, taken from the HartRAO image gallery).

On 3 October 2008, the 26m antenna suffered a casualty in the bearing in its polar drive shaft (the tube at ~26 degrees from horizontal just above the smaller tree in the picture). The polar shaft supports the ~200 ton moving structure, so repair of the bearing was a major engineering undertaking. A series of photographs documenting the repair work (installation of the A-frame support, pictures of worn roller-bearings and bearing race fragments, etc.) is also available.

The 26m antenna was repaired by August 2010, and participated in its first post-repair EVN observations on 26 Aug, using e-VLBI. The inset plot shows amplitude vs. frequency on baselines from the array {Medicina, Onsala, Torun, Hart} in a 1024 Mbps observing set-up at L-band. There are good fringes to Hart over a total data rate of 896 Mbps, using the same channel-dropping mode employed regularly for other EVN stations with a net 1 Gbps link (e.g., Mc). The 896 Mbps correspond to the lower 7 dual-pol, 2-bit sampled, 16MHz subbands. The observations on 26 Aug were the first fringes we've had from Hart since their polar-shaft bearing casualty, and the highest-rate real-time e-VLBI fringes we've ever had from them -- excellent news on both fronts. Inclusion of Hartebeesthoek in 1024 Mbps observations should significantly improve the performance of the e-EVN for low-declination sources.
Copyright: HartRAO, JIVE, EVN
 
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