Daily Image
26-05-2010
The orientation of the LBA dipoles is correct
| Submitter: | Wijnholds, Norden, Gerbers |
| Description: | The daily image of 20-4-2010 "Is the orientation of LBA dipoles correct?" showed that a difference in polarization is found between Dutch LOFAR stations and international LOFAR stations. The root cause of this difference is the size of a Dutch and an International station. An international station has 96 Low Band Antenna (LBA / 30-80MHz) and 96 High Band Antenna (HBA / 110-250MHz). Astronomical observations can be executed with all 96 antennas with 2 polarizations (X and Y). A Dutch LOFAR station has 2x48 LBAs and 48 HBAs. In this situation 48 antennas can be used. For the LBA we have 96 antennas available but only 96 receivers (RCU's). We need 2x96 receivers for both polarizations. One of our colleagues is very clever and made a proposal for different combinations of LBAs (spring 2008): 1. 48 LBA antennas with 2 polarizations in the outer ring 2. 48 LBA antennas with 2 polarizations in the inner ring 3. 24 LBA antenna with 2 polarizations in the outer ring and 24 LBA antenna with 2 polarizations in the inner ring 4. 96 LBA antennas with one polarization (only X dipoles) 5. 96 LBA antennas with one polarization (only Y dipoles) With this configuration we can use optimized configurations for different science cases. In 2008 a hardware installation and cabling plan was made for this configuration. We made approximately 300.000 connections between antennas and receivers. Each antenna has 2 polarizations (X and Y). Distinctly colored labels on cables and colored connectors helped us to install the cables according to design. Several people from three different companies are installing the cables. The verification of the stations showed a very small amount of polarization failures but these are all corrected. The daily image of 20-4-2010 ends with the conclusion: "It will be corrected in software". Indeed, the software still requires some changes to handle this feature, but the feature itself was designed into the system with a clear purpose. |
| Copyright: | ASTRON |
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