Daily Image
25-09-2009
Sensitivity of APERTIF front-end prototype makes sense!
| Submitter: | APERTIF team |
| Description: | Last week, a new prototype of the APERTIF front-end (AJDI 13-09-2009) was installed in one of the WSRT dishes. The new front-end reduces the antenna losses, and features an improved LNA to further reduce the system temperature. The antenna array is also much more stable (electrically and mechanically) than the previous design. The sensitivity of the on-axis FPA beam has been determined from an interferometer measurement on 3C147. In this measurement 52 FPA elements are recorded along with RT3 and RT4 (both MFFE-equipped dishes). The FPA elements are combined using weights that optimize the sensitivity. From the correlation coefficient between RT3 and RT4 and the flux density of the source, the sensitivity of the MFFE is determined. The MFFE sensitivity has been used to solve the FPA compound beam sensitivity from the RT4-FPA correlation coefficient. The above plots show the measured system temperature, assuming an efficiency of 75%, and the System Equivalent Flux Density (SEFD) of the MFFE and the focal plane array (the blib at 1420 MHz is due to absorption by Galactic neutral hydrogen). A system temperature of 70 K is demonstrated, which is even better than our target for this prototype (75 K) and almost equal to our prediction (68 K) ! This is a very important step toward the final APERTIF performance. |
| Copyright: | ASTRON, 2009. |
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