SCUBA-2 with a fully populated focal plane

Map of the 8 arrays in the SCUBA-2 focal plane. The data is of the responsivity of the arrays following a flatfield observation.

For several months now we have been operating SCUBA-2 with 7 of the 8 arrays – 4 at 850µm and 3 at 450µm. This is because the performance of one of the 450µm arrays, referred to as s4b, was much worse than all of the others. In troubleshooting, it was discovered that a short circuit was present on the array. During the last warm up, this short was removed by identifying the pixel responsible and then switching off the column and row it resides on. Since then we have worked  at optimising the s4b array and bringing it back into the fold. As it turns out, the s4b array is one of the better performing arrays (and there are plans to improve it further by recovering some of the lost row and columns you can see in the image above).

This is a really important milestone for the project, not least because it was never a certainty that there would be 8 working arrays, and to emerge with 8 out of 8 is fantastic. Well done to everybody involved.

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