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PIIC processing of run 74 beam maps (taken on 2025/07/13)

Three beam maps were taken on 2025/07/13, i.e. scans

On 2025/07/17 SB processed the three beam maps using PIIC. Below here I copy the usual FOV plots, that show the quality of the beam maps. They are self-explanatory (cfr also the previous re-commissioning runs for more information). It is worth to point out few features, though:

• also in this re-commissioning session, the Ar3 beam maps are bad. My feeling is that the main culprit is the focus offset of Ar3 with respect to Ar1 and Ar2.
• there is a focus difference of ~0.3 mm between Ar2 and Ar1, a difference of ~0.3 mm between Ar1 and Ar3, and therefore a difference of ~0.6 mm between Ar2 and Ar3. These values are preliminary and come from the quick focus analysis carried out during the observing session. Note that during the first re-commissioning (run 72), Ar1 and Ar3 seemd to have a similar focus offset, but things changed after re-opnening. The idea is that this is not a real hardware change, but rather due to the fact that in run 72 the Box C was missing. In my opinion this is not so obvious, though.
• the consequences of these focus offsets between the three arrays are that: focusing on Ar2, Ar3 is completely out of focus and not usable; fcusing on Ar1, Ar3 is still out of focus (but less dramatically) and only marginally usable.

• there have been issues with focusing at 1.2 mm during the observing session, because the Ar1 and Ar3 preliminary DAFs (run 72) are offset wrt the Ar2 DAFs (run 68). The solution would have been to use a combination of pointing offsets when focusing (see suggestions for the next re-commissioning run). The consequence of a sub-optimal Ar3 focus is that the Ar3 beam map is sub-optimal.

• All three beam maps are ok for Ar2, because the beam of Ar2 is much larger than for Ar1,3 and therefore the beams maps of Ar2 are usable even under sub-optimal focus conditions.

Quality of the beam maps:

Decision about DAFs:

• given that having the Ar1 and Ar3 DAFs with an offset wrt Ar2 has created confusion during the observations in both runs 73 and 74,
• I am going to try to produce DAFs out of these run 74 beam maps also for Ar1 and Ar3, although they are sub-optimal
• consequently, at the telescope there will be two sets of DAFs that can be used (chosen) by the AoD:
  • the default will be a set of DAFs RPPs with all three arrays referring to the central KID (as it should be), produced in run 68 for Ar2 and in run 74 for Ar1 and Ar3. Note that Ar3 will be missing a non-negligibe number of KIDs and note that both Ar1 and Ar3 DAFs RPPs are sub-optimal
  • a special verson of DAFs RPPs, already used during run 73 and 74, with Ar2 using the central KID as reference (as it should be), but Ar1 and Ar3 having an offset. In this case the Ar2 RPPs were produced in run 68 and the Ar1 and Ar3 RPPs come from run 72.
• using one or the other version will have slightly different behaviours of the PIIC QL: in the first case it should be possible to study the focus of all three arrays at once (unless the focus range does not cover the optimal focus of all three at the same time; in the second case, an extra pointing offset and focus sequence must be used to determine the focus of either Ar2 or Ar1,3, because the offset between the RPPs of Ar2 and Ar1,3 is larger than ~30 arcsec (see email exchange of the past days 2025/07/15-16).

• once everything is installed at Pico, I will update the page with the suggsestions for the next re-commisisoning run, so to include instructions for both possible DAFs RPPs choices.

• I stress again that this should not be necessary, given the experience of the observing team.

Wishes for the next re-commissioning:

• please, next time produce good beam maps, in order to be able to produce the "final" DAFs RPPs for the new Ar1 and Ar3.
• I keep reducing and analysis these beam maps, but they are always bad, not only because the sky conditions were not favorable, but also because the observing strategy was sub-optimal. It starts to be too much a waste of time (both telescope and mine). I would like to avoid to go on much longer on this. Thank you.

Figures of the beam maps FOV, as usual: