the branch is implemented, I've added this parameter in fps.yaml in pfs_instdata

notConvergedDistanceThreshold: 0.1 # in mm

Now cobras which match those conditions will be set with fiberStatus.NOTCONVERGED

• no match with mcs
• matched but distance to target > notConvergedDistanceThreshold

I've set the distance to 100 microns, but I don't know if it's quite right yuki.moritani ,cloomis ,rhl, chyan opinions ?

Thank you for modifying the flags.

given tolerance is one of the options for convergence sequence, there may be a case to set tolerance to 0.1 (mm).. (maybe mainly test purpose thought.) I wonder if we could set threshold as factor xx of tolerance.. What do you think?

Yes, I agree, that could be an option too, we could set that factor to between 5  and 10 I guess.

now applying with notConvergedDistanceThreshold=0.05 # 50 microns

And just in case the tolerance is large :
notConvergedDistanceThreshold = max(notConvergedDistanceThreshold, 5*tolerance)

Hi Arnaud I did some analysis on the low/no FLUXSTD stars observed in run 18 visits and we think that a notConvergedDistanceThreshold of 25um may be a bit more realistic based on the observed data.

Please see the following ticket for some plots and suggestions:

https://pfspipe.ipmu.jp/jira/browse/PIPE2D-1578#

Sadman Ali thank you for analysis. As discussed at the 2D DRP telecon, it should be taken into account that your analysis contains uncertainty of pfsNominal position unless you use measured offset by raster scan data. (the raster scan performance shows that 95% of Cobras have configuration error of 20-30um in most of case, I guess you are seeing this) Also, seeing that this flag is based on cobra convergence sequence itself, I'm not sure if it should be flagged flux loss. (If yes, I think we can set the threshold by modeling flux loss.)

yuki.moritani Thank you for the information. I slightly updated my ticket with information on how the pfs offsets were calculated, just for clarification. They are calculated using the pfssingle.observations nominal/center positions. I wasn't aware of the 20-30um configuration error, which as you said may explain some of the observed behavior. I will check with Tanaka-san further about this.

My understanding from the technical telecon a while ago is that the distance used to set NOTCONVERGED is the distance between pfiNominal and pfiCenter. Maybe I misunderstood because I am not sure what Moritani-san meant by "this flag is based on cobra converged sequence itself".

I'm sorry for confusion. It s right that NOTCONVERGED is set based on distance between pfiNominal and pfiCenter, which is calculated cobra convergence sequence. And this flag is use to mark fibers with unexpectedly large offset. (Convergence itself has threshold, for which 5um is used now, and Cobra stops when its distance to pfiNominal gets below it.) What I mean is that you should be careful that convergence assumes pfiNominal has negligible error, but in reality, pfiNominal still has uncertainty. That's why raster scan data shows larger error than convergence error. So, if you see flux loss distance is larger than xx um, I'm not sure this means cobra is not converged.

Thank you, Moritani-san! I think the uncertainty in pfiNominal explains why (at least in part) Sadman's plot does not look quite similar to Arnauds's one. (1) Sadman's plot shows a sequence of objects at flux loss ~ 0 with ~ 0.2mag scatter. Most of these objects are located at offset < 30um. So, their offsets are dominated by the uncertainty in pfiNominal, and we see little correlation between the offset and flux loss. (2) At larger offsets, we start to see objects with a significant flux loss. I think this is the regime where the real offset becomes dominant over the uncertainty. Because we use the distance between pfiNominal and pfiCenter to set the UNCONVERGED flag, perhaps it makes sense to define the distance threshold based on the observed data (i.e., Sadman's plot)?

Thank you, Tanaka-san, for explanations. I see... it makes sense to determine by using observed data for larger offset. But I'm confused why you selected 25um  (<30um) was selected? And probably we should analyze all available data not limiting to one FoV or something... (And you should work under a new ticket, as this is already closed.)