[DAMD-73] PfsArm needs additional information to recover raw counts Created: 25/Dec/19  Updated: 05/Jan/21  Resolved: 10/Mar/20

Status: Done
Project: Data Model
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Story Priority: Normal
Reporter: hassan Assignee: price
Resolution: Done Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Relates
relates to DAMD-75 Correct flux units for pfsArm Done
relates to PIPE2D-492 Miscellaneous changes to the 2D DRP p... Done
Story Points: 3
Sprint: 2DDRP-2021 A
Reviewers: hassan

 Description   

The datamodel.txt information for the pfsArm object mentions that 'the pfsFiberTrace file contains enough information to recover the raw counts and the widths of the fiber traces'. However, this is not currently possible as the pfsArm object only contains a FLUX HDU (in units of nJy), but no additional calibration vector or equivalent to recover the raw counts.

It may not even be necessary to store the flux in nJy at this stage, as flux calibration is performed later in the pipeline.

Please add an additional HDU to this object such that raw counts can be derived. In addition consider whether the FLUX HDU really needs to carry absolute fluxes, or store 'flux' measurements relative to the illuminating quartz lamps.



 Comments   
Comment by price [ 25/Feb/20 ]

The fiber trace normalisation is that of the quartz lamp, and so pfsArm fluxes (extracted using the fiber trace) are relative to the quartz lamp (i.e., the fluxes are relative, not nJy). So I think the required condition ("the pfsFiberTrace file contains enough information to recover the raw counts and the widths of the fiber traces") is already met, without the need to add anything more.

hassan, could you verify that this is sufficient?

Comment by hassan [ 06/Mar/20 ]

Following discussions with rhl: following DAMD-73, the datamodel.txt will be updated such that the fluxes are relative, not nJy. We would then need a function that can recover the raw counts given a pfsArm object (eg for a science observation). Once that's done, this ticket can be closed.

Comment by price [ 10/Mar/20 ]

I've added a PfsFiberTrace.calculateCounts method.

Comment by price [ 10/Mar/20 ]

Merged to master.

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