Some checks and adjustments must be made following a typical HET engineering run. In particular, any work that involved removal of the IHMP (input head mounting plate) or a full FPA (focal plane assembly) take-down will require a series of checks before observations on sky can be resumed.

There is an appendix that covers past engineering runs and other archival notes.

The shuffle code is used to set up an observation with the HET. It is used to create a command sequence and acm finding chart that allows the observers to locate a sky target onto a particular detector (i.e. LRS2-B or VIRUS IFUSLOT 094, etc...). The shuffle code uses two fundamental input files: fplane.txt and shuffle.cfg. The first file specifies locations of IFUs and other fiber bundles (BIB, HPFacq) on the IHMP. The fplane.txt file will not be changed here, but a number of parameters in shuffle.cfg will almost certainly require adjustment after an engineering run beofre reliable observing can proceed.

There are two important shuffle files that determine how shuffle (and hebce target_setup) will operate. To see these files (on mcs) we can do the following:

  
[astronomer@mcs ~]$ target_setup 10 E -log  

  
 shuffle.cfg:  
/opt/het/hetdex/lib/python2.7/site-packages/hetdex_shuffle/configs/shuffle.cfg

fplane.txt: 
/opt/het/hetdex/etc/Virus/vhc_config/fplane/fplane.txt

  
 shuffle.cfg: 
# ACAM coordinates for clarity and use in defining candidate stars that fall within the acam
acam_x_origin = 182.10
acam_y_origin = 397.56
acam_pix_scale = 0.2709
# section with the angle offsets in degrees for the various parts of the focal
# plane assembly. The offset should be 0 degree for all of them. The overall 90
# degrees rotation is already accounted for in the code
acam = 1.05
fplane = 1.43

fplane.txt: 
# IFUSLOT X_FP   Y_FP   SPECID SPECSLOT IFUID IFUROT  PLATESC
056  -50.000    -150.000    998 998 998 0.000   1.000
066   50.000    -150.000    999 999 999 0.000   1.000
555    0.700     -73.130    901 901 901 0.000   1.000
600  -39.990       9.970    902 902 902 0.000   1.000

You can see a visualization of the HET focal plane with fgstar. This routine is like shuffle, except the field is viewed with ds9 and the user can zoom into areas of interest. If you are on mcs, just try:

 

% fgstar 06:15:20.46 +39:51:50.6 304.0 gc1 N  

The figure below shows a view from this run where we have zoomed into the acm portion of the field. It shows 4 of our 5 points of interst. First, it shows a RED CIRCLE where the IHMP center is located. The X,Y used for this are the shuffle parameters acam_x_origin and acam_y_origin.

We have zoomed into the central portion of a view from fgstar. The yellow square is the outline of the acm (ACquisition caMera) and the small yellow circle indicates the corner of the acm with pixel X,Y coordinates 1,1. The thicker yellow line indicates the Y=0 X axis of the acm image. The thick red circle indicates the center of the IHMP. This position is also sometimes referrred to as the "boresite". The LRS-R (066) and LRS2-B (056) IFU outlines are drawn in. The position of of the BIB camera is shown by the string "BIB". The actual field of the BIB is much smaller than this label, but the BIB position is centered on the "I" character in this text string. Note that fgstar pre-dated the HPF and hence no HPF markeres are indicated.

We'll derive estimates for these parameters using the observed acm positions of 4 positions, three of which are marked in the fgstar image: LRS2-B (056), LRS2-R (066), and the BIB (555 in the fplane.txt file). After a lot of this work was done, we began to also use the position sof the HPFacq camera (600 in the fplane.txt file). There are two other numbers we need to make an fgstar picture: the pixel scale of the acm in arcesconds per pixel (this is the shuffle parameter named "acam_pix_scale") and a correction for the field rotation present because the HET is an alt-az telescope (this is related to the shuffle parameter named "acam"). The value of acam_pix_scale is 0.2709 -+ 0.0001 arcsec/pixel. This value has been very stable for about five years and we'll not solve for this again here. The rotation parameters (really an angle offset value) given by the shuffle "acam" parameter will be derived using the WCS (world coordinate system) derived for acm images of various fields on the sky. The astute reader will notice that there is a shuffle parameter named "fplane". Its purpose is unknown and the shuffle authors (?) should be consulted.

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Determine acam_x_origin and acam_y_origin.

I use two methods to derive the values of (acam_x_origin,acam_y_origin). The two methods, implemeneted in the routines find_ihmp_on_acm and acm_xy_graphical are discussed generally HERE. Below I show an example of the input file for this routine, a combination of measured acam positions and values from the fplane.txt file.

% cat Data.ALL
# IHMP-acm positions after Sep2018 FPA take-down
# name     X,Y_ihmp         X,Y_acm      X,Y_acm _prev
# data
555       0.7  -73.1     455.0  398.7    455.0  398.7
600     -39.9   9.97     148.7  250.3    148.7  250.3
056     -50.0 -150.0     738.6  211.6    738.6  211.6
066      50.0 -150.0     739.7  577.3    739.7  577.3

Notice that the last two sets of coordinates are the same. These are the acm positions we observe (using lmap and ds9) after the FPA take-down work has been finished and we are back on sky. I used to tabulate the new values (columns 4,5 above) and the old values (columns 6,7 above) from the RA wiki. The routine used to make a comparison between the old and new values. I have since removed that feature to make the output simpler.

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Determine angle offset parameter (acam).

The shuffle parameter "acam" is best determined by using multiple acm images that have good-quality WCS determinations installed int the header. The routine tzgather is typically used for this.

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