FLAMES FPOSS 'Avoid FLAMES/UVES fibre 37' Tutorial

This tutorial aims to provide users with the information they need in order to effectively avoid using the FLAMES/UVES fibre 37 for any of their important science targets. The tutorial assumes that users are already generally familiar with the use of FPOSS. If not, users should first read the FPOSS User Manual, where step-by-step instructions in the use of the software are given in addition to many other details.

Background

In mid-September 2012, fibre 37 of Plate 2 was damaged, and has been disabled since. Efforts to repair the fibre and restore plate 2 to full operational status are ongoing. This issue means that there will be no light in this fibre for any OB executed with Plate 2. Plate 1 is unaffected, but since there is no way to control which plate will be used for the execution of any given OB, there is a roughly 50-50 chance that plate 2 will be used. Therefore, in order to avoid the risk of no light for important objects, this fibre should not be allocated to scientifically important targets, or to sky, if this is the only fibre allocated to sky and sky subtraction will be important for the science.

The issue affects:

  • All FLAMES/UVES modes (6FIB/7+1FIB/8FIB) OBs executed with plate 2

The issue does not affect:

  • Medusa-only, IFU-only or ARGUS-only OBs.

During Period-90, Paranal Science Operations as been making an effort to avoid using Plate 2 for any OBs which use the FLAMES/UVES fibres, but this is done on a best-effort basis and execution of an such an OB with plate 2 will not be deemed cause for re-execution of the OB.

For Period-91 and onward, no special treatment in this sense will be given to OBs using FLAMES/UVES fibres.

Avoiding use of fibre 37

Overview

There is no direct way to avoid allocating a specific fibre (or fibres). Instead a workaround is required. The basic procedure is:
  1. Complete the usual initial, pre-allocation FPOSS steps, set the Magnitude filter (if necessary), Open input fileSelect guide star, select the required Fibre combination.
  2. Before starting an automatic allocation, manually allocate fibre 37 to a sky position
  3. Proceed with the usual allocation procedure using the Allocate fibres interface. Note that the already allocated fibre 37 will not count amongst the fibres allocated to sky positions, so if in the Allocate fibres interface there are, for example, 2 sky fibres speficied in the "Number of UVES fibres to asign to sky" field, another 2 fibres will be assigned to sky, giving a total of 3 fibres assigned to sky including fibre 37.
It is recommended to manually allocate fibre 37 to a sky position, this way if the OB(s) is(are) executed with plate 1 this fibre will provide an additional sky spectrum.
Note that in case sky subtraction will be important to your science, insure that you assign at least one other fibre to sky so that in the case of execution of your OBs with plate 2, you will still have at least one sky spectrum.
You may also need to define a 'special' sky position particularly suited for fibre 37 as the exisiting sky positions in your input file may not be accessible to fibre 37.

Step-by-Step

The following is s step-by-step guide following the above overview of the procedure. For the purposes of this we shall use the M67.fld input file that comes included in the FPOSS distribution tarball in the FPOSS/test subdirectory.
  1. Complete the usual initial, pre-allocation FPOSS steps:
    *) Open input file (here we use the M67.fld file from the FPOSS/test directory included in the distribution tarball)
    *) Select guide star (Guide Star U0975_06070301 is a within the new recommended guide star brightness limits)
    *) Select the required Fibre combination, for the purposes of demonstration we select Medusa + UVES (8 fibres)
    After completing these steps as described above the mimic display should then look something like the image below.

    Fibre 37 is, in this view and orientation, located in the upper right corner. Moving the mouse over the buttons will display the fibre IDs in the left end of the info bar across the top of the mimic window. In the selected Fibre combination mode, the UVES fibres are displayed as cyan buttons. If you have trouble locating fibre 37, it may be useful to switch temorarily to one of the UVES only fibre combination modes where just the UVES buttons (red) and FACB buttons (green) will be displayed. Once you have located fibre 37, you can then switch back to the desired/required Fibre combination mode.




  2. For clarity it is useful to zoom in around the area of interest, either click with the right-mouse-button on the sky position Sky_00028 (see above image), or else select that star by clicking on it with the left mouse button, then select the x2 menu item from the Zoom menu in the control panel window. The resulting mimic view will now be centered on Star_00028 and fibre 37 should just be visible in the top-right corner of the window (see image below).



  3. Now select the Sky_00028 position (small cyan circle) by clicking on it with the left-mouse-button and then fibre 37. Both should now be highlighted in dark blue (though it can be difficult to see that the sky position is highligted as it is so small) and listed in the information bar at the top of the mimic window (see image below).



  4. You can now allocate fibre 37 to sky position Sky_00028, either press the F3 key, or select the "Allocate Fibre (F3)" menu item from the Command menu of the control panel window, the allocated fibre will now be shown in the mimic window (see image below).



  5. Zoom back out to see the full field (select the "Normal" menu item from the Zoom menu of the control panel window)




  6. Now proceed with the normal procedure for allocation of the remainig fibres. Once completed the mimic window should resemble the one shown below.



Instrument selector