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GRACES OT Details (2016A and after)

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This page explains how to configure the Gemini Remote Access to CFHT ESPaDOnS Spectrograph (GRACES) in the Observing Tool. There is only a small number of steps to follow, as they consist on a SINGLE sequence using GMOS-N combiing both Acquisition and Science sequences.

The GRACES "hack" 

The OT does NOT have a special instrument component for GRACES. Everything is made of GMOS components. This is a natural preference for the acquisition, done using GMOS, but it is also convenient for how to prepare the science sequence. One should keep in mind that it is a "hack" of the OT, so it tells the system to do what we want. Also, only the first few steps consisting of GMOS imaging are going to be actually observed using the OT. The other steps are either used to configure GMOS and GRACES, or used to display what are the required steps for the science spectra, observed on a different system that does not communicate with the OT. For examples, visit the GRACES library.

What to edit

The number of items to edit are kept to a minimum. It is important to edit the right ones and to avoid changing anything else. Once again, because we are using a "hack" of the OT, not everything means what it says... Therefore, if you have any specific needs that do not seem to be satisfied with the way the program has to be prepared, please contact your Contact Scientist. Here are the steps to prepare a typical program:

1. In the GMOS Static component, set the Exposure Time and the Position Angle for the Science frames.
2. Under Sequence -> GMOS-N: GRACES Acquisition -> Offset, go to GMOS-N: Set Exp. Time, Filter and Ctrl Wvl
3. In that component, set:
a. the "Exposure Time" for the GMOS Acquisition images*
b. the GMOS "Filter" used for the GMOS Acquisitions images*
c. the central wavelength ("Grating Ctrl Wvl") for the Science spectra
4. Under GMOS-N: GRACES Science -> Offset, go to the Observe component.
5. In that component, set the number of frames desired.
6. Please create a note entitled GRACES set-up, and write down the spectral mode, the readout mode and the central wavelength that you want to use (you can copy the template in the GRACES library). This way, the Gemini staff can double check that the program does what it is expected to.
7. Edit the target component (see below).

*: Please, go here to see what filter and exposure time to use.

Once everything is in order, you can click on the Sequence component to display the whole sequence. In the next figure, we display the sequence of 3 x 600sec spectra observed in 1-fiber mode with a Normal readout mode. Steps 1 to 3 are the GMOS acquisition images. The step 4 only used to configure the instrument. The steps 5 to 7 are the actual spectra, and they are observed from a system specific to GRACES. 

Target component

It is recommended to use the GMOS-N OIWFS for guiding. The peripheral sensors can be used for non-siderial targets. Make sure the guide star is reachable by the wavefront sensor.



To add nighttime ThAr spectra

ThAr calibration spectra are part of the baseline calibrations and are observed during the daytime. But if your program requires ThAr spectra to be observed close to the science, we can arrange ThAr spectra to be taken during the night. In this case, extra steps need to be added to the sequence. Please, find in the GRACES-library program 2 EXAMPLES showing how to do that. The examples cover the 2 spectroscopic modes. The following figure shows the example for the 2-fiber mode.

Ignore the following errors/warnings

Because of the GRACES hack, you will see several warnings in your program. The following warnings can be safely ignored:

  • A slit, mask, or IFU is defined, but no grating is selected
  • In IFU one slit mode it is recommended to use the red slit
  • Slow readout and high gain is not recommended
  • Exposure time exceeds recommended maximum for the GMOS instrument due to excessive contamination of the image due to cosmic rays

Note this last one refers to the GRACES science exposures which should be kept under 2400s if possible. The warning will show up for exposure times above 1200s which is the GMOS limit.

What shall never be edited  

Certain items should never be changed. This includes the Focal Plane, set to "IFU Left Side (blue)" in the GMOS static component, and anything under the component entitled GMOS-N: Set-up (DO NOT EDIT). Also, note that, for the Acquisition imaging, it is crucial to keep the binning to 1x1 and he Region Of Interest for reading the GMOS-N detector is set to Xmin = 2172, Ymin = 1570, Xrange = 1800, Yrange = 1100. Changing any of these may make your program impossible to schedule in the night plan or, worse, impossible to execute at all.

As part of the "hack", certain items are set in what may looks unusual at first look, but these set-ups are very useful to distingish the modes that were selected. These items, and their meaning are:

Where to find the item Item name Value What it means
GMOS static component Filter  DS920 spectroscopic mode = 1-fiber 
HeIIC spectroscopic mode = 2-fiber
GMOS static component   Read Mode Fast read/Low Gain  readout mode = Normal
Slow Read/High Gain  readout mode = Slow 
Sequence -> GMOS-N: GRACES Science Builtin ROI Custom ROI  readout mode = Normal
Full Frame Readout readout mode = Slow

How to open the GRACES library

There is a library in the OT showing how GRACES sequences are prepared in different situations. That library cannot be accessed using the "Libaries" icon in the OT top menu. To open the library you need to:

1. Go to the Open menu
2. Select the check box for Libs
3. Select and open the program "GN-GRACES-library", entitled: GRACE OT library.

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