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OT Details

A set of basic calibrations for your observations will be acquired by the Gemini staff for all queue-scheduled data (see the calibration section of the relevant instrument pages for details). These and any additional calibrations must be defined by the PI in the OT. This page shows how to configure GCAL calibration observations in the OT.

Of the eight observe elements that take data, seven are associated with calibrations (the eight takes regular exposures of the sky). Each observe command generates one dataset. A dataset is one file and may contain multiple frames within the multi-extension FITS structure depending on the specific instrument (e.g. the number of coadds, if supported and not coadded within the instrument, whether it has multiple detectors etc.). Each observe is shown separately in the sequence list and timeline. The seven calibration observes are:

 

  • Flat - takes flat-field lamp calibration exposures with GCAL using the current instrument configuration. The GCAL and instrument detector settings (exposure time, number of coadd, and number of observers) are set automatically from lookup tables. The observation classes are set to either Nighttime Partner Calibration or Nighttime Program Calibration depending on whether flats are considered night baseline calibrations for that instrument.
  • Arc - takes arc lamp calibration exposures with GCAL using the current instrument configuration. The GCAL and instrument detector settings (exposure time, number of coadd, and number of observers) are set automatically from lookup tables. The observation classes are set to either Nighttime Partner Calibration or Nighttime Program Calibration depending on whether flats are considered night baseline calibrations for that instrument.
  • Night Baseline GCAL - takes flat and/or arc exposures with GCAL depending on what is defined as nighttime basline calibration for the instrument.  The GCAL and instrument detector settings (exposure time, number of coadd, and number of observers) are set automatically. The observation class is set to Nighttime Partner Calibration.
  • Day Baseline GCAL - takes flat and/or arc exposures with GCAL depending on what is defined as daytime basline calibration for the instrument.  The GCAL and instrument detector settings (exposure time, number of coadd, and number of observers) are set automatically. The observation class is set to Daytime Calibration.
  • Manual Bias - takes a very short exposure dark (usually only relevant for destructive-read stare exposures with IR detectors). The parameters available in the detailed element editor are the number of coadds per observe and the number of observe commands issued for each observe element. (At present the bias exposure time defaults to a nominal value of 1 sec for display in the sequence).
  • Manual Dark - takes dark data (shutter closed and/or detector blanked off) with the exposure time, coadds and observes specified in its detailed element editor. (The default is 1 observe containing 1 exposure of 10s).
  • Manual Flat / Arc - takes flat-field or arc lamp data using the current instrument configuration illuminated by GCAL. All settings must be made manually. See below for more details about the flat/arc detailed editor.

Note, for MOS observations you must set the MOS Slit Width in the GMOS static component to match the slit widths of the MOS mask before the automatic, or "smart", calibaration nodes can find the calibration settings.

An observation may contain multiple calibration (or for that matter, science) observes. For example, if the highest precision of wavelength calibration is required (or, there is significant instrument flexure as a function of telescope elevation) you might choose to take arc frames and flat-field data immediately before or after the science data. The sequence below shows an observation in which arc frames are taken before and after the telescope offset sequence collects science data:

calibration sequence example

You can of course specify the calibration data in a completely separate observation and include both it and the science observation in a group.

The four automatic or "smart" GCAL components all behave similarly. All will show the calibration settings for the observation steps that they've created in a short version of the sequence table. Be default the table only includes the steps created by that component. If the component is in an instrumnet iterator, then there wil be a line corresponding to each step in the iterator.

By clicking the box labeled "Show full execution sequence", then the entire sequence is shown. This view is similar to the sequence summary table in the Sequence node, but the the steps created by the GCAL component are in normal fonts while the other steps are shown in a grey font. This allows you to see the calibration steps in the context of the entire sequence.

The tables that the OT uses for displaying the GCAL observation settings are maintained by Gemini instrument scientists. If the OT has an  internet conection then once a day it will automatically check for new versions of the tables and update them. The versions and modification times of the tables installed can be viewed by selecting "Smart Calibrations Info..." from the Help menu.

Clicking the Check for Updates Now button will cause the OT to check for new tables and download them if any are found. The displayed settings in the autmomatic calibration nodes will update immediately as the calibration tables change. However, the settings for observed steps will show the values used for the observation and will not change as the calibration tables are updated.

If the GCAL settings are not defined for an instrument configuration then a "smart" calibration component will give an error as shown below.

If you are working on a MOS observation, first make sure that the MOS slit width is defined in the GMOS component. If no calibrations are defined you may either remove the "smart" component and add the Manual Flat/Arc component or do the same thing by clicking the button labeled Configure Manually. Then refer to the OT libraries or the instrument web pages for advice on the calibration settings.

The Configure Manually button is also useful for overriding the default settings. If automatic settings are defined as in the sequence below

then Configure Manually will create separate Manual Flat/Arc nodes for each configuration in the "smart" component. For example, the sequence above becomes

 

Warning: if the automatic component is in an instrument iterator then Configure Manually creates Manual Flat/Arc components with settings for the first step in the iterator. Therefore, care must be taken when editing ongoing sequences with instrument iterators.

Finally he components also include a Class menu where the default observation classes can be manually overridden. 

The manual editor for taking flat/arc data is accessed by selecting the Manual Flat/Arc observe element in your science program:

gcal component

This editor is used to define the GCAL configuration:

  • lamp (choice of flat-field and arc lamps)
  • neutral density and colour-balance filters
  • optical or IR diffuser

The exposure time, coadds (if supported by the instrument) number of observe commands must also be specified, along with the appropriate observation class.

The Save button accepts the latest changes and stores the program to the local database, and the Close button closes the science program editor (saving any changes to the local database).