Calibration Plan

Standard Calibrations

The most commonly used observing configurations of each instrument are calibrated by means of the Observatory's Calibration Plan. Calibration Plans for each instrument and mode are described in detail in their corresponding User Manual, and their execution times are not charged to the Service Mode programmes.

Additional Calibrations

Please check carefully in the User Manual whether or not the instrument configurations that you plan to use are included in the instrument's Calibration Plan. If this is not the case, you must provide additional OBs for calibration appropriate for each mode not included in the Calibration Plan. Their execution time is then charged to your time allocation.

User-supplied OBs for calibration are only executed once. You should assume that your science OBs will be executed completely independently of each other, possibly on different nights, and take into account that no user-supplied OB (for a science or a calibration target) will be executed more than once. You should submit enough OBs to cover that situation. For example, if you need to observe and flux-calibrate six targets in a filter that is not supported by the calibration plan of the instrument, you need to provide six OBs for photometric calibration to allow for the case in which each target is observed on a different night. This must be done even if the same calibration star can be used for all the science targets.

Please indicate in the User Comments fields of science OBs when a user-provided calibration must be executed contiguously.

Since P90 'concatenation containers' can be used within P2PP version 3 to link science and calibration observations that must be executed contiguously.

Please note that there are two separate kinds of calibrations in operational terms:

  • Calibrations that observe a reference celestial source, like a spectrophotometric standard star or a nearly-featureless star for the measurement of telluric lines. The OBs prepared for this kind of calibration are generically considered as normal OBs (to be prepared within an "OB" in P2PP3), and their construction is the same as for other science OBs. However, depending of the instrument they use either templates whose name contains the indicator calib, or flags in the templates that indicate that the observation is intended for calibration.
  • Calibrations with no celestial source associated, like flat fields taken with a flat field lamp or dark exposures. OBs for this kind of calibration should be prepared within the "CB" (Calibration Block) in P2PP, as no acquisition template needs to be specified in this case. Calibrations to be executed in daytime are the most common examples in this category.

CRIRES Calibration Plan

The CRIRES instrument is calibrated by the Science Operations staff in the morning after the science observations. All instrument setups used in the science observations are calibrated automatically.

The standard calibration products provided by the observatory are given in the CRIRES User Manual.

If additional calibrations are required, this must be discussed in advance with the support staff at USD (usd-help@eso.org).

IMPORTANT NOTE:  Telluric and/or spectro-photometric standard stars are not part of the Observatory CRIRES Calibration Plan. Users should submit dedicated OBs (using the template CRIRES_spec_cal_AutoNodOnSlit) and the total execution time will be charged to their OPC allocated time. The user is also required to specify in the Instrument Comments field of each 'telluric' OB the spectral type of the standard star, as well as a range of permitted spectral types. This is very important, as the Observatory, in order to optimize the quality of a given observation, may need/decide to observe a different telluric standard star, which will then be chosen according to the spectral type specified by the user. This usually happens if the difference in airmass between the science target and the user-provided telluric star is larger than 0.2 (except if specifically mentioned otherwise in the README file), or if meteorological conditions do not allow to observe the telluric specified by the user. In such case, exposure times will be adjusted according to the targeted S/N ratio per pixel (also to be provided in the Instrument Comments field).

In particular, the README file should explicitly mention OBs that do not require observations of a telluric standard star.

At present no high precision IR atlas of standard stars with bona fide spectra exists, but the CRIRES team plans to compile such a list and make it available on the CRIRES webpage.

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