p2 - Help

In the following we provide some key definitions which will help the users to familiarize with the ESO Phase 2 basic concepts.

We recommend our users to refer to the instrument user’s manuals or template manuals for an extensive description of the templates of a specific VLT instrument. All manuals available for downloads from the ESO web pages. Moreover, we recommend users to check the documentation available on the ESO web pages or a full description of the functionality of P2PP.

Before starting to use p2 to design your Phase 2 material please have a look at the new features implemented and benefits introduced with p2 with respect to P2PP3.

Please see the 2 minutes video showing the basic concept of OB preparation and notification report.


ESO Phase 2 observing material

  • Basic concept

    The VLT Data Flow System (DFS) is a set of protocols, interfaces and tools developed by ESO for linking together the telescope and instruments with simple observation description tools, on-line data processing capabilities, and automated data archiving. The VLT DFS is implemented for all ESO Telescopes in Paranal and La Silla observatory. This includes the survey telescopes VISTA and VST. The basic unit for the observations, central to the VLT Data Flow System is the Observation Block (OB). Astronomers specify their programmes in terms of OBs, which contain all the information necessary to obtain a ”single” observation. These include the target position, the instrument and exposure setup parameters, special scheduling requirements, the time constraints, the finding charts, and possibly also ephemerides lists. Such a single observation can contain in principle one or multiple exposures, or even multiple instrument configurations with multiple exposures, although multiple instrument configurations are usually discouraged, as they may complicate the calibrations. The product of the execution of an OB is normally the smallest dataset consistent with the scientific and technical goals of a given observing programme.
  • Science Observation Blocks (OBs)

    Science Observation Blocks (OBs) can be used to obtain scientific observations of an astronomical target, as well as reference data that require the observation of a specific target (such as photometric standards). As a minimum they include an acquisition and a science template and target information.
  • Calibration Blocks (CBs)

    Calibration Blocks (CBs) are used to acquire reference data such as lamp flat fields, biases, comparison lamps, etc. that do not require the observation of an astronomical target. Calibration blocks do not have acquisition template.
  • Core contents/structure of OB

    - an acquisition template, describing how the target acquisition is to be performed: it includes the information on the basic instrumental setup necessary for the acquisition; for example, which filter or slit is to be used in the (acquisition) observation, which exposure time the acquisition image should have, which position angle on the sky the slit should have, etc.

    - One or more science templates, describing the instrument setup and the exposure parameters: for example, which mask should be loaded in a MOS observation, which grism should be used, which grating central wavelength should be set, which jitter pattern should be obtained, what integration time should each exposure have, etc.

    - In some cases, the OB may end with an attached calibration template, such as for instance an arc lamp exposure for precise wavelength calibration to be obtained right after the last scientific exposure with the instrument in the same configuration. The set of acquisition, science, and possible attached calibration templates in a given OB compose the Observation Description.

  • In addition to the templates, a science OB contains other important, instrument-independent information:

    Target information, including coordinates, proper motion, and, for Solar System targets, differential motion

    The Constraint Set, to be used in Service Mode only, specifying under which external conditions (airmass, seeing, transparency, lunar illumination...) the OB can be executed.

    The Time Intervals information, also to be used in Service Mode only, specifying possible absolute time intervals (UT date and time) within which the OB need to be started - note that the OB may end after the end of its specified time interval.

    The Sidereal Time Intervals are used for Service Mode to specify intervals in local sidereal time within which the OB need to be executed - this means that the Sidereal Time interval must encompass both start and end of an OB execution.

    The Calibration Requirements information, a free text field where comments can be given to the Service Mode observer or where the Visitor Mode observer can include reminders on the calibrations needed.

    Some instruments (e.g. VIRCAM, FORS2, FLAMES, KMOS, NACO...) require the insertion in the templates of parameter files (PAF) generated by instrument-specific observation preparation software (SADT, FIMS, VMMPS, FPOSS, KARMA, NAOS PS...).

    Optionally, one or more Finding charts, especially for use in Service Mode (exception: VST and VISTA survey observations do not need finding charts).

    Also optionally, an Ephemeris file for moving targets providing their coordinates at different dates.

    Obviously, none of these items are present in Calibration Blocks (CBs)

OBs and scheduling container status

Please check here for a legend explaining the meaning of OB icons used in p2 and the meaning of different OBs and scheduling container status flags.  

The p2 web tool


You can structure the contents of your observing run by creating folders under it. Folders can contain observing blocks (OBs), calibration blocks (CBs), Group/Time-link/Concatenation Containers (G/T/C) and sub-folders (Fld). Please see above for specific definition of these items.

Creating an item: OB, CB, G, T, C or Fld



Expand an observing run or folder by clicking its icon, then press the button labelled OB, CB, Fld (for Folder), G/T/C (for group/time-link/concatenation) at the bottom of the expanded items. The new item is appended and selected.





Defining an OB - Add/remove templates


Select an Acquisition Template (AT) from a pull-down menu in the lower part of the Observing Description tab. Click on “add template” to add the selected AT to the OB. Once an AT is added to an OB, one or more Science Templates (ST) can be appended to the same OB. Any template can be removed by clicking on the “remove” icon inside each template.

Changing order of items




Within the same run or folder, you can change the order of its contained items by dragging a single OB, CB, container or folder and dropping it at the desired position.





Selecting several items



Within the same container (run, folder or scheduling container), you can select several consecutive items by clicking on one item to start a selection and then Shift+Click another item to select all consecutive items from the first one to the second one clicked. Additionally, you can Ctrl+Click (Cmd+Click on MacOS) to add/remove single items to/from a selection.

The action of Check, Certify and Revise can be done on multiple selected items. It is also possible to estimate the total exposure time of the selected items.


Moving and/or Copying items

Select one or several items, then press Ctrl+X (Cmd+X on MacOS) to cut or Ctrl+C (Cmd+C on MacOS) to copy them to the clipboard. Select a destination run or folder and press Ctrl+V (Cmd+V on MacOS) to paste them. The items will be duplicated (in case of copying) and appended to the existing content.

Visitor Execution Sequence (VES)

p2 provides the user with the possibility to create a visitor execution sequence. The latter hence allows any observer to create via the web interface, a sequence of OBs that should be executed at the telescope. The VES is instrument and user dependent. This means that a designated user will not see a VES created by the PI and vice versa.

Add an OB to the VES

Once a given instrument for which the VES should be created is selected, the list of runs associated or delegated to the user for that particular instrument are listed on the left hand section under Your Observing Runs. Please notice that only OBs that have been certified (i.e. are in status ‘+’) can be added to the VES. The same OB can be added multiple times to the VES. Once one or more OBs are added to the VES, they can be executed. The OB will be executed following the numerical order. The order of the OBs in a VES can be changed via simple Drag&Drop action.