Phase 2 preparation: start here

For a successful Service Mode run it is absolutely essential that all users read the following documentation.


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)
  • Scheduling Containers: Groups

    A group container is a simple collection of OBs that may be executed independently of each other in any order. Once you place the OBs in a group and one of them is executed then the remaining OBs belonging to the group will be executed preferentially before any other part of the programme.  

    The use of group containers may be envisaged by the following examples:

    • The observing programme contains several targets located very close to each other on the sky, and for each target more than one OB is needed. If possible, you want that all observations of a single target are completed before a new target observation is started. This can be achieved by creating a group containing all the OBs for a given target.
    • The observing programme contains  a target  observed repeatedly through many different setups (i.e. filters/grisms). If possible, you want that all observations for a given setup are executed before starting a new one. This can be achieved by creating a group containing all the OBs for a given setup.
  • Scheduling Containers: Time-Link

    The time-link container defines a sequence of OBs that has to be executed in a given order, respecting the relative time intervals specified for each linked OBs.

    There are two kinds of time-link container:

    • OPEN time-link: only the lower limit - earliest after previous - of the separation interval is defined
    • CLOSED time-link: both lower - earliest after previous - and upper limit - latest after previous - are defined

    Because there is a number of rules applied to the OBs belonging to a time-link container  the reader is strongly encouraged to consult the Servince Mode Guidelines pages before making use of this type of container.

  • Scheduling Containers: Concatenation

    A concatenation container consists of two or more OBs that must be executed back-to-back without breaks. The sequence of the execution of OBs in a concatenation cannot be specified.

    If the execution of one OB within a concatenation fails, then the whole concatenation fails too and it must be repeated, irrespective whether any other OBs of the concatenation has been successfully executed or not.

    The typical use of concatenation may be envisaged in the case of observations of science targets which should be immediately followed by the observations of a calibrator source (i.e. NACO: science target and PSF calibrator; CRIRES: science target and telluric standard; HAWK-I: science target and photometric standard star etc.).


P2 tutorials are available for a number of instruments from the p2 Tutorial menu on the left hand side.

A dedicated p2 demo environment at can be used to make test. Please note that template OBs with different observing modes and strategies are avaiable in dedicated Instrument Tutorial folders for each instrument.   

Also available are some general general tutorials on the use of scheduling containers, on the attachment of finding charts, on filling out the README, and on finalizing the overall Phase 2 submission.

p2 for Phase 2 preparation: what's new

p2 is a user interface (UI) that allows ESO users to create, modify, or delete observation blocks (OBs), containers and an accompanying Readme file that define an observing run. While the web tool p2 includes most of the features available in P2PP3, there are few changes in the Phase 2 process.

Most of the new features originate by the new paradigm that any new item created by the user (OB, scheduling container) is immediately recorded on the ESO database. Please check here for further details.

In the following we describe the critical features of the new Phase 2 process.

- Check, Certify and Revise (for OBs, scheduling containers, folders)

Users can at any time verify any OB/scheduling container to ensure that they comply with ESO general and instrument specific observing requirements and they are hence executable at the telescope. All the verifications are done via the External Verification Modules (EVMs), which perform consistency checks across the templates in an OB or Container. Moreover the EVM ensures the compliance of Service Mode OBs with rules that Service Mode users need to follow so that their observations can be scheduled and executed. The EVMs can also be used to verify the contents of OBs prepared for Visitor Mode observations.

Below follows a short description of the web interface's functions involved in this process. The user should get familiar with the meaning of the status icons and flags of OB/scheduling containers.


Users can run the OB verification anytime during the preparation of their OBs. To do it, simply highlight the OB or group of OBs, or scheduling container to be verified, and select the Check button on the UI. A verification report will then appear in a pop-up window. In addition to information messages on the checks performed on the OBs, the verification report also issues error and warning messages mainly related to Service Mode policies.

The use of the "Check" button leaves the OBs and scheduling containers in a fully editable status allowing the user to revise their content.

It is important to consider that the check of OBs is not a submission of Phase 2 material. The latter is in fact replaced by a notification. Please see explanations below.



The "Certify" button performs the same verification checks described in the case of the "Check" button, including the display of a verification report.

The use of the "Certify" button on OBs and/or scheduling containers changes their status from fully editable into partially-editable status. The OBs will appear as greyed out and a small check icon appears next to them. After certification the user will only be allowed to change the OB priority, or scheduling container priority and the specific contribution of individual OBs in a group container. These properties are accessible from the "Schedule" tab.

It is important to consider that the certification of OBs is not a submission of Phase 2 material. The latter is in fact replaced by a notification. Please see explanations below.


The user has the possibility at any time during the preparation of the Phase 2 observing material to revise any OBs or scheduling container that was certified to retrieve a fully editable status and apply any further change. This is done by selecting one or more OBs and/or scheduling containers and pressing "Revise".

The use of the "Revise" button on OBs and/or scheduling containers will reversed their status to fully-editable. After that, modification of the content of the OBs is allowed.

- A Notification replaces the Submission


Any OB and/or scheduling container created using p2 inside a given run is immediately recorded on the ESO database. Hence, it is not necessary anymore to submit the Phase 2 material. Once the Phase 2 observing material is certified (please see Certify above), a notification must be sent to inform the User Support Department (for Service Mode runs) or the staff at Paranal (for Visitor Mode runs) that there is Phase 2 material (OBs/containers and the Readme) that requires a review. This is simply done by selecting the run and clicking the "Notify ESO" button.

Hence the notification replaces the "submission" of OBs normally foreseen as final step when working with P2PP3 and triggers the following operations:

  • all and only the OBs and/or scheduling containers which were certified become locked and read-only. Moreover, the Readme must be prepared at the time of the notification and will be included as part of the material ready for the review. Also the Readme will appear as read-only after that a notification is sent. In the case of a Service Mode run OBs are subject to the revision by the User Support Department. In case of a Visitor Mode run the prepared material will be fully editable. In both cases the user will be contacted with some feedback by the astronomer in charge;
  • a message is displayed on the p2 interface to acknowledge the fact that ESO has been informed. The user is presented with a list of items that are ready for review;
  • a notification email is sent to the user;
  • a notification email is sent to the ESO User Support Department (Service Mode) or Paranal (Visitor Mode);


- Phase 2 revision for Service Mode runs: check-in/check-out not needed

After the notification is sent (see previous section) a support astronomer (at the ESO User Support Department) starts the task of reviewing your Phase 2 material. The PI (and delegate) will be contacted by the support astronomer in charge of the run. In case that any problems or suggestions for improvement are identified the OBs will be released and the user will be asked to make modifications. Such OBs are identified within the run in the p2 UI by an exclamation mark ! icon.


The user can work on released OBs following the instructions of the support astronomer. The OB will have to be certified (see description above). Once all the issues are solved and the material is fully certified the user will inform ESO by using the "Notify ESO" action. 

- New functionalities

- The Visitor Execution Sequence (VES)


p2 provides the possibility to create a Visitor Execution Sequence (VES). This 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. It is important to remember that only OBs that have been certified (please see text above) can be added to the VES. The same OB can be added multiple times to the VES, as the VM OBs can be executed multiple times.

- The Target Visibility


By selecting the Target Visibility tab of a given OB, the observability of the object is displayed as altitude vs time for a particular night. On the same plot, the trajectory of the object is shown together with the altitude of the moon on the given night while labels indicate the moon angular distance. Red points indicate violation of some observing constraints indicated in the OB.

For Visitor Mode runs the same feature is available for all the OBs that are included in the Visitor Execution Sequence.

- The OB/scheduling container status Overview


At any time during a given observing period users can check the status of the observing OBs of their run. The status of an OB describes the stage of the lifetime in which it is. Please consult here the meaning of the status and the corresponding icon. The overview of the statuses, together with other information, can be found in the Overview tab of the UI.  

In the example above 3 OBs in a time-link container are fully approved and hence ready to be observed (status +; eye icon).  As a consequence, the status of the scheduling container within which the OBs are collected is fully approved. The OBs are read-only  (greyed out). The user is allowed to change the priority of the scheduling container.

A problem was found with OB-ID=5059977 OB-NAME=My OB_1. The OB is then marked with a status "-" and flagged by an exclamation mark. The user is asked to fix the OB. As such the OB is fully editable and must be certified by the user before being considered for review. The same applies for OBs in a scheduling container.