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Observation Preparation (Phase 2) - Knowledgebase / Observation Preparation and Execution (Phase 2) - ESO Operations Helpdesk

Observation Preparation (Phase 2)

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  • Do I need to account for overheads in my total exposure time when submitting Service Mode OBs?

    Answer: Yes. Total allocated time = integration time + all standard operational overheads. To estimate your operational overheads, see the individual instrument User's Manuals and/or use the Execution Time Report function in the p2 tool.

  • How many special calibration OBs do I have to submit?

    Answer: 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 calibration OB will be executed more than once. You should submit enough special calibration OBs to cover that situation. Example: if you need to observe and flux-calibrate six targets in a filter that is not supported in the calibration plan of the instrument, you need to provide six special calibration OBs to allow for the case in which each target is observed on a different night. This must be done so even if the same calibration star can be used for all the science targets. For assistance, contact the User Support Department through the helpdesk system (

  • Can I specify different observing constraints (e.g. seeing, transparency) at Phase 2 with respect to those specified in my Phase 1 observing proposal?

    Answer: You can relax your constraints to increase the chances of execution of your OBs (for example, if you specified Seeing = 1.0 or better at Phase 1, you can specify Image Quality that corresponds to V band Seeing at zenith of 1.2 or better at Phase 2). However, more stringent constraints (like Image Quality that corresponds to V band Seeing at zenith of 0.8 at Phase 2, in the previous example) are not allowed, as an essential ingredient of the long-term scheduling of Service Mode programmes over the semester is the constraints that users of approved programmes specified at Phase 1. Allowing more stringent constraints at Phase 2 would thus endanger the completion of even the highest ranked programmes. An allowed exception to this are OBs needed to flux-calibrate observations that can be mostly done under non-photometric conditions, provided that accurate flux calibration is needed for the scientific goals of the programme and that the execution time under photometric conditions does not exceed 20% of the allocated time.The values in the OB constraint sets that are selected (and approved) during Phase 2 preparation (and review) cannot be changed later during the observing period. This is explained in more detail in the Phase 2 Service Mode Guidelines web pages.

  • How do I get my p2 username and password?

    Answer: The p2 username and password correspond to the ESO User Portal username and password of the Principal Investigator (PI), or of the Phase 2 Delegate (in case the PI has delegated Phase 2 access to another User Portal registrant).  If you as PI of a scheduled run, or as a Phase 2 Delegate, have forgotten your User Portal username and/or password please use the appropriate corresponding link(s) on the User Portal login page.

    If you have no accepted programs as PI but wish to learn the use of p2, you can use the p2 demo server set up for this purpose.

  • After reviewing my Phase 1 proposal, I have realized that I can observe a better set of targets than the ones I listed then. Since the scientific goal is the same, can I simply change the list of targets?

    Answer: No. There are multiple reasons. One is to avoid duplication of observations unless scientifically justified and conflict/scooping between different scheduled programs. Furthermore, the allocation of time in Service Mode is made to balance pressure factor on each right ascension interval, derived from the distribution in the sky of the targets that the accepted programmes proposed at Phase 1. The Long Term Schedule that results from the time allocation process would thus be invalidated if changes of target were allowed at Phase 2, this is, after the time allocation has been made.

    It is however possible to accept a limited number of target change requests in cases for which a sound scientific justification exists, such as the existence of new observations that demonstrate that a given object of the original sample had been misclassified and is not relevant to the purpose of the programme any more. Target change requests are reviewed by ESO to ensure the strength of the justification and also that there is no other approved programme that intends to execute observations of the new target in a similar configuration.

    Target change requests must be submitted via a dedicated web form in the Phase 2 preparation tool p2 (or p2ls for La Silla instrument observations). Once logged in to p2 (p2ls) select the Run for which Change Request needs to be submitted. By clicking on the Run, the Change Request menu can be accessed on the top right.  Further information about using p2 is provided here

  • How do I prepare my Phase 2 observational material for APEX?

    Answer: APEX does not use p2, but a web-based form. On the said form you will have to provide your email: please make sure that it is exactly the same as the one present in your ESO User Portal profile. The APEX Phase 2 deadline is the same as the P2PP deadline. 

  • I have an accepted proposal which consists of a pre-imaging run and a follow-up multi-object spectroscopic (MOS) run. May I submit only the pre-imaging OBs now, by the Phase 2 deadline, and the spectroscopic OBs later?

    Answer: Yes, you should submit only the pre-imaging OBs (i.e. no dummy MOS OBs should be submitted at the general Phase 2 deadline). ESO will make every possible effort to execute all pre-imaging as early as possible, and will release pre-images immediately. In effect all pre-imaging OBs will be treated as ``carry-under OBs'', meaning that they will be executed as soon as they are ready, even if that is before the period starts. For the Phase 2 proposers this means that it is important to submit pre-imaging OBs as soon as possible, even long before the deadline. The earlier valid OBs are submitted, the earlier the pre-images will be taken, and the higher the probability that follow-up MOS observations will be completed within the narrow window of opportunity.

  • What is the accuracy of the UTs pointing and tracking?

    Answer: The UTs have a pointing accuracy of 3 arcsec RMS, driven by the guide star catalogue accuracy. The expected tracking accuracy under nominal wind load is 0.1 arcsec RMS over 30 minutes when field stabilization is active. The UTs also have the capability of tracking targets with additional velocities (e.g. Solar System targets) under full active optics control. Proposers who need this capability should specify the additional velocities in RA and Dec for their targets. Please check here for further details on UTs performances.

  • Can I get an overview of all my ESO Service Mode runs? 
    Answer: Yes. After logging into the User Portal ( in the main screen you will see a card labelled, "Phase 2". Within that card you will see the link, "Check the status of your observing runs". Clicking on that link will bring you to an overview page for your observing runs. You can subscribe to receive an email notification from the nightlog tool each time one of your OBs is executed. The subscription is managed through the "Subscribe to night reports" link in the upper right of the Overview of ESO Observing Runs page in User Portal. The nightlog tool can also be accessed directly through