Phase 2 Waiver Requests and Programme Change Requests

Phase 2 Waiver Requests

To ensure the observing efficiency and flexibility of Service Mode observing, ESO has implemented a number of rules, procedures and limitations on programmes scheduled for Service mode. Typically, these have to do with OB construction, observing strategy, or instrument modes available.

In some special cases it is possible to admit some justified exceptions to these rules with a reduced operational impact. However, it is necessary that the exceptions have been reviewed and authorized by ESO well in advance. The Phase 2 Waiver Request procedure is the channel to make this possible.

Instrument independent conditions where a Phase 2 Waiver Request is needed

  • OBs that will take longer than one hour to execute.
  • Concatenated OBs that will take longer than one hour to execute . Please note that justifications based on the reduction of execution overheads cannot be accepted, as sequences of OBs decrease the flexibility of Service Mode observing and thus the operational efficiency of the telescopes
  • Concatenated OBs that have large angular separations between the OB targets (>75 deg) which would result in a very difficult scheduling.
  • OBs that contain multiple instrument configurations. As an exception, multiple broad-band filters in a single OB can normally be allowed without a waiver, and for FORS2 up to two interference filters may be used in a single OB without a waiver.
  • Delayed submission of Phase 2 material needed. This is admissible only under exceptional circumstances justified by scientific reasons, such as the need to wait for the outcome of another observing run before preparing the OBs. Users whose schedule prevents them from submitting their Phase 2 package by the due date are strongly encouraged to find a collaborator who can do it, rather than submitting a waiver request, as ESO cannot guarantee the prompt review and validation of Phase 2 packages submitted after the Phase 2 deadline.
  • The time interval between succeeding time-linked OBs is < 1hr.

Additional conditions for Waiver Requests regarding HAWK-I

In addition to the general Phase 2 Waiver Request policies, waiver requests have to be submitted for any of the following conditions:

  • If bright objects that strongly saturate are within the FOV. Like many other infrared detectors the HAWK-I detectors show a persistence effect if the observed sources are too bright. In Service Mode, this problem would seriously compromise subsequent observations of other programs. Therefore, the following rules apply:
    • When using DITs smaller than 30 secs, persistence effects can be neglected.
    • When using larger DITs the maximum accepted saturation is 7 times the saturation level.
    Requests for imaging observations not compliant with these limits must be submitted as a Phase2 Waiver request. If judged acceptable, ESO will try to devise operational strategies (e.g. observations at the end of the night, scheduling other BB imaging OBs after the observations in question).
  • The DIT is larger than 120s and NOT one of [150,180,240,300,600,900]
  • If a VLT telescope guide star is provided and its distance to the target is smaller than 5.5arcmin, in which case the guide probe arm potentially vignets the target.
  • The detector window sizes for the FastPhot mode are different from those listed in the table below


Number of columns for each window stripe DET.WIN.NX  128
First column of window within a stripe   DET.WIN.STARTX  1
Number of rows for each window stripe DET.WIN.NY 32, 64, 128
First row of window within a stripe DET.WIN.STARTY any from 1 to 2048

Submission of Phase 2 Waiver Requests and Programme Change Requests

As a reminder, Waiver Requests are petitions to override one or more operational rules or technical limitations.  Programme Change Requests are petitions to deviate from observations as proposed at Phase 1 (e.g. new targets, new instrument, new/different observing modes, etc.).  Formulation and submission of both types of petition is now fully supported in the p2 (Paranal) and p2ls (La Silla) user interfaces. Once logged in, the user should select the Run for which they intend to submit the Waiver Request or Change Request. By clicking on the Run, the user will be able to access the Change Request menu on the top right.  Further information is provided here

Note that all Phase 2 Waiver Requests and Programme Change Requests must be approved by ESO before Phase 2 package submission. Users should understand that such requests can take a number of days to process, especially when consultation with the Chilean Science Operations team is needed.  Until they are processed no further progress can be made in processing of the run.  Hence users are strongly encouraged to plan ahead and submit such requests in a timely fashion.

All approved requests (either waivers or programme change) should be summarized in your README file.

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