Service Mode Rules and Recommendations for Observation Blocks

Preparing Observation Blocks

Both Visitor and Service Mode programmes are carried out at all ESO telescopes by executing Observation Blocks (OBs) provided by the users. OBs are constructed and submitted to ESO using the Phase II Proposal Preparation (P2PP) tool. Please refer to the P2PP User Manual and to the User Manuals of the different instruments for more specific information on the structure and contents of OBs, and how to build OBs for different instruments. A number of tutorials describing step-by-step the construction of OBs for different instruments is available.

Service Mode OBs: rules and advices

It is important to keep in mind the Service Mode policies and the following rules and guidelines when designing a Service Mode programme or when preparing a Phase II package:

• Some observing strategies cannot be supported in Service Mode; in particular, real-time decisions about the sequencing of OBs, complex OB sequencing, or decisions based on the outcome of previously executed OBs (like adjustment of integration times or execution of some OBs instead of others).
• OBs are only executed once. If you want to repeat an identical observation multiple times, you must submit multiple OBs. This requirement applies to standard stars as well.
• OBs are normally executed non-contiguously. Since efficient Service Mode operations require continuous flexibility to best match the OB constraints with actual observing conditions, OBs for a given programme are normally scheduled non-contiguously. Therefore, users should not expect their OBs to be executed on a specific sequence or in a linked way, unless a sound scientific justification (to be approved with a Phase II Waiver and indicated in the README file) exists. Exceptions to this rule are cases in which one OB observing a calibrations source needs to be executed contiguously to a science OB.
• Multi-mode, multi-configuration OBs are normally not permitted in Service Mode. Although multiple configurations within one OB may sometimes reduce overheads, scheduling and calibrating such OBs is extremely inefficient and can increase the calibration load to an unsustainable level. Examples of such multi-configuration OBs are those combining imaging and spectroscopy in a single OB, spectroscopy with multiple grisms or central wavelength settings, or imaging with a large number of filters (although most imagers allow multiple broadband filters in one OB). Multiconfiguration OBs are accepted only if duly justified and authorized by means of a Phase II Waiver Request.
• OB execution times must be below 1 hour. Long OBs are more difficult to schedule and execute within the specified constraints because of the unpredictable evolution of the observing conditions. For this reason, OBs taking more than one hour to execute time are accepted by ESO only in exceptional cases and provided that a Phase II Waiver Request is submitted and approved. In such cases, ESO will consider the OB successfully executed if the constraints were fulfilled during the first hour of execution, even if conditions degrade after that time.
• User-provided calibration OBs that need to be executed contiguously with science OBs need to be indicated in the User comments entry of the relevant science OBs.
• Time constraints must be indicated in the OBs. If you intend to observe time-critical events or monitor a target at specific time windows, you need to indicate this under the Time Intervals tab of the OBs. This information needs to be provided also in the corresponding section of the README file. Specifying time windows as broad as possible will reduce the possibilities that your OBs are not executed because of higher priority programmes or because the external conditions did not allow the observations during the interval that you specified.
• Specify the weakest possible Constraint Set values. OBs that can be executed under a broad range of conditions are easier to schedule, especially if they belong to priority groups B or C. In particular, if photometry is needed of a field, it is normally sufficient to obtain a short integration under photometric conditions (transparency = PHO) and carry out the rest of the integration with OBs having a transparency = CLR constraint.

Additional Service Mode Requirements for VLTI

Target coordinates

Special care should be taken when entering the target coordinates in P2PP. We have made the best experience with 2Mass coordinates. Also, to ease fringe finding during the observations, proper motions of the target (if available) must be entered in P2PP).

Visibility Calculator

To prepare and plan your VLTI observations, we recommend to use the Visibility Calculator VisCalc. The assessment of the feasibility of an observation requires an estimate of the expected visibility for the chosen VLTI configuration. Furthermore, the scientific goal of an interferometric observation campaign can often only be reached if visibility measurements at different projected baseline lengths and/or baseline angles are combined. VisCalc provides calculations of simulated visibilities as a function of hour angle based on software models of the VLTI instruments. The best suited hour angles can be identified using VisCalc, and the corresponding LST (Local Sidereal Time) interval for each OB, i.e. each instantaneous visibility measurement, must be specified in each OB. In case that, from a scientific point of view, there is no restriction for the LST range to be used, the LST range in the OB must still reflect the range when the target is higher than 30 degree above the horizon, and exclude the range when the observation is not feasible due to delay line restrictions or shadowing effects. Since we encountered in the past period that a few proposed targets were clearly larger than estimated, and thus over-resolved, we strongly encourage you to collect as much information on your target as possible. It may be advisable to organize imaging studies with single-telescope instruments before conducting VLTI observations if you have strong doubts about the extension of your proposed target.

Matching of Science target and calibrator OB names

In each OB of a scientific target, the name of the corresponding calibrator OB (or OBs) must be indicated in the p2pp comment field labeled "Name of associated OB of SCI/CAL pair". Likewise, in each OB of a calibrator, the name of the corresponding scientific target OB must be indicated in this comment field. If additional calibrators shall be observed instead of the regular cal/sci pair (sequence of cal/sci/cal), this information has to be inserted into the special calibration sections of the OB and the ReadMe file.

Additional Service Mode Requirements for AMBER

An overview on the pointing restrictions for 3-telescope baselines triples offered for AMBER can be found at the AMBER pointing restrictions page.