Service Mode OBs: rules and advices

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 may be scheduled non-contiguously. Therefore, users should not expect their OBs to be executed in a specific sequence or in a linked way, unless a sound scientific justification (indicated in the README file and approved with a Phase 2 Waiver in case of a contiguous execution lasting longer than 1 hr) exists. Approved OB sequences should then be prepared as concatenations. Exceptions to this rule are cases in which one OB observing a calibration source needs to be executed contiguously to a science OB. In such a case place both OBs into a concatenation scheduling container to enforce their contiguous execution.

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 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 multiple central wavelength settings, or imaging with a large number of filters (although most imagers allow multiple broadband filters in one OB). Multi-configuration OBs are accepted only if duly justified and authorized by means of a Phase 2 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 are accepted by ESO only in exceptional cases and provided that a Phase 2 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.

Concatenation scheduling container execution time must be below 1 hour. Only in exceptional cases, and provided that a Phase 2 Waiver Request is submitted and approved, longer concatenations may be submitted. In such cases, ESO will consider the concatenated OBs 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 specified via concatenation scheduling containers.

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. Please note that absolute (UT) time constraints refer to the interval in which the OB can be started, whereas for Local Sidereal Time (LST) time intervals, the time interval refers to the entire duration of the OB. For monitoring observations it is often more appropriate to put OBs in a time-link container. 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 observing conditions did not allow the observations during the interval that you specified. Usage of absolute time intervals must be scientifically justified in the README file. Please read carefully the time-critial OB execution policy.

Specify the weakest (most relaxed) possible Constraint Set values. OBs that can be executed under a broad range of conditions are easier to schedule. In particular, for photometric calibration 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.

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