Moving Target Procedures

This page describes the Phase 2 procedures for Moving Target (i.e. Solar System target) programmes.

Programme Definition

Programmes for Moving Targets can be divided into two broad categories:

  • programmes with undefined targets at Phase 2 submission time, such as for example bright comets that may discovered during the course of the observing semester.
  • programmes with pre-defined targets at Phase 2 submission time, such as for example planetary satellites.

The procedures described here refer to both classes of programmes, with the difference that the submission of the ephemeris files for programs with undefined targets must take place at the time when the target becomes known rather than at the time of the Phase 2 deadline.

Programmes with undefined targets appearing at short notice (such as faint near-Earth asteroids) are considered to be Target of Opportunity programmes and should follow the established ToO procedures. Still, an ephemeris file must be submitted in such cases in the format described below at the time of triggering the ToO observations.

Ephemeris files

Users must submit a detailed ephemeris file for each target for the whole duration of the ESO Period in question, or for the whole duration of the observability period in case that observations must be executed within a specific time window. The ephemeris files are ASCII files compatible with the VLT parameter file (PAF) format.

Courtesy of the IMCCE, we provide here below a convenient form that will produce an ephemeris file for your target, for the relevant period of time. In case you wish not to use this form, or need to refer to the specification for the ephemeris file, please consult our page on ephemerides format.

Miriade - VO Solar system portal

PAF Ephemeris Generator

To fill in the form, enter your values in each input element with the correct syntax. By putting the cursor on the label of each field you will access its description. The request is submitted by clicking the button 'Request ephemerides' at the bottom of the form. The results are shown below the form, and can be downloaded by clicking on the dedicated button. If an error occurs, a message will be displayed below the form instead of the results.
TargetEnter the name or the official number or the provisional designation of a solar system object. Starting from 2 letters, autocompletion is available.
Cutoff parametersEnter an airmass value lower than 2.6, and a sun elevation (degrees) below the horizon (<0).
Start epoch (Year-Month-Day h:m:s)Enter the start epoch of the ephemeris. Click into the input field to pick a date.
Stop epoch (Year-Month-Day h:m:s)Enter the end epoch of the ephemeris. Click into the input field to pick a date.
Step sizeEnter the step size and choose its unit (day, hour, minute).
Observer locationSelect the observing site.

Please wait, computation in progress...

OB Requirements

In addition to the standard OB requirements (see the Phase 2 preparation procedures), OBs for moving targets must have the following features:

  • The OB Name must begin with the prefix MOV_
  • All OBs for moving targets must have an ephemeris file attached to it.
  • All OBs for moving targets must use time intervals. In case the timing of the observation itself does not matter, the time intervals should be set to the start and end times of the period covered in the ephemeris file. The ephemeris file should have a minimum of one entry per day for each time interval set in the OB.


Target Acquisition and Verification

Bright Targets

For targets brighter than V = 14, a DSS-based finding chart will be prepared by the ESO operations team to verify the acquisition of the target.

Faint Targets: Blind Presets

If a blind preset is enough for the purposes of the observation(i.e. if a pointing accuracy of order of one arcsecond is sufficient), the identification of the field-of-view will be carried out by the ESO astronomer in charge of performing the observations using a DSS-based finding chart. Normally no attempt will be made to identify the exact target.

Faint Targets: Accurate Presets

In cases where an accurate preset is needed (for example, spectroscopic observations), the user will need to provide two pre-imaging OBs for each science OB, with names containing the MOV_PRE_ prefix. The parameters of these OBs (instrument setup and integration time) must be identical in both pre-imaging OBs, and defined so that the target is visible in both images. The constraint set of pre-imaging OBs must also be identical to that of the science exposures that they precede. These two pre-imaging OBs will be executed with a time separation sufficient to detect the apparent motion of the target between both images. This time difference will be determined by the ESO operations team based on the user-supplied ephemerides. Note that the time needed to execute these pre-imaging OBs will be deducted from the total time allocated by the OPC.

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