Moving Target Procedures

This page describes the Phase 2 procedures for Moving Target (i.e. SolarSystem 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 thedifference that the submission of the ephemerides 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 ephemerides file must be submitted in such cases in the format described below at the time of triggering the ToO observations.

Ephemerides Files

Users must submit a detailed ephemerides 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 ephemerides files are plain ASCII files and must contain the following items:

  • Target name and run ID.
  • Date and time in UT for the ephemerides positions.
  • Topocentric right ascension and declination refered to the J2000 equinox ICRF or FK5 system. Please note that the VLT telescope control system already corrects for precession, nutation, annual aberration and refraction, so topocentric astrometric coordinates (and not apparent coordinates) are required.
  • Topocentric apparent motions in right ascension (mu_alpha cos delta) and declination (mu_delta), in arcsec/sec.
  • The predicted magnitude of the target.
  • Any other instrument information if applicable, such as the desired slit orientation. This information must be provided so that it can be entered directly in the OBs without any transformation: please consult the corresponding instrument user's manual for information regarding orientation conventions.

The time intervals at which the ephemerides are given should be defined so that the displacement of the target does not exceed 30 arcsec (3 arcsecin the case of SINFONI due to its much smaller acquisition field of view) between two consecutive entries. The ephemerides files must be submitted as attachments to the OBs to which they refer. To attach them, use the options available under the Ephemerides Files menu in the P2PP main GUI (see the P2PP User Manual for a detailed explanation).

OB Requirements

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

  • Target coordinates must be entered in the OB and must correspond to the middle of the observable period. This information is needed by ESO for long-term scheduling purposes.
  • The OB Name must begin with the prefix MOV_

Target Acquisition and Verification

Bright Targets

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

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 ESOastronomer 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. Theparameters 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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