The EMIR Optimised Slit Positioner (OSP) is an application, using the JSkyCat library, to create the necessary configuration files to observe with EMIR in multi-object mode. In this mode, it is a requirement of the GTC Phase II process to configure the instrument using the EMIR-OSP. The OSP allows one to configure the 55 moveable slits of the EMIR Configurable Slit Unit ( CSU) on predefined targets of unquestional astronometry. A dedicated python script is used to provide several checks on the result of the OSP.

Recent updates

The OSP updates page details the most recent changes to the OSP and should be checked regularly to ensure that the most recent version of the OSP is being used.

EMIR OSP Overview and Usage

This section provides an overview only, for the full and correct usage of the OSP, please read the EMIR-OSP-cookbook document.

The OSP takes as input an image of the region of interest as well as a catalogue, either user defined or using one of the available catalogue tools, and allows the user to allocate slitlets to targets in an optimised way. The result is then taken as input for the GTC to create the appropriate masks at the telescope.

To use the EMIR OSP one must have two input files:

  1. A user input catalogue
  2. An image covering the field of view

A template input catalogue can be found here. The input image must be in the correct orientation (North up, East left) and contain no distortions.

Once the targets have been selected and the user is happy with the results, three output files will be created:

  1. <name>.xml - a mask file containing relevant information on the mask, slits and allocated objects
  2. <name>.csu - the file required to configure and acquire the EMIR CSU
  3. <name>.conf - a summary file


Facility tool to check the OSP result

To ensure the results of the OSP tool are precise and accurate, an additional tool has been developed to provide several checks on the resulting OSP files. This tool is described and a working example detailed here. At present, the use of this tool is mandatory before submission of the GTC Phase II material.  This tool will help you to check your results to make sure that there are no unexpected issues at the telescope. Please use it to avoid observing delays.

Download and Install

The EMIR-OSP-cookbook is a guide on how to use the OSP and contains the necessary information to produce an observable configuration. We strongly recommend the careful use of this document when working with the OSP.

The EMIR OSP can de downloaded here.

To install unpack the tar.gz file using (for example) the command:

     $ tar -zxvf EMIR-OSP-v<version>.tar.gz

To run the OSP simply use the commands:

     $ cd OSP-v<version>/
     $ ./osp.sh

Please make sure that the osp.sh file is executable to run the final command (by default it should be).


To send comments or bug detection please, do not hesitate to send an email to: alina [at] iac.es or lee [at] lrp-astro.org