EMIR Optimized Slits Positioner ( OSP) is an aplication written in java, using the JSkyCat library and implementing algorithms to search and validate optimized project masks. The Multi-Object Spectroscopic (MOS) system of EMIR is composed of a robotic reconfigurable multi-slit mask or Cold Slit Unit ( CSU). It can be able to obtain 55 spectra simultaneously and this tool is needed to optimize the science targets in our field, simulate the final characteristics of the 2D spectra on the detector, and allow the user to perform the configuration of all the slits though a Graphical User Interface.

How to use the EMIR OSP

The first use of the OSP requires an exception.  By adding the application URL to the exception list allows users to run Rich Internet Applications (RIAs) that would normally be blocked by security checks.  See: https://www.java.com/en/download/faq/exception_sitelist.xml.

The current version of the OSP can be accesed via the link below:

The EMIR OSP documentation is currently being improved. Currently there exists two helpful documents listed below.

The OSP Tutorial contains a detailed description of the various functionailities of the EMIR OSP, whereas the User notes (version 1.0) contains a more up-to-date summary of some of the new features of the OSP.

Briefly, 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.


The output is an XML file describing the complete shape of the mask. Individual slits are specified by their central position on the field, their length, and their width. These values have to be specified for each slit, together with the position of the center and the orientation of the field. The OSP will be mainly used during the preparation phases of an observation (Phase II of GTC).

To send comments or bug detection please, do not hesitate to mail @: osp-support(at)ast(dot)obs-mip(dot)fr