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Strong Lens Line-of-sight and Substructure Challenge

Welcome to our challenge to detect and quantify line-of-sight structures and substructure in galaxy-galaxy strong lenses!

The challenge is divided into four levels of increasing difficulty, complexity, and/or realism from level 0 (simple source, simple main lens mass, single substructure, simple instrument without noise, all parameters known) to level 3 (complex source, complex main lens, multiple l.o.s. structures and substructures, realistic instruments).

The challenge design is described in more detail here:

The simulated data for the first two levels (sorry radio data still missing) can be found here:

You can also clone or download the repository:

Please submit your results for the first two levels as described in the example submission files:

To report any issues or to ask questions regarding the challenge, you may send an email to