  The first LHC application ever to be executed in a computational Grid
environment is the so-called ATLAS Data-Challenge 1, more specifically, the
part assigned to the Scandinavian members of the ATLAS Collaboration. Taking
advantage of the NorduGrid testbed and tools, physicists from Denmark, Norway
and Sweden were able to participate in the overall exercise starting in July
2002 and continuing through the rest of 2002 and the first part of 2003 using
solely the NorduGrid environment. This allowed to distribute input data over a
wide area, and rely on the NorduGrid resource discovery mechanism to find an
optimal cluster for job submission. During the whole Data-Challenge 1, more
than 2 TB of input data was processed and more than 2.5 TB of output data was
produced by more than 4750 Grid jobs.
