  We describe the BOOMERanG experiment, a stratospheric balloon telescope
intended to measure the Cosmic Microwave Background anisotropy at angular
scales between a few degrees and ten arcminutes. The experiment has been
optimized for a long duration (7 to 14 days) flight circumnavigating Antarctica
at the end of 1998. A test flight was performed on Aug.30, 1997 in Texas. The
level of performance achieved in the test flight was satisfactory and
compatible with the requirements for the long duration flight.
