Field Testing the EUSO-SPB instrument

In September of 2016 the the Extreme Universe Space Observatory on a super pressure balloon (EUSO-SPB) instrument was tested in the west Utah desert with a laser "test beam" system. Laser tracks were measured at distances of 24 km with the laser tilted away from the detector. This geometry is similar to the expected geometry of downward going cosmic ray air showers during the planned balloon flight. We describe the test beam system and the tests.