Testing an array differs from testing a single patch. The aperture is larger and the pattern directional, so the fixture must enclose the whole radiating surface to produce a coupling factor that is meaningful, which is what the 160 mm square footprint provides. Because the array operates across a narrow 100 MHz band rather than the 275 MHz of the omni antennas, coupling is held to a 2 dB window with a 3 dB typical at 2:1 VSWR. That precision suits production acceptance testing where units are compared against each other and against a baseline. The RF shielded enclosure contains bench transmit and protects technicians working near a radiating S-band array. Mounting uses interface features already integrated into the array, so nothing is added to the spacecraft structure, and the fixture comes off without tooling. The envelope is 160 x 160 x 33 mm (6.3 x 6.3 x 1.3 in) at 440 g, rated -70 to +100 °C. CSA-S-008-RH is the matching antenna.