Wavelength at 8 GHz is approximately 37 mm, so a seating variation of a millimetre is a meaningful fraction of it. A purpose-machined fixture that indexes off the antenna's own mounting features is what produces X-band coupling figures repeatable enough to compare. Coupling is 4 dB minimum, 5 dB typical and 7 dB maximum across the band. The usual role is the post-environmental functional check: after vibration and thermal cycling, confirming the RF path survived without booking chamber time for a measurement that takes minutes on a bench. The RF shielded enclosure contains X-band transmit and protects technicians. Mounting uses interface features already integrated into the array, so no bracket is added to the spacecraft, and the hat comes off without tooling. The envelope is 74 x 74 x 19 mm (2.9 x 2.9 x 0.73 in) at 90 g, rated -70 to +100 °C operating and storage. CSA-X-001-RH is the matching antenna.