Polarization mismatch is a fixed loss that cannot be corrected once a spacecraft is in orbit. Presenting both hands from a single aperture removes that risk from the design. The antenna is fully passive, so there is no bias, no current draw and no active device requiring radiation qualification. VSWR is 2:1 across the band through an SMA female interface, and power handling is 20 W CW. At 81 x 81 x 12 mm (3.2 x 3.2 x 0.46 in) and 100 g it is the thinnest and among the lightest antennas in the S-band range. Designed for the harsh conditions of space operation across LEO, MEO and GEO, the sealed and vented housing addresses corona, multipaction, atomic oxygen and MMOD. Qualification follows NASA GEVS (GSFC-STD-7000) with random vibration to 14.1 GRMS across a -70 to +100 °C operating and storage range. ATH-S-001-DC is the matching dual-CP test hat and exercises each polarization path independently during integration. Certain small-volume orders can ship within days rather than the months typically quoted for space-qualified hardware.