The launch, which was originally scheduled for 2024, was part of the SpaceX Transporter-15 mission from Vandenberg Space Force Base.
The three satellites, equipped with ultra-wideband radio frequency (RF) sensors, will orbit the Earth every 90 minutes at an altitude of 350 miles (560km).
They are teamed with a fourth, Finnish-designed synthetic aperture radar (SAR) satellite that can see through darkness and clouds, BAE Systems said.
The “novel RF and SAR cluster” will be trialled with potential customers, including the UK government, over the coming months, the company added.