Vela 4A

Vela 4A was a United States early warning satellite, part of the Vela program. Launched on April 28, 1967, it was designed to detect nuclear detonations in the atmosphere and in space. Vela satellites were crucial in monitoring compliance with the 1963 Limited Test Ban Treaty, which prohibited nuclear weapon tests in the atmosphere, underwater, and in outer space.

Vela 4A carried a suite of sensors, including X-ray, gamma-ray, and neutron detectors, as well as optical sensors to detect the characteristic double flash of light associated with nuclear explosions. These instruments allowed the satellite to differentiate between natural phenomena and nuclear detonations.

The Vela program, including Vela 4A, played a significant role in verifying the Limited Test Ban Treaty and contributed to the development of technologies for detecting and monitoring nuclear proliferation. The data collected also proved valuable for astrophysical research, providing insights into gamma-ray bursts and other cosmic events. Vela 4A operated successfully for several years, contributing valuable data before being decommissioned.