The program is now called the Integrated Operational NuDet (Nuclear Detonation) Detection System (IONDS).

The first Vela Hotel pair was launched on 17 October 1963,[3] one week after the Partial Test Ban Treaty went into effect, and the last in 1965.

Subsequent Vela satellites were switched to the Titan IIIC booster due to their increased weight and complexity.

The Advanced Vela satellites were additionally equipped with two non-imaging silicon photodiode sensors called bhangmeters which monitored light levels over sub-millisecond intervals.

The effect occurs because the surface of the early fireball is quickly overtaken by the expanding atmospheric shock wave composed of ionised gas.

As the shock wave expands, it cools down becoming more transparent allowing the much hotter and brighter fireball to become visible again.

No single natural phenomenon is known to produce this signature, although there was speculation that the Velas could record exceptionally rare natural double events, such as a meteoroid strike on the spacecraft that produces a bright flash or triggering on a lightning superbolt in the Earth's atmosphere, as may have occurred in the Vela incident.

Additional power was required for these instruments, and these larger satellites consumed 120 watts generated from solar panels.

[8] Uncertain what had happened but not considering the matter particularly urgent, the team at the Los Alamos Scientific Laboratory, led by Ray Klebesadel, filed the data away for investigation.

As additional Vela satellites were launched with better instruments, the Los Alamos team continued to find inexplicable gamma-ray bursts in their data.

[10] After thorough analysis, the findings were published in 1973 as an Astrophysical Journal article entitled "Observations of Gamma-Ray Bursts of Cosmic Origin".

In front of each crystal was a slat collimator providing a full width at half maximum (FWHM) aperture of c. 6.1 × 6.1 degrees.

President Jimmy Carter initially deemed the event to be evidence of a joint Israeli and South African nuclear test, though the now-declassified report of a scientific panel he subsequently appointed while seeking reelection concluded that it was probably not the event of a nuclear explosion.