Спутники для обнаружения ядерных взрывов: Проект Vela

Group of satellites to detect nuclear detonations
the satellite program

Vela was the name of a group of satellites developed as the Vela Hotel element of Project Vela by the United States to detect nuclear detonations and monitor Soviet Union compliance with the 1963 Partial Test Ban Treaty. Vela started out as a small budget research program in 1959. It ended 26 years later as a successful, cost effective military space system, which also provided scientific data on natural sources of space radiation. In the 1970s, the nuclear detection mission was taken over by the Defense Support Program (DSP) satellites. In the late 1980s, it was augmented by the Navstar Global Positioning System (GPS) satellites. The program is now called the Integrated Operational NuDet (Nuclear Detonation) Detection System (IONDS).

The original Vela satellites were equipped with 12 external X ray detectors and 18 internal neutron and gamma ray detectors. They were equipped with solar panels generating 90 watts. The Advanced Vela satellites were additionally equipped with two non imaging silicon photodiode sensors called bhangmeters which monitored light levels over sub millisecond intervals. They could determine the location of a nuclear explosion to within about 3,000 miles. Atmospheric nuclear explosions produce a unique signature, often called a "double humped curve": a short and intense flash lasting around 1 millisecond, followed by a second much more prolonged and less intense emission of light taking a fraction of a second to several seconds to build up. The effect occurs because the surface of the early fireball is quickly overtaken by the expanding atmospheric shock wave composed of ionised gas. Although it emits a considerable amount of light itself it is opaque and prevents the far brighter fireball from shining through. 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. They were also equipped with sensors which could detect the electromagnetic pulse from an atmospheric explosion. Additional power was required for these instruments, and these larger satellites consumed 120 watts generated from solar panels. Serendipitously, the Vela satellites were the first devices ever to detect cosmic gamma ray bursts.

On July 2, 1967, at 14:19 UTC, the Vela 4 and Vela 3 satellites detected a flash of gamma radiation unlike any known nuclear weapons signature. 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. By analyzing the different arrival times of the bursts as detected by different satellites, the team was able to determine rough estimates for the sky positions of sixteen bursts and definitively rule out a terrestrial or solar origin. Contrary to popular belief, the data was never classified. After thorough analysis, the findings were published in 1973 as an Astrophysical Journal article entitled "Observations of Gamma Ray Bursts of Cosmic Origin". In addition to the x ray Nova announcement indicated above the XC Detector aboard Vela 5A and 5B also discovered and announced the first X Ray Burst ever reported. The announcement of this discovery predated the initial announcement of the discovery of gamma ray bursts by 2 years. In front of each crystal was a slat collimator providing a full width at half maximum (FWHM) aperture of ~6.1 × 6.1 degrees. The effective detector area was ~26 cm2. The detectors scanned a great circle every 60 seconds, and covered the whole sky every 56 hours. Sensitivity to celestial sources was severely limited by the high intrinsic detector background, equivalent to about 80% of the signal from the Crab Nebula, one of the brightest sources in the sky at these wavelengths.) satellite detected the characteristic double flash of an atmospheric nuclear explosion near the Prince Edward Islands. Still unsatisfactorily explained, this event has become known as the Vela incident. 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. In 2018, a new study confirmed that it is highly likely that it was a nuclear test, conducted by Israel. An alternative explanation involves a magnetospheric event affecting the instruments. An earlier incident occurred when an intense solar storm on August 4, 1972, triggered the system to event mode as if an explosion occurred, but this was quickly resolved by personnel monitoring the data in real time.