Soviet probes Venera 11, Venera 12 and the German-American solar satellite Helios II all are hit by "off the scale" gamma rays leading to the discovery of soft gamma repeaters.

The Venera 11 was a Soviet uncrewed space mission which was part of the Venera program to explore the planet Venus. Venera 11 was launched on 9 September 1978 at 03:25:39 UTC.

The Venera 12 was an uncrewed Soviet space mission designed to explore the planet Venus. Venera 12 was launched on 14 September 1978 at 02:25:13 UTC.

Helios-A and Helios-B are a pair of probes that were launched into heliocentric orbit to study solar processes. As a joint venture between German Aerospace Center (DLR) and NASA, the probes were launched from Cape Canaveral Air Force Station, Florida, on December 10, 1974, and January 15, 1976, respectively.

In gamma-ray astronomy, gamma-ray bursts (GRBs) are extremely energetic events occurring in distant galaxies which represent the brightest and most powerful class of explosion in the universe. These extreme electromagnetic emissions are second only to the Big Bang as the most energetic and luminous phenomenon ever known. Gamma-ray bursts can last from a few milliseconds to several hours. After the initial flash of gamma rays, a longer-lived afterglow is emitted, usually in the longer wavelengths of X-ray, ultraviolet, optical, infrared, microwave or radio frequencies.

A soft gamma repeater (SGR) is an astronomical object which emits large bursts of gamma-rays and X-rays at irregular intervals. It is conjectured that they are a type of magnetar or, alternatively, neutron stars with fossil disks around them.