Which Space Probes Were Sent To Observe Halley’s Comet and Why Was Giotto Knocked Out of the Comet’s Path?

An international fleet of probes were launched to intercept the orbit of Halley’s comet in 1986.

The Soviet Vega 1 probe was the first to reach its destination, on March 6, coming within 5,000 miles (8,000 km) of the comet’s nucleus.

Vega 2 arrived to take photos from a distance of 13,000 miles (21,000 km) 3 days later.

Vega 1 transmitted data that helped to ensure the success of the ESA’s Giotto probe, which reached the comet 7 days later.

On March 8, the Japanese probe Suisei passed Halley’s comet at a distance of 91,000 miles (146,000 km) in order to get a long view.

Also from Japan, the probe Sakigake was sent to study the comet’s tail.

Giotto’s mission was to fly directly into the comet’s coma and photograph it for as long as possible before it collided head-on with the nucleus.

The probe transmitted its live television footage almost to the point of impact.

Instead of a collision, however, the probe was knocked out of the comet’s path by a grain of dust weighing only 3 one-hundredths of an ounce (1 g).

An hour or so later, Giotto again began sending data as it flew past the comet.