Spacecraft Meet Halley’s Comet

In March 1986, an international armada of spacecraft converged on Halley's Comet as it swept through the inner Solar System. Although chroniclers worldwide had recorded the object across millennia, Edmond Halley first recognized in 1705 that appearances occurring roughly every seventy-six years were returns of the same body. The 1986 return presented difficult viewing conditions from Earth because the comet and the planet sat on opposite sides of the Sun in February, but the passage offered scientists their first opportunity to examine a cometary nucleus directly from robotic probes.

The multi-nation flotilla carried diverse instruments to measure the comet. The Soviet Union sent Vega 1 and Vega 2, which flew past the nucleus on 6 and 9 March at distances of 8,890 kilometers and 8,030 kilometers, respectively. Vega 1 returned the first direct photographs of the nucleus, establishing its physical shape and thermal characteristics. Two Japanese probes, Suisei and Sakigake, joined the campaign, while the repurposed International Cometary Explorer made distant measurements, passing between the Sun and the comet in late March.