Goals: The Soviet Union's twin Vega spacecraft were designed primarily to deliver advanced landers and balloons to Venus, but the return of comet Halley to the inner solar system provided an opportunity for additional science.
Accomplishments: Both Vega 1 and its twin Vega 2 were tremendously successful. After successfully delivering its payload at Venus, Vega 1 flew on to a close encounter with comet Halley, transmitting hundreds of image as it through through the comet's gas cloud, or coma. Vega 1 collected valuable data on Halley's nucleus, dust production rate, chemical composition and rotational rate. The encounter provided key groundwork for the Giotto mission, which arrived at Halley a few weeks later.