Did you see Halley’s Comet? Last in the inner solar system in 1986, a new mission concept could see a spacecraft travel alongside the nine-mile-long and five-mile-wide comet when it next returns.

Researchers have designed a trajectory that could launch a spacecraft in the 2030s and rendezvous with Halley in 2060, ahead of its next perihelion (closest pass of the sun) in 2061.

Published on the preprint server arXiv, the study proposes using gravity assists from Jupiter and Saturn, combined with low-thrust electric propulsion, to make the extraordinary journey possible.

Halley’s Armada Made History In 1986

The last visit of spacecraft to Halley’s Comet in 1986 produced one of the great international campaigns of early planetary exploration — but it was a brief tryst. The Soviet Union’s Vega 1 and Vega 2 and the European Space Agency’s Giotto formed part of an international fleet nicknamed the “Halley Armada.” The Vega spacecraft encountered Halley first and provided tracking information that helped refine Giotto’s trajectory before its exceptionally close encounter.

Giotto passed just 370 miles from Halley on March 13-14, 1986, sending back close-up images of the comet’s dark nucleus and powerful jets. But the spacecraft were racing past Halley at relative speeds of around 43-50 miles per second, leaving little time for close-up observations.

Fleeting Flyby To Revolutionary Rendezvous

Unlike the fleeting encounters of 1986, a rendezvous would allow a spacecraft to match Halley’s motion and conduct sustained observations of the comet. While Halley’s Comet is well known and has been seen throughout human history — the first confirmed sighting was recorded by Chinese astronomers in 240 BC, according to NASA — scientists still have questions. They don’t fully understand how its nucleus rotates, what its surface looks like, where its most active areas are, how much material it loses when it gets close to the sun, or what lies inside it. A rendezvous could allow scientists to take high-resolution images covering the entire nucleus while watching Halley become increasingly active as it approaches the sun.

Jupiter And Saturn Solve A Difficult Problem

Halley travels around the sun in the opposite direction to the planets and has an orbital inclination of about 162 degrees. That makes it a very difficult object to rendezvous with because any spacecraft would need to radically change its direction of travel. According to the researchers, electric propulsion would help carry the spacecraft from Earth to Jupiter. Jupiter’s gravity would then give it a major energy boost, sending it toward Saturn. The Saturn encounter would then place the spacecraft on a retrograde trajectory, enabling it to intercept Halley’s comet.

A 2036 Launch Could Reach Halley In 2060

The researchers identified two particularly promising launch opportunities — both involving a journey of at least 23 years.

Launch in 2036: spacecraft to leave Earth on Aug. 21, fly past Jupiter on Feb. 4, 2038, and encounter Saturn on Dec. 21, 2039. After more than two decades on its final leg, it would rendezvous with Halley on Aug. 14, 2060 — well ahead of its perihelion on July 28, 2061.

Launch in 2037: spacecraft to leave Earth on Sept. 24, 2037 and rendezvous on Sept. 23, 2060.

“It is imperative to start mission planning as soon as possible,” the researchers write. With the best launch opportunities arriving in 2036 and 2037, there is only about a decade to turn the concept into a real spacecraft. The researchers say it is, as far as they know, the first practical Halley rendezvous concept based entirely on proven technologies. The prize would be something never achieved before: not simply racing past Halley, but meeting the comet and travelling alongside it as it returns toward the sun.

Wishing you clear skies and wide eyes.