Right now, a billion-dollar NASA mission is on its way to visit an asteroid, and return a sample to Earth. Only a handful of missions have ever seen an asteroid close up.
But there are thought to be millions of asteroids in the Solar System. To truly understand them, we need to visit and study as many as possible.
That’s the rationale behind a new mission study proposed by the Finnish Meteorological Institute at the European Planetary Science Congress 2017 in Riga, Latvia yesterday. They suggest that using a fleet of 50 extremely small spacecraft, we could visit and study more than 300 asteroids, drastically improving our knowledge of them.
“Asteroids are very diverse and, to date, we’ve only seen a small number at close range,” Dr Pekka Janhunen, lead author on the study, said in a statement. “To understand them better, we need to study a large number in situ. The only way to do this affordably is by using small spacecraft.”
Each tiny spacecraft would weigh 5 kilograms (11 pounds), equipped with a telescopic camera. To reach an asteroid, the spacecraft would use an electric solar wind sail – or E-sail – to harness the power of the Sun. E-sails were invented by Janhunen back in 2006. We’ve never actually flown one, although NASA has been looking into the idea.
An E-sail is a bit different to your more classic, flat solar sail. It involves using a spinning tether, about 20 kilometers (12 miles) long in this study, and running a 10 kV voltage through it. This produces a tiny amount of thrust, about 1 millimeter per second. But it would be enough, the team says, for their spacecraft to each explore six or seven asteroids.
Janhunen told IFLScience that the idea had been presented to ESA, and the agency was actively looking into it. “Presenting the idea as a concrete ESA mission requires that we reach a certain technical readiness level,” he said.
The spacecraft would fly past each asteroid at a distance of about 1,000 kilometers (620 miles). From here, they would be able to take images with 100 meters (330 feet) per pixel. A near-infrared spectrometer instrument could also be used to work out what the asteroids are made of.
The team estimates that the spacecraft would be able to reach the asteroid belt between Mars and Jupiter and then return to Earth within 3.2 years. That final Earth flyby would be necessary to download the 10 GB of data on board each vehicle.
Perhaps most enticingly of all, they estimate that each spacecraft would only cost $240,000 to build and launch, with the possibility of a multi-launch similar to that achieved by India earlier this year. The total cost of the mission, including research and development, comes to $72 million.