The solar system is rife with space rocks that never became planets, many of them orbiting between Mars and Jupiter in the asteroid belt. Scientists have been able to examine a few asteroids close up, and the OSIRIS-REx mission will soon grab a sample from one asteroid and return it to Earth. However, it would take ages to get a full overview of the wide variety of asteroids by visiting one at a time. A team of scientists from the Finnish Meteorological Institute (FMI) has presented a plan to study dozens of asteroids with a fleet of nanoprobes.
All current robotic deep space missions rely on large, high-power probes that carry a lot of instrumentation. The so-called Asteroid Touring Nanosat Fleet would be composed of 50 small probes, each one with a limited suite of instruments. While they might not gather as much data as a larger probe, researchers would get readings from a wide range of targets in a single mission. Mission designers estimate the nanoprobes would be able to perform flybys of around 300 objects in the asteroid belt before returning to Earth. Yes, they would actually have to come back, too. The small, lightweight design allows only for a small antenna that can’t transmit data from such extreme distances.
The individual probes are expected to weigh in at about 11 pounds (5 kilograms). They would be equipped with a 4-centimeter telescope for optical imaging and a spectrometer to analyze the chemical composition of target asteroids. When passing within 62.1 miles (100 kilometers) of an object, the telescope should be able to resolve about 100 meters per pixel. That’s not amazing, but it’s better than we can do on Earth. We could determine the asteroid’s overall shape, if there are craters, and whether there are any “moons.” The spectrometer could also tell us if there is water present on the surface.
These probes need to be small and light because they’re not powered by conventional rocket engines. The FMI devised an electronic solar sail or “E-sail” that would propel the probes (see above). The spacecraft comes in two parts; there’s a main unit and a remote module connected by a 12.4-mile (20-kilometer) electrically charged tether. As ions are swept out from the sun by the solar wind, they hit the tether and generate a small amount of thrust — enough to push the tiny, lightweight nanoprobes along. The entire contraption rotates, and changing the angle of rotation can alter the direction of thrust.
The FMI claims the entire project could be launched for around $72 million, significantly less than the $1 billion or more other deep space missions cost. The team plans laboratory and orbital CubeSat testing to confirm its E-sail technology works. FMI is still looking for a space agency partner to make this happen, but it’s a fascinating proposal.
