SANTA FE, N.M. — People often think of space as a vast emptiness. That’s true on a cosmic scale, but space near Earth is full of 1,300 operating satellites, and tens of thousands of pieces from dead satellites, discarded rockets and all kinds of junk that has accumulated in orbit in the 60 years since Sputnik launched. These objects range from the size of a grapefruit to that of a school bus.
Meanwhile, traffic in the orbital region around Earth is increasing as inexpensive, lunchbox-sized satellites called CubeSats become popular for scientific experiments, communications and national security missions. Plus, a new wave of constellations of hundreds or thousands of satellites will soon launch to provide internet service worldwide.
There’s a lot of stuff whizzing around out there.
Errant space junk is a real threat. The density of objects in low Earth orbit (LEO) means that a collision could trigger a runaway chain reaction, as the resulting debris from one crash collides with other objects, creating more junk, which crashes into another satellite, or two or three, ad infinitum. It won’t take much to push us over the tipping point into disaster, not only for our satellites, but also for manned spacecraft like the International Space Station, which orbits in LEO, and for an array of satellite-dependent technologies. If space junk disrupts communications, GPS systems, weather forecasting and national security space craft, then the health of our economy and safety of our nation are at stake.
Against that backdrop, the U.S. Space Surveillance Network keeps an eye on things. The trouble is, they sometimes can’t tell one satellite from another, making it hard to predict their flight paths – or to know whom to warn of an impending crash so it can be averted.
To solve that identity crisis, Los Alamos National Laboratory has created an optical “license plate” the size of a paperback book that can be seen from Earth. That work is part of the lab’s mission as a national security laboratory, charged with finding scientific solutions to some of the world’s most complex problems, which include keeping our satellites and spacecraft safe. Dubbed the Extremely Low Resource Optical Identifier (ELROI) and still in prototype form, its solar-powered red laser flickers on and off, repeating a unique identifying pattern – the satellite’s serial number – several times a second. To see it from the ground, you view it through a camera mounted on a small, relatively inexpensive telescope with a filter that blocks all light but that particular red. Identifying the satellite is then a matter of watching the pattern and looking it up in a registration database. Problem solved.
This space-borne laser-based technology might one day travel aboard every object that goes into outer space, whether it’s a CubeSat, a multi-million-dollar satellite or a passenger-carrying spacecraft, so that ground-based observers will know exactly which satellite it is, what company or country owns it, and what orbital path it follows.
Now it’s time to see how well it works. The Los Alamos team has tested ELROI on Earth and recently delivered the first flight unit to New Mexico Tech, which installed it in a CubeSat for launch in early 2018.
After ELROI proves itself in space, the Los Alamos team plans to shrink it to the size of a postage stamp and bring the cost down below $1,000 for one suited for LEO, so it can be widely used – even, for instance, by a high-school class sending a CubeSat into LEO. (Higher-flying satellites will require an ELROI with more power, costing more, but still cheap compared to the satellite itself.)
By identifying objects in space, ELROI has the potential to help satellite operators fend off collisions, which could solve one of the biggest threats caused by space clutter. ELROI could also help reduce that clutter as space agencies and others develop technologies to snatch inoperable, defunct satellites from orbit. However, international treaties require that you know exactly what you’re grabbing and who it belongs to, and then get permission. ELROI will make that possible.
People have been using space for 60 years, and it will become ever more important as nations and corporations seek advantages over their adversaries and competitors. But we can no longer regard space as an infinite domain. The lab team’s hope is that, by developing this little optical license plate, we can grow our presence in space while making it a little less crowded.
David Palmer is an astrophysicist and the principal investigator of the Extremely Low Resource Optical Identifier (ELROI) in the Space and Remote Sensing group at Los Alamos National Laboratory.