MIT’s Lincoln Lab helps speed space communication
Building a broadband connection to outer space requires something entirely sci-fi: a laser beam that can hit the moon.
Researchers from Massachusetts Institute of Technology’s Lincoln Laboratory in Lexington recently tested just such a contraption. They fired a laser from a NASA base station in White Sands, N.M., at a lunar satellite about the size of a small car some 240,000 miles from Earth and nailed it with a stream of data.
Beyond demonstrating impressive marksmanship, the test did something even more extraordinary: It sent data back to Earth at the fastest transfer speed ever recorded for deep-space communication, six times the rate of the best technology and quicker than the fastest Internet connection that most people on the planet can buy.
Currently scientists use radio communications to send information between Earth and space. But given the enormous size of the data collected — photos and video of the surface of Mars, atmospheric conditions around planets — there is a huge time lag between sending and receiving those files, akin to downloading a high-definition movie on a dial-up modem.
But new laser technology promises to close that gap, and open many new methods for scientists to conduct space exploration. The successful demonstrations with NASA showed that the space agency could get video feeds from the moon in nearly real-time, and eventually stream high-definition or 3-D video to astronauts in deep space.
“They could watch Netflix or the Super Bowl,” said Donald Cornwell, NASA’s mission manager for the laser communication demonstration. “NASA has been using radio systems to communicate with space for 50 years. Meanwhile, on the ground, we are using fiber-optics. We’d like to get in the game of broadband for space.”
NASA and MIT Lincoln Laboratory have been working together to advance planetary research by getting information to and from space much faster. That would allow scientists to gather even more complex data and photographic evidence from the surface of Mars, for example, and get it back to Earth without waiting days or weeks.
“In space, there is no high-speed system yet, so this thing is blowing the doors off other ways to transmit data,” said Thomas Bifano, director of the Photonics Center at Boston University.
The Lincoln Lab-NASA experiment, dubbed the Lunar Laser Communication Demonstration, occurred in October and November. When the moon was in a good position above New Mexico, researchers at Lincoln Lab fired the laser beam at the Lunar Atmosphere and Dust Environment Explorer satellite, orbiting some 156 miles above the surface of the moon.
Both the NASA base station in New Mexico and the lunar satellite were outfitted with sophisticated reflecting telescopes that can transmit and receive laser beams. Unlike radio waves that are transmitted with antennas, laser communication requires telescopes that can read optical frequencies. The data are transmitted in the form of light pulses that are fired hundreds of millions of times per second.
That produces enough bandwidth for the lasers to download the entire memory of the satellite’s on-board computer in about five minutes. That’s roughly 1 gigabyte in size, or enough to store about 350 songs. Using the satellite’s standard radio system, that kind of space-to-Earth download would take about three days.
When the beam starts out on Earth it is only 6 inches wide. But like a spotlight shot at the sky, the laser beam spreads as it travels and is more than 12 miles wide by the time it reaches the moon’s orbit. Even at that width, it is still a feat to get the laser beam to travel all that distance and still be close enough for a spacecraft about 8 feet tall to capture its signal.
“The technical challenge is to point your laser and hit that little dot in the sky,” said Don Boroson, who headed up the laser demonstration for Lincoln Lab.
Boroson led a team of about 60 people who have been working on the $60 million Lunar Laser Communication Demonstration for more than five years. The recent series of demonstrations with the satellite orbiting the moon was the culmination of that work, but far from the final destination for Lincoln Lab’s laser technology.
Boroson is aiming much farther — at Mars, more than 30 million miles past the moon. Boroson imagines a time in the not too distant future when spacecraft orbiting Mars — or vehicles such as a Mars rover — could beam back high-resolution photos of the planet to create something like a Google map of the Red Planet.
“If they took all those pictures and tried to send them back using radio waves, it would take decades,” he said. “With a laser, we could do it in about a year.”
The possibilities extend far beyond that, said Boroson. With this kind of technology, scientists will be able to extract all kinds of images and data from space that otherwise would be too big — or take too long — to transmit back to researchers on the ground.
“Every space scientist that I talk to wants more data,” he said. “They will come up with countless new uses for this technology.”
NASA already has plans to launch another satellite in 2017 that will be used to further test the laser capabilities for space. MIT will work with NASA on that project, as well.
To be sure, this is not the first time lasers have been used in space. Researchers in Europe demonstrated the use of lasers to transmit data between satellites more than a decade ago. And here on Earth, lasers have been used in some instances to send and receive data.
But even though laser communication is the speediest way to transmit data in space and on land, it is unlikely lasers will usurp cables for broadband on land. Lasers do not do well in bad weather, and cannot penetrate mountains and buildings. For moving data on land, wires are still the best option.
“In space, it is a wonderful thing,” said Bifano of Boston University. Earth is another story altogether. “It’s almost always cheaper to use a fiber-optic cable — and there are no weather problems to deal with.”