Watching a Spacecraft Wreck Tumble Through Space
Astronomers are developing a ground-based technique to spy the light glinting off orbiting satellites, dead spacecraft, cubesats and space junk to help safeguard low-Earth orbit.
On a clear night sky, you might spot an occasional shooting star or even glimpse the fast-moving International Space Station as it circles the Earth.
But there are a lot of other objects up there too, including a massive new Japanese x-ray telescope called Hitomi that broke up a few weeks ago, and hundreds of tiny four-inch cube-shaped satellites ("cubesats") that are filling an ever more crowded orbital playground.
Now a group of astrophysical researchers say they can track bits of broken satellites and space junk using regular optical telescopes to record flashes of sunlight that reflect off these wandering probes. This week, they have been watching several big chunks of Hitomi as they tumble uncontrollably through space.
"As these things are going across the sky, they flash as the sunlight reflects on them," said Aroh Barjatya, associate professor of engineering physics at Embry-Riddle Aeronautical University in Daytona Beach, Fla. "Using photometry, we wrote a piece of code that centers them and measures the brightness of the object. When you are looking at controlled satellite, the brightness curve behaves in a known way. When you look at Hitomi, it's tumbling up and down. It has spin rate."
"It's as if a mirror were spinning in space," said Forrest Gasdia, a graduate student at Embry-Riddle, who made the observations this month.
Barjatya said the group's observatory is specializing in tracking small cubesats -- many of them inexpensive, short-lived probes launched by university researchers that might fall through the cracks of the Pentagon's space junk tracking system.
"There are hundreds of universities launching them each year," Barjatya said. "We are potentially putting a lot of orbiting objects in the sky, many can breakup and fail and destroy other satellites. It hasn't happened. But as we put more and more up there, there is that possibility."
Barjatya says that half of the cubesats have lost contact with their operators. With a better optical tracking system, he hopes that provide more information about their fate.
The Pentagon's Joint Space Operations Center at Vandenberg Air Force Base is currently tracking 23,000 objects in space using radar and optical cameras. Their position are posted on this website each day.
JSpOC spokesman Capt. Nick Mercurio agreed that the space above Earth is getting more crowded. Every day, more than 3,000 automated messages are sent out to satellite operators about drifting debris or other satellites that may pose a risk. JSpOC is currently tracking 11 separate pieces of Hitomi since its breakup on March 26, Mercurio said, and has made five notifications warning other spacecraft operators that these bits are getting close to existing satellites.
In 2015, nearly 150 satellites had to be moved from their orbit to avoid colliding with something else. Astronauts aboard the ISS had to boost its orbit four times last year to avoid trouble.
"Low earth orbit is congested," Mercurio said. "Things are moving at 17,500 miles per hour and it can get dangerous. A two-centimeter ball bearing has same impact (energy of a) Jeep Wrangler driving at 70 miles per hour."
The Embry-Riddle team says they hope to improve their imaging capabilities with spectroscopic cameras that will be able to analyze the light reflecting off the space debris to determine whether it's a solar panel, piece of Teflon, aluminum or other kind of metal.
Artist's impression of the Japanese Hitomi spacecraft (left) and ground-based observation of the damaged spacecraft in orbit.
The world's newest satellite launch site is off to a busy start, with 16 spacecraft put into orbit within a week -- and no rocket required. What’s the trick? Well, the launch site itself is in space. The satellites -- tiny Earth-imagers owned by Silicon Valley startup Planet Labs -- were deployed into orbit over the past week from aboard the International Space Station.
Read on to see stunning orbital photographs of one of the launches.
Planet Labs is the first customer to make use of a new small satellite launcher owned by NanoRacks, another commercial space firm. NanoRacks' so-called "cubesat deployer" (photographed here in action) was flown to the station last month and installed in Japan’s Kibo laboratory. The module includes an exposed back porch, accessible via a small airlock and robotic arm. Japan also operates its own cubesat launcher on Kibo.
Planet Labs’ satellites are part of a planned 28-member network of tiny spacecraft equipped with cameras to continuously image Earth.
Like the station, the Planet Labs constellation, known as Flock 1, will fly in orbits inclined about 52 degrees above and below the equator. They will be lower than the station’s 250-mile altitude to prevent any potential collisions.