In the clear night sky, you can find a random falling star or even a glimpse of a fast-moving International Space Station as it orbits the Earth.
But there are many other objects there, including the massive new Japanese X-ray telescope called Hitomi, which was parted a few weeks ago, and hundreds of small four-inch cuboid satellites (“Cubesat satellites”) that are increasingly filling the orbital site.
Currently, a group of astrophysicist researchers say they can track bits of broken satellites and space debris using regular optical telescopes to record flashes of sunlight that is reflected from these wandering probes. This week, they observed several large pieces of Hitomi as they fall uncontrollably into space.
“As these debris fly in the sky, they blink when sunlight reflects on them,” said Aroh Barjatya, an associate professor at the Engineering Physics Department of Aviation University Embry-Riddle in Daytona Beach, Florida. "Using photometry, we wrote a piece of code that centers and measures the brightness of an object. When you look at a controlled satellite, the light curve behaves in a known way. When you look at Hitomi, it does up and down tumbling. It has a rotation speed." The team shot a single-piece video of Hitomi blinking like a star with a high-speed camera mounted on a telescope, and this is a video of Hitomi’s main body.
“It’s as if the mirror were rotating in space,” said Forrest Hasdia, a graduate student at Embry-Riddle, who made observations this month.
Barjatya said their group’s observatory specializes in tracking small Cubesat satellites — many of them are low-cost, short-lived probes launched by university researchers that may fall out of sight of the Pentagon’s space tracking system.
“There are hundreds of universities running them every year,” said Barjatya. "We have potentially introduced a lot of objects rotating in orbit in the sky, many of them can disintegrate and destroy other satellites. This has not happened yet. But how we put it where there is such a possibility."
Barjatya says half of the Cubesat satellites have lost contact with their operators. With an advanced optical tracking system, he hopes to provide more information about their fate.
The Pentagon’s Joint Space Operations Center (JSpOC) at Vandenberg Air Force Base currently tracks 23,000 objects in space using radar and optical cameras. Their positions are posted on this site every day.
JSpOC spokesman Captain Nick Mercurio agreed that the space above the Earth’s surface is getting tighter. Every day, more than 3000 automatic messages are sent to satellite operators about drifting debris or other satellites that may be dangerous. JSpOC is currently tracking 11 separate parts of Hitomi since its collapse on March 26, Mercurio said he made five notifications, warning other spacecraft operators that these bits are approaching existing satellites. In 2015, about 150 satellites had to be moved from their orbit to avoid colliding with something else. Astronauts aboard the ISS had to increase their orbit four times last year to avoid trouble.
“The Earth’s low orbit is overloaded,” Mercuio said. "The bodies move at a speed of 17,500 miles per hour, and this can be dangerous. A two-centimeter bearing ball has the same effect (energy) as a Jeep Wrangler, moving at a speed of 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 light reflected from space debris to determine the type of material: is it a solar panel, a piece of Teflon, aluminum or other metal .