Lasers learn to accurately spot space junk

Scientists applied a set of algorithms to laser-ranging telescopes and succeeded in increasing accurate detection of the space litter in Earth’s orbit threatening spacecraft safety

American Institute of Physics

Beijing Fangshan Satellite Laser Observatory.  Credit: Beijing Fangshan Satellite Laser Observatory

Beijing Fangshan Satellite Laser Observatory. Credit: Beijing Fangshan Satellite Laser Observatory

WASHINGTON, D.C., December 24, 2019 – Chinese researchers have improved the accuracy in detecting space junk in earth’s orbit, providing a more effective way to plot safe routes for spacecraft maneuvers.

“The possibility of successfully navigating an asteroid field is approximately 3,720 to one!” exclaimed C-3PO as Han Solo directed the Millennium Falcon into an asteroid field in “Star Wars: The Empire Strikes Back.” Earth’s orbit is nowhere near as dangerous, but after more than half a century of space activity, collisions between jettisoned engines and disintegrated spacecraft have formed a planetary scrapheap that spacecraft need to evade.

Scientists have developed space junk identification systems, but it has proven tricky to pinpoint the swift, small specks of space litter. A unique set of algorithms for laser ranging telescopes, described in the Journal of Laser Applications, by AIP Publishing, has significantly improving the success rate of space debris detection.

“After improving the pointing accuracy of the telescope through a neural network, space debris with a cross sectional area of 1 meter squared and a distance of 1,500 kilometers can be detected,” said Tianming Ma, from the Chinese Academy of Surveying and Mapping, Beijing and Liaoning Technical University, Fuxin.

Laser ranging technology uses laser reflection from objects to measure their distance. But the echo signal reflected from the surface of space debris is very weak, reducing the accuracy. Previous methods improved laser ranging pinpointing of debris but only to a 1-kilometer level.

Application of neural networks – algorithms modeled on the human brain’s sensory inputs, processing and output levels – to laser ranging technologies has been proposed previously. However, Ma’s study is the first time a neural network has significantly improved the pointing accuracy of a laser-ranging telescope.

Ma and colleagues trained a back propagation neural network to recognize space debris using two correcting algorithms. The Genetic Algorithm and Levenberg-Marquardt optimized the neural network’s thresholds for recognition of space debris, ensuring the network wasn’t too sensitive and could be trained on localized areas of space. The team demonstrated the improved accuracy by testing against three traditional methods at the Beijing Fangshen laser range telescope station.

The observation data of 95 stars was used to solve the algorithm coefficients from each method, and the accuracy of detecting 22 other stars was assessed. The new pointing correction algorithms proved the most accurate, as well as easy to operate with good real-time performance.

Ma aims to further refine the method. “Obtaining the precise orbit of space debris can provide effective help for the safe operation of spacecraft in orbit.”


The article, “Research on Pointing Correction Algorithm of Laser Ranging Telescope Oriented to Space Debris,” is authored by Tianming Ma, Chunmei Zhao and Zhengbin He. The article will appear in the Journal of Laser Applications on Dec. 24, 2019 (DOI: 10.2351/1.5110748). After that date, it can be accessed at

From EurekAlert!

46 thoughts on “Lasers learn to accurately spot space junk

  1. … space debris with a cross sectional area of 1 meter squared and a distance of 1,500 kilometers can be detected …

    How about a satellite with an area of one square meter can be detected at a range of 1500 km.

    Am I being too cynical?

      • I think Bob’s point is that chinese want to know about the position of US military satellites, which probably are not included in the NASA public tracking data. The principal motivation here is not space junk.

        1m^2 target size is not much help if you are wanting to avoid space junk but may be very relevant if another world power has just decided to militarize space.

        Remember the very public stunt of knocking out one of their old weather satellites ? The message is clear. They are not going to sit back and be sitting space ducks.

        Bob is correct, this is not about space junk.

        • “Remember the very public stunt of knocking out one of their old weather satellites ? The message is clear. They are not going to sit back and be sitting space ducks.”

          Which is why Trump just created the U.S.Space Force.

        • We, includes both the Chinese and the Russians.
          They tracked them being launched and have tracked them while they are in orbit.

      • Satellite position knowledge includes uncertainty at the time of a particular measurement and that uncertainty grows until the next measurement. Generally, satellite position knowledge is not as accurate as you seem to think.

        Debris and/or dead satellite position knowledge is generally less accurate due to the less frequent updates and the problems with tumbling / uncontrolled movements impacting position detection and the smaller size of most debris. Anything larger than a “BB” is of concern to satellite operators.

          • It’s a more accurate measurement, generally at the cm to even mm level (1-sigma) on on a per pulse basis (range), and with multiple shots cm level orbit. The beam width errors (ten or tens of meters) are improved with lots of measurements and the orbit model updated each time the object is tracked, although at low Earth orbits gravity anomalies cause other movements.

            Long ago, I used to build systems to do this for geophysics purposes.

      • Not every bit of new tech/science with explicit military consequences is kept secret. Intimidation is important too. Bragging rights to the plebs is also crucial for totalitarian regimes.

  2. So is a manhole cover orbiting this planet?
    Was flipping channels,hit something called strange evidence?
    And the host was talking about a pre Sputnik American Underground Atomic bomb test,that put the access cover into orbit.
    If true another factoid of the facts are stranger than fiction type.

    • The Chinese have been accused of working on it, but not, I think, with lasers. Just using traditional projectiles to knock out US military satellites.

      • before launching a projectile you need to know position AND trajectory. Two of the stated aims in this project.

        Even passive militarization of space would make this a necessity for another world power, the recent declaration by Trump for official funding and creation of a military “Space Force” makes it even more essential.

        Oh well , demilitarization of space was nice while it lasted….

      • “The Chinese have been accused of working on it, but not, I think, with lasers. Just using traditional projectiles to knock out US military satellites.”

        Try reading again, this was about laser range finding , not laser weapons !

        • Greg, I was addressing markl’s question, which appeared to asking about using lasers as weapons to cause physical damage, not locating of satellites.

  3. Various plans are afoot by the likes of Google and Amazon to put unto 40,000 satellites in low earth orbit to allow better coverage for internet access and streaming “services”.

  4. Oh yeah, let’s applaud the Chinese both the crap that they are tracking up there and the technology from the West they stole to make it happen.
    The Chinese created a crap load of the debris up there with their irresponsible ASAT test in January 2007.

    To wit:

    “On January 11, 2007, China conducted an anti-satellite missile test. A Chinese weather satellite—the FY-1C polar orbit satellite of the Fengyun series, at an altitude of 865 kilometres (537 mi), with a mass of 750 kg[1]—was destroyed by a kinetic kill vehicle traveling with a speed of 8 km/s in the opposite direction (see Head-on engagement). It was launched with a multistage solid-fuel missile from Xichang Satellite Launch Center or nearby.”

    “This event was the largest recorded creation of space debris in history with more than 2,000 pieces of trackable size (golf ball size and larger) officially cataloged in the immediate aftermath, and an estimated 150,000 debris particles.[24][25] As of October 2016, a total of 3,438 pieces of debris had been detected, with 571 decayed and 2,867 still in orbit nine years after the incident.

    More than half of the tracked debris orbits the Earth with a mean altitude above 850 kilometres (530 mi), so they would likely remain in orbit for decades or centuries. Based on 2009 and 2013 calculations of solar flux, the NASA Orbital Debris Program Office estimated that around 30% of the larger-than-10 centimetres (3.9 in) debris would still be in orbit in 2035.

    In April 2011, debris from the Chinese test passed 6 km away from the International Space Station.

    As of April 2019, 3,000 of the 10,000 pieces of space debris routinely tracked by the US Military as a threat to the International Space Station were known to have originated from the 2007 satellite shoot down.

    Nearly 1/3 of junk that is threat today to LEO satellites and manned platforms is from that Chinese irresponsible ASAT test 13 years ago.
    Exactly like global CO2 emissions (if we want to believe they are problem), when will the baizuo western liberal-socialists wake up to the real threat?

    Climate leaders my butt.

    • Before anyone points out that the US also destroyed a satellite in orbit, that satellite was hours/days from re-entry when it was destroyed. All of the debris from the collision entered the atmosphere within days of the impact.

  5. If they feel compelled to blow up a satellite to show their tech prowess, they should be able to track their mess afterwards. Now for that Kevlar catcher’s mitt to help collect it.

    • They need to protect their satellites from their own killer sats debris. Don’t expect this information would be shared to other nations in a crisis.

    • Instead of breaking a piece if space junk into many fragments that are each as hazardous as the original whole piece, how about dispensing a cloud of gas in front of the piece of junk? The projectile that spews out the gas would be lobbed into a sub-orbital ballistic trajectory so that it will not become space junk itself. When the junk plows into the cloud of gas it will be slowed enough to spiral in toward the Earth, re-enter the atmosphere , and burn up. The gas cloud would dissipate rapidly, so it would not be a hazard to desired orbital objects.


      • Sounds great… until you start doing real calculations. Calculations to determine how long the debris moving at 7.8 km/sec would have to experience drag, and the amount of drag possible, a drag dependent on gas density. What the delta-v would be from that one pass. All that leads to a very very large amount of gas dispersed across a very wide path (thousands of kilometers long, a hundred or so kilometers wide, tens of kilometers thick).

        On the ground-side, such a gas release would create quite a spectacular ground show in the sky.

  6. Headline says lasers can learn. Scary thought, especially for us carbon based, carbon footprinted life forms. We would make interesting targets.

  7. Lasers in space could be used to deorbit debris in low-Earth orbit, so improving the targeting would help that type of enterprise.

    But I agree with others here that this is probably more about anti-satellite developments than about safe travel to orbit.

      • re: “German government has published some useful info on this topic…”

        Are the citizens living near the ground station to be issued laser safety goggles to be used during periods of laser operation?

  8. “Scientists applied a set of algorithms to laser-ranging telescopes”

    Sooo, lasers didn’t “learn” anything.

  9. Here are some interesting facts about orbital debris from the December 2019 issue of Astronomy magazine:

    Space debris can travel up to 17,500 mph (28,100 kph)

    Since the start of the space age in 1957, humans have placed nearly 9,000 satellites in Earth orbit as of January 2019. Of those, more than 5,000 are still in orbit and 1,950 are still functioning.

    The rest are space debris and pose a risk for collisions with functioning satellites or even crewed spacecraft.

    The European Space Agency estimates there are nearly 130 million pieces of debris larger than 0.04 inch (1mm) in orbit today.

    There are estimated to be about 34,000 objects 4 inches (10cm) or larger in orbit; about 900,000 objects 0.4 to 4 inches (1-10cm) in orbit; and about 128,000,000 objects 0.04-0.4 inch (1mm-1cm) in orbit.

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