Geoff FordenHangzhou Light Show

Something interesting apparently happened last Wednesday (7/7/2010) in the skies over Hangzhou, China. As regular Wonk-readers will quickly agree, trying to extract reliable information from regular media reports is difficult at best. Unfortunately, almost all the news reports of this incident that I have seen of it have something like “…UFO over Hangzhou…” in the title. That makes it even harder to believe the reports. It doesn’t help that some of the pictures seem inconsistent with each other. (Editors seem to believe that UFOs in the title means you can photoshop the photos as you like.)

Some of the most interesting photos remind me of the images of the reentry of the Japanese Hayabusa spacecraft. Here, the break-up of the object appears behind buildings reportedly in Hangzhou has a tremendously large apparent angle, making it very, very close to the city of Hangzhou. Too close, in my view, to be credible. ( See here for a discussion of “apparent angle.”) I believe these are photoshopped and I am ignoring them. (I freely admit it could be a mistake to dismiss these images but they just don’t seem credible even if they are extremely well done if photoshopped.)

Instead, let us consider some of the most obvious causes of what appears to have been seen. First, NASA does not list any satellite decays—a satellite reentering the Earth’s atmosphere after being in an established orbit—for that day, nor were there any predictions for satellites even near that date. So it is highly unlikely that the “UFO” was a reentering satellite. Furthermore, there were no satellites put into orbit that day so we can eliminate a lower stage reentering.

A DF-21?

The most credible image shows an arc streaking across the sky soon after (near?) local sunset. Assuming this is actually the “UFO” and that it really was taken at Hangzhou, then we can say some interesting things about its trajectory. First, it appears in the Northwest and the end of the trajectory (in this image) is roughly due North. Let’s make that a little more quantitative. At sunset (which happened at Hangzhou that day at 11:00 GMT), the Sun had an azimuth of approximately 300 degrees and remained in that approximate azimuth for a considerable time after setting; though, of course, its elevation continued to go negative. Therefore, the image—assuming it was not zoomed and that it was a typical cell phone camera—shows the end of the trajectory having an azimuth of at least 350 degrees. (That’s 10 degrees West of North.) The peak of the trajectory appears at an azimuth of about 335 degrees. I would say there is about a +/- 5 degree error in my heading estimates, depending mainly on where the Sun really is in the image. Of course, that does not have to be the actual point where the trajectory had its highest altitude. It could simply be the highest point on the apparent trajectory: the curve of the Earth’s surface and the angle the trajectory makes relative to the observer could make a different point appear to have the highest elevation in the image.

click on the image for a larger version

The red line represents the reconstructed line of sight for the “end” of the trajectory while the yellow line represents the reconstructed line of sight for the “peak” of the trajectory. The white line is the ground track for a hypothetical DF-21 trajectory.

The image above shows these reconstructed observation angles from Hangzhou; the red line represents the reconstructed line of sight for the “end” of the trajectory while the yellow line represents the reconstructed line of sight for the “peak” of the trajectory. I have added another line running roughly East to West from the Jiuquan Satellite Launch Center with a length of 1,800 km, roughly the range of a DF-21. Amazingly (perhaps an amazing coincidence) the halfway point of that trajectory corresponds roughly to the angle on which the apparent trajectory reaches its maximum. This peak appears to be about 25 degrees above the horizon in the image of the trajectory. Is that possible for a hypothetical trajectory so far away (~1,400 km) from the camera?

The apparent elevation of the peak of such a hypothetical DF-21 trajectory as seen from Hangzhou can be calculated from a simple geometric relationship as about 17 degrees. That is really amazingly close to the “observed” 25 degrees considering all the simplifications in the calculation I have introduced to make a quick calculation! So we certainly cannot rule out this possibility on geometric grounds alone.

Problems with a DF-21 Hypothesis

The major problem with a DF-21 hypothesis is that the peak of the trajectory occurs nearly 600 km above the Earth’s surface! So the arc we see in the image cannot be the trail produced by reentry heating. Perhaps we should rule a DF-21 launched from Jiuquan out on those grounds alone. But it is possible that continued discharge after burnout from the DF-21’s solid-propellant second-stage motor could be illuminated by the Sun if there was just the right geometry. Any other missile trajectory has to have the reentry much, much closer to Hangzhou. That creates lots of range safety issues and presumably are ruled out. (An errant missile trajectory would never have been allowed to get so close to such a large population center. All missiles, even SCUD combat missiles, have a self-destruct charge on board to prevent such large discrepancies from the planned flight path.)

So it seems to me that a DF-21 launch somewhere near Jiuquan and aimed at a point somewhere in the eastern Gobi desert is the most likely cause of this “UFO” even given the problem of illuminating the solid-motor discharge above the Earth’s atmosphere. Unfortunately, I doubt that we will learn anything new about the DF-21 from this image, given the uncertainty of where it took off, its heading, and its range.

A General Disclaimer

I have made a tremendous number of approximations and simplifications in this analysis in order to get a feeling for this event. Many of you will object to those and say more care should have been taken. I agree with you in principle but think such accuracy is unwarranted at this time considering the tremendous amount of uncertainty in judging which pictures are accurate and even what basic timing data to believe. Let me emphasize once again that this analysis assumes that the image at the top of this post is what caused the alarm in Hangzhou. I have no idea if that is the case. If some of the images I have discarded are really images of the phenomena, than this analysis’s assumptions are wrong at the start.

It is always hard to use media reports for quantitative analysis but particularly so for anything with UFO in the title. It seems that editors see that as a license for any kind of photoshopping they like. So, until better information is available, I think the most likely explanation is a DF-21.

Editor’s Note: Don’t even think about making a comment suggesting it was a real UFO, those comments will not get approved. This is a serious blog and is not interested in UFO theories. Get your own blog if you want to discuss that sort of thing.

Update (7/15/10)
The embedded video below shows both how difficult it is to get quantitative information off of the internet about “UFO” events and is a great example of a rocket plume in outer space. As an added bonus, there is a staging event at about 30 seconds. By the way, this is almost certainly a Progress-M launch from Biakonur.

Update (7/19/10) The video I posted above (which has at least temporarily disappeared during our move to this new format) has been picked up by <a href=,0,4283795.story > the LA Times with the wrong attribution: </a> The LA Times is attributing it to the Hangzhou incident.  Oh well, it just goes to show how hard it is to straighten anything out once it makes the internet.  However, I hope the editors of the LA Times look here (and perhaps try harder to check the provenance of the videos they find on Youtube.)


  1. Tom (History)

    Elsewhere, the “ufo” was reported to be traveling from East to West across the sky. One of the commenters at Information Dissemination ( pointed out that if this were true then the object could be the upper stage of an Israeli launch vehicle reentering, since they have to launch to the West out over the Med.

    An intel satellite that the Israelis launched last month apparently also has a ground track near to Hangzhou at the right time (again, from Info. Diss.).

  2. Allen Thomson (History)

    Any chance it was going in the opposite direction? If so, could you get it to go the vicinity of 40.45 N, 93.50 E ?

    BTW, Google Earth seems to have come down with a case of screwed-upedness. One trusts they’ll get it fixed sooner rather than later.

  3. Mike

    What about the Proton-M launch with EchoStar 15 on July 10, 2010 at 18:40Z. More information here:;all
    and here

  4. jim oberg (History)

    Since such reports really do often have clues about activities of interest such as the antimissile test in january’ i’ve been paying a lot of attention to this story. NONE of the photos seem to have any authentic connection to the event, which appears to have been sparked by an approaching aircrew seeing a bright twinkling light ‘above’ the runway. ATC could not locate it on radar and prudently waved off landing flights for a little while. Based on the runway alignment and the celestial sphere at the time, the most plausible explanation to me is just another typical pilot misperception of Venus — they actually do that a lot, the last famous airport case was Barnaul, Siberia, in 2001.

  5. Rwendland (History)

    I’ve looked at the theory it was the Shavit upper stage that launched OFEQ 9, by examining the orbit data at

    OFEQ 9 passed in visible range at 20:31, but on a bearing of about 250 degrees – about 140 km SSE of Hangzhou Xiaoshan International Airport.

    This newspaper says claims the event took place “around 9 pm” (13:00 GMT), which is at variance with your 11:00 GMT estimate.

    So while the timing and distance is maybe plausible for an upper stage dropping from that orbit, the trajectory does not match your estimate from sun angle. So this is looking unlikely.

    For the record, observation data for Hangzhou (30.2550°N, 120.1690°E) China Standard Time (GMT + 8:00) says OFEQ 9 was observable three times that evening:

    Date Starts Max-Altitude Ends

    07 Jul 20:29:17 10 ENE 20:32:05 62 SSE 20:34:45 10 WSW
    07 Jul 21:58:35 10 NE 22:01:19 31 NNW 22:03:51 10 WNW
    07 Jul 23:27:42 10 NE 23:30:13 21 N 23:32:35 10 NW

    The later two orbits were further to the north, at approx bearings 260 and 270 degrees, approx distances 600 km and 1000 km to the north.

  6. Rwendland (History)

    Geoffrey, this China Daily article gives more precise times, making it about 12:30 GMT (+- 5 mins I’d guess) for the event. Also competent observers report the object to be more like high flying object than a re-entry:

    “A staff member at Xiaoshan Airport in Hangzhou said a twinkling object was first spotted over the city’s sky around 8:30 pm on Wednesday. However, the object did not show up on the airport’s radar.

    Xiaoshan Airport was then closed at 8:45 pm over security concerns, and only resumed operation at 9:41 pm.”

    The twinkling object could have been a light below the horizon reflecting on an airplane flying very high, given good visibility in the sky, said Zhu Dayi, who works at the Shanghai Observatory, adding such phenomena usually happen around an hour after sunset.

    “If the speed of the twinkling object is extremely high, it could be a military aircraft,” he said, “But no conclusion can be drawn now, as the information is limited.”

    Coincidentally the event was to the minute when OFEQ 9 was nearly overhead, so it probably had an excellent view! Not that this implies it was the OFEQ 9 upper stage, which must have been on a different orbit by then.

  7. jim oberg (History)

    but was ofeq still illuminated? serious question.

    the press report did not refer to motion across the sky — that apparently was filled-in-from-supposition material.

    a non-angular-motion celestial object that shortly set still remains an attractive hypothesis untl more original eyewitness accounts surface.

  8. jim oberg (History)

    here are some recent links, and a revised comment:

    Since such reports really do often have clues about activities of interest such as the antimissile test in january (link below) i’ve been paying a lot of attention to this story. NONE of the photos seem to have any authentic connection to the event (the June 30 .comet. video is of a Russian space rocket — too bad the reporter neglected to mention that ironclad ID). The event appears to have been sparked by an approaching aircrew seeing a bright twinkling light ‘above’ the runway. ATC could not locate it on radar and prudently waved off landing flights for a little while. Direct eyewitness testimony, and not news media garble, remains essential to obtain. But based on the runway alignment and the celestial sphere at the time, the most plausible conjecture to me is just another typical pilot astronomical misperception — they actually do that a lot, the last famous UFO closing an airport case was Barnaul, Siberia, in 2001.

    jan 2010 story

  9. Eric (History)

    Chinese aviation authorities shut down the airport for two hours. This wasn’t Venus, my God. People such as Jim posting on here have a serious problem with simple logic.

    • Martin (History)

      The airport remained open until flight controllers realized the object was in the sky above the vicinity of their airspace. Why would the Chinese military test a ballistic missile along a trajectory which took it on a course above or anywhere near a busy international airport? And more to the point, why would they not close the airport before launch?

  10. Jim Oberg (History)

    Eric, it may shake your model of the known universe, but lots of very smart people — especially pilots — often misperceive Venus and other bright celestial objects as craft in the sky. The example of the Barnaul, Siberia, airport shutdown in January 2001 is germane — a flight crew ready for takeoff noticed a very bright light at the end of the runway they had taxied onto, interpreted it (prudently) as the landing lights of an approaching plane not under ATC guidance, and held their position. The light was in precisely the position that setting Venus would have been at. The aircrew subsequently reported the ‘UFO’ had vanished (Venus has set), and took off.

    Leave the deity out of your expressions of sincerity and learn a little about human perceptual foibles, especially those of pilots, who have been shown in statistical studies to be among the WORST observers/identifiers of aerial apparitions, especially celestial objects. This may conflict with your instincts, but that’s a problem with your assumptions and your openness to real study results, not with the conjecture.

  11. Jim Oberg (History)

    The airport management decision process, as described below by an official’s on-the-record explanation, was straightforward and prudent. Observers (including aircrew) saw a light (or light — the number of the original Chinese is not clear to me) twinkling ‘above’ the airport (as viewed from their approaching aircraft), and were concerned about interference in the controlled airspace. ATC tower could not detect any a/c on radar, and so could not verify that what the observers saw was NOT somewhere overhead, so they followed prudent procedures and halted all aircraft movements through the ambiguous airspace.

    The rest is popular panic, a collection of neat-looking visuals to feed the TV audience, and general news media freak-out. Standard stuff.

    Without access to first-hand observer testimony, no conjecture can yet rise to the level of a decent testable hypothesis, but an awareness of the wide array of potential prosaic stimuli for such apparitions [and what has actually happened in the past of a similar nature, such as at Barnaul) is an important basis for sound brainstorming.

    • Jim Oberg (History)

      Here’s what I meant to append:

      “China Airport UFO”: Xiaoshan Airport Staff Interview
      Ruan Zhouchang, spokesperson, Xiaoshan Airport in Hangzhou
      [through interpretor]
      “There was an unknown object seen in the skies over the airport. So according to our regulations we had to close the airspace. Aircraft movements were suspended from 8:45 PM to 9:41 pm. “

      Reporter: “Airport staff say the first reports of the UFO came in just after 8 PM from both air traffic controllers and civilians. The object at the center of the commotion, visible as a light in the sky, was captured in this photo. It may not look like much but it does not belong to a civilian aircraft. Nor does it match the flight plan of any aircraft supposed to be operating in the area at the time. ….

      “Ruan Zhoucheng said there were few eyewitnesses because the incident occurred at night. When most staff members were not present and passengers were in the waiting hall.”

      Ruan Zhoucheng [through interpretor]: “I heard that some of the passengers whose flights just landed saw the object which appeared as glowing light[s]. It was not a normal civil aviation flight. What it actually was, no one knows.”

  12. Anthony (History)

    The video that has been circulating predates the “UFO” stories in china – it was actually the Progress M-06M launch on June 30th as seen downrange in Kazakhstan. This video – – was uploaded on the 30th, and the uploader identified it as the progress launch. All of the vids purporting it to be a UFO removed the original (Russian?) background audio.

  13. geoff (History)

    There have been a number of comments (that I have not approved because of their lack of general interest) that have pointed out the similarity between UFO and “Unidentified Flying Object.” All of these commenters seem to think they have found some sort of error in my posting and yet I am sure that they know exactly what I meant. I am sure that every one of them knows that by “real UFO” everyone understands that to mean little green men and aliens from outer space. So future word police can relax and know that they are far from the first to think that they are making a contribution by trying to impose their own concept of grammar.

  14. Dave Dickinson (History)

    Good job sleuthing this one out; we were suspicious as no good video of the object was produced, even in this age of flipcams. Most of the China images of the object looked like time exposures. The Kazakhstan vid was outstanding and reminded us of the recent STS-131 launch from Florida:

  15. ranel (History)

    just want to ask.. if

    does a rocket or missile nowadays does not create smoke? instead they made light rays downward?

  16. Galrahn (History)


    Great stuff. What if the launch came from the Xichang Satellite Launch Center. Give serious thought to doing a model, because I think you would find your answer.

  17. marius (History)

    My Girlfriend was at that time in China for a businesstrip and told me about the UFO’s and delays on the airport. She took some pics and didnt realize that she actually shot 3 of them in one picture. If anyone has interest or know where i can send it in, please send me an email to
    Not a joke and not photoshopped image!

  18. Benoit Racine (History)

    I have posted a commentary on your brilliant analysis on the Fortean Times UFO forum. I am trying to link the Hangzhu sighting – and your explanation of it – with the Urumqi sighting a week earlier (June 30, 2010). This last one could also have been a genuine sighting of the Kazakhstan rocket launch for the refueling of the International Space Station but it also could have been a Chinese DF-21 missile. This all depends of course on the exact trajectory of the Russian missile. Your opinion?

    I also write a short history of the Internet fakes that have bogged down the investigation.

    My post is on this page:

  19. Sean (History)

    The photo I saw was in the abc video here:

    have you done any analysis of those? They were more interesting to me than the video. The lights shining down are curious. Is this a photoshopped image?

    Thanks for the time you’ve put into this. It’s very interesting reading.

  20. T Crandell (History)

    Look at the mess of colliding information that Yahoo! is putting together about this piece. lol

    They mention Geoffrey’s analysis of the Kazakhstan video. Which, I agree, is most likely a photoshopped staged missle launch. But they have confused it with the still shots listed in the article.

    They finally linked to the still photos for 7/7/10 over the airport in this article, which was missing in the original run last week. ABC News reported on them. They are a series of creepy shots. Not sure what to think of them.
    The video on the bottom was the only link in the first run of this story. It was uploaded 2 1/2 years ago, and is a total piece of crap.
    Unfortunately you can’t comment on Yahoo! News.
    Sorry you got caught up in this Geoff.

  21. OcraM (History)

    “Let me emphasize once again that this analysis assumes that the image at the top of this post is what caused the alarm in Hangzhou. I have no idea if that is the case. If some of the images I have discarded are really images of the phenomena, than this analysis’s assumptions are wrong at the start.”

    Most comments touching upon this must have been disapproved, but still it’s been already pointed out that the analysis WAS done on an UNRELATED image.

    It’s a real shame, Mr. Forden, that you took so much time to analyze besides the point.

    • Benoit Racine (History)

      You wrote: “Most comments touching upon this must have been disapproved, but still it’s been already pointed out that the analysis WAS done on an UNRELATED image.”

      Pointed out by whom? Where? How? When?

  22. Jim Oberg (History)

    The problem with connecting the top photo with the airport event is the solar illumination condition. Local sunset was about 7:02 PM local time. An hour later, the sky is dark and rockets or satellites may remain sunlit, but not aircraft or their contrails. One has to ask, how would a naive observer in the city be prompted to take a photo BEFORE the UFO was reported, and even recognize that such a photo was relevant once they had heard of the report, later? If any of those images really IS from the day of the event, they were probably random tourist photos later examined for anything unusual in the sky.

    While a missile ID is a reasonable going-in conjecture (one of many), there remains no other reports of such an event on that date and time, and the observation conditions across vast stretches of China were ideal for eyewitness detection.

    We still don’t have raw eyewitness accounts of the airport event. Whether there was one light or many, what azimuth/elevation it was seen at, or whether it was moving across the sky or not, or steady or twinkling — nothing is reliably known.

    • Benoit Racine (History)

      I live in Toronto and the sky stays lit until almost 10 PM on a July night. I didn’t check the longitude of Hangzhu versus Toronto but a lit sky at 8 PM doesn’t seem so strange to my Canadian eyes.

    • Benoit Racine (History)

      I meant latitude, of course. I should have checked. Toronto: 43 degrees North. Hangzhu: 30 degrees North.

  23. Benoit Racine (History)

    I posted the following video on YouTube in order to bring a little sanity to that quagmire of falsehoods and fakes:

    • Jim Oberg (History)

      Benoit, of course twilight lasts longer in Canada in summer, since the Sun is passing just below the northern horizon. Satellites can be visible all night long. It’s one of the blessings of your geography. But don’t generalize the solar illumination conditions too far southwards.

  24. Jim Oberg (History)

    I just found this highly valuable website on Chinese (Xinjiang) ‘UFOs’ and Russian rockets. The English is awkward but the author’s knowledge of the subject is very, very helpful to this discussion:

    Xinjiang UFO phenomenon and the Russian space launch activities — July 13, 2010

    • Benoit Racine (History)

      Thank you for that link. From what I can make out, it is about the June 30, 2010 sighting of a rocket in Urumqi (Xinjiang region), China (a week before the Hangzhou incident). The author seems to be saying (correct me if I’m wrong) that it couldn’t have been an American missile fired in the Pacific (or over the Pacific, it’s not clear) and that it most certainly had to be a rocket fired from the Kazakhstan launch site, 1,255 miles away from Urumqi. The official Chinese press release about that incident does show a photo of what is “clearly” the Kazakhstan rocket – when compared to other available videos of that event (see: ).

      No mention, of course, of the possibility of a Chinese DF-21 rocket fired from the Jiuquan Satellite Launch Centre, just 631 miles away from Urumqi…

      This report also totally ignores the Hangzhou incident.

  25. Jim O (History)

    Chinese ‘official report’ released today, dismisses famous ‘light smear’ photo as aircraft unconnected with sighting, doesn’t mention other images of small lights leaving contrails, admits cluelessness about cause of original pilot report of light over airport, and displays unrelenting garble and confusion.

    In other words, no progress.

    But meanwhile, the absence of evidence for a DF-31 test launch diminishes in my view the likelihood of that suggestion. Without more specific eyewitness descriptions — appearance, motion, azimuth, etc.. — there are too many potential prosaic explanations to select from.

    Investigation: UFO seen in Xiaoshan airport is aircraft
    14:58, July 26, 2010

    Hangzhou’s UFO was definitely not aliens, experts say
    Elaine Chow in News on July 26, 2010 10:00 AM