Chasing the Meteor Storm in Mongolia

Getting used to Mongolia

That was to be the place for the astronomical event of the century? Whole window panes were missing. The single light bulb on the ceiling was dangling freely, all shades long gone. Instead of a light switch there were two pieces of metal carrying the full 220 Volts which you had to bring into contact with your bare hands. And there was no liquid water whatsoever. So this was the famous "Hotel Edelweiss", the guest quarters of Mongolia's only professional astronomical observatory "Khurel Togoot", some 11 km Southeast of the capital Ulaanbaatar. It must have been a state-of-the-art site once - back in the late 1950's and early 1960's, that is, when the socialist "brother nations" from the Comecon had donated the buildings and half a dozen telescopes to their poor Far-Eastern partner. There are a coronagraph, a Coude refractor, a Schmidt camera, meridian instruments and more - but all equipment is sitting idle now: The state cannot afford to maintain the place anymore. And the only science that's normally taking place here is geodesy, thanks to German equipment monitoring the orbit of the ERS-2 satellite.

Meteor observing, IMO-style

My best (few) meteors

Meteor observing: the pro's

(Links for readers who can't wait for the action - these
links return in the proper places below :-)

It had been evident from the first minute we had arrived here on Nov. 15, 1998, that this was a strange place. We, that was "ALEX'98", 14 amateur astronomers from all over Germany, led by Jürgen Rendtel, president of the International Meteor Organization (IMO), among us many veteran visual, photographic and video meteor observers. We were to join a similarly big professional Canadian expedition here, which in turn had teamed up with the United States Air Force. Upon our arrival at the place we were immediately shown the way to the bar and the disco - but no one ever bothered to show us even one of the astronomical instruments. (That they still exist I only learned later from a Russian-versed Canadian who had obtained brief access to some of the domes.) It was clear now that these "astronomers" would rather go for a drink or likely several more when night falls rather than ever observe. And the Edelweiss "hotel" had apparently been home recently not to visiting astronomers either but to youth groups from the city - this demonstrated by some ill-fated attempts to spray "Backstreet Boys" in latin letters onto the walls (Mongolia uses a modified Cyrillian alphabet).

Operation Meteor Storm...

Still, this unlikely place had distinct advantages over having no roof over your head at all or staying at a ger, the traditional Mongolian nomad tent. First of all there was electricity, a rare commodity outside of Ulanbaatar aka. UB, and it was even stable now (after the Canadians had blown several fuses during the past week that had mysteriously repaired themselves). This was good news for the batteries of image intensifier video cameras and VCR's our group had brought. And there was - at least during the nights - some heating available in the rooms. This was particularly good news now since we had heard about a major mass of cold air arriving shortly from Siberia. During the past 7 days it had been surprisingly mild in the Mongolian countryside, sometimes even above freezing at night - leading some to complain that "Mongolian winters are too warm". No one would say that now: We were to expect clear nights but temperatures of -20 to -25 degrees Celsius, a meteorologist from the U.S. Air Force informed us, whose forecasts - based on public and military weather pictures - were always amazingly precise.

Maj. Mike Bedard was responsible for good weather for the Canadian-American expedition that we now had joined loosely: If he couldn't guarantee clear skies, there would have been a plan B in principle, transporting everybody by helicopter into a clear spot - in the middle of nowhere in the Mongolian steppe, that is. While this option sounded nice, it probably wouldn't have worked, U.S. team members readily admit: It had been difficult enough to get the hi-tech equipment working in the warm Edelweiss rooms. What were the Canadian astronomers and U.S. military people doing here anyway? The exact beginnings of this joint meteor hunt - that has cost the Canadian and the U.S. tax payers about 1 million Canadian dollars (who paid how much is not clear) - go back to a scientific conference in Canada. It had been organized by Peter Brown, a graduate student at UWO and already a widely respected authority on meteor streams. And among the participants was Col. Pete Worden of the U.S.A.F., originally a solar astronomer who had also been involved in the BMDO's Clementine lunar orbiter mission and had made himself a name in science circles as well. Both scientists eventually agreed to join forces in getting the most accurate record of the upcoming Leonid meteor activity.

For Brown it was basic science. He had already published countless scientific papers on meteor streams and was highly regarded in this field. Like many he had tried his luck in predicting the 1998 activity level of the Leonids. Using historical observations, orbital models and the observed activity of the past few years his final statement (of Nov. 5th) was: There will be 1200 +/- 280 meteors per hour for a single visual observer under optimum conditions (the so-called Zenithal Hourly Rate or ZHR) during peak time, i.e. the evening of Nov. 17 UTC, and possibly more. This prediction fell well into the range of other estimates (that had been anywhere between 200 and 15 000 per hour). Brown's intention was to record the time profile of the Leonid activity as accurately as possible, using not only the established method of visual counting but especially video methods. Modern video cameras, combined with image intensifier tubes (i.e. night vision equipment) give you a live image of the sky (at video rate, i.e. 30 frames per second for NTSC) with a limiting magnitude around 8m. So you could record everything on tape for later detailled analysis - without the danger of being overwhelmed by very high rates that were still thought to be a distinct possibility.

Col. Worden's intentions were more of the practical kind. Since about a year before the predicted Leonid peak there had been worries among satellite operators all over the world. While there is still no hard evidence that even one satellite has ever been knocked out by a meteoroid, a probability of several in a thousand was calculated that any given working satellite in orbit could be damaged by a Leonid particle - if there would be high activity. With their high speed - 71 km/s - the Leonids were even more dangerous than ordinary interplanetary dust particles. Different approaches were taken by commercial and government operators, with some basically ignoring the possible threat and others turning their satellites into the least vulnerable positions. But the Air Force wanted to go one step further: It asked for near real-time analysis of the Leonids activity level, to aid its operations in making decisions. The Khurel Togoot team was one of three that had been dispatched by the Canadians and Americans: another visual/video group was located some 50 km to the South of Khurel Togoot (staying in gers) while a radar/visual team had gone to the Tindal AFB in Northern Australia and a Bombing Range 170 km away. All were to report the meteor rate every 15 minutes to a data center set up at Western University in Canada. It was an operation never tried before - let alone from one of the most isolated and lonely places of Earth.

Surveying the countryside: into the unknown

While the Canadians and Americans had installed and debugged their video, computer and communications equipment at the observatory, the German group had spend its first week travelling around Mongolia. Or rather, trying to gather some impressions of the two Mongolias. There is probably no other country in the world with such a sharp contrast between the one major city, Ulaanbaatar or "UB", and the remainder of the land - all 1.6 million square kilometers of it. Of the about 2.4 million inhabitants, some 700 000 live in UB while the rest is all but vanishing in the vast open spaces. With 1.5 people living on one square kilometer on average, Mongolia has one of the lowest population densities in the world (the respective value for Germany is 228/sqm!). On the other hand, Mongolia also has a livestock population of 31 million, including 14 million sheep: Long before you encounter a human in the Momgolian steppe, you're likely to find some sheep, goats, cattle, horses or yaks - or the ominous traces they've left behind in the short grass of the late fall... The landscape in this part of central Mongolia is largely rolling terrain without any trees, somewhat depressing in November maybe - but tons of it, and after the next hill more of the same. And having no streets and no cities also means having no lights: The night skies over our gers were wonderfully dark, leading some to start their meteor counts (some Taurids and sporadics).

Into the central Mongolian steppe!

To get around easily we had rented four Russian jeeps, including drivers, that brought us to the ger village of Chugun Chaan 280 km West of UB - set up only for tourists, all right, but otherwise pretty authentic. The gers were exactly the same ones used by the nomads around the country, with a powerful stove in the center - but no running water anywhere and 'toilet' facilities defying description (a good preparation for the encounter with the related, err, 'installations' at the observatory, though). The food was fine, however, one night the drivers even gave an excellent folk concert for us - and ever having gotten to the remote place between imposing rocks and next to a fancy sand dune had already been half the fun. At first the road leading out of UB had been surprisingly good, but eventually it dissolved into something more adventurous - and some of the drivers obviously felt much better driving off-road through the steppe than dodging potholes. A daytrip from Chugun Chaan to Charchorin - the old Karakorum of Chinggis Khaan's time, now mainly famous for a large monastery - had then exposed us to the full spectrum of Mongolian 'road' conditions, with jeeps getting stuck in rivers for a change.

A visit with the nomads

Karakorum

Later one of the drivers sped past a police check point what lead to a interesting chase (two policeman on a small motorbike vs. his jeep) up a steep hill overlooking Charchorin - while the driver got his license confiscated (a fact that didn't stop him continue driving) we enjoyed an extremely bright sun dog halo phenomenon. There was also the obligatory confrontation with the original nomad culture (when one ignores the nowadays almost ubiquitous solar arrays on the ger roofs): We were led to a nomad family that the travel agency is doing horse business with. While the language barriers prevented any useful communication, we did get to get to taste the (in-)famous airag (fermented mare's milk), mutton cooked with hot stones (and even more bones) in a big milk can, and other food items we still haven't identified. Maybe that's for the better... Decidedly more fun for some in the group were the close encounters with some of the family's cattle that one of us actually got to milk - vacation on a farm, Mongolian style. At this point the weather had started to turn nasty, with a snow front approaching - for the first time during the journey there would be no blues skies and brilliant sunset. But it was time to return to UB anyway, to treat those who had already fallen sick - quite a number - and to prepare for the 4-day stay at the observatory (known to us just as "the obs").

The night of the fireballs

Sometimes it pays when "the Pentagon is sending its best meteorologist" (London Free Press) to be on your astronomical field trip. It was snowing heavily in UB - where one week earlier I had seen a brilliant green flash of the setting Sun from our hotel roof - when we boarded our buses for the obs. But Maj. Mike Bedard had assured me that the system would pass and that the next four nights would be o.k. - no need for the choppers. But he had also predicted very cold air following the snow front, and indeed the temperature forecast map of CNN's Asian service had painted Siberia and our part of the world in deep blue and purple tones I had never seen before. And they were also predicting one of the harshest winters in Russia in 30 years! Now we would get an early taste of it, but then again some in the group had spent over 1000 DEM for special arctic-proof clothing. In this respect the mood was upbeat. And the first night of observations - Nov. 15 to 16 Mongolian Time = the evening of Nov. 15 UTC - lived up to expectations in that hardly any meteors were sighted. This was what everyone had predicted, and actually most also believed that there wouldn't be many meteors the next night. That would be exactly 24 hours before nodal crossing, and the general expectations were that any background activity from older Leonid particles would only start to ramp up 12 hours before the crossing. How wrong the experts could be sometimes...

Usually we would go to bed around 8 p.m. to get up again around 2 a.m. when Leo and the radiant would already have risen (the Lion's had came above the horizon almost exactly at midnight local time, which is 8 hours ahead of UTC). But tonight there was no need for an alarm clock: Those observers who had gotten up early made sure no one overslept tonight. Something totally unexpected was going on: We were literally under fire from a hail of large meteoroid particles. There was at least one meteor visible every minute - normally no big deal, but all of them were very bright. Not one was faint. This was a most unusual brightness distribution: Normally you have many more fainter than bright ones, and we would have seen the faint ones easily (the limiting magnitude was always better than +6m). But now they were all brilliant - and some strikingly so. One, for example, had about the brightness of the full moon and exploded right in the zenith: Its train (the ionized trail of atmosphere where the particle burnt up) kept on glowing for many minutes, and you could see it being distorted by the winds in the upper atmosphere. At times there would be several meteor trains visible in the sky at the same time - something exceedingly rare, as you normally have only a few significant trains during a whole night. Who cared that it was -30 degress Celsius or below?

With Leo and the radiant climbing higher and higher, the number of meteors per hour climbed, too. This was not simply due to the improving geometrical conditions: The meteor rate was really rising fast, as the IMO Analysis would later show - the peak rate wouldn't be reached until 1:30 UTC = 7:30 Mongolian time. But we were in a good spot nonetheless: A single observer in Mongolia could easily see 100 Leonids, all rather to very bright, in one hour around 6 a.m. on Nov. 17th (22:00 UTC on Nov. 16th).The ZHR at the time was around 200, according to the global analysis. As usual, there would be lulls in activity and then rapid fire from the sky, like 5 meteors within less than half a minute. Now imagine 5 meteors within a second - some optimistic models had thought that possible 24 hours from now. But would it happen after all? The models had been dead wrong about the ramping up of the background particle component we had seen so spectacularly tonight (and that the Europeans were just now starting to experience - if they had clear skies and had bothered to observe one night "early"). There was a distinct possibility now that the whole prediction business was off and that the "real" maximum the next night could be a dud. There was only one way to find out...

The colonel calls off the storm...

During the expected "maximum" night the Khurel Togoot observatory - normally a largely deserted place - was not only host to about 30 astronomers from all over the world but also a surprisingly large number of journalists apparently called there by the Americans and Canadians. Most were international correspondents based in UB, but one had actually flown in from Canada just for the night. By pure coincidence a handfull of bright meteors kept the spirits of the freezing crowd high just when Leo's head rose around midnight Mongolian time (which is 16:00 UTC on Nov. 17). But it soon became clear that there would be no replay of the stunning fireball show from 20 hours ago (that had peaked with a ZHR of roughly 340 meteors per hour near 1:30 UTC or 9:30 Mongolian time this morning, according to the IMO paper). Mainly faint meteors could be spotted now, all right (with a ZHR somewhat around 100), but there was no serious increase of the rate when the 'magical' time of nodal crossing (ca. 3:30 local time) came closer. At 2:20 Mongolian time (18:20 UTC) Col. Worden broke the bad news to the press: "We're not seeing any increase that would indicate we'll have a major storm in the next few hours," he stated and suggested that one might as well go home. "Do you have any idea what happened?" someone inquired - Worden: "No!" But let there be no mistake: Last night's "very very strong bright shower of fireballs," according to Worden, "was probably one of the more impressive fireball shows on record." For him personally "that's the most impressive thing I've ever seen in the sky."

The authors's Leonid pictures
(same link as above)

Amazingly the fireball storm - if one chooses to call that rare phenomenon that - had been a global phenomenon: It had "persisted obviously for at least 18 hours, because we have reports from across Europe and N. America, some of them visible in daylight - this is a very unusual situation," Worden summarized the first news that had reached him. A preponderance of fireballs long before nodal crossing is not exactly new, however, as Worden reminded the reporters: "1965 had a broad peak of very very bright meteors that lasted for 36 hours" - and was followed by a no-show at nodal crossing. 1966, however, had then brought a tremendous meteor storm at crossing time. For 1998 nearly all models had anticipated a profile similar to 1966, with a pronounced - although much smaller - peak at nodal crossing. Why the forecasts failed so completely is now a major mystery. It only seems clear that the big particles that the Earth had encountered well before - but not during - nodal crossing had been released by comet Tempel-Tuttle several hundred years ago. Since there were so many, Tempel-Tuttle must have experienced "a pretty major set of events" (Worden) back then. The small particles the Earth was encountering right now in contrast were young.

It's science, after all...

With this night's fresh insights into the vagaries of meteoritical science swallowed with the help of a few free beers (courtesy of the U.S. embassy) most of the press had left by 3:30 a.m., leaving behind the astronomers on the observatory who had largely missed Worden's 'official' cancellation of the show an hour earlier. There were the other members of our German IMO expedition who had mostly gathered on an isolated rock and were recording the meteor activity with an array of video cameras with image intensifiers, photographic cameras and visually. The video equipment had been deemed particularly important because it would have yielded the first-ever objective record of a meteor storm - if there had been one. The has been much debate about the actual number of meteors in the sky during the famous 1966 Leonids storm: Video would nail the number down reliably and even help re-calibrate the old visual counts (and finally prove that there were really 40 meteors per second visible then). Last night individual visual observers had seen up to 100 meteors in one hour, most of them very bright or fireballs, often leaving spectacular trains behind.

IMO at work
(same link as above)

Now still some 35 to 40 meteors could be spotted in an hour, but the fireballs were largely gone, and the ZHR was clearly down. And by the next night (18/19 Nov.) the observed meteor rate would have dropped off dramatically, to some 10 Leonids per hour. The observing logs, photographs (hopefully) and especially the roughly 100 hours of videotape from all 4 nights will be a major source for further studies, perhaps helping in the end to explain "what went wrong" or rather why everything went so differently from the expectations this year. Rather similar data material has been collected by the Canadian-U.S. expedition: Here, too, a battery of video cameras had been pointed at the sky, even from two sites (to get redundancy, plus 3D vectors for selected meteors), and visual counts had been made as well. But the highly organized effort had had that second objective well beyond basic research, of course: The visual counts as well as the data gleaned in real-time from one of the video cameras (by an experimental computer program, 'Meteorscan', as well as from someone constantly watching a monitor) were telephoned every 15 minutes to Canada.

The pro's at work
(same link as above)

A typical message going out via satellite telephone would sound like this (an actual example from the morning of Nov. 18): "Mongolia Observatory. We have counts of 11 for automated detection, 4 for TV and the human observer, limiting magnitude was 8.0, the visual observer outside was 22, and the limiting magnitude now is 6.0 - over." Canada would read back the numbers, and that would be it for the next 15 minutes - satellite time is expensive. From the Canadian center the information - now transformed to ZHR's - would eventually be passed on to the 55th Space Weather Squadron at Schriever AFB in Colorado Springs, Colorado, U.S.A., which would have warned satellite operators in case of a real storm brewing. None had been, of course, and no obvious satellite anomalies were reported either: The Mongolian experiment had mainly become a demonstration of principle. But interestingly the prolonged exposure to comparatively large meteoroids for 24 hours could in principle be as harmful to satellites as a strong but short peak of activity. The further analysis of the Mongolian tapes and data in the coming months will help to quantify this possibility - and will hopefully lead to better predictions for the 1999 Leonids (that no one dares to make right now).

Afterthoughts - and getting stuck in UB

The generally positive experience with the real-time analysis of meteor videos could one day lead to a world-wide network of automated monitoring stations - perhaps associated with an already existing network of U.S.A.F. telescopes keeping an eye on the Sun. The 1998 Leonids didn't live up to some peoples' expectations, no doubt, but they will eventually bring forward meteor science a great deal. And on an 'operational' level they have already made history. As Aviation Week & Space Technology further reports, the whole ZHR-in-real-time business with the two Mongolian sites and the Australian one was deemed a success: "Field teams in northwestern Australia and Mongolia sent radar and optical data every 15 min. to a laboratory at the University of Western Ontario. After processing, ZHR readings were forwarded to the 55th Weather Sqdn. at Schriever AFB, which provided the information to squadrons charged with controlling about 60 military satellites, including the Navstar constellation" (that provides the Global Positioning System). Staffing had been increased at the control centers, but nothing happened. The satellite controllers, at least, had 100% reason to celebrate.

Impressions of "UB"

November 19th was the day of packing up, and by nightfall most of the Khurel Togoot observers had returned to the civilization of UB, with liquid water and even WC's. A quick survey of the - few - Mongolian-language dailies for sale in the city yielded only one obvious result: a nice time-exposure of Leo with two meteors, clearly pointing back to the radiant near the Lion's neck. This picture, of course, had been taken on the now-famous morning of Nov. 17. The next day would give me the opportunity to scan the WWW from the International School of Ulaanbaatar (ISU) for 8 hours, yielding tons of articles on the Leonids from several continents. I could also use their computer - after an hour-long fight with Windows95 to get a job done that Unix accomplishes in seconds - to send a first report to various mailing lists. In exchange for so much hospitality I gave a presentation on our Leonids experience to the school's students: Many of them had been at the observatory on the night of Nov. 17/18. That was the first public talk on our expedition - and the video material premiered later that day as well, during a reception at the German embassy. Many spectacular Leonids had been captured by the cameras, including one so bright that the image intensifier was completely saturated for a second. Even more spectacular were timelapse movies of bright meteor trains.

At the Circus

People of Mongolia

This party would normally have been almost the conclusion of our Mongolian experience - but on Saturday rumors consolidated that there was a problem with the airplane that was supposed to get us back to Berlin on Nov. 22. It turned out that the Mongolian airline MIAT had only two Airbus planes capable of this journey: One was undergoing maintenance in Japan - and the other was stuck in Frankfurt where two engines had to be replaced! Incidentally, MIAT's services had broken down one week before as well, because of ice on the runway ... Before the plane finally showed up in UB on the morning of Nov. 24, there was ample time to explore more of the city, check out some of the newer restaurants (UB is far more evolved in this respect than the large Siberian cities such as Irkutsk), markets (full of fresh fruits and merchandise from around the globe) and the Mongolian State Circus. Also, another visit to the ISU allowed us to send more e-mails back to Europe. And when the plane finally took off, the 8-hour-long return to Germany was almost boringly uneventful. The journey was suddenly over, but the analysis of the data material has hardly begun. And then someone has to step forward and make a prediction where the 1999 Leonids would be seen best. All bets are off at the moment - and most Europeans have already vowed not to venture farther than the Southern Mediterranean next time...

Pictures added and text slightly updated (with new IMO results) on Dec. 11. Originally written on Nov. 27, 1998. A minor part of this story had already been typed at the International School of Ulaanbaatar on Nov. 20, 1998 - thanks a lot for the unique opportunity!