The Asteroid/Comet Connection's
daily news journal about
asteroids, comets, and meteors

Today's issue status: done, updated & corrected

• Perseids 2004 by Marco Langbroek
• News briefs – sample returns, FMOP discoveries + rings & rogues
• Risk monitoring

Cover: A Perseid meteor from the night of 11-12 August, ©Copyright 2004 Robert Haas, caught with a Canon T-70 with Canon 50mm optics at the Dutch Meteor Society Biddinghuizen meteor observatory. The image is sectored. A rotating shutter was moving in front of the lens, interrupting the exposure 50 times a second. This allows determining the duration of a meteor by counting sector breaks. See below for an updated report on this year's Perseid meteor shower.

Perseids 2004   by Marco Langbroek

Skywatchers all over the world, but especially in Europe, were treated to a very fine display of Perseid meteors on August 11-12. Finnish amateur meteor astronomer Esko Lyytinen had predicted an encounter with a dust trail shed by the stream's parent comet, 109P/Swift-Tuttle, during its perihelion passage of 1862. This dust trail was to be met around 2054 UTC, August 11, and the Earth did indeed meet it.

Data gathered by the International Meteor Organization (IMO) show that rates briefly soared to ZHR values of 175-200 around 2100 UTC on the 11th. The peak was not too intense, consisted mostly of faint meteors, and was much wider than anticipated. Its visibility suffered from twilight and low radiant altitude for observers in northwestern Europe. Hence, many observers were not quite impressed, and some even doubted whether there had been a peak at all. Apart from the visual data gathered by the IMO, it was video observations that settled that the peak did occur. For example, it is well seen in video data obtained by one of our teams,

ZHR: Zenithal hourly rate is the number of meteors a “standard” observer would see if he or she was observing with the radiant at zenith (directly overhead) and a limiting magnitude of +6.5. As this is rarely the case, ZHR values are obtained by correcting observed rates for deviations in real limiting magnitude and radiant altitude.

(Johannink et al.) of the Dutch Meteor Society (DMS), temporarily located at Britzingen, Germany (see figure, next panel), while it is also present in video data gathered by Sirko Molau, also in Germany. The fact that the peak was not so strong, and more wide than anticipated, probably means

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that the dust trail center was located further from Earth's orbit than calculated in the models.

Much more impressed were the observers by what happened in the next few hours. Quite unanticipated, the Earth met another concentrated cloud of Swift-Tuttle's meteoroids, and this time the larger ones. For several hours spanning the transition from August 11 to August 12, rates soared again to values some 1.5 to 2 times over normal annual rates. The meteors during this apparition were unusually bright, with many seen in the magnitude 0 to -3 range. According to meteor astronomer Peter Jenniskens at the SETI institute, it may have been the the “filament,” a clump of larger particles shed during several perihelion passages of Swift-Tuttle, that have been shielded from perturbation by Jupiter and remain in a concentrated cloud. This cloud showed up prominently in 1993, and the thin 1862 dust trail was also visible in 1993. Apparently, these two clouds of meteoroids are spatially close together. In 1993, however, we passed closer to their centers than in 2004.

The annual peak of the Perseid shower, with a ZHR close to 90, was observed as usual on August 12-13. Usually the stream's highlight, this year it was outdone by the night of 11-12 August.

Marco Langbroek is a professional archaeologist and an amateur meteor astronomer active with the Dutch Meteor Society. He is published scientifically on topics as diverse as Neanderthals and comet dust trails. See also his first A/CC Perseids report, which is accompanied by links to more reports and pictures, and see the “cover” image above.

Sample returns:  The Genesis solar wind sample return capsule is planned to be caught in mid-air by helicopter as it descends by parachute over Utah on the 8th of next month, as shown with a NASA news release yesterday (see also Space.com's report). Reuters has a wire story that has the NASA contractor in charge of the helicopter operation, Vertigo, Inc. CEO Roy Haggard, saying that, “If successful, [this] will make aviation history as the first man-made object captured by aircraft as it entered Earth's atmosphere from space.” He tells A/CC that it was not him, but, as NewsFactor reports today, one of the helicopter pilots who made that statement. In fact, U.S. Air Force C-119 “flying boxcars” caught film canisters under parachutes returning from U.S. spy satellites during the 1960s and 70s (see a photo and illustrations, and a Space.com September 2000 article). Some of the people involved then, he says, are on the Vertigo team now. “The real news here is that the Genesis mission will bring back the first samples from outside lunar orbit.”

The NewsFactor article also says that, “If the midair retrieval works, NASA will be using it again soon” for the Stardust comet mission 2006 sample return. Haggard notes that this capsule is designed to parachute to the ground and an

aerial catch isn't currently planned. Indeed, the Stardust Mission page says, “Following touchdown, the SRC will be recovered by helicopter or ground vehicles.”

Rings & rogues:  The Greensboro, North Carolina News-Record says today about GTTC astronomy professor David Herrick's study of Saturn's rings that, “If a rogue asteroid heads toward Earth one day, Herrick's studies just might teach scientists how to knock it off course and save the planet.” Asked about that, he tells A/CC that “I'm not working specifically on the rogue asteroid threat, but the core of our

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computer model deals with how debris is scattered over several parameters (direction, speed, particle size) under various collision scenarios. That coding certainly could in principle be adapted to simulations of how best to pulverize an asteroid, but I suspect that those involved with such a project would prefer to start from scratch and optimize for their particular application.”

Risk monitoring 20 August

There is no risk monitoring news to report today.

Note: The European Spaceguard Central Node Priority List on the 17th showed that 2004 ME6 won't go out of view for most observers until the 16th of next month, but gave its sky uncertainty as 99999 arcseconds. The next day SCN dropped it from the list. This object, estimated at roughly 100 meters/yards wide and having very low-rated impact solutions, hasn't been reported observed since its discovery MPEC (June 27th news), when it had a 21-hour observation arc. Since the SRT and CRT tables are used by A/CC to illustrate the progress of the night-and-day cycle of observation and risk analysis, we will drop this object from the tables tomorrow.