Leonids control center monitors meteor activity

International team will provide meteor counts for satellite operators. Data summaries will be posted at LeonidsLive.com.

Nov. 16, 1999: Tucked away in a small building between the wings of a larger office and laboratory complex is the room where scientists will collect information about this week's Leonids meteor shower, and then pass it on to waiting users.

Right: An Air Force officer prepares for the coming shower at the Leonids Environment Operations Center. Links to 413x281-pixel, 30K JPG. Credit: NASA/Marshall.

It's spartan, but at least it's heated. In order to phone in their data, the team at Alert, Canada, will have to huddle inside an igloo: the metal shed where their radar equipment is located won't let them use their satellite phones.

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Their data, along with that from optical sites at balmier locations - Canary Islands, Hawaii, Key West, and Kwajalein Atoll, Central Pacific - will converge on the Leonids Environmental Operations Center.

The room looks more like a low-key stock brokerage than the focal point for the one of the most ambitious real-time meteor observation projects ever attempted. From five to ten people will be working at all times during the 90-hour period when the Leonids are expected to occur.

"We'll get continuous optical coverage except for about three hours over China," said. Dr. Jeff Anderson of NASA's Marshall Space Flight Center. He will help coordinate the operation. "We do get continuous coverage from radar at Alert, Canada."

Visit LeonidsLive.com for up-to-date data from
the Leonids Environment Operations Center

Trained observers from the U.S. Air Force and the University of Western Ontario will count the meteors themselves and use high sensitivity video cameras and software to measure the speed and direction of the fireballs down to two magnitudes fainter than the human eye can see. They will cover 7/8th of the globe, missing only a 3-hour slice of the globe over eastern Asia because of logistical and other limitations. Because of its high latitude, the radar at Alert will see over the North Pole to detect particles before they hit the atmosphere.

At the start the observers will telephone their data every hour to one of the three Optical operators at NASA/Marshall. Their data will be collated by the Science Lead into a single report that is posted to a special password-protected web site to ensure timely access by NASA, the Air Force Space Command, and about 150 users including Iridium, and Inmarsat. Iridium and Inmarsat will provide satellite-based phones for the observers to report their data.

Parents and Educators: Please visit Thursday's Classroom for lesson plans and activities related to this story.

The report will include a graph depicting the estimated mass and quantities of the meteors, plus the zenith hourly rate, or ZHR, that tells the rate at which the particles are visible from the ground.

As the meteor count picks up, the reports will become more frequent: every 30 minutes when they reach 100 per hour, and every 15 minutes when they reach 300 per hour.

"It's going to get pretty hectic," Anderson said.

What is done with the data is up to the satellite operators. NASA has been careful to stress that it is providing "situational awareness," not something comparable to a weather service. Without any instruments upstream in the Tempel-Tuttle trail - and with hundreds to thousands of kilometers of open space between any two particles in the stream - no one can predict what will happen next. All NASA can do is report sightings.

Neither can anyone predict when the shower will peak, thus forcing NASA to schedule a 90-hour watch period centered on the predicted time.

Left: The Leonids Environment Operations Center will be warm and comfy as compared to the radar site at Alert, Canada. What the team here gains in creature comforts they will pay in sweat as the Leonids count picks up and reports are compiled and issued every 15 minutes. This view is from the Network Lead's position. Links to 469x352-pixel, 43KB JPG. Credit: NASA/Marshall.

"You know where the comet is," Anderson said, "but you don't know where the tail is, you just don't have any prediction."

As the counts reach certain levels, satellite operators may decide to turn off high voltage systems that could short out if the satellite is hit by a small particle and a plasma cloud forms, or turn solar panels and sensitive optics away from the stream to reduce the chances of damage.

Satellites in geostationary orbit over the Atlantic Ocean will be closer to the center of the 1899 stream and will see about 14 times the flux expected at low altitudes (assuming a correct prediction for the time of peak flux). Satellites in geostationary orbit over the Pacific Ocean will be farther away and see even less flux. The Chandra X-ray Observatory is expected to be distant from the heaviest exposure.

The chances of getting hit are less than 1 percent, but still, "People are being cautious," Anderson said. "They don't want to upload any complex commands during this."

"The important thing is the size range that satellites are sensitive to," Anderson explained. Even small chunks of the comet will be few and far between. It's the small stuff, ranging down to 0.00005 gram - dust particles, really - that pose the greatest hazard.

They are also too small to detect, so the Leonids team will estimate their quantity based on the larger particles. The team isn't sweating the really tiny stuff, 0.000001 gram, because it has already been swept into deep space by the pressure from sunlight.

"What we're worried about encountering is the stream from the 1899 comet passage," Anderson said. "We'll be passing between the 1932 and 1899 streams, which is why we're pretty confident that we'll have a big shower."

After the shower, the room will be set up for a different operation.

"This is definitely a one-shot deal," Anderson explained. Planetary tidal forces will take the stream farther out in 2032, Tempel-Tuttle's next passage.

"It'll be 100 years before the storm comes back," Anderson said.

Heads Up! - The upcoming Leonids meteor shower (Nov. 17-18) is expected to be the biggest in decades and perhaps for the next century. While we are safe on the ground, satellite operators are concerned that even small impacts could short-circuit satellites. NASA will coordinate a team that helps track changes in the shower that could be a storm.

Leonids Live! -site of the live webcast of the 1999 Leonids

North American Meteor Network - home page

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