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RE: (meteorobs) Re: Leo 2001 coverage in S&T 3/2002



At 10:06 AM 2/6/02, George Gliba wrote:


>But the American Meteor Society plot of the american Leonid Shower Outburst
>today shows a peak ZHR of 2500 near 11 UT on November 18, 2001! At the time
>the March issue went to press the earlier IMO ZHR was about 1500 for the
>same time, which is much different than the AMS ZHR of 2500. No wonder S&T
>was confused. They even wrote that the experts don't agree. We should be
>asking, why are the AMS rates so much higher than the IMO?


The answer is in the caption for the figure, George:

-------------------------------------------------------
A **very** preliminary graph of the Leonid meteor shower activity curve as 
seen from Mt. Lemmon, Arizona, on Sunday, November 18, 2001:  plotting the 
Leonid shower single-observer corrected meteor rate (Zenith Hourly Rate, 
ZHR), in meteors per hour, VS. Universal Time (UTC), in quarter hour 
tick-marks. The beginning time of 0800 UTC corresponds to 1:00 AM MST 
(Mountain Standard Time) and 1300 UTC corresponds to 6:00 AM MST......

.....These mean rates were determined using a team of experienced visual 
observers:  consisting of Jure Atanakov, David Holman, Javor Kac, Tom 
Kucharski, Robert Lunsford, Ana Mancic, and Jure Zakrajsek.  All observers 
operated remote "smart-mice," which feed into a PC operated by James 
Richardson, using software developed by Morris Jones to perform real-time 
ZHR calculations from multiple observers for the NASA / AMES Leonids 
Campaign.  Further analysis of this data will be conducted by Peter 
Jenniskens and his team.
-------------------------------------------------------

This was not any sort of extensive analysis --> but a smoothed curve 
generated in real time by computer and posted on the web-site the following 
day.  It includes only the inputs from seven observers operating from a 
single location, with the personal perception factors derived from sporadic 
meteor observations made the night before.  I have left the more extensive 
analyses to the IMO, Peter Jenniskens' team, and Peter Brown's team.

The reason for the higher rates as compared to what Peter J. is posted for 
our observations now (located at: 
http://leonid.arc.nasadot gov/recent_updates1.html) is in the selection of a 
"standard observer" and in how everyone else is scaled to that observer 
(the personal perception factors).  Our Slovac team contained a few very 
high-perception observers, and I tended to be a bit conservative in scaling 
**down** their reported numbers -- thus leaving us with somewhat higher 
ZHR's than were later reported.  Based upon one night of sporadic 
observations, I made the best estimate that I could for the real-time data 
feed from Mt. Lemmon.  Later, in combining their data with the aircraft 
observations and observations from other locations, their perception 
factors were increased and their Leonid rates subsequently suppressed to 
more closely match the rest of the data.

I have been meaning to yank down that preliminary curve for a couple of 
weeks now, but have been busy with work.  I'll take it down by the end of 
the week and prevent any further confusion.

regards,

Jim

------------------------------------------------------------------------
James Richardson
Department of Planetary Sciences
Lunar and Planetary Laboratory
University of Arizona
Tucson, AZ  85721-0092

LPL email:  jrich@lpl.arizonadot edu
LPL office:  (520) 621-6960
Home office:  (520) 877-2715 or 877-2555
Cell phone:  (520) 401-9095
Home page:  http://www.lpl.arizonadot edu/~jrich/

Operations Manager
American Meteor Society (AMS)
AMS email:  richardson@amsmeteors.org
AMS webpage:  http://www.amsmeteors.org/
------------------------------------------------------------------------

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