A new hybrid technique of visual and video meteor observations was developed to provide high precision near real-time flux measurements for satellite operators from airborne platforms. A total of 33,000 Leonids. recorded on video during the 1999 Leonid storm, were watched by a team of visual observers using a video head display and an automatic counting tool. The counts reveal that the activity profile of the Leonid storm is a Lorentz profile. By assuming a radial profile for the dust trail that is also a Lorentzian, we make predictions for future encounters. If that assumption is correct, we passed 0.0003 AU deeper into the 1899 trailet than expected during the storm of 1999 and future encounters with the 1866 trailet will be less intense than. predicted elsewhere

Butow, Steven J.

Crawford, Chris

Holman, David

Houston, Jane

Jenniskens, Peter

Jobse, Klaas

Koop, Mike

Kronk, Gary

Nugent, David

NASA Technical Reports Server

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Source of Acqu i ition 
CAS l Acquired 
0 .27 
LORENTZ·SHAPED COMET DUST TRAIL CROSS SECTION 
FROM NEW HYBRID VISUAL AND VIDEO METEOR 
COUNTING TECHNIQUE - IMPLICATIONS FOR FUTURE 
LEONID STORM ENCOUNTERS 
PETER JENNISKENS, CHRIS CRA WFORD1, STEVEN J. BUTOW, 
AND DAVID NUGENT 
SETI Institute, NASA/Ames Research Center, Mail Stop 239-4, Moffett Field, CA 
94035, USA; J) 2349 Sterling Creek Road, Jacksonville, OR 97530, USA 
E-mail: pjenniskens@mail.arc.nasa.gov 
MIKE KOOP, DAVID HOLMAN, AND JANE HOUSTON 
California Meteor Society, 1037 Wunderlich Drive, San Jose, CA 95129-3159, USA 
KLAAS JOBSE 
Dutch Meteor Society, Lederkarper4, 2318 NB Leiden, The Netherlands 
GARY KRONK 
American Meteor SocietY, North American Meteor Network, 1117 Troy-O'fallon Road, 
Troy, Il62294, USA 
and 
KELL Y BEATTY 
Sky & Telescope, 49 Bay State Road, Cambridge, MA 02138-1200, USA 
(Received 4 June 2000; Accepted 18 August 2000) 
Abstract. A new hybrid technique of visual and video meteor observations was 
developed to provide high precision near real-time flux measurements for satellite 
operators from airborne platforms. A total of 33,000 Leonids. recorded on video during 
the 1999 Leonid storm, were watched by a team of visual observers using a video head 
display and an automatic counting tool. The counts reveal that the activity profile of the 
Leonid storm is a Lorentz profile. By assuming a radial profile for the dust trail that is 
also a Lorentzian, we make predictions for future encounters. If that assumption is 
correct, we passed 0.0003 AU deeper into the 1899 trailet than expected during the 
storm of 1999 and future encounters with the 1866 trailet will be less intense than. 
predicted elsewhere. 
Keywords: Comet, comet: 55Pffempel-Tuttle, dust trail, flux, Leonids 1999, Lorentz 
profile, meteor, meteor storm, predictions, satellite impact hazard , observing techniques 
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https://ntrs.nasa.gov/search.jsp?R=20110022636 2019-08-30T18:07:44+00:00Z
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LORENTZ SHAPED DUST TRAIL CROSS SECTION --193 
of each viewing sess ion _ This permitted the computer to identify the 
-';'f starting and ending times of each viewing session, and detennine which 
observer was watching from what camera at all times_ Rotating the 
observer/camera pairings enabled calculation of individual observer and 
camera coefficients of perception from systematic differences in the 
. -
counts. 
Figure 1_ Observer Jane Houston with video head display_ 
During the 1999 Leonid meteor storm, ARIA flew from the UK to Israel, 
from Israel to the Azores , and from the Azores to Florida on three 
consecutive nights_ The peak of the storm occurred while enroute from 
Greece to Italy. Near--real time flux measurements were automatically 
transferred to a communication station on-board the aircraft, where the 
counts were sent to NASA/Ames Research Center bye-mail, telephone 
or direct internet access using INMARSA T satellite telephone lines. 
From NASA/ARC, the counts were further distributed to operation 
centers, such as the NASA and USAF sponsored LEOC at Marshall 
Space Flight Center and ESA's orbital debris center at ESOC, Dannstadt. 
Shortly after the mission, several observers gathered at NASA/Ames 
Research Center to view, in the same manner, the video tapes that were 
recorded by four similar intensified cameras on-board the twin "Flying 
Infrared Signature Technology Aircraft (FISTA)" . FISTA was about 150 
km north from ARIA and the bulk of meteors are independent records. 
----------
LORENTZ SHAPED DUST TRAIL CROSS SECTION 195 
These are probably the result of imperfect corrections for observer 
perception, observing conditions or other factors that affect visual 
observations. For the same reason, such features in the profiles from 
individual locations can not be trusted. In the remainder of this pap'~~ we 
will concentrate on the gross fea1Jlres of the curves that are confinUed by 
both video and visual results. 
4000 
3000 
2000 
1000 
800 
235.26 235.28 235.30 235.32 
solar longitude (2000.0) 
Figure 2. The peak of the 1999 Leonid storm. Solid points are our I-minute 
counts (no smoothing applied). Open squares are data from Arlt et al. ( 1999). 
The dashed line shows the stonn component (main peak), while the solid line is 
the best fit of all components together. 
When plotted on a logarithmic scale, as in Figure 2, it is clear that the 
slopes of the storm peak are linear and well represented by an 
exponential equation like (Jenniskens, 1995): 
-B I A - A maxI 
o 0 
ZHR = ZHR.nax 10 (1) 
From a least squares fit, we find B = 24 ± 2 per degree solar longitude 
for ZHR larger than 700. A slightly larger B = 25 ± 1 value (and ZHR.nax 
= 4,100 per hour) results when a composite of such curves is fitted to the 
--_.- --------
- ._-_.-.. - .. -. -" 1 
r --
I 
I 
I~, 
--------- _.- ------- -- - - - .-~ 
LOREN1Z SHAPED DUST TRAIL CROSS SECTION 197 
1866 and 1966 profiles - Jenniskens, 1995). And that suggests strongly 
that both components are caused by the same physical processes, with no 
intrinsic merit to make a distinction between the two components. We 
expect to be able to verify from the video record that the two 
components can not be discriminated on ground of the magnitude 
distribution index, but will take this as a task for a future paper. 
I 
234 .0 
Nov. 17 
lI-
1998 + 
1965 ~ 
1932 .. 
I 
-
235.0 
1899 
Nov. 18 
1800 
1833~ 
1866 .. 
236.0 
Nov. 19 
Figure 4. The Earth's path by debris trails ejected at various epochs du ri ng the 
return of 1999. Courtesy: David Asher, Annaugh Observatory. 
3.2. THE 1866 TRAILET 
This material is though to have been ejected in 1899 (Kondrateva and 
Reznikov, 1985; McNaught and Asher, 1999b; Lyytinen , 1999). In 
Asher's diagrams of the path of Earth through the meteor shower, 
reproduced in Figure 4, the Earth approaches dust trails from 1866, 1833 
and 1800 shortly after passing the 1899 and 1932 trails. Earlier during 
the 1998 return, we observed a peak in activity when Earth passed rather 
far from the calculated center of the 1899 debris trail (Jenniskens, 1999) 
Hence, we anticipated a second peak of activity just after solar longitude 
236.0. Based on observations from Hawaii, Japan and China, Arlt et at. 
(1999) show this second maximum peak at solar longitude 235.87 ± 
0.04. Leonid MAC observations in the night after the main peak show 
enhanced rates that appear to trace the declining branch of this 
component, showing a relatively fast decline (Figure 5). A curve with B 
= 1.6 would best fit the descending branch. However, a symmetric curve 
-'-
S 1 000 
Q) 
..... 
'" 0::: 
~ 
g 100 
:r: 
..c: 
~ 
c:: 
Q) 
N 
1 0 
LORENTZ SHAPED DUST TRAIL CROSS SECTION 199 
234 235 236 237 
solar longitude (2000.0) 
Figure 6. Possible presence of the Leonid Filament component (sol id line). 
Symbols as in Figures 2 and 5. 
3.3. THE LEONID FILAMENT? 
In prior years, another dust component called the Leonid Filament was 
responsible for fireball showers in all years from 1994 until 1998 
(Jenniskens, 1996). Its characteristic feature is the width, with B = t: 1 ± 
0.1 in all years-;a.nd its low magnitude distribution index. Jenniskens and 
Betlem (2000) predicted a return of this component at a lower level than . 
in 1998, assuming that the Filament was the accumulation of many years 
of dust ejecta. Ash~r (1999) , on the other hand, predicted no activity at 
all if the Filament was due to ejecta of the return of 1333 only. 
The 1999 profile does not show a clear broad component that is readily 
defined as the Leonid Filament. This appears to confirm Asher's 
prediction. However, Leonid MAC observations in the night prior to the 
peak night (at solar longitude 234.5) show a significant enhancement of 
rates above expected levels that may in fact be caused by the Filament. 
The expected level being a mere extrapolation of the contribution from 
the annual Leonid shower, the main and background storm peak, and the 
second 1866/1833 component (Figure 6). This is consistent with few 
----
- -----
- - ----------
LORENTZ SHAPED DUST TRAIL CROSS SECTION 201 
.s 
ns 
0:::1000 
>. 
i: 
:::s 
o 
:c 
E 
I: 
Q,) 
N 
100 
235.2 235.3 235.4 
solar longitude (2000.0) 
Figure 7. Fit of a Lorentz profile to the meteor stonn profile. In order to bring 
out the small dispersion, error bars are not shown. 
.. -
We find that data from past meteor storms show a similar good fit (Table 
I), which implies that each dust trailet itself has a Lorentzian cross 
section. This condition is necessary to account for the fact that we passed 
the dust trailets at different distances from the center in 1999, 1966 and 
1866. If the dust distribution in a trailet (index "t") follows a Lorentz 
function as a function of r = distance from trailet center, then: 
(3) 
In that case, the cross section is also Lorentzian if we pass the center of 
the trailet along the Earth's orbit in a direction X = ).,0 (now in AU, with 
roughly 2 1t AU = 360 degrees neglecting curvature of the Earth's path) 
at a distance Y = Yo (measured in a direction perpendicular to Earth's 
orbit). Because, by substituting r = Yo2 + (X-xy: 
--- - - -- ----
LORENTZ SHAPED DUST TRAIT... CROSS SECTION 203 
It is not clear, at present, what physical mechanism is responsible for 
this tail in the distribution. Lorentzian distributions are characteristic for 
damped oscillators, and perhaps a natural consequence of the orbital 
evolution in the three body system meteoroid-Sun-Jupiter-
Given the good representation in the case of the 1999 Leonid storm, we 
applied the Lorentzian fit to other shower components (Table I). We find 
that this year's shower profile is well represented with three Lorentz 
curves representing storm, 1866 peak, and Filament (Figure 8)_ 
TABLE! 
Year From I:!. C-E *)Mo **) WI2 ZHRm>x '" max 
° (AU) (0) (AU) (hr· I) (0) 
observed: 
1999 1899 -0.0007 18.4 0.018±0.001 3300±100 235.285 
1998 1899 (+0.0044)# 16.6 0.050±0.005 70±20 (235.28)# 
1966 1899 -0.0001 16.6 0.0 14±0.0003 15000±3000 235.166 
1965 1899 +0.0017 5.8 0.14±0.04 l00±50 235.40 
1969 1932 +0.0000 49.1 0.015±0.003 200±50 235.265 
1999 1866 +0.0016 19.0 0.155±0.015 130±15 235.95 
1998 1866 +0.0040 16.6 0.2±0.1 1O±10 236.0 
1866 1733 -0.0004 9.1 0.014±0.004 14000±2000 233.323 
1867 1833 -0.0002 19.9 0.014±0.007 5000±1000 233.411 
predicted: 
2000 1866 +0.0008 29.5 (0.0011) (70) 236.28 *) 
2000 1932 -0.0012 29.5 (0.0009) (207) 235 .29 *) 
2001 1866 +0.0002 40.3 (0.00053) (72) 236.46 *) 
2002 1866 +0.0000 51.1 (0.00035) (38) 236.86 *) 
2002 1966 +0.001851.1 (0.0021) (4) 235 .27 *) 
*) Minimum distance between Earth and Comet orbit, from McNaught & Asher 
(1999b) 
**) Mean anomaly of trail particles 
#) Large uncertainty because of perturbation by Earth in earlier encounter 
LORENTZ SHAPED DUST TRAIL CROSS SECTION 205 
the profiles of 1998, 1965 and the second peak of 1999 are cases of 
further out. If we plot the width versus the distance to the trailet center 
(Yo)' as calculated by McNaught and Asher (l999b), then we find-that 
Equation 5 (solid line in Figure 9) indeed does fit the result, allowing for 
at least ± 0.0001 AU uncertainl¥ "in the calculated trailet positions. The 
intrinsic width of the dust trailet is calculated at W[ = 0.00032 ± 0.00008 
AU. 
However, the fit is good only if the calculated trailet pattern (together 
making up the comet dust trail) is shifted outward by about +0.0003 AU. 
The curve in Figure 9 should center on zero. We conclude that the Earth 
crossed about 0.0003 AU deeper into _the.debris trail ejected in 1899 than 
predicted. Unfortunately, that means that the Earth will not cross quite as 
deep into the 1866 epoch trailet in 2001 and 2002. 
On top of that are two more factors that influence the peak rate in 
future years: 1) the rate of decrease of dust density away from the comet 
for a pristine trailet of 1 revolution, and 2) the decay of dust density with 
each subsequent revolution. 
Regarding the decay of dust density with subsequent revolutions, we 
assume that the dust density falls off inversely with the number of 
revolutions (N), which is expected if the spreading is mainly due to 
differences in orbital period of the particles in the dust trailet. Here, we 
ignore the fact that the peak of the particle density also shifts 
progressively along the comet orbit in time. In that case, the peak dust 
density at a given position after 1 revolution is: 
ZHR[max (1 rev.) = ZHR[max X N (7) 
Figure 10 shows the density of dust in the center of the trailet after one 
revolution, calculated from the observed peak ZHR value. This value 
was corrected to a center-of-tr"ailet value for a Lorentz distribution with 
adopted W[ = 0.00032 AU perpendicular to Earth's orbit centered on the 
trail centers calculated by McNaught and Asher (1999b), and by taking 
Equation 7 into account. Unfortunately, only one data point (the return of 
1969) is available to constrain the slope of the dashed line in Figure 10. 
All other observations fall in a rather narrow range of mean anomaly. 
Any error in the 1969 result will bear heavily on the assumed 
dependence on mean anomaly and the predictions that follow from it. 
LORENTZ SHAPED DUST TRAn.. CROSS SECTION 207 
4.1. FUTURE OBSERVATIONS 
The video record of the 1999 Leonid meteor storm is a treasure trove of 
information that can be further analyzed. Unlike the hybrid visual-video 
observation technique, such in-depth analysis is time consuming. Some 
preliminary results are presented tn Gural and Jenniskens (2000). 
After full analysis of the 1999 shower, the big unknown will still be the 
dispersion perpendicular to Earth's path and the exact position of the dust 
trail center. Only the year 2000 encounter can shed light on this. The - -
predicted distances to the trailet centers are small enough to get 
significant increased rates and recognize the component from other 
shower components. Also, the distance to the trailet center is not as small 
as in 2001 and 2002, when we are on the steep slope of the Lorentz 
profile. Small natural shifts in the trail center can cause great variations 
in rates that are can not easily be interpreted in terms of the width of the 
dust trail perpendicular to the Earth's path. On the other hand, while the 
year 2000 provides a 2-dimensional picture of what is now only a 1-
dimensional view of dust trails, the years 2001 and 2002 will provide a 
three dimensional perspective by providing important clues to how 
quickly the dust density falls off away from the comet position. 
The method described in this paper promises a detailed picture of the 
dust density in comet dust trailets by combining theory and observations 
of future Leonid showers . Observations in future years will test the 
assumptions that go into the model, such as the cylindrical geometry and 
the position of the trail. Each future encounter will be a strong test for 
refining the theoretical multi-trailet model of comet dust trails . 
Acknowledgements 
We thank ESA's Michael Schmidhuber for assisting in the "flux 
measurement team" and Morris Jones and Pete Gural who assisted in the 
visual examination of the FIST A tapes after the flight. The flux 
measurements in the Leonid MAC 1999 mission were supported by 
grants from USAF/XOR and the NASA Planetary Astronomy and 
Suborbital MITM programs. Editorial handling: Noah Brosch. 


Lorentz-Shaped Comet Dust Trail Cross Section from New Hybrid Visual and Video Meteor Counting Technique - Implications for Future Leonid Storm Encounters

Lorentz-Shaped Comet Dust Trail Cross Section from New Hybrid Visual and Video Meteor Counting Technique - Implications for Future Leonid Storm Encounters

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