2007 09 01 Aurigids Results

The 2007 NASA Aurigid Multi-Instrument Aircraft Campaign (MAC)








As a member of NASA’s Global Meteor Scatter Network I was asked to monitor the 2007 theta Θ-Aurigids shower. Dr. Peter Jenniskens of NASA  was conducting an elaborate airborne observation campaign, the Aurigid MAC.  Some of my radio data results for this campaign can be found on NASA’s Ames Research Center Aurigid MAC web pages.

Why was this shower important?

The shower is produced by the debris field from the passage of  Comet Kiess, C/1911 N1, over 2000 years earlier. The comet is long period comet; it made it’s first passage of the sun around 83 B.C. and competed it’s perihelion approach in 1911. It has been classified as a potential earth impactor. There have been other outbreaks in 1935, 1986, and 1994. Jenniskens and Lyytinen (2003) and Jenniskens and Vaubaillon (2007) predicted a strong outburst in 2007 lasting only an hour and a half. A pdf of the later can be found here.

The comet originated in the Oort cloud some 4.5 billion years ago. Gravity finally perturbed it enough to set it free from the cloud and sent it in bound for an orbit around the sun.

These are the preliminary results of the Aurigids as seen from Kelowna, British Columbia, Canada.

The station for this event consisted of two receivers and two antennas. My primary station listens at 61.260 MHz and uses an ICOM PCR-1000 software driven receiver was used with a 7 element log periodic antenna pointing due south. Counting software: Spectrum Lab FFT and mAnalyzer program.

My secondary station listens a 83.260 MHz an ICOM R-8500 receiver and a no gain, omni directional discone vertical were utilized. Counting software: mAnalyzer with 10 minute splits and Spectrum Lab running in parallel. Transmitters monitored were located in Bilings, Montana, and Bend, Oregon.

Saturation and Under Counts

The primary station began showing a decrease in echo counts starting at 1050 UT and continued depressed counts for about 60 minutes there after. This decline in echo counts was due to saturation, the overlapping of over dense echoes, keeping the software timers and counting routines triggered which led to some under counting the hourly echo counts. The secondary station is much less sensitive and as was hoped for, it did not have this problem during the peak shower.

Primary frequency 61.260 MHz, channel 3 plus offset,  shows the onset of long over dense echoes beginning at 1055 UT and continuing nearly 50 minutes. The recording starts at 0141 UT, blue ticks = 1 minute, red = 1 hour. For display, the spectrogram was set up to show only the brightest echoes, those equal to or stronger than 20 dB . The software  itself recorded all strengths of echoes from 10 dB, 20 dB, 30 dB, and greater than 30 dB  bins as well as the  the duration of each bin.

Brower's Aur outbreak

A very sharp increase in strong, overdense echoes began at 1050 UT. Based on the 10 minute data from both stations, the shower peaked around 1110-1125 UT, September1, 2007.

Results were summarized in CBET 1049:

Electronic Telegram No. 1049
Central Bureau for Astronomical Telegrams
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
URL http://www.cfa.harvard.edu/iau/cbat.html

P. Jenniskens, SETI Institute, reports that observations onboard
two research aircraft over Nevada and California indicate that the
anticipated Aurigid outburst (cf. CBET 1045) from the 1-revolution
dust trail of comet C/1911 N1 (Kiess) did occur on Sept. 1 between
10h30m and 12h00m UT, with a peak at 11h15m +/- 5 minutes (the predicted
peak time was 11h33m +/- 20 min).  The peak rate was within a factor of
two of that expected.  Most meteors were in the magnitude range -2 to +3,
as anticipated.
C. Steyaert, Vereniging Voor Sterrenkunde, Belgium, writes that
several stations of the ‘Radio Meteor Observatories On Line’ collaboration
(http://radio.data.free.fr/main.php3) report high Aurigid activity on
September 1.  A. Smith, Tavistock, U.K., observing at 143.050 MHz, found the
Aurigids to be “very active with big fireballs” between Sept. 1d10h45m
and 1d12h10m UT.  J. Brower, Kelowna, B.C., Canada, observing at 61.26 MHz,
found that “heavy, overdense echoes had a sudden onset starting” during
Sept. 1d10h50m-1d11h00m and continued to be heavy for an hour.  W. Camps,
Tessenderlo, Belgium, observing at 49.990 MHz, observed the following
counts at 10-minute intervals starting:  Sept. 1d10h00m, 6; 1d10h10m, 3;
1d10h20m, 4; 1d10h30m, 2; 1d10h40m, 4; 1d10h50m, 2; 1d11h00m, 7; 1d11h10m,
4; 1d11h20m, 7; 1d11h30m, 7; 1d11h40m, 3; 1d11h50m, 3; 1d12h00m, 4;
1d12h10m, 2; 1d12h20m, 2; 1d12h30m, 1; 1d12h40m, 1; 1d12h50m, 2.
J. M. Trigo-Rodriguez, Institut de Ciencies de l’Espai and Institut
d’Estudis Espacials de Catalunya, Bellaterra (Barcelona), reports that no
signs of Aurigid activity were recorded from Catalonia, Spain, via the
all-sky CCD cameras of the Spanish Meteor Network on Sept. 1d00h30m-
1d04h30m UT.  Meteors of magnitude 3 or brighter were recorded radiating
from the Aurigid radiant, and there were no signs of fireballs from the
dust trail of comet C/1911 N1.

NOTE: These ‘Central Bureau Electronic Telegrams’ are sometimes
superseded by text appearing later in the printed IAU Circulars.

(C) Copyright 2007 CBAT
2007 September 3                 (CBET 1049)              Daniel W. E. Green


Graphs Depiction of the outbreak at West Kelowna.

61.260 MHz Primary frequency Echo Count data:


61.260 MHz Primary frequency Echo Duration data:


61.260 MHz Primary frequency Mean Echo Duration data:


83.260 MHz Secondary frequency Echo count data:


83.260 MHz Secondary frequency Duration data:


83.260 MHz Secondary frequency Mean Duration data:


Jenniskens, P., and J. Vaubaillon (2007), An Unusual Meteor Shower on 1 September 2007, Eos Trans. AGU, 88(32), doi:10.1029/2007EO320001.

Lyytinen, E., and Jenniskens (In press 2003), P. Meteor Outburst from Long-Period Comet Dust Trails. Icarus.


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