Forward Scatter Meteor Observations of Geminids 1999
Observer: Ton Schoenmaker
E-mail: schoenmaker@nfra.nl
Location: Roden, Netherlands (06 26' E, 53 08' N)
Frequency: 55.274 MHz
Transmitter: Spanish TV channel E3 (video); transmitters in La Muela (30 kW),
Gamoniteiro (50 kW) and Aitana (60kW); all stations within
100 Hz of nominal frequency; distance 1650 km
Antenna: 4-element horizontal Yagi, geographical azimuth 105 degrees (ESE),
elevation 15 degrees
Receiver: Yupiteru MVT-9000 in FM mode; sensitivity 0.5 µV at 12 dB S/N
Observing: audio (noise) signal from ear-phone socket was rectified and
recorded with a Servogor stripchart recorder with a chart speed
of 120 mm/hour
The somewhat uncommon geometry described above (receiving antenna pointing perpendicular to the direction of the transmitters) resulted in a peculiar observability function, so the counts are difficult to interpret in terms of Geminids activity. Apparently the observability function peaks at about 23h UTC when the main lobe of the 4-element yagi points to the radiant of the Geminids. The highest activity occurred on 13/14 December with counts of about 4 times the sporadics level. For the midpoint between The Netherlands and Spain the setting and rising of the radiant occurred at 11h30m and 15h30m UTC respectively. In the following table the uncorrected hourly counts for signals stronger than 0.1 µV are given. The activity on 21/22 December 1999 may be considered to be caused by sporadic meteors. Figure 1 shows the results graphically.
December 1999
UTC | 12 13 14 15 16 21 22
-----------------------------------------------------------
00 | - 162 189 162 50 - 36
01 | - 98 158 73 43 - 50
02 | - 58 97 45 42 - 50
03 | - 69 96 43 33 - 48
04 | - 70 116 57 39 - 40
05 | - 50 103 47 30 - 39
06 | - 59 98 41 - - 53
07 | - 49 106 30 - - 35
08 | - 55 115 20 - - 25
09 | - 53 74 34 - - 30
10 | - 33 54 26 - - 35
11 | - 19 24 18 - - 26
11h30m setting of Geminids radiant
12 | - 12 26 21 - - 21
13 | - 7 23 9 - - 13
14 | - 6 12 10 - - 11
15 | - 3 5 2 - - 9
15h30m rising of Geminids radiant
16 | - 9 15 3 - - 12
17 | - 22 26 7 - - 12
18 | - 62 63 13 - - 9
19 | 99 136 94 25 - - 18
20 | 117 152 124 27 - - 25
21 | 154 166 177 40 - - -
22 | 176 199 197 58 - 35 -
23 | 186 214 195 63 - 54 -
-----------------------------------------------------------
UTC | 12 13 14 15 16 21 22
| December 1999
- no observations
Figure 1. The hourly counts of the Geminids on 12 - 16 December 1999. Apparently the observability function peaks around 23h UTC. At that time the main lobe of the receiving antenna points to the azimuth of the Geminids radiant.
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This page was last modified on January 3, 2000 by Ton Schoenmaker and Casper ter Kuile |