STCE Workshop : radio and optical observations of meteors 30/01/2014 BRAMS : status and perspectives...
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Transcript of STCE Workshop : radio and optical observations of meteors 30/01/2014 BRAMS : status and perspectives...
![Page 1: STCE Workshop : radio and optical observations of meteors 30/01/2014 BRAMS : status and perspectives Hervé Lamy Belgian Institute for Space Aeronomy (BISA)](https://reader036.fdocuments.us/reader036/viewer/2022081518/551c4c925503469d6a8b49d2/html5/thumbnails/1.jpg)
STCE Workshop : radio and optical observations of meteors 30/01/2014
BRAMS : status and perspectives
Hervé LamyBelgian Institute for Space Aeronomy (BISA)
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Outline of the talk
1. Status of the BRAMS network
2. Current activites
3. Perspectives
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STCE Workshop : radio and optical observations of meteors 30/01/2014
The BRAMS team
Hervé Lamy Sylvain Ranvier Emmanuel Gamby Stijn Calders Michel Anciaux Johan De Keyser
Antonio Martinez Picar (ROB)
+ support from mechanical/electronic workshop at BISA
+ regular help from Pierre Ernotte, Felix Verbelen, Jean-Louis Rault
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Meteor scatter observations
2 advantages on optical observations
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Reflection is specular
Information on only one point of the trajectory
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Observability of a given meteor
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Status of the BRAMS networkStatus of the BRAMS network
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STCE Workshop : radio and optical observations of meteors 30/01/2014
BRAMS: current status
Tx in Dourbes
25 receiving stations
Distance E-R <<
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STCE Workshop : radio and optical observations of meteors 30/01/2014
The beacon in Dourbes
49.97 MHz
150 W
pure sine wave
circular polarisation
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Typical receiving stationAGC off
RG213
Spectrum Lab
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Material
Gent
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Material
Behringer U-Control UCA222
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Synchronisation of stations with GPS
Sampling frequency 22 KHz
PPSNMEA
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Recording of the data
• Signals are recorded locally on the PC with Spectrum Lab. Configuration file of this software is provided by BISA.
• Data are recorded in audio WAV format with 2 channels (stereo mode)• Sampling frequency 22 KHz in order to decode the NMEA• Every day at 2 AM, a script developed at BISA allows to decode
automatically the GPS data from the day before. The decoded signal is added to the file as a « chunk ».
• Before that, the signal from the receiver is decimated by a factor to reach an effective sampling frequency of 5512 Hz.
• One new file with data is created every 5 mins. Size of one file is 3 MB. 288 files per day 1 GB of data / day
• Data are stored locally for 1 mnth and then sent to BISA via USB sticks for archiving.
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Spectrograms
Code to generate spectrograms Nb samples = 16384Covering factor = 90%
f =
200
Hz
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Spectrograms
Overdense meteor echo (+ head echo)
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Spectrograms
« Epsilon » meteor echo (Draconides 2011)
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STCE Workshop : radio and optical observations of meteors 30/01/2014
BRAMS viewer
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Current activitiesCurrent activities
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Automatic counting
• Many meteor applications require an accurate counting of the number of meteors detected per unit time (e.g. observability function, fluxes of meteors, activity of a meteor shower, etc..)
• Since the BRAMS network provides every day around 25 x 288 WAV files need for an efficient algorithm for automatic counting of meteor echoes
• So far method mostly based on recognition of specific shapes in the spectrogram considered as an image. Developed mainly by P. Ernotte and some of his students.
• Works quite well for underdense meteor echoes• Not so well for overdense meteor echoes / epsilon echoes
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Automatic counting
Main problems :
•Intersection of plane echoes•Difficult to define a specific shape for overdense/epsilon echoes
2 detection methods for underdense / overdense meteor echoes
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Manual counting• Mandatory to assess the accuracy of the automatic detection
method• Online tool developed by Emmanuel Gamby
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Interferometric station in HumainInterferometric station in Humain
Jones et al (1998)
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Interferometric station in HumainInterferometric station in Humain
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Interferometric station in HumainInterferometric station in Humain
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Calibration & antenna characterization
• Determination of the 3D radiation pattern of the antenna in order to obtain G(,)
• At least for the interferometer, Tx in Dourbes and crossed Yagi in BEUCCL (but hopefully also for other BRAMS stations)
• Two complementary studies :
1. software simulations2. campaign of measurements to validate the simulations and estimate the
impact of the immediate environment of the antennas
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Calibration & antenna characterization
Single Yagi antenna pointing vertically
Horizontal Vertical
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Calibration & antenna characterization
Tx antenna
Horizontal Vertical
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Calibration & antenna characterization
In situ measurements
Payload : source of known amplitude (see next slides)Must fly in the far-field region of the antenna ( 2D2/ 3m)
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Calibrator for BRAMS
Purpose :
1. Check the gain and frequency offset/drift at every station2. Identify sudden jumps or anomalous behaviour of a station3. Calibrate the gain and phase differences at the interferometer
and at BEUCCL. In particular, the phase offset of each receiver is susceptible to jumps after a power recycle (receivers not phase locked to a common reference).
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Calibrator for BRAMS
1. Signal of a known frequency and amplitude fed into the front end
2. Frequency is in the useable band so that the signal can be monitored continuously while gathering echo data
3. Small USB powered unit, frequency and amplitude are programmable and can be adjusted as needed (10 dB range, 1Hz steps)
4. For the phase calibration, the same signal is fed to multiple receivers at the same time. The phase difference between the receiving chains can then monitored.
Method :
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STCE Workshop : radio and optical observations of meteors 30/01/2014
PerspectivesPerspectives
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Meteor radar in Dourbes
• Goal : comparison of fluxes measured by a back scatter and forward scatter system
• Status : preliminary design done, material procured, work should start this year …
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Trajectory reconstruction
R2
• Softwares need to be developed & tested• Applicable mostly to underdense meteors• Need for a dense and extended network
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Trajectory reconstruction
• Importance of adding optical cameras to reconstruct trajectories of bright objects
• These bright objects correspond to overdense meteor echoes for which the specularity condition is not strictly followed
• It will be important to compare quality of reconstruction methods
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Extension of the BRAMS network
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STCE Workshop : radio and optical observations of meteors 30/01/2014
Le site web BRAMS
brams.aeronomie.be