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STCE Workshop : radio and optical observations of meteors 30/01/2014 BRAMS : status and perspectives Hervé Lamy Belgian Institute for Space Aeronomy (BISA)

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Presentation on theme: "STCE Workshop : radio and optical observations of meteors 30/01/2014 BRAMS : status and perspectives Hervé Lamy Belgian Institute for Space Aeronomy (BISA)"— Presentation transcript:

1 STCE Workshop : radio and optical observations of meteors 30/01/2014 BRAMS : status and perspectives Hervé Lamy Belgian Institute for Space Aeronomy (BISA)

2 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

3 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

4 STCE Workshop : radio and optical observations of meteors 30/01/2014 Meteor scatter observations 2 advantages on optical observations

5 STCE Workshop : radio and optical observations of meteors 30/01/2014 Reflection is specular Information on only one point of the trajectory

6 STCE Workshop : radio and optical observations of meteors 30/01/2014 Observability of a given meteor

7 STCE Workshop : radio and optical observations of meteors 30/01/2014 Status of the BRAMS network

8 STCE Workshop : radio and optical observations of meteors 30/01/2014 BRAMS: current status Tx in Dourbes 25 receiving stations Distance E-R <<

9 STCE Workshop : radio and optical observations of meteors 30/01/2014 The beacon in Dourbes MHz 150 W pure sine wave circular polarisation

10 STCE Workshop : radio and optical observations of meteors 30/01/2014 Typical receiving station AGC off RG213 Spectrum Lab

11 STCE Workshop : radio and optical observations of meteors 30/01/2014 Material Gent

12 STCE Workshop : radio and optical observations of meteors 30/01/2014 Material Behringer U-Control UCA222

13 STCE Workshop : radio and optical observations of meteors 30/01/2014 Synchronisation of stations with GPS Sampling frequency  22 KHz PPS NMEA

14 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.

15 STCE Workshop : radio and optical observations of meteors 30/01/2014 Spectrograms Code to generate spectrograms Nb samples = Covering factor = 90%  f = 200 Hz

16 STCE Workshop : radio and optical observations of meteors 30/01/2014 Spectrograms Overdense meteor echo (+ head echo)

17 STCE Workshop : radio and optical observations of meteors 30/01/2014 Spectrograms « Epsilon » meteor echo (Draconides 2011)

18 STCE Workshop : radio and optical observations of meteors 30/01/2014 BRAMS viewer

19 STCE Workshop : radio and optical observations of meteors 30/01/2014 Current activities

20 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

21 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

22 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

23 STCE Workshop : radio and optical observations of meteors 30/01/2014 Interferometric station in Humain Jones et al (1998)

24 STCE Workshop : radio and optical observations of meteors 30/01/2014 Interferometric station in Humain

25 STCE Workshop : radio and optical observations of meteors 30/01/2014 Interferometric station in Humain

26 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 simulations 2.campaign of measurements to validate the simulations and estimate the impact of the immediate environment of the antennas

27 STCE Workshop : radio and optical observations of meteors 30/01/2014 Calibration & antenna characterization Single Yagi antenna pointing vertically Horizontal Vertical

28 STCE Workshop : radio and optical observations of meteors 30/01/2014 Calibration & antenna characterization Tx antenna Horizontal Vertical

29 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 (  2D 2 /  3m)

30 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 station 2.Identify sudden jumps or anomalous behaviour of a station 3.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).

31 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 :

32 STCE Workshop : radio and optical observations of meteors 30/01/2014 Perspectives

33 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 …

34 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

35 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

36 STCE Workshop : radio and optical observations of meteors 30/01/2014 Extension of the BRAMS network

37 STCE Workshop : radio and optical observations of meteors 30/01/2014 Le site web BRAMS brams.aeronomie.be


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