1. Status of the BRAMS project & plans for the future
Hervé Lamy & BRAMS team
Royal Belgian Institute for Space Aeronomy
METRO annual meeting 2016
Brussels – 29 November 2016

2. Meteor forward scatter

3. BRAMS network 2 new stations in 2016 : Haacht and Sivry-Rance
f = MHz
P=150 Watts
Circularly polarized
32 stations
2 stopped
2 inactive

4. Typical receiving station
AGC off
RG213
Spectrum Lab

5. Typical receiving station

6. BRAMS data BEOTTI – 01/02/16 – 12H40 Raw WAV data
5 minutes
Fs = 5512 Hz
Spectrogram : 0 to Fs/2 =2756 Hz
nFFT=16384 ; overlap=90%

7. BRAMS data
Filtered raw data between for frequencies > 1200 Hz and < 1000 Hz
f  0.33 Hz
t  3 sec

8. BRAMS data
BEUCCL – 04/01/16 – 04H55
Quadrantids – More noisy station

9. BRAMS data

10. Future plans for hardware
2-3 more stations per year (see strategy during talk on trajectories)
Use SDR-like receiver (e.g. Dongle) instead of ICOM-R75 + external sound card. Also use single-board computer (e.g. Raspberry-Pi) instead of local PCs. Internship of a student from EPHEC in early Goal is to increase reliability, control, decrease cost & keep stability & sensitivity.
Answer an important question about using Yagi antenna vertical vs inclined

11. Antenna vertical vs tilted
BEOVER
BEMAAS
BEGENK

12. 9 meteors
Local effects only? Or also influence of the direction of the antenna?
14 meteors
6 meteors

13. What is at stake? 2 questions : 1) are we detecting the same meteors?
2) can we accurately determine the radiation pattern of an inclined antenna?

14. Tests in BEUCCL
Sensitivity too low for tilted antenna due to use of a set of connectors and/or oxydation

15. Automatic detection of meteor echoes in BRAMS data

16. Method using the time signal
See Roelandts (2014)

17. Method using the time signal
Band-pass filtered signal to remove noise / possible parasitic signals

18. Method using the time signal
Ratio of energy content in a short window (101 points  101/5512  sec) and in a large window (30001 points  30001/5512  5.44 sec)
Indicator signal
3 parameters :
Short window length
Large window length
Threshold

19. Test of the method : manual counts
Fichier csv with coordinates of all the rectangles

20. Comparison manual – automatic counts
Detection: everything detected by TR/automatic method
Manual: everything manually counted (lines of the CSV files)
TRUE POSITIVE: TR method detects something which falls into a rectangle
FALSE POSITIVE: TR method detects something else than a meteor echo
FALSE NEGATIVE: TR method misses a meteor that was manually counted

21. Variation of the threshold
BEUCCL : 0H00 – 0H55

22. Variation of the threshold
BEUCCL : hour by hour
Goal : check if threshold varies during the day

23. Variation of the threshold
BEUCCL – Whole day

24. Choice of the threshold
Varies from station to station
Does not seem to vary significantly during one day
Difficult to define a simple criterion to select it, so mostly chosen empirically so far.

25. Interferences
Visual inspection of the FP reveals that % of them are due to broad-band interference
Some may be weak and barely visible
Easy to remove a posteriori by filtering the signal inside the 200 Hz range where meteor / airplane echoes occur. Remaining peaks are interferences

26. Interferences

27. Origin of some FP ?

28. Gaussian noise with mean=0.1 and std=0.1
Simulations of IS
Gaussian noise with mean=0.1 and std=0.1

29. Simulations of IS
Noise + beacon

30. Simulations of IS

31. Future plans
Finalise the tests with TR’s method : comparison with manually counted data from several stations, data from the Quadrantids (HL + RMZ) & Perseids (RMZ).
Continue simulations of IS with 2 goals : 1) automatically select a range of threshold to search for the optimal value, 2) try to understand some of the false detections
Set up this automatic method and apply it to archived data from January/February 2017 in order to produce raw counts per day & per station
Continue to investigate other methods