BRAMS : status and perspectives

1. BRAMS : status and perspectives Hervé Lamy Belgian Institute for Space Aeronomy (BISA)

2. Outline of the talk Status of the BRAMS network Current activites Perspectives

3. 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. Meteor scatter observations 2 advantages on optical observations

5. Reflection is specular Information on only one point of the trajectory

6. Observability of a given meteor

7. Status of the BRAMS network

8. BRAMS: current status 25 receiving stations Distance E-R << Tx in Dourbes

9. The beacon in Dourbes • 49.97 MHz • 150 W • pure sine wave • circular polarisation

10. Typical receiving station AGC off RG213 Spectrum Lab

11. Material Gent

12. Material Behringer U-Control UCA222

13. Synchronisation of stations with GPS NMEA PPS Sampling frequency  22 KHz

14. 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. Spectrograms f = 200 Hz Nb samples = 16384 Covering factor = 90% Code to generate spectrograms

16. Spectrograms Overdense meteor echo (+ head echo)

17. Spectrograms « Epsilon » meteor echo (Draconides 2011)

18. BRAMS viewer

19. Currentactivities

20. Automatic counting • Manymeteor applications require an accuratecounting of the number of meteorsdetected per unit time (e.g. observabilityfunction, fluxes of meteors, activity of a meteorshower, etc..) • Since the BRAMS network provideseverydayaround 25 x 288 WAV files  need for an efficient algorithm for automaticcounting of meteorechoes • So far  methodmostlybased on recognition of specificshapes in the spectrogramconsidered as an image. Developedmainly by P. Ernotte and some of hisstudents. • Works quitewell for underdensemeteorechoes • Not sowell for overdensemeteorechoes / epsilon echoes

21. Automatic counting • Main problems: • Intersection of plane echoes • Difficult to define a specificshape for overdense/epsilon echoes 2 detection methods for underdense / overdense meteor echoes

22. Manual counting • Mandatory to assess the accuracy of the automatic detection method • Online tool developed by Emmanuel Gamby

23. Interferometric station in Humain Jones et al (1998)

24. Interferometric station in Humain

25. Interferometric station in Humain

26. 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 : • software simulations • campaign of measurements to validate the simulations and estimate the impact of the immediate environment of the antennas

27. Calibration & antenna characterization Single Yagi antenna pointing vertically Vertical Horizontal

28. Calibration & antenna characterization Tx antenna Vertical Horizontal

29. 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)

30. Calibrator for BRAMS • Purpose : • Check the gain and frequency offset/drift at every station • Identify sudden jumps or anomalous behaviour of a station • 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. Calibrator for BRAMS Method : • Signal of a known frequency and amplitude fed into the front end • Frequency is in the useable band so that the signal can be monitored continuously while gathering echo data • Small USB powered unit, frequency and amplitude are programmable and can be adjusted as needed (10 dB range, 1Hz steps) • 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.

32. Perspectives

33. Meteor radar in Dourbes • Goal : comparison of fluxes measured by a back scatter and forwardscatter system • Status : preliminary design done, materialprocured, workshouldstartthisyear …

34. R2 Trajectory reconstruction • Softwares need to be developed & tested • Applicable mostly to underdense meteors • Need for a dense and extended network

35. 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. Extension of the BRAMS network

37. Le site web BRAMS brams.aeronomie.be