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Instruments

RALI platform gathers two active remote sensing instruments, RASTA and LNG.

-RASTA (RAdar SysTem Airborne)

RASTA is a 95GHz Doppler radar exists in several configurations, the 6 antennas configuration allows one to retrieve 3D cloud dynamic above and below the aircraft.


Example of antennas configuration


Airborne

Ground (in a few occasions RASTA has been operated at the ground )

Antennas

1 to 6 antennas, 30 cm

1 antennas, 120cm

Emitting Power

1.5 kW (klystron)

1.5 kW (klystron)

Sensitivity

-40dBZ,but depending on antenna orientation and configuration

60 dBZ

Integration time

250 ms

250 ms

Vertical resolution

60 m

60 m

Range

15 km

15 km

Ambigous velocity

8m s-1

8m s-1

Frequency (wavelenght)

95GHz (3.2 mm)

95GHz (3.2 mm)

-LNG (Leandre New Generation)


Leandre stands for Lidars aéroportés pour l'Etude des Aérosols, des Nuages, de la Dynamique, du Rayonnement et du cycle de l'Eau.
LNG is operated in its backscatter version at three wavelengths (355 nm, 532 nm, 1064 nm) lidar and depolarization at 355 nm. The high spectral resolution capability at 355nm was added in 2010.


355nm

532 nm

1064nm

Laser

Spectral width

200 MHz, stability 12 MHZ

Frequency

20 Hz

Impulsion length

6 ns

Full angle beam width

0.16 mrd

4 mrd

6.5 mrd

Beam width

Between 38.6 and 40.5 mm (super gaussian)

Vertical resoltuion>

7.5 m

Horizontal resolution

minimal integration time 50 ms

Range

15 km

Sensitivity

molecular scattering

Atmospheric mirror

  • effective optical surface : ellipse 310 mm x 435 mm
  • 3 positions : upward, downward, lateral

Telescope

  • Cassegrain type
  • Diameter 300 mm, central obturation 90 mm
  • focal 2250 mm
  • max field 8 mrd

Detection device

  • polarisation at 335 nm
  • 2 signals at 335 nm on photomultiplier (non HRS)

1 signal at 532 nm on photomultiplier

1 signal at 1064 nm avalanche on photodioder

Interferometer

  • March-Zender
  • Four channels
  • optical path difference 20 cm
  • ouputs : 4 atmospheric signals on photomultiplier and 4 references signals

Input : parallel polarisation signal at 355 nm from detection device


Atmospherics signals for LNG

with HRS : 7 channels ADC, 20 MHz, 14 bits

no HRS : 4 channels ADC, 20 MHz, 14 bits

no HRS : 4 channels ADC, 20 MHz, 14 bits

References signals

  • Laser : energy value of the 3 wavelengths : EIR, Evis , EUV
  • HRS : 4 references values E1, E2, E3 and E4