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
