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EUSO Onboard LIDAR M.Teshima Discussion by Valentin Mitev Neuschatel Observatory [email protected] Options for EUSO Lidar 1. Stand-alone laser diode based (near-IR) 2. Stand-alone one-wavelengths Nd:YAG based 3. Stand-alone three-wavelengths Nd:YAG based EUSO: Laser Diode based, PRN- cw lidar (Pseudo-Random Noise continuous wave) + PRN code Lidar detected signal Atmospheric response function Laser Diode based LIDAR Low power, compact, and long life Assumed performances of the PRN lidar subsystems: Sensor Sub-systems parameters Parameter Value Laser diode, wavelength 800nm Laser diode, power 20W Transmitter diameter/divergence 100mm/1mrad Receiver primary/secondary diameter 500mm/120mm Receiver divergence 2mrad Detector APD – Quantum Efficiency/gain 50%/300 Filter FWHM/transmission 2nm/60% Optical efficiency (no filter transmission included) 45% Platform and measurement parameters Parameter Value Platform Altitude 480km Altitude resolution 150m Candidate: Upgrade of ‘Beacon laser’: Based on several laser diodes at 808nm, combined in a single multimode fiber/Total of 8W without redundancy PRN-cw lidar: Detection conditions: 1. Desert dust: SR=5@532nm OD =0.89@800nm 2. Subvisible cloud: SR=100@532nm OD=0.62@800nm 3. Optical background: Full Moon/45° 4. Integration time: 1s PRN-cw lidar: Detection conditions: 1. Opaque cloud: SR=1000@532nm OD =3.81@800nm 2. Subvisible cloud: SR=20@532nm OD=0.12 3. Optical background: Full Moon/45° 4. Integration time: 0.01s Conclusion Laser Diode based, PRN- cw lidar compact package + long life + low power But: Only opaque cloud top altitude EUSO: One- (single-) wavelength pulsed lidar Assumed performances of the single wavelength, pulsed lidar subsystems: Sensor Sub-systems parameters Parameter Value Laser, wavelength 1064nm Laser, pulse energy/pulse rep. rate/ mean power 50mJ/100Hz (2x50) /5W (2x2.5W) Transmitter diameter/divergence 50mm/0.1mrad Receiver primary/secondary diameter 400mm/60mm Receiver divergence 0.3mrad Detector APD – Quantum Efficiency/gain 38%/300 Filter FWHM/transmission 0.4nm/50% Optical efficiency (no filter transmission included) 33% Platform and measurement parameters Parameter Value Platform Altitude 480km Altitude resolution 150m Range resolution: 150m; Int. time: 0.01s Opaque cloud SR = 7993 at1064 at 4km; OD=2.28 Subvis. cloud SR = 1585 at 1064nm at 10km; OD=0.12 Range resolution: 150m; Int. time: 5s Opaque cloud SR = 7993 at 1064 at 4km; OD=2.28 Subvis. cloud SR = 1585 at 1064 at 10km; OD=0.12 Range resolution: 150m; Int. time: 1s Dust layer SR = 33.5 at 1064 at 0-4km; OD=0.67 Range resolution: 150m; Int. time: 1s Dust layer SR = 33.5 at 1064 at 0-4km; OD= 0.67 Subvis. cloud SR = 1585 at 1064 at 10km; OD=0.12 Conclusion about the singlewavelength pulsed lidar compact package +developed technology + long life + sufficiently low consumption 1. Opaque cloud top altitude 2. Subvisible clouds optical depth@1m 3. Dust layer transmisson profile @1m EUSO: Three- wavelength pulsed lidar Nd-YAG Pulsed Laser > simplified ‘clone’ of the laser for ALADIN 1064nm, 532nm, 355nm Pulse rep rate: 100pps (operational mode)/ 50pps (stan-by mode) Power we need: ~ 50-70mJ per wavelength > NOT 120 mJ per harmonic AS FOR ALADIN > NO WAVELENGTH LOCKING AND STABILISATION, AS FOR ALADIN Assumed performances of the single wavelength, pulsed lidar subsystems: Sensor Sub-systems parameters Parameter Value Laser, pulse rep rate /total pulse ehergy&optical power 100/ ~180mJ/18W Laser wavelength/ pulse energy / mean power 1064nm/50mJ//5W Laser wavelength/ pulse energy / mean power 532nm/50mJ//5W Laser wavelength/ pulse energy / mean power 355nm/50mJ//5W Transmitter diameter/divergence 50mm/0.1mrad Receiver primary/secondary diameter 300mm/60mm Receiver divergence 0.3mrad Detector APD – Quantum Efficiency/gain 38%/300 Detector PMT (532nm) – Quantum Efficiency 15% Detector PMT (355nm) – Quantum Efficiency 25% Filter FWHM/transmission – all wavelength 0.4nm/50% Optical efficiency (no filter transmission included) 33% Platform and measurement parameters Parameter Value Platform Altitude 480km Altitude resolution 150m Range resolution: 150m; Int. time: 0.01s Opaque cloud SR = 297 at 355nm at 6km; OD=6.38 Subvis. cloud SR = 4.6 at 355 nm at 10km; OD=0.11 Range resolution: 150m; Int. time: 5s Range resolution: 150m; Int. time: 0.01s Opaque cloud SR = 1000 at 532nm at 6km; Subvis. cloud SR = 20 at 532 nm at 10km; OD=0.1 Range resolution: 150m; Int. time: 5s Conclusion: the three-wavelength pulsed lidar More complicated and less compact, less redundancy, higher consumption 1. Opaque cloud top altitude 2. Subvisible clouds optical depth@355nm 3. Dust layer transmisson profile @355nm 4. Redndancy in information output, due to more power/wavelength 5. Calibration for EUSO detector in Chapter 5 – EUSO Red Book Fig. 5.2.4-11.1 in Chapter 5 – EUSO Red Book Laser Detection box Beam pointing mirror Telescope Mirror Lidar Probing, line-of-sight EUSO Lidar: concept with honeycomb panels (closed) Mass ~140Kg Power ~ 300W EUSO LIDAR Conclusion • Laser Diode PRN-cw Lidar is very interesting technology, however the current performance is not enough for EUSO • Three wave lengths Lidar is very powerful, but Mass and Power are problem • One wave length Lidar is perhaps optimum in performance and hardware resources. – Cloud top information – Thin cloud transmission – Dust layer transmission