Lidar technology pre-developments in support of A-SCOPE, the ESA mission to measure CO 2 from space

Transcription

1 Lidar technology pre-developments in support of A-SCOPE, the ESA mission to measure CO 2 from space Yannig Durand, Jérôme Caron, Jean-Loup Bézy, Roland Meynart European Space Agency esa.int CLRC XV Toulouse June 2009 Page 1 CLRC XV Toulouse, June

2 CLRC XV Toulouse June 2009 Page 2 CLRC XV Toulouse, June Outline ASCOPE mission overview Technology pre-development needs Detectors Transmitters Airborne campaigns

3 Earth Observation Missions involving Lidars ADM-Aeolus Doppler Altimetry & DIAL EarthCARE Backscatter WALES DIAL CLRC XV Toulouse June 2009 Page 3

4 Advanced-Space Carbon and Climate Observation of Planet Earth Mission A-SCOPE: Scientific objective: The observation of the spatial and temporal gradients of atmospheric XCO 2 with a precision and accuracy sufficient to constrain CO 2 fluxes within 0.02 Pg C yr -1 on a scale of 1000 x 1000 km 2. MISSION PARAMETERS Orbit: Sun-synchronous Altitude ~ 400 km Local time 06:00 descending node PAYLOAD Integrated Path Differential Absorption lidar (IPDA) Mass: ~ 1000 kg Power: ~ 1.5 kw Mission life: 3 years CLRC XV Toulouse June 2009 Page 4

5 A-SCOPE Observation principle: Integrated Path Differential Absorption Lidar Direct detection lidar based on the differential measurement of the pulses backscattered from ground Pulsed laser transmitters Distance between measurements ~ 150 m Laser footprint on ground < 100 m λ on Surface backscattering λ off CLRC XV Toulouse June 2009 Page 5

6 Instrument overview: design drivers Low random error: 0.5 ppm wrt 380 ppm (0.13 % of DAOD) for ~ 350 measurements high laser power telescope aperture low detector noise maximize the on and off-lines pulses overlap on ground Very low systematic error: 10 % of random error for 1000 x 1000 km 2 laser spectral stability and knowledge laser spectral purity stability of power monitoring of emitted laser pulses stability and knowledge of the S/C pointing CLRC XV Toulouse June 2009 Page 6

7 A-SCOPE Technology Developments Needs Detector at 2 µm: APD with the required performance not commercially available. Development of detectors Transmitter subsystem: combination of high pulse energy, frequency stability and spectral purity not demonstrated Development of laser sources at 1.57 and 2.05 µm Ongoing efforts on reliability of laser pump source New generation of laser diodes arrays at 808 nm Frequency management and power monitoring subsystems: Development and space qualification of key components: integrating sphere, optical frequency comb, CO 2 gas absorption cell Development of complete subsystems Ground-based and airborne systems to optimise the measurement principle CLRC XV Toulouse June 2009 Page 7

8 Detector: HgCdTe APD for detection at 2.1 µm Contractor: SELEX S&AS Time frame: Q Q Design baseline: APD based on loophole junctions Amplifier based on CMOS TIA MCT hybridised directly onto the silicon chip Amplifier design and manufacturing status: preamplifier ROIC based on a low-noise, high bandwidth TIA with output buffer. 50 die have been ordered and taped-out to the foundry in April Performance simulations: BW: 20MHz Noise: 2.2nA within 20MHz bandwidth Slew rate: 80V/μs QE > 70 % Active area diameter > 150 µm Excess noise < 1.5 NEP < 100 fw/hz 0.5 Bandwith Gain stability Linearity > 20 MHz < 0.1 % rms (short term) < 5 % rms Requirements derived from ASCOPE Bandwith response of TIA at 150 and 200 K CLRC XV Toulouse June 2009 Page 8

9 Detector: HgCdTe APD for detection at 2.1 µm APD design and manufacturing status: APD based on 19 loopholes combined in parallel, grown in short wave liquid phase epitaxy APD/amplifier mounted into an encapsulation to enable cooling and handling Uniqueness of the expected results: The solution permits exceptionally low excess noise, excellent gain-bias properties Hybrid loophole robust configuration Performance simulation QE traded against SNR at low flux 2Mpk/50ns Loophole hybrid structure & layout 8kpk/200ns CLRC XV Toulouse June 2009 Page 9 Preliminary detector design

10 Detector: InAlAs APD for detection at 2.1 µm Contractor: SSTL/University of Sheffield Time frame: Q Q Design baseline: Type-II superlattice heterojunction SAM structure MBE growth Results achieved: 11 wafers grown RT cutoff wavelength Dark current density Quantum efficiency Multiplication 2.6µm 0.04mAcm -2 at 200K >30% at 2.1µm >20 at 2.1µm, 200K Possible improvements: Reduce low temperature leakage by effective passivation Increase external quantum efficiency Type-II APD device structure InGaAs p + InAlAs p + Absorption InGaAs/GaAsSb i Charge InGaAlAs p + Multiplication InAlAs i InGaAs n + InP substrate n + SEM of processed device with BCB passivation QE/F > 0.2 Active area > 150 µm diameter Current (A) NEP < 25 fw/hz 0.5 Bandwith Gain stability Linearity T=200K λ=2.1µm > 20 MHz < 0.1 % rms (short term) < 0.1 % rms IV characteristics of Type-II APD Dark current Photocurrent Multiplication Reverse Voltage(V) Multiplication CLRC XV Toulouse June 2009 Page 10

11 Detector: InAs APD for detection at 2.1 µm Contractor: SSTL/University of Sheffield Time frame: Q Q Device structure p p i n Design baseline: InAs MBE and MOVPE growth SAM structure AlAsSb InAs InAs InAs Energy band diagram Results achieved: 5 wafers grown Device fabrication procedure constantly improved RT cutoff wavelength Dark current density Quantum efficiency Multiplication 3.5µm ~0.1mAcm M~10 >30% at 1.55µm and 3.4µm >50 at 77K and 295K Possible improvements: Improve fabrication of mesa-devices Reduce low temperature leakage by effective passivation p Extremely low noise at 295K and 77K 4.0 Excess Noise Factor, F Typical good InGaAs based 1.55µm APD i Multiplication, M n CMT APD 295K InAs APD 295K InAs APD 77K Modelled optimum APD CLRC XV Toulouse June 2009 Page 11

12 Transmitter: Pulsed Laser Source at 2.05 µm Contractor: ONERA Time frame: Q Q Goal: Frequency conversion from 1.06 µm laser to 2.05 µm Design trade-off: Raman shifting: 2 chains (CH 3 D & O 2 ) conversion 11 % Parametric conversion in MOPA configuration Baseline: Doubly resonant parametric oscillator (DROPO) parametric amplifier (OPA) based on 1 ppln crystal followed by type II KTP crystals Energy Frequency stability Optical efficiency M2 < 2 > 50 mj < 1.5 MHz over 10 sec > 35 % Spectral purity >99.98% in 1 GHz Linewidth < 60 MHz CLRC XV Toulouse June 2009 Page 12

13 Transmitter: Pulsed Laser Source at 2.05 µm Uniqueness of the design: Frequency tunable from 1.5 to 4 um with ppln crystal Low oscillation threshold: suitable for both direct and coherent lidar Very compact No need for a injection seeder => Highest frequency stability achieved so far with a nanosecond OPO/OPA set-up Results achieved: Temporal profile of the pump without and with OPO; Signal output of OPA Signal Frequency (THz) 146, , , , , , Standard dev. 30s < 2050 nm 5 MHz t (s) Frequency locking based on wavemeter; DROPO frequency recording with drift compensation with idler PZT Energy Frequency stability Optical efficiency 11.3 mj < 3 MHz over 30 sec % M2 ~ 1.9 Spectral purity Linewidth Pulse duration >99.8% in 820 MHz (multi-pass cell) < 50 MHz 10 ns Side mode suppression of a 10 khz DROPO based on the same dual cavity architecture CLRC XV Toulouse June 2009 Page 13

14 Transmitter: Pulsed Laser Source at 1.57 µm Contractor: ASG/DLR Time frame: Q Q Goal: Parametric frequency conversion of a 1.06µm laser to 1.57 µm using an optical parametric oscillator (OPO) / parametric amplifier (OPA) Baseline design: Energy Mean Frequency stability > 50 mj < 70 khz Spectral purity > % in 1 GHz PRF Bandwdith Time separation 50 Hz < 60 MHz < 250 usec CLRC XV Toulouse June 2009 Page 14

15 Transmitter: Pulsed Laser Source at 1.57 µm Experimental Status: Existing OPO used to trade off OPA configuration and crystals 52 mj measured Double pulse pump laser being installed OPO to be optimised Full characterisation Initial OPO (5-10 mj) Possible 4 stages OPA CLRC XV Toulouse June 2009 Page 15

16 Transmitter: 2.05 µm all-fibre laser system Contractor: Qinetiq Time frame: Q Q Energy PRF Spectral purity Status: Initial definition concepts and modelling Pulse duration MOPA configuration selected Time separation DFB diodes chosen as laser source 4-stage fiber amplification using Thulium-doped fiber amplifier Simulation: see poster from L. Michaille Frequency stability > 2 mj 4 khz > % in 1 GHz 200 khz over 10s 50 ns 200 ms Uniqueness of the design: Peak power requirement (40 kw) exceeds by one order of magnitude the state of the art achieved fibre-based MOPA systems Novel fiber laser approach based on Thulium-doped amplifiers Final fiber amplifier requires a larger core than produced previously for thulium doping employing a microstructured fibre or novel glass host CLRC XV Toulouse June 2009 Page 16

17 Transmitter: 2.05 µm all-fibre laser system System concept: frequency stabilisation Active frequency stabilisation with the National Physical Laboratory (NPL) ON wavelength at and OFF wavelength at nm Reference laser locked on top of absorption line ON wavelength shifted by 3 GHz from the maximum absorption of the line 3 GHz shift controlled by an actively stabilised Fabry-Perot cavity OFF wavelength passively stabilised by DFB temperature controller Locking electronics ON REF ON OFF di D REF o fm0 CO2 cell fm1 PD Locking electronics PD D OFF Scanning FP cavity f m2 D ON di Locking electronics CLRC XV Toulouse June 2009 Page 17

18 System concept: fiber amplifiers Choice of silica-glass fibre amplifiers Germanate glass or fluoride glass possible Silica damage and non-linear threshold higher Use of commercially available fibres for the first two amplifier stages Transmitter: 2.05 µm all-fibre laser system ON OFF PC1 PC2 beam combiner Choice of Thulium as a dopant for the fibres Holmium is another possibility but not as mature Pumping is efficient using diodes at 795 nm IS1 Commercial amplifier module s PCF1 790 nm pump Develop novel rod-type PCF for 790 nm pump the last two amplifiers (collaboration with Crystal Fibre A/S) Rod - type Tm Silica-glass Thulium-doped fibres DM2 doped PCF cm long polarisation-maintaining fibres Large core size (50 µm) or more Aim is to avoid end-facet damage and Stimulated Brillouin Scattering (SBS) IS3 NBPF2 L1 DM1 IS2 Radiation and damage testing of the fibres will be carried out CLRC XV Toulouse June 2009 Page 18

19 Transmitter: Efficient and robust pump laser source Contractor: ASG/ILT Time frame: Q Q Pump laser Specification ATLAS performance Energy > 80 mj Up to 85 mj PRF 100 Hz 100 Hz Optical efficiency > 7 % (UV) Up to 10 % (UV) Energy stability < 10 % 3% M2 < 2 < 1.7 Boresight stability < 75 urad < 40 urad Pulse duration < 50 ns < 35 ns Linewdith stability < 10 MHz < 8.5 MHz Goal: To design and manufacture a pressurised laser source so as to demonstrate the performance achieved for ATLAS in a quasi-engineering model configuration. Performance will be demonstrated through an environmental test campaign and an endurance test campaign. CLRC XV Toulouse June 2009 Page 19

20 Transmitter: Long lifetime stacks Contractor: Quantel Laser Diodes & Jenoptik Time frame: Q Q & Q Goal: For the first time, laser diodes manufacturers involved in the development of a stack optimised for a space application: long lifetime high efficiency Uniqueness of the results: 1000 Wavelength ( ) nm Spectral width 2-3 nm Peak output power > 700 W Pulse width µs Repetition rate Hz Total efficiency > 50% Emitting area < 10 mm x 14 mm Divergence < 10 x 60 deg Polarisation Linear >95% Lifetime 10 billion shots 800 Power (W) QE_07001 QE_07002 QE_07004 QE_07008 QE_07009 QE_ Time (GShots) CLRC XV Toulouse June 2009 Page 20

21 Contractor: DLR, ASG Time frame: Q Q Airborne campaigns Goal: Investigation of the ground reflectance variability and its impact on spaceborne IPDA- Lidar measurements like A-SCOPE 3 campaigns: Lidar measurements at 1.57 µm onboard the DLR research aircraft. More than 5000 km flown above Germany, France, Spain, Portugal, Baltic and Mediterranean seas. CLRC XV Toulouse June 2009 Page 21

22 Airborne campaigns Uniqueness of the results: First dataset of laser groundreflectivity for a wide range of surface Refine A-SCOPE error assessment A-SCOPE simulation: CO2 retrieval error caused by ground reflectance variations RMS(δXCO 2 ) in ppm 100-m-flat top beam profile m-FWHM Gaussian beam profile CLRC XV Toulouse June 2009 Page 22

23 Conclusion This work has been carried out by many European academic and industrial partners. It responds to the ESAC recommendation: However, ESAC views the A-SCOPE approach as offering the potential of an enormous step forward in our understanding of the carbon budget which is not obtainable by other means. Therefore ESAC very strongly recommends the following: further development of the measurement and sensor concept and technology, as spelled out by the evaluation panel report ESA/ESAC(2009)1, Att of ESA/PB-EO(2009)28, Paris, 3 February 2009 Within ESA it has been supported by: Errico Armandillo, Michael Jost, Nick Nelms, (Technology Support Dept.) For further information, please visit us at: CLRC XV Toulouse June 2009 Page 23

24 Thank you for your attention Please visit CLRC XV Toulouse June 2009 Page 24