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Airborne and Marine Quantum Gravimetry

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Airborne and Marine Quantum Gravimetry Airborne and marine quantum gravimetry Yannick Bidel Workshop on « Quantum gravimetry in space and on ground » May 27, 2021 Presentation outline • Introduction • Marine and airborne atom gravimetry • Atom accelerometer for space geodesy • Conclusion 2 Gravimetry Measuring the Earth's gravity field and its spatial and temporal variations : g = 9.81… m/s² Applications : Navigation Gravity map, terrain aided navigation - 2.10 -3 m/s² 0 2.10 -3 m/s² Geodesy Measuring the Earth's gravity field to improve knowledge of the geoid, which serves as a reference for altitude Geophysics / Exploration Measurement of mass distribution and variations Earthquake, volcano, ice melting, hydrology Fundamental physics/ metrology Kibble balance, equivalence principal, gravitation theory test Gravity field measurement from space - Measuring satellite orbital perturbations GRACE 2002 - 2017 GRACE FO 2018 - Use of electrostatic accelerometers to measure non- gravitational accelerations Resolution ~ 400 km, temporal variations - Measuring the gravity gradient in a satellite Resolution ~ 100 km Three pairs of electrostatic accelerometers - Measuring sea heights by space altimetry Mean sea height ~ gravity equipotential Resolution ~ 20 km Only sea area are covered Better resolution terrestrial gravimetry Terrestrial gravimeter i Grav KSS32 Micro-g Lacoste (MGS-6) iMAR Static Dynamic (plane, boat) 0.001 - 0.01 mGal 0.1 - 1 mGal Relative Superconducting, Spring, force Spring balanced accelerometer Absolute Optical, Atomic Atomic FG5 ? 1 mGal = 10 -5 m/s² ~ 1µg Quantum gravimeter / accelerometer principle - Measurement of the acceleration of a test mass in free fall Test mass = gas of cold atoms - Acceleration measurement technic = atom interferometry - Matter wave = cold atoms h De Broglie wavelength : λ = m ⋅v - Matter wave manipulation = atom laser interaction Light pulse atom interferometry Cloud of cold atoms in free fall submitted to three laser pulses z a Atoms detection by fluorescence b 1− cos( φ) P = a b 2 r a r φ = k ⋅ g ⋅T 2 b 0.9 0.8 0.7 0.6 Laser pulse Laser Laser pulse Laser pulse Laser 0.5 0.4 b 0.3 a 0.2 25.1420 25.1425 25.1430 25.1435 25.1440 25.1445 25.1450 α MHZ/s t T T Scale factor proportional to T² and thus First experimental demonstration : 1991 to the instrument size Cold atom accelerometer principle - Creation of a cloud of cold atoms (10 6-10 9 atoms, µK, mm) MOT, Optical molasses, Zeeman selection - Cloud of cold atoms in free fall - Acceleration measured by light pulse atom interferometry Two photon Raman transition - Detection by fluorescence Cold atom accelerometer - Strong points - Absolute measurement, no calibration needed, no drift - Excellent sensitivity - No moveable mechanical parts (low maintenance constraints, high repetition rate) - Weak points Developments needed on reliability - Experimental complexity: laser, electronics, RF, vacuum chamber and miniaturization - Output signal proportional to the acceleration cosine limited acceleration range (50 µg pour T=20ms) Hybridization with a classic - Measurement dead times (cold atoms preparation, detection) accelerometer - Rotations induces contrast lost need a gyro-stabilized platform 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 25.1420 25.1425 25.1430 25.1435 25.1440 25.1445 25.1450 α MHZ/s Girafe 2 gravimeter • Sensor head miniaturized (22x32 cm) Sensor head • Integration in a gyro-stabilized platform Control unit (0,1 mrad) • Short falling distance (14 mm) T=20ms • High repetition rate (10 Hz) • Hybridization with a classical accelerometer (Qflex) • Static tests (accuracy 0.06 mGal) Gyro stabilized platform • Dynamic tests on motion simulator motion simulator 10 Hybridization with classical accelerometer 100 ms t 40 ms Deadtime meas. 0.9 0.8 0.7 0.6 0.5 S. Merlet et al., « Operating an atom interferometer beyond its 0.4 linear range », Metrologia, vol. 46, p. 87, 2009. 0.3 J. Lautier et al. , « Hybridizing matter-wave and classical Signal de Signal de atomique l'acc. 0.2 accelerometers », Appl. Phys. Lett. , vol. 105, p. 144102, 2014 25.1420 25.1425 25.1430 25.1435 25.1440 25.1445 25.1450 α MHZ/s Accélération (U.A.) Implementation of a robust hybridization algorithm - Continuous estimation of offset and contrast of atom interferometer fringes - Continuous estimation of the bias and the scale factor of the classical accelerometer - Automatic determination of the atom interrogation time 11 Marine and airborne campaigns Oct. 2015, Jan. 2016 : First marine campaign (Shom, DGA) First marine absolute gravity measurement Precision : 0,4 - 0,9 mGal Y. Bidel et al., Nat. Com. 9, 627 (2018) April 2017 : Airborne campaign in Iceland (DTU, ESA) First airborne gravity measurement with a quantum sensor Precision : 1.7 - 3,9 mGal Y. Bidel et al., J. of Geodesy 94:20 (2020) April - Oct. 2018 : Long term marine campaign (Shom) Precision : 0,2 - 0,5 mGal April, Mai 2019 : Airborne campaign in France (GET, DTU, SHOM, CNES, ESA) Precision : 0.7 - 1.4 mGal Jan. - Oct. 2020 : Long term marine campaign (Shom) Precision : 0.3 - 0.5 mGal 1 mGal = 10 -5 m/s² 12 Integration of the atom gravimeter in a boat and a plane 13 Marine gravity surveys 14 Airborne gravity surveys Ice cap and volcanoes Vatnajökull Coastal areas Mountain areas 15 Measurement errors estimation Repeated line over a profile Crossing points differences mGal 16 Comparison with classic gravimeters Estimated precision over the different marine gravity campaigns (mGal) 2015-2016 2018 2020 GIRAFE 0.6 0.3 0.4 KSS32 n°1 1.1 0.5 0.6 KSS32 n°2 / / 0.8 GT2M / 0.5 / 3 times more stable Estimated precision during the 2019 airborne campaign in France (mGal) Measurement stability over the reference profile Bay of Reference Pyrenees Biscay profile GIRAFE GIRAFE 1.38 0.91 1.08 iMAR 1.44 1.02 1.24 iMAR Lacoste & / 2.45 5.6 Romberg L&R 17 Comparison with satellite altimetry (Sandwell v24) Strong interest of marine gravimetry for coastal areas 18 Comparison with ground measurements Ground measurement in Iceland 19 Hybrid electrostatic-atomic accelerometer for space missions Future space geodesy missions need high performance accelerometers - Electrostatic accelerometers in CHAMP, GRACE, GOCE, GRACE FO, … + : Short term sensitivity, cont. meas., maturity - : Long term stability, accuracy Complementary - Atom accelerometer technologies + : Long term stability, accuracy, sensitivity - : Low measurement rate, dead-times, low measurement range ONERA has expertise on both technologies Study of the hybridization between electrostatic and atom accelerometer - Gravity field retrieval performance simulation - Experimental study of a atom/electrostatic accelerometer - long term stability improvement of electrostatic accelerometer - rotation compensation with the electrostatic proof mass - Preliminary design of space accelerometer Experimental demonstration of atom/electrostatic hybridization Cellule en quartz Passages courants dispensers Passages courants getters Vers pompe ionique 60 l/s tube à queusoter Pompe ionique Hublot bridé Improvement of low frequency noise of the electrostatic accelerometer Long term drift of the electrostatic accelerometer corrected by the atom accelerometer Rotation compensation - Satellite rotation contrast loss Validation of the impact of contrast to atom accelerometer contrast - Satellite rotation compensation Proof mass in rotation during atom interrogation compensation of satellite rotation 23 Preliminary design of the atom/electrostatic space accelerometer Estimated volume, masse and power consumption of the overall hybrid instrument ~ 58 L ~ 90 kg ~ 145 W 24 Conclusion - Onboard quantum gravimeter - Absolute airborne and shipborne gravimetry demonstrated (classical sensors perform only relative measurements) - Better precision than classical sensors - Reliability of the technology on long term demonstrated (10 month) - Toward the industrialization of onboard quantum gravimeter (Muquans) - Preparation of the second generation of onboard quantum gravimeter - Strap down decrease mass, volume and cost new carrier (drone) - Improved precision access to time variable gravity signal - Quantum accelerometer for space geodesy - Hybridization between atom and electrostatic seems promising for future space geodesy mission 25 Thanks ONERA, Cold atom inertial sensor team Shom Y. Bidel French hydrographic and oceanographic office J. Bernard D. Rouxel I. Perrin M.F. Lequentrec-Lalancette N. Zahzam C. Salaun A. Bonnin S. Lucas C. Blanchard G. Delachienne M. Cadoret S. Schwartz DTU, Technical University of Denmark A. Bresson T.E. Jensen A. V. Olesen ONERA, Electrostatic accelerometer team R. Forsberg E. Hardy P. A. Huynh GET V. Lebat Geosciences Environment Laboratory Toulouse B. Christophe S. Bonvalot L. Seoane G. Gablada Support from : TUM, Technical University of Munich P. Abrykosov R. Pail T. Gruber 26.
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