Airborne and marine quantum gravimetry
Transcript of Airborne and marine quantum gravimetry
Airborne and marine quantum gravimetry
Workshop on « Quantum gravimetry in space and on ground »May 27, 2021
Yannick Bidel
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Presentation outline
• Introduction
• Marine and airborne atom gravimetry
• Atom accelerometer for space geodesy
• Conclusion
Gravimetry
Navigation
Gravity map, terrain aided navigation
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
Applications :
0 2.10-3 m/s²- 2.10-3 m/s²
Measuring the Earth's gravity field and its spatial and temporal variations : g = 9.81… m/s²
Gravity field measurement from space
- Measuring sea heights by space altimetry
Mean sea height ~ gravity equipotentialResolution ~ 20 kmOnly sea area are covered
- Measuring satellite orbital perturbations
- Measuring the gravity gradient in a satellite
Use of electrostatic accelerometers to measure non-gravitational accelerations
Resolution ~ 100 kmThree pairs of electrostatic accelerometers
Resolution ~ 400 km, temporal variations
Better resolution � terrestrial gravimetry
GRACE 2002 - 2017GRACE FO 2018 -
Terrestrial gravimeter
Static0.001 - 0.01 mGal
Dynamic (plane, boat)0.1 - 1 mGal
Relative Superconducting, Spring
Spring, force balanced accelerometer
Absolute Optical, Atomic Atomic
FG5
i Grav
Micro-g Lacoste
(MGS-6)
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KSS32
iMAR
1 mGal = 10-5 m/s² ~ 1µg
Quantum gravimeter / accelerometer principle
vm
h
⋅=λ
- 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
De Broglie wavelength :
- Matter wave manipulation = atom laser interaction
Light pulse atom interferometry
ab
b
a
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Lase
r pu
lse
Lase
r pu
lse
Lase
r pu
lse
t
z
b
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Cloud of cold atoms in free fall submitted to three laser pulses
2
)cos(1 φ−=bP
2Tgk ⋅⋅= rrφ
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Atoms detection by fluorescence
Scale factor proportional to T² and thus to the instrument sizeFirst experimental demonstration : 1991
Cold atom accelerometer principle
- Creation of a cloud of cold atoms (106-109 atoms, µK, mm)MOT, Optical molasses, Zeeman selection
- Cloud of cold atoms in free fall
- Acceleration measured by light pulse atom interferometryTwo 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- Experimental complexity: laser, electronics, RF, vacuum chamber- Output signal proportional to the acceleration cosine
� limited acceleration range (50 µg pour T=20ms)- Measurement dead times (cold atoms preparation, detection)- Rotations induces contrast lost
�need a gyro-stabilized platform
Hybridization with a classic accelerometer
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Developments needed on reliability and miniaturization
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Girafe 2 gravimeter
• Sensor head miniaturized (22x32 cm)
• Integration in a gyro-stabilized platform (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)
• Dynamic tests on motion simulator
motion simulator
Control unit Sensor head
Gyro stabilized platform
Hybridization with classical accelerometer
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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
100 ms
40 mst
Deadtimemeas.
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Accélération (U.A.)
Sig
nal d
e l'a
cc. a
tom
ique
S. Merlet et al., « Operating an atom interferometer beyond its linear range », Metrologia, vol. 46, p. 87, 2009.J. Lautier et al., « Hybridizing matter-wave and classical accelerometers », Appl. Phys. Lett., vol. 105, p. 144102, 2014
Marine and airborne campaigns
Oct. 2015, Jan. 2016 : First marine campaign (Shom, DGA)First marine absolute gravity measurementPrecision : 0,4 - 0,9 mGalY. Bidel et al., Nat. Com. 9, 627 (2018)
April 2017 : Airborne campaign in Iceland (DTU, ESA)First airborne gravity measurement with a quantum sensorPrecision : 1.7 - 3,9 mGalY. 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
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1 mGal = 10-5 m/s²
Integration of the atom gravimeter in a boat and a plane
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Marine gravity surveys
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Airborne gravity surveys
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Coastal areas
Mountain areas
Ice cap and volcanoesVatnajökull
Measurement errors estimation
Repeated line over a profile
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Crossing points differences
mGal
Comparison with classic gravimeters
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Estimated precision during the 2019 airborne campaign in France (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 /
Estimated precision over the different marine gravity campaigns (mGal)
Bay of Biscay
Reference profile
Pyrenees
GIRAFE 1.38 0.91 1.08
iMAR 1.44 1.02 1.24
Lacoste & Romberg
/ 2.45 5.6
Measurement stability over the reference profile
GIRAFE
iMAR
L&R
3 times more stable
Comparison with satellite altimetry (Sandwell v24)
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� Strong interest of marine gravimetry for coastal areas
Comparison with ground measurements
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Ground measurement in Iceland
Hybrid electrostatic-atomic accelerometer for space missions
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
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
- Atom accelerometer+ : Long term stability, accuracy, sensitivity- : Low measurement rate, dead-times, low measurement range
Complementary technologies
ONERA has expertise on both technologies
Experimental demonstration of atom/electrostatic hybridization
Cellule en quartz
Pompe ionique
tube à queusoter
Passages courants getters
Passages courants dispensers
Hublot bridé
Vers pompe ionique 60 l/s
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 toatom accelerometer contrast
- Satellite rotation compensation
Proof mass in rotation during atom interrogation� compensation of satellite rotation
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Preliminary design of the atom/electrostatic space accelerometer
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Estimated volume, masse and power consumption of the overall hybrid instrument~ 58 L~ 90 kg~ 145 W
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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
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Thanks
ONERA, Cold atom inertial sensor teamY. BidelJ. BernardI. PerrinN. ZahzamA. BonninC. BlanchardM. CadoretS. SchwartzA. Bresson
ONERA, Electrostatic accelerometer teamE. HardyP. A. HuynhV. LebatB. Christophe
ShomFrench hydrographic and oceanographic officeD. RouxelM.F. Lequentrec-LalancetteC. SalaunS. LucasG. Delachienne
GET Geosciences Environment Laboratory ToulouseS. BonvalotL. SeoaneG. Gablada
DTU, Technical University of Denmark T.E. JensenA. V. OlesenR. Forsberg
TUM, Technical University of MunichP. AbrykosovR. PailT. Gruber
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