Positioning currently relies heavily on Global Navigation Satellite Systems (GNSS). Combined with classical accelerometers and gyroscopes, precise determination of orientation and position at any given time become available. However, but the availability of GNSS (e.g. GPS) is limited and not guaranteed at all times.In this paper we present an alternative based on atom interferometry using cold atom ensembles. An inertial sensor based on cold atoms allows, in theory, for nearly drift-free measurements of inertial forces with accuracies unreached by classical sensors, but the technology is still locked away in large physics laboratories [1].This paper introduces a compact device called SECAMP, which is capable of cooling atoms down to μ-Kelvin. SECAMP has the potential to measure inertial acceleration in three degrees of freedom. In the following, we present the current experimental setup of the apparatus and outline the next steps for the inertial sensor.
Positioning currently relies heavily on Global Navigation Satellite Systems (GNSS). Combined with classical accelerometers and gyroscopes, precise determination of orientation and position at any given time become available. However, but the availability of GNSS (e.g. GPS) is limited and not guaranteed at all times.In this paper we present an alternative based on atom interferometry using cold atom ensembles. An inertial sensor based on cold atoms allows, in theory, for nearly drift-free measurements of inertial forces with accuracies unreached by classical sensors, but the technology is still locked away in large physics laboratories [1].This paper introduces a compact device called SECAMP, which is capable of cooling atoms down to μ-Kelvin. SECAMP has the potential to measure inertial acceleration in three degrees of freedom. In the following, we present the current experimental setup of the apparatus and outline the next steps for the inertial sensor.
Inertial sensors based on cold atom interferometry exhibit many interesting features for applications related to inertial navigation, particularly in terms of sensitivity and long-term stability. However, at present the typical atom interferometer is still very much an experiment—consisting of a bulky, static apparatus with a limited dynamic range and high sensitivity to environmental effects. To be compliant with mobile applications further development is needed. In this work, we present a compact and mobile experiment, which we recently used to achieve the first inertial measurements with an atomic accelerometer onboard an aircraft. By integrating classical inertial sensors into our apparatus, we are able to operate the atomic sensor well beyond its standard operating range, corresponding to half of an interference fringe. We report atom-based acceleration measurements along both the horizontal and vertical axes of the aircraft with one-shot sensitivities of 2.3 × 10−4 g over a range of ∼ 0.1 g. The same technology can be used to develop cold-atom gyroscopes, which could surpass the best optical gyroscopes in terms of long-term sensitivity. Our apparatus was also designed to study multi-axis atom interferometry with the goal of realizing a full inertial measurement unit comprised of the three axes of acceleration and rotation. Finally, we present a compact and tunable laser system, which constitutes an essential part of any cold-atom-based sensor. The architecture of the laser is based on phase modulating a single fiber-optic laser diode, and can be tuned over a range of 1 GHz in less than 200 μs.
This report assesses the potential of gyroscopes and accelerometers based on cold atom interferometry (CAI) for space and defence applications, by analysing their strengths and weaknesses in comparison with devices based on other working principles. Indeed, it is widely recognized that quantum sensors based on atomic interferometry provide absolute measurements with the potential for high sensitivity and long-term stability. This last property is particularly valuable for accelerometers and gyroscopes to be used for inertial navigation, since it guarantees precise positioning without the need for frequent recalibrations, a shortcoming which affects several devices presently in use. \nHigh-performance inertial sensors play an important role both in space applications, where gyroscopes are widely used e.g. to orientate a satellite and its on-board communications and sensing equipment, and in defence, where gyroscopes and accelerometers constitute the core of the inertial measurement units to be used for autonomous navigation, e.g. in GNSS-denied conditions. The EU has a well-established role in space with the Copernicus and Galileo programmes, and a fledging but increasing involvement in the defence industry. An independent assessment of a quantum technology such as cold atom interferometry which may in time acquire a significant role in these fields is a precondition to advance well-grounded suggestions for EU policy initiatives.
In recent years, quantum technology has attracted attention in inertial navigation, especially due to its extreme sensitivity to inertial forces and strong immunity to drifts, which plague conventional sensors. There are multiple groups around the world working on cold atom interferometry aiming to develop high sensitive inertial sensors for very high accuracy autonomous navigation. Recent advancements in micro-fabrication technologies have helped in development of robust and miniaturized atom interferometry based high performance inertial systems. These, in future, will pave way for autonomous satellite inertial navigation sensors based on cold atoms. Here we discuss the achievements towards realizing cold atom inertial sensors and their indomitable role as inertial sensors for future satellites. A detailed survey on the initiatives taken by different space agencies, their achievements and their plans to explore its potential in space are also discussed.
Classical inertial navigation systems integrate inertial measurements from triads of accelerometers and gyroscopes to determine their position, but the computed trajectory is typically limited by the intrinsic time-varying bias of these inertial sensors. In addition, the exploitation of quantum physics led to the development of matter-wave interferometers, sensitive to inertial effects due to the mass of the atoms. While they are free-falling, these atoms constitute a perfect inertial frame of reference and allow for an absolute measurement with outstanding accuracy and stability. Substantial technical developments have allowed bringing quantum gravimeters to the market, enabling static, long-term measurements. Nevertheless, the use of cold-atom sensors for navigation and positioning still requires addressing many scientific and technological challenges to be compatible with onboard applications such as compactness, measurement continuity and operation in the presence of strong vibrations and rotations.The Joint Laboratory iXAtom brings together the expertise of the Laboratoire de Photonique, Numérique et Nanosciences (LP2N) in matter-wave interferometry and the French technology company Exail, specialized in high-performance inertial navigation systems and industrial quantum sensors, with the aim of building a new generation of high-end inertial sensors through the hybridization of classical accelerometers and gyroscopes with quantum sensors based on matter-wave interferometry.After successfully building a multi-axis cold-atom interferometer measuring the three components of the acceleration vector with a static apparatus, this quantum inertial sensor has been fully hybridized with a triad of classical accelerometers, increasing the bandwidth and dynamic range without the usual limitation due to the bias drift of the mechanical accelerometers. Moreover, this hybridization technique features a real-time correction of the laser phase which allows retrieving the acceleration information out of atomic fringes scrambled by parasitic vibrations. As regards the rotations of the instrument throughout an interferometer, their compensation remains the next major issue to tackle for strapdown applications as they induce a drastic reduction of the atomic fringes’ visibility coupled to a scrambling of the interferometric phase shift.This thesis work focuses on the mitigation of the rotation-induced performance deterioration of the hybrid accelerometer. Through a theoretical investigation, a model for both the angular velocity-dependent decay of the fringes contrast and the systematic phase shift arising from the complex trajectory of the atomic cloud in the rotating frame of the interrogation laser is established. A real-time rotation compensation system, employing the measurement of the rotation rate with high-end fiber-optic gyroscopes to drive a piezo-actuated tip-tilt platform, has been implemented to stabilize the orientation of the interrogation laser in the external frame in order to preserve the contrast of the atomic interference pattern and extend the measurement range of the rotating atom interferometer. A rectification of the theoretical model accounting for the rotation of the laser as well as the hybridization with the classical accelerometers enables reconstructing the atomic fringes and retrieving the inertial measurement, paving the way for strapdown onboard hybrid accelerometry.
Autonomous navigation has become increasingly important for deep-space missions, which cannot use GPS and receive limited, delayed tracking from Earth. Inertial navigation systems, aboard a spacecraft itself, offer an alternative, but they drift as errors accumulate over time. This review assesses whether cold-atom interferometry, a sensor with far lower drift than systems currently in use, could support such navigation. It outlines the physics of atom interferometry, the advantage of operating in the microgravity of space, and demonstrations in spaceflight so far. It then considers what would be required to make the technology practical, such as reducing its size, weight, and power demands. An estimate of position drift shows that, although the cold-atom sensor accumulates far less error than a conventional one, it is unlikely to be able to support multi-year autonomous navigation without periodic external corrections. It would therefore need to be paired with position updates rather than used as a standalone navigation system.
The exquisite precision of atom interferometers has sparked the interest of a large community for uses ranging from fundamental physics to geodesy and inertial navigation. However, their implementation for onboard applications is still limited, not least because rotation and acceleration are intertwined in a single phase shift, which makes the extraction of a useful signal more challenging. Moreover, the spatial separation of the wave packets due to rotations leads to a loss of signal. We present an atom interferometer operating over a large range of random angles, rotation rates and accelerations. A model of the expected phase shift allows us to untangle the rotation and acceleration signals. We also implement a real-time compensation system using fiber-optic gyroscopes and a rotating reference mirror to maintain the full contrast of the interferometer. We demonstrate a single-shot sensitivity to acceleration of 24 μg for rotation rates reaching 14° s−1. Cold atoms inertial sensors offer great precision and sensitivity, yet their use in mobile applications has been hindered by the effects of rotations on their measurements. Here, authors demonstrate an atom interferometer operating over a wide range of orientations and rotation rates, thanks to hybridisation with accelerometers and gyroscopes.