Detecting and analysing the extremely sparse environments of the upper atmosphere, exosphere, and beyond demands innovative sensing technologies. Rafal Gajewski, Ravindra T Desai, and James Bateman, from the University of Warwick and Swansea University respectively, alongside Bengt Eliasson, Daniel K L Oi, and Animesh Datta, present a new approach called LEVITAS, which utilises the dynamics of a levitated nanoparticle to detect individual particle impacts. This sensor employs optical trapping to hold a single nanoparticle in place, effectively creating a highly sensitive harmonic oscillator, and tracks its movement with exceptional precision. The team demonstrates that by analysing these minute disturbances, LEVITAS can accurately determine the density, velocity, temperature, and composition of the surrounding medium, offering unprecedented capabilities for studying rarefied environments ranging from low Earth orbit to the interstellar medium and providing insights into the flow of particles through our solar system.
Current methods struggle with weak signals and inherent noise, limiting our ability to characterise composition and dynamics. This new technique levitates a charged particle within a Paul trap and monitors its motion to infer forces exerted by external fields or impinging particles. By carefully controlling levitation parameters and employing advanced signal processing, the system achieves a force sensitivity of 10−15 N, a significant improvement over existing technologies.
This enhanced sensitivity enables the detection of particles with cross-sectional areas as small as 10−16 m2, allowing for detailed analysis of their size, charge, and composition. The team demonstrates the feasibility of levitodynamics through experiments using micron-sized silica particles, accurately measuring their drag coefficient and charge-to-mass ratio. Furthermore, the research explores the potential of levitodynamics for in-situ measurements in space, proposing a compact and robust instrument design suitable for integration into future planetary and interstellar probes.
Investigating the upper atmosphere, exosphere, and planetary environments
Investigating the upper atmosphere, exosphere, and planetary environments requires highly sensitive metrological techniques. This work presents the operating concept and architecture of an in-situ sensing solution based on the dynamics of a levitated nanoparticle, termed ‘levitodynamics’. The sensor detects and measures impacts of individual particles in rarefied media. This includes optical trapping and manipulation, cooling particles to extremely low temperatures using lasers and feedback control, and employing levitated particles for precision measurements such as detecting gravitational waves, forces, and accelerations. A key aspect of this research is exploring techniques to evade backaction and achieve quantum control of levitated particles. A strong emphasis is placed on developing highly sensitive sensors, extending beyond levitated optomechanics to encompass gravitational wave detection, force and acceleration sensing, and the detection of weak signals.
The research also delves into quantum optics and quantum control, exploring quantum entanglement, quantum feedback control, and the quantum limits to measurement. Sophisticated algorithms are needed to extract weak signals from noisy data, and the research suggests potential research directions based on these findings. The research connects laboratory-based experiments with space-based observations, suggesting applications of these precision measurement techniques to space exploration. The overarching goal is the development of ultra-sensitive sensors using levitated nanoparticles, a rapidly growing field with potential applications in fundamental physics, metrology, and environmental monitoring. This instrument operates by levitating a nanoparticle using a laser and precisely tracking its movement; impacts from surrounding particles cause measurable disturbances to the nanoparticle’s position, allowing for the estimation of the surrounding medium’s density, velocity, temperature, and composition. This achievement offers a new approach to in-situ sensing in environments previously challenging for particle detection.
The team acknowledges that detecting even smaller impacts
The team acknowledges that detecting even smaller impacts remains a key challenge, limited by optical losses and the potential for false detections caused by noise in the system. Future work will focus on refining the methodology to lower the detection threshold and reduce false positives, potentially through techniques like matched filtering. Further enhancements could extend the sensor’s capabilities to three-dimensional tracking, enabling the measurement of wind velocity vectors and providing insights into particle scattering mechanisms, and adapting the methodology to analyse non-Maxwellian gas distributions, which are common in certain atmospheric conditions.
🗞 LEVITAS: Levitodynamics for Accurate Individual Particle Sensing in Space
🧠 ArXiv: https://arxiv.org/abs/2510.24524
