ABSTRACT
Interest in measuring displacement gradients, such as rotation and strain, is growing in many areas of geophysical research. This results in an urgent demand for reliable and field-deployable instruments measuring these quantities. In order to further establish a high-quality standard for rotation and strain measurements in seismology, we organized a comparative sensor test experiment that took place in November 2019 at the Geophysical Observatory of the Ludwig-Maximilians University Munich in Fürstenfeldbruck, Germany. More than 24 different sensors, including three-component and single-component broadband rotational seismometers, six-component strong-motion sensors and Rotaphone systems, as well as the large ring laser gyroscopes ROMY and a Distributed Acoustic Sensing system, were involved in addition to 14 classical broadband seismometers and a 160 channel, 4.5 Hz geophone chain. The experiment consisted of two parts: during the first part, the sensors were co-located in a huddle test recording self-noise and signals from small, nearby explosions. In a second part, the sensors were distributed into the field in various array configurations recording seismic signals that were generated by small amounts of explosive and a Vibroseis truck. This paper presents details on the experimental setup and a first sensor performance comparison focusing on sensor self-noise, signal-to-noise ratios, and waveform similarities for the rotation rate sensors. Most of the sensors show a high level of coherency and waveform similarity within a narrow frequency range between 10 Hz and 20 Hz for recordings from a nearby explosion signal. Sensor as well as experiment design are critically accessed revealing the great need for reliable reference sensors.
ABSTRACT
We present a three-telescope space-based interferometer prototype dedicated to high-resolution imaging. This project, named multiaperture fiber-linked interferometer (MAFL), was founded by the European Space Agency. The aim of the MAFL project is to propose, design, and implement for the first time to the best of our knowledge all the optical functions required for the global instrument on the same integrated optics (IO) component for controlling a three-arm interferometer and to obtain reliable science data. The coherent transport from telescopes to the IO component is achieved by means of highly birefringent optical fiber. The laboratory bench is presented, and the results are reported allowing us to validate the optical potentiality of the IO component in this frame. The validation measurements consist of the throughput of this optical device, the performances of metrological servoloop, and the instrumental contrasts and phase closure of the science fringes.
