Papers by Oana van der Togt
Multi-angle spectro-polarimetry is the tool for the remote detection and characterization of aero... more Multi-angle spectro-polarimetry is the tool for the remote detection and characterization of aerosol and clouds in the Earth's atmosphere. Using a novel technique to measure polarization, we have developed a 30 kg instrument design to simultaneously measure the intensity and state of linear polarization of scattered sunlight, from 400 to 800 nm and 1200 to 1600 nm, for 30 viewing directions, each with a 30° swath. Aerosols affect the climate directly by scattering and absorption of solar radiation, and by scattering, absorption, and emission of thermal radiation. Aerosols also affect the climate by changing the macro- and microphysical properties of clouds (the so-called indirect and semi-direct effects). Estimates of aerosol effects on the climate are hampered by insufficient knowledge of aerosol properties (size distribution, shape, and single scattering albedo) at a global scale. From several studies we know that these properties can only be determined with sufficient accurac...
International Conference on Space Optics — ICSO 2010, Sep 5, 2019
International Conference on Space Optics — ICSO 2012
Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2019
Composite constructions are indispensable in current and future society. Fiber Bragg Gratings (FB... more Composite constructions are indispensable in current and future society. Fiber Bragg Gratings (FBGs) embedded in composite need to be carefully aligned with the material fibers to reduce inhomogeneous lateral load exerted onto the FBG which occurs due to the inhomogeneous nature of composite materials. Inhomogeneous load causes distortion of the reflection spectrum. We proposed to solve the FBG spectral distortion by incorporating a dedicated design structure inside the optical fiber. This allows the FBG to sense the strain in the axial direction accurately regardless of the optical fiber alignment with respect to the composite matrix. In this paper, the basic design will be discussed and the results of the first prototype of this structured fiber will be presented. Prototype FBGs are embedded in different composite samples of various thicknesses and materials (glass or carbon fiber based). The spectrum before and after curing is measured and direct comparisons are performed with embedded standard commercial FBG to verify the improvement. Effects of depth of the embedding and FBG direction with respect to the composite material fiber are investigated. Bending and tension tests are performed to ensure the special FBG in the structured fiber has the directional sensitivity to the strain applied. During all experiments, the special FBG is found to have a better or comparable spectrum than the standard FBGs. The improvement varies for the different tests. This can be caused by the unknown orientation of the structure inside the fiber. According to the first FEM analysis, this affects the effectiveness depending on the detail design of the structure. Information of the FEM analysis will be used to further optimize the design and for the development of a prototype.
IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium, 2018
As both possible adjuncts to institutional atmospheric chemistry remote sensing missions (e.g. Se... more As both possible adjuncts to institutional atmospheric chemistry remote sensing missions (e.g. Sentinel 5) and as state of the art instruments in their own right, TNO has developed an all reflective instrument design to cover UV to SWIR wavelengths. An initial breadboard development (Spectrolite) has been designed to target urban atmospheric pollution with a design for a high spatial ($1\mathrm{x}1\ \mathrm{km}^{2}$) at 700km altitude, and similar radiometric detection capability as current instruments. The Spectrolite instrument has been flown in an airborne campaign (Aromapex, April 2016) and, given limitations in COTS elements used, has demonstrated the performance to confirm that this design approach will achieve the expected performance for an in orbit instrument. The success of Spectrolite leads the way for other future instruments aimed at applications for land and water remote sensing.
25th International Conference on Optical Fiber Sensors
The presented interferometer concept enables high-accuracy target displacement measurement in dif... more The presented interferometer concept enables high-accuracy target displacement measurement in difficult accessible locations and the development of small fiber optic sensor to measure other physical parameters e.g. pressure, vibration, gravity force, etc.. Furthermore, this configuration is basically insensitive to disturbances to the lead fiber between the passive sensor head and the measurement system including the electro-optical parts and the detection interferometer. Two test setups are built and tested to demonstrate the feasibility of high-speed measurement up to 50 kHz, low system drift of ~0.5 nm over 500 s and a low displacement noise level down to 2.8 pm/√ Hz.
International Optical Design Conference and Optical Fabrication and Testing, 2010
Sensors, Systems, and Next-Generation Satellites XXV
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Papers by Oana van der Togt