Spectral Calibration of the SLSTR Focal Plane Assemblies

<p>We describe a novel technique – Fourier transform spectroscopy – that we have developed to characterise the spectral and polarisation responses of the Sentinel-3 SLSTR optical channels. Our method has a number of advantages over conventional approaches employing a grating monochromator, including excellent spectral registration and resolution, intrinsic rejection of self-emission from the test setup and fast measurement times. Our measurements are traceable, through the spectral responsivity of a reference detector and the wavelength of a HeNe laser, to national standards.</p><p>We illustrate our method with sample results from the spectral calibrations of the four SLSTR focal plane assemblies tested to date. </p>

An optical metrology system for the measurement of the refractive index of glass

The measurement of the refractive index of parallel plated, optically simple, glass samples is a common and fundamental activity in numerous fields of expertise. This work aimed to optimize a known technique to a simple, cost-effective and reliable system to be implemented in a lab environment, with an accuracy in the results better than 10-2. A setup with a 632.8nm HeNe laser, automatic stage and CMOS camera was used and data was acquired with the help of LabVIEW controlling software. All system components were carefully controlled and optimized with the help of an uncertainty budget. Measurements had an associated uncertainty in the range from 10-3 to 10-4.

Picometer mechanical displacement measurement using heterodyne interferometer with phase-locked loop

In this paper, we show picometer-order mechnical displacmment measurements using a heterodyne interferometer with a phase-locked loop (PLL). A heterodyne light source for the interferometer is implemented with a frequency stabilized HeNe laser and two acousto-optic modulators. A real time phase measurement is performed by the PLL, whose software is programmed in a field-programmable gate array (FPGA). A stiff parallel spring stage combined with a high-voltage piezoelectric actuator is used to generate picometer-order mechanical motion. With the above implementations, mechanical displacement of 10 picometer or less can be measured.