Mr. James Grant Profile

James Grant

Opto Mechanical Engineer

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Publications (2)

Proceedings Article | 17 November 2017 Open Access

The Tropomi instrument: last steps towards final integration and testing

J. Doornink, J. de Vries, R. Voors, J. Dingjan, B. Ording, N. van der Valk, R. Vink, R. Hoogeveen, J. Grant, T. Canas, Q. Kleipool, P. Veefkind

Proceedings Volume 10563, 1056342 (2017) https://doi.org/10.1117/12.2304148

KEYWORDS: Sensors, Short wave infrared radiation, Spectroscopy, Space telescopes, Telescopes, Astronomical imaging, Calibration, Electronics, Near infrared, Space operations

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Proceedings Article | 18 July 2014 Paper

Cryogenic optical mounting for short-wave infrared spectrometers

J. Grant, T. Wood, I. Bhatti, A. Cañas, P. Reddick, P. van Wyk, S. Bharadia, T. Storey, T. Potterton, W. Rits, H. Meijer

Proceedings Volume 9151, 91513Z (2014) https://doi.org/10.1117/12.2057986

KEYWORDS: Adhesives, Prisms, Sensors, Short wave infrared radiation, Silicon, Spectrometers, Optical mounts, Germanium, Cryogenics, Titanium

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In order to measure atmospheric concentrations of carbon monoxide, methane, water and carbon dioxide from spaceborne platforms, Short-Wave Infrared (SWIR) immersed grating spectrometers are employed. Due to the need to minimise detector dark current and internal black body radiation from the spectrometer’s own structure, these instruments are operated at cryogenic temperatures. ESA’s Sentinel 5-Precursor is a small satellite science mission; the platform comprises the Tropospheric Monitoring Instrument (TROPOMI), which includes a SWIR module. Optical mounts have been developed for the SWIR module which meet the requirements to cope with the differences in thermal expansion between the optical elements and their structural mounts over cryogenic temperature ranges, be robust against the mechanical environment during launch, and maintain optical alignment stability with a tight volume constraint. Throughout the design of the SWIR spectrometer, flexures were deployed to control deformations due to thermal expansion, the design of interfaces between materials of differing coefficient of thermal expansion was carefully managed, and the geometry of adhesive pads was tightly controlled. Optical mounting concepts were evaluated using finite element analysis (FEA). A breadboard programme was undertaken to verify these concepts. FEA and breadboard results were correlated to provide confidence in the design. The breadboard programme consisted of thermal cycling and pull-testing of adhesive joints, as well as environmental and optical testing of representative subsystems. Analysis and breadboarding demonstrated that the optical mounting design will survive the mechanical and thermal environments, and verified the stability of the optical alignment requirements. Novel optical mounting structures have been designed, analysed, assembled, tested and integrated into the optical assemblies of the TROPOMI SWIR spectrometer, creating a compact and robust state of the art instrument. These concepts are applicable to instruments for astronomical missions aiming to characterise exoplanets, as well as Earth observation missions.

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