In the frame of the ESA Sentinel-5 mission, as part of the Copernicus program, Airbus is the prime contractor for the S5 Instrument. As part of the S5 instrument, which is using the METOP SG satellite as a platform, Leonardo is developing the Short-Wave Infrared Spectrometer (SWIR-SS), comprising two parallel channels covering the wavelength ranges of 1589÷1676 nm (SWIR 1) and 2304÷2386 nm (SWIR 3). Major objective of the S5 is the monitoring of the Earth atmosphere by taking measurements of trace gases and aerosols impacting air quality and climate, with a swath width of ca. 2670 Km providing daily coverage of Earth atmosphere at an unprecedented resolution of 7x7 Km2 at nadir. Main characteristic of the SWIR-SS compared to other spectrometers is the high spectral position one orbit stability less than 1um and high spectral pixel resolution of 0.1nm. High stability and optical quality requires accurate optical elements mounting design and high resolution is reached by using new developments regarding Immersed Grating (grating immersed on a prism) and the implementation of a cutting edge 3D Slit Homogenizer system, positioned on the object plane of the spectrometer, to mitigate radiometric errors arising from scene heterogeneity. In order to demonstrate the system performance the optical design has been validated by means of flight representative optical assemblies. These breadboards are representing all relevant optical elements of the system. This paper presents the tests, which have been performed on the flight representative optical elements and the test results. As the Optical Element Mounting, the Slit Homogenizer and the Immersed Grating are major elements to fulfil mission requirements the development approach is described. Special emphasis for Lens mounting is put on the stability and WFE, for the Slit Homogenizer is put on the requirements regarding the slit width variation and the quality of the entrance edge while the major design driver for the Immersed grating is the optical quality. This paper presents the development approach of these two major optical elements and the validation test results.
In the frame of the Sentinel-5 mission, Leonardo is developing the Short-Wave Infrared Spectrometer (SWIR-SS), part of the UVNS instrument foreseen to be embarked on board of the MetOP-SG satellite. S5 instrument objective is to monitor the composition of Earth atmosphere by taking measurements of trace gases and aerosols impacting air quality and climate, providing daily coverage of Earth atmosphere at an unprecedented resolution. SWIR-SS baseline architecture is a pushbroom imaging spectrometer with two channels,[1589÷1676] nm and [2304÷2386] nm, with a spectral resolution of less than 0.25 nm. At the object space is located a Slit-Homogenizer, a special component which guides the optical path across the slit in order to mitigate radiometric errors arising from scene heterogeneity. Its behaviour introduces an astigmatism which is corrected at collimator level by making use of a cylindrical lens. Light is then guided towards the dispersers and is focused onto the detector by the cameras lens. Pupil anamorphism, smile and keystone due to dispersers, immersed gratings, are corrected by using a prism and combining the distortion/lateral color of collimator and focusing cameras in both optical channels. A low pass filter at the dichroic splits the wavelengths, while, for each channel, two successive coatings on front and back faces of the prisms select the band and mitigate outof- band straylight. The design has the purpose to keep the alignment of each subsystem simple, as no aberration compensations have been foreseen between collimator and focusing camera. It shows robustness, stability vs temperature and high optical quality.
Jean-Michel Reess, Pierre Drossart, Alain Semery, Marc Bouye, Olivier Dupuis, Yann Hello, Gerard Huntzinger, Driss Kouach, J. Parisot, Didier Tiphene, J. Romon, Y. Ghomchi, Jean-Pierre Bibring, G. Bonello, S. Erard, B. Gondet, Yves Langevin, Alain Soufflot, Angioletta Coradini, Fabrizio Capaccioni, Enrico Suetta, Michele Dami, A. Cisbani, C. Pasqui, I. Ficai Veltroni, Gabriele Arnold, Johann Benkhoff, G. Peters
Virtis-H is the high spectral resolution channel of the visible and infrared imaging spectrometer VIRTIS, an instrument of the ESA/ROSETTA mission devoted to the in-orbit remote sensing study of the comet P/46 Wirtanen. After successful tests and calibration, the flight model has been delivered to the European Space Agency for integration on the satellite before the launch foreseen in January 2003. The Virtis-H channel is a cross-dispersion spectrometer in the spectral range 2-5um with a resolution between 1200 and 3000. Its design consists in an afocal telescope-collimator off-axis parabola mirrors, a prism-grating system performing the cross-dispersion, and a three-lens objective imaging the entrance slit on a 436x270 HgCdTe array from Raytheon/IRCOE. At each recorded image, a full spectrum of the observed scene is reconstructed allowing the study of the fine spectral details of the coma and the cometary nucleus. The calibration have shown the fully compliance of the instrument performances with the simulations in terms of spectral resolution, radiometric accuracy and sensibility. For example, spectra of gas, water ice and mineral powders have been measured with Virtis-H showing either its ability to resolve fine spectral lines but also its sensitivity to low fluxes; furthermore, measurements on a 250K blackbody shows its sensibility to relative temperature variation lower than 0.5oC..
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.