TROPOMI - the Instrument
2D detector
The design of the TROPOMI instrument is based on that of OMI and uses two dimensional (2D) detector technology. With this technique the complete 'spoorbreedte' of 2600 km is 'afgebeeld' along one axis of the 2D focal plane array. The spectral information wil be projected along the other axis. TROPOMI uses state-of-the-art 2D radiation hard detectors.
SWIR
To continue and improve on the SCIAMACHY data record of CO and CH4 a SWIR channel is included in the design studies[1]. The SWIR channel is the most innovative part of the instrument as it combines for the first time immersed grating technology, a polarization scrambler, a hybrid-CMOS focal plane array (FPA), and SWIR LED’s for in-flight detector calibration. The immersed grating technology is mandatory to transfer the push-broom imaging concept to the SWIR spectral domain without a huge increase of instrument size compared to the SCIAMACHY SWIR channels. The TROPOMI-SWIR instrument study will test essential elements of the TROPOMI / TROPI SWIR channel on component level and will join them together with the immersed grating to realize a breadboard model. The feasibility of the immersed grating-based SWIR channel will be demonstrated on instrument level by performing gas cell absorption measurements on CH4 and CO. The silicon-based immersed grating technology developed by SRON and TNO offers a factor 3.42 more diffraction than a conventional grating.
Measurements of sources of spectral lines
First tests with the SWIR breadboard have shown the feasability of the extension of the OMI technology to the SWIR spectral band by using the immersed grating and 2D CMOS detector technology. The measured dispersion is as expected and the resolution of 0.25 nm is within the secifications.
