Breadboarding activities of the TROPOMI-SWIR module

摘要

The TROPOMI instrument concept is part of the TRAQ mission proposal to ESA in response to the Call for Ideas in 2005. TRAQ (TRopospheric composition and Air Quality) has been accepted for a further pre-phase A study for the next Earth Explorer core Mission. A very similar instrument has been proposed for the CAMEO platform to the US National Research Council decadal study, which has also been accepted for further study. TROPOMI is a nadir-viewing grating-based imaging spectrometer using the Dutch OMI and SCIAMACHY heritage. It includes an UV-VIS-NIR module that consists of three UV-VIS channels continuously covering the 270-490 nm range to determine O_3, NO_2, HCHO, SO_2, aerosols and a NIR-channel covering 710-775 nm for cloud detection and information on the aerosol height distribution using the oxygen A band. TROPOMI also includes a SWIR module covering 2305-2385 nm that mainly focuses on determination of CO and CH_4 total columns. All species are measured with sensitivity down to the Earth's surface, thus addressing issues of anthropogenic emissions and their impact on air quality and climate. In the TRAQ mission, unique diurnal time sampling with up to 5 daytime observations over mid-latitude regions (Europe, North-America, China) is foreseen by using a non-sun-synchronous, medium-inclination drifting orbit and a 2600 km wide observational swath.Several more general aspects related to the TROPOMI instrument are discussed in a separate paper in this conference. This paper focuses on the development of the SWIR module. A breadboard model (BBM) has been designed and constructed which is as much as possible functionally flight representative. Critical technologies to be demonstrated with the BBM are the SWIR HgCdTe-based 2D focal plane array, the on-board SWIR calibration LED, and in particular, the SRON/TNO developed silicon-based immersed grating that allows a hugely reduced instrument volume. In the presentation the results of a performance analysis of the TROPOMI-SWIR channel will be discussed, as well as results of the detector characterization program on a representative off-the-shelf FPA, and details of the photolithographic production of the immersed grating.