Envisat was an ESA satellite (2002-2012), devoted to environmental studies, notably in the areas of atmospheric chemistry and ocean, ice and landsurface studies. Up to now, it is the largest Earth Observation spacecraft ever built. It carried ten sophisticated optical and radar instruments to provide continuous observation and monitoring of the Earth's land, atmosphere, oceans and ice caps. Envisat data collectively provided a wealth of information on the workings of the Earth system, including insights into factors contributing to climate change.
One of the more than ten instruments onboard was the German-Dutch-Belgian SCIAMACHY instrument which was built to perform measurements of the Earth's atmosphere. Dutch industry and institutes were responsible for the development of the optical unit of SCIAMACHY including the detectors for ultraviolet up to short wave infrared (SWIR) radiation. SRON designed, constructed and tested the detector modules of the SCIAMACHY instrument. Based on the measurements with the SWIR modules SRON also delivered the scientific data products - carbon monoxide (CO), methane (CH4) and heavy water (HDO/H2O).
TROPOMI, SCIAMACHY'S successor, will be launched in 2017. After its launch onboard the ESA satellite Sentinel-5 Precursor TROPOMI will observe the Earth for more than seven years, at an altitude of 800 kilometers. By combining the high spatial resolution and wide coverage of predecessor OMI (still operational) with SCIAMACHY's big spectral range TROPOMI can collect an unprecedented amount of crucial information.
The SCIAMACHY measurements of nitrogen dioxide (NO2), an important indicator of air pollution, were the first to clearly show the air pollution over the Netherlands in the European context. 'This alarmed environmentalists and politicians in the Netherlands, who put air quality high on the Dutch political agenda,' SRON researcher and co-lead scientist Ilse Aben says. SCIAMACHY measurements also determined that elevated concentrations of carbon monoxide (CO) over Australia could be traced back to originate from South American wildfires some 13000 km away.
One of the important breakthroughs of SCIAMACHY was the registration of enhanced methane concentrations above the Tropics. 'Methane is a relatively potent greenhouse gas and an important factor in global warming' says Aben, 'so these findings are very relevant. They have inspired a lot of new research, including speculations on new sources of methane.' SCIAMACHY measurements also gave rise to the conclusion that higher temperatures on the Earth’s surface at higher latitudes cause an increase in the emission of methane. Therefore higher temperatures are not just a consequence of climate change but also a cause of it.
Furthermore the instrument is responsible for the first global observations of heavy water with sensitivity towards the lowest layers of the atmosphere, where most of the water vapour resides. This has enabled us to deepen our current understanding of the hydrological cycle which determines the Earth's climate to a large extent. Ultimately this leads to better climate models. 'All in all you could really label ENVISAT/SCIAMACHY one of the giants of Earth observation research,' says Aben.
SRON designed, constructed and tested the detector modules of the SCIAMACHY instrument. SCIAMACHY, as one of the instruments on board of Envisat, was a UV-VIS-NIR spectrometer designed to detect a large number of trace gases in the stratosphere and troposphere relevant to ozone chemistry and global warming. Furthermore, SCIAMACHY collected data on cloud coverage, aerosol and ground reflection. High accuracy and stability enabled the recordings of minimal, longer-term changes in atmospheric gas concentrations. Sciamachy provided continuation of the data record started with the GOME instrument on ERS-2, with better accuracy and with more atmospheric trace-gas species.
SCIAMACHY was a Dutch-German co-production with Belgium contribution, headed by the German Space Agency (DLR) and its Dutch counterpart, the Netherlands Agency for Aerospace Programmes (NIVR). SRON's task was to design, construct and test the detector modules; this included all relevant detector, mechanical, thermal, electromagnetic and vibration aspects. SRON was involved in the in-flight calibration of the instrument, the retrieval of geophysical data products, and their scientific interpretation.