Explore the vast range of titles available.

Retrofitting regional turboprop aircraft with hydrogen (H2)-electric powertrains, using fuel cell systems (FCSs), has gained interest in the last decade. This type of powertrain eliminates CO2, NOx, and fine particle emissions during flight, as FCSs only emit water. In this context, the “Hydrogen Aircraft Powertrain and Storage Systems” (HAPSS) project targets the development of a H2-electric propulsion system for retrofitting Dash 8-300 series aircraft. The purpose of the study described in this paper is to analyze the performance of the retrofitted H2-electric aircraft during critical operating conditions. Takeoff, as well as climb, cruise and go-around performances are addressed. The NLR in-house tool MASS (Mission, Aircraft and Systems Simulation) was used for the performance analyses. The results show that the retrofitted H2-electric aircraft has a slightly increased takeoff distance compared to the Dash 8-300 and it requires a maximum rated shaft power of 1.9 MW per propeller. A total rated FCS output power of 3.1 MW is sufficient to satisfy the takeoff requirements, at the cost of lower cruise altitude and reduced cruise speed as compared to the Dash 8-300. Furthermore, a higher-rated FCS is required to achieve the climb performance required for the typical climb profile of the Dash 8-300.

The Sentinel-5 Precursor satellite was successfully launched on 13 October 2017, carrying the Tropospheric Monitoring Instrument (TROPOMI) as its single payload. TROPOMI is the next-generation atmospheric sounding instrument, continuing the successes of GOME, SCIAMACHY, OMI, and OMPS, with higher spatial resolution, improved sensitivity, and extended wavelength range. The instrument contains four spectrometers, divided over two modules sharing a common telescope, measuring the ultraviolet, visible, near-infrared, and shortwave infrared reflectance of the Earth. The imaging system enables daily global coverage using a push-broom configuration, with a spatial resolution as low as 7×3.5 km2 in nadir from a Sun-synchronous orbit at 824 km and an Equator crossing time of 13:30 local solar time. This article reports the pre-launch calibration status of the TROPOMI payload as derived from the on-ground calibration effort. Stringent requirements are imposed on the quality of on-ground calibration in order to match the high sensitivity of the instrument. A new methodology has been employed during the analysis of the obtained calibration measurements to ensure the consistency and validity of the calibration. This was achieved by using the production-grade Level 0 to 1b data processor in a closed-loop validation set-up. Using this approach the consistency between the calibration and the L1b product, as well as confidence in the obtained calibration result, could be established. This article introduces this novel calibration approach and describes all relevant calibrated instrument properties as they were derived before launch of the mission. For most of the relevant properties compliance with the calibration requirements could be established, including the knowledge of the instrument spectral and spatial response functions. Partial compliance was established for the straylight correction; especially the out-of-spectral-band correction for the near-infrared channel needs future validation. The absolute radiometric calibration of the radiance and irradiance responsivity is compliant with the high-level mission requirements, but not with the stricter calibration requirements as the available on-ground validation shows. The relative radiometric calibration of the Sun port was non-compliant. The non-compliant subjects will be addressed during the in-flight commissioning phase in the first 6 months following launch.