SIW, Stratospheric Inferred Winds, is one of the upcoming Swedish research satellites, aiming to study the winds in the middle atmosphere by measuring the Doppler shifts in molecules such as O3 with a limb viewing sub-mm spectrometer. By conducting simulations on the expected observations, the pointing sensitivity requirement of the satellite was investigated to be able to optimise the matching of the wind vectors. The development of SIW is in the early phases and therefore few studies of this topic has been conducted. The Python program AMATERASU (Advanced Model for Atmospheric TeraHertz Radiation Analysis and Simulation) developed by P. Baron has been used to calculate the radiative transfer through the atmosphere with the aim of simulating the satellite observations and the induced pointing errors, both horizontal and vertical. The results indicate that the effects of the horizontal pointing errors are neglectable due to their small contributions to the measurements. If horizontal pointing errors were induced the scan bias could be corrected for in the retrieval to a good degree for all species and the wind. If not corrected for, H2O and O3 were the most affected species and something to take into consideration during further development of the satellite design. The optimisation of the wind vectors showed that the bias of the matching could get decreased by changing the angle between the satellite antennas. / SIW, Stratospheric Inferred Winds, är en av de nästkommande svenska forskningssatelliterna som ämnar att studera vindarna i mellanatmosfären genom att mäta dopplerskift från molekyler så som O3 med en sub-mm spektrometer som skannar atmosfären från sidan. Simuleringar av de förväntade observationerna genomfördes för att bestämma gränsen för känsligheten i pekningen i kravspecifikationen och optimera matchningen av vindvektorerna. Utvecklingen av SIW är fortfarande i ett tidigt stadie och studier kring detta är få. Pythonprogrammet AMATERASU (Advanced Model for Atmospheric TeraHertz Radiation Analysis and Simulation) som är utvecklat av P. Baron har använts för att räkna ut strålningstransfern genom atmosfären och därmed kunna simulera satellitens förväntade observationer och de inducerade pekfelen, både horisontella och vertikala. Resultaten indikerar att effekterna av de horisontella pekfelen är försumbara på grund av deras låga påverkan på mätningarna. Vid vertikala pekfel kunde pekfelet korregeras för i återvinningen i hög grad för alla ämnen och vinden. Om pekfelet inte korregerades för var H2O and O3 de mest påverkade molekylerna och något som måste tas i beaktning under vidare utveckling av satellitdesignen. Optimeringen av vindvektorerna visade att skillnaden för matchningen kan minskas genom att ändra vinkeln mellan satellitantennerna.

This dissertation revisits, develops, and documents methods that can be used to calibrate spaceborne microwave radiometers once in orbit. The on-orbit calibration methods discussed within this dissertation can provide accurate and early results by utilizing Calibration Attitude Maneuvers (CAM), which encompasses Deep Space Calibration (DSC) and a new use of the Second Stokes (SS) analysis that can provide early and much needed insight on the performance of the instrument. This dissertation describes pre-existing and new methods of using DSC maneuvers as well as a simplified use of the SS procedure. Over TRMM's 17 years of operation it has provided invaluable data and has performed multiple CAMs over its lifetime. These maneuvers are analyzed to implement on-orbit calibration procedures that will be applied for future missions. In addition, this research focuses on the radiometric calibration of TMI that will be incorporated in the final processing (Archive/Legacy of the NASA TMI 1B11 brightness temperature data product). This is of importance since TMI's 17-year sensor data record must be vetted of all known calibration errors so to provide the final stable data for science users, specifically, climatological data records.