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Long-term Stability Analysis of Antenna Temperature & Brightness Temperature from ESA's SMOS Satellite
KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
2011 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The European Space Agency’s Soil Moisture and Ocean Salinity (SMOS) satellite is designed to accurately detect the energy of the electromagnetic radiation naturally emitted from Earth, from which the level of soil moisture and ocean salinity content can be derived. Studies of these two geophysical parameters will increase the knowledge of the Earth’s water cycle and improve the understanding of the climate. The single payload of the SMOS satellite is the Microwave Imaging Radiometer by Aperture Synthesis (MIRAS). Researchers at Universitat Politècnica de Catalunya in Barcelona have developed the MIRAS Testing Software which basically translates SMOS raw data into useful data. The data is continuously analyzed and it has been discovered that some parameters of the MIRAS instrument are drifting more than expected.The objective of this Master’s thesis project was to create a long-term stability analyzing tool with which the long-term trends of the MIRAS parameters antenna temperature and brightness temperature can be investigated. The long-term stability analyzing tool has been coded in Matlab and the analysis is based on flight data from January to November 2010. The data has been processed in the MIRAS Testing Software with different inversion and calibration options before it has been used as input to the long-term stability analyzing tool. The main goal of this project was to find out which of the options gave the least drifting and most accurate results.The calibration options that have been studied are the 1-point and 4-point calibration, referring to the number of reference points used in each calibration respectively. The long-term stability analysis of the antenna temperature shows that the 1-point calibration gave more stable results than the 4-point calibration. This was expected since the 4-point calibration makes use of the so called NIR (Noise Injection Radiometer) antennas so a drift in the calibration of the NIRs is added to the uncertainty of the 4-point calibration.The inversion options refer to different approaches of inverting the measured visibility to brightness temperature. The two approaches that have been studied differ from each other by a correction term of the visibility that is included in Approach 3 and not in Approach 5. The long-term stability analysis of the brightness temperature shows that the inversion Approach 5 gave more stable results than the inversion Approach 3, which means the correction term causes instability in the results. If the correction was modified though, Approach 3 could possibly give more stable results which might imply a change of this conclusion.This long-term stability analysis aimed to contribute to the assessment of the stability of the MIRAS instrument, and so it has. This Master’s thesis project’s main contribution to the SMOS project is the demonstration of a new kind of systematic long-term stability analysis, which uses the same set of data when comparing things, in this case different inversion and calibration options. As a consequence of this Master’s thesis project, the SMOS calibration community is now discussing the options for finding metrics that can help to establish the SMOS long-term stability.

Place, publisher, year, edition, pages
, TRITA-GIT EX, ISSN 1653-5227 ; 11-004
URN: urn:nbn:se:kth:diva-35299ISRN: KTH/GIT/EX--11/005-SEOAI: diva2:427051
Educational program
Master of Science - Engineeering Physics
2011-06-23, 14:30 (English)
Available from: 2011-08-26 Created: 2011-06-27 Last updated: 2011-09-16Bibliographically approved

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