The ROSA Project for Radio-Occultation: Findings and Current Status

L. Marradi, A. Zin, S. Zago, S. Landenna, E. Mangolini, V. Catalano, R. Notarpietro, S. Radicella, B. Nava

Abstract:	ROSA is a dual-frequency GPS receiver developed for space applications and tailored for GPS radio occultation studies. It is developed and manufactured by Thales Alenia Space Italia under a contract with the Italian Space Agency (ASI) and is designed to establish accurate global profiles of temperature and water vapour in the lower atmosphere. Moreover, ROSA antenna extended coverage allows the retrieval of total electron count (TEC) profiles in the ionosphere for space weather applications. ROSA instrument is flying in three satellites: the first one launched on September 2009 OCEANSAT-2, the second one on SAC-D launched on June 2011 and the third on MEGHATROPIQUES launched on October 2011. Availability of Rosa data is seen as an opportunity by the scientific community, to cover the 2013-2016 gap that will be left by the decommissioning of the Taiwan/US COSMIC-FORMOSAT3 constellation. The available scientific results are shortly recalled here: The prototype of the processing software developed by EUMETSAT (namely YAROS) and the one developed by ROM-SAF (ROPP) were recently updated for the ROSA data handling (observations collected on board OCEANSAT-2). Despite problems related to the strong local multipath due to the not optimal ROSA Radio Occultation antenna accommodation which impacts L2 availability (in particular in lower troposphere), ROSA processed data are in line with those of other Radio Occultation payloads. Results will be detailed in this paper. As a matter of fact, the discrepancy between bending angle profiles and profiles obtained forward modelling ECMWF collocated data is unbiased, and shows a standard deviation of 2.5% from 10 km to 40 km. The effectiveness of ROSA receiver in sounding the ionosphere will be demonstrated in terms of electron density profiles retrieved using the standard approach based on the Onion Peeling inversion of measured TECs and, if the data are available, comparing results with independent observations (e.g. other COSMIC-FORMOSAT3 Radio-Occultation observations). Moreover the sensitivity and accuracy of the ROSA receiver will be utilized to search for possible sporadic E-layer signatures. These aspects are very important since, for the next few years, ROSA will be the only Radio Occultation receiver devoted also to Ionospheric observations. And this will be particularly important now that solar maximum is approaching. signal reflections from oceans and ice: some considerations are done about observability and possible useful information retrieval. The now-standard open-loop technique allows to infer important properties of the atmospheric signal alone. In fact, one of the major issues in testing radio-occultation GPS receivers in ground is the realism and accuracy in the test signal injected in the simulation. Observation of the response of the instrument in factory is fundamental to tailor it for an optimal use in space. Here we provide insights in the experience gained in this step of receiver manufacturing. In summary, analysis of data output from ROSA instruments flying nowadays and presented in this paper allow insights on different aspects of GNSS remote sensing, especially important nowadays that COSMIC-FORMOSAT is going to be decommissioned and in period of solar maximum
Published in:	Proceedings of the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2012) September 17 - 21, 2012 Nashville Convention Center, Nashville, Tennessee Nashville, TN
Pages:	1990 - 1997
Cite this article:	Marradi, L., Zin, A., Zago, S., Landenna, S., Mangolini, E., Catalano, V., Notarpietro, R., Radicella, S., Nava, B., "The ROSA Project for Radio-Occultation: Findings and Current Status," Proceedings of the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2012), Nashville, TN, September 2012, pp. 1990-1997.
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