Development of SARAL/AltiKa altimetric data over the Antarctic ice sheet

• Main Author: Michel, Aurélie
• Other Authors: Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales Toulouse (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Université Paul Sabatier - Toulouse III, Frédérique Rémy, Annabelle Ollivier
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2016
• Subjects: Antarctica; SARAL; Altimetry; Signal processing; Data processing; Remote Sensing; ENVISAT; ICESat; Antarctique; Altimétrie; Traitement du signal; Traitement de données; Télédétection; [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; Antarctic; The Antarctic; Antarc*; Antarctique*; Ice Sheet; Iceberg*
• Online Access: https://tel.archives-ouvertes.fr/tel-01398061; https://tel.archives-ouvertes.fr/tel-01398061v2/document; https://tel.archives-ouvertes.fr/tel-01398061v2/file/2016TOU30091b.pdf

Antarctica still remains a fascinating place to be explored. With ice corings, the past Earth climate can be retraced. Studying its surface, its climate variability and its dynamic are better known : ice velocity, iceberg calvings. . . Through the height variations monitoring, ice gains and losses are estimated, leading to the contribution to the sea-level rise, from which is deduced the impact over coastal areas or the oceans. To explore this continent, we use the sensor called altimeter : a radar or laser wave is sent from the satellite to the surface and the reflected signal is recorded. From this signal we extract relevant parameters and the height. The satellites have observed this area, notably since the altimetric mission ERS-1 launching, until 82æ S in 1991, following the still famous explorations from the beginning of the twentieth century. SARAL, launched in February 2013, innovates because of the major change in the frequency used, the Ka-band (36.75 Ghz) instead of the Ku-band (13.6Ghz) and the S-band (3.2 Ghz) implying a different interaction between the radar wave and the snowpack that needs to be investigated. Using almost three years of observations, we focus on the altimetric signal processing and its validation. The geographic and the technical aspects are introduced and we show the limitations in the altimetric data processing. Using the crossover method (explained in greater detail later), we compare two simultaneous missions, ENVISAT and ICESat in order to better constrain the penetration effect of the radar-wave into the snowpack and correct it. The method that is used will be of great interest to compare SARAL with the future mission ICESat- 2. A new calibration and validation tool has been implemented, allowing a long-term survey of the Antarctic area, providing statistics, diagnostics and temporal series. The slope effect is the major limitation in the precision assessment of the mission. Thanks to a new way of selecting the data and the oceanic tide correction, we quantify with metrics ...