Experiences on altimeter calibration at Ibiza island and Cape of Begur (Spain)

Three preliminary camp aigns for TOPEX /POSEIDON (T/P) wer e made in March 1999 and July 2000 and for JASON-1 in August 2002, in the NW Mediterran ean Sea at th e Begur Cape area. Dir ect abso lute altimeter calibration , and mapping of the sea surface, w ere made in these camp aigns from dir ect overflights using GPS buoys with a toroidal design performed at the I CC based in the orig inal design of the Univ ersity of Colorado at Boulder and a estimation of the TOPEX A lt- B bias w as made. A Spanish JASON-1 geoid gradien t campaign with Fench support has been made in June 2003 at the Ibiza island in the NW Mediterr anean Sea. Th e main objectiv e has b een to map w ith a new d esign ed, builded and calibrated GPS catamar an, the lo cal geoid gradien t in three ar eas around Ibiza island under the ascending (187) and descending (248) Jason-1ground tracks. The catamaran equ ipped with two GPS antennas to perform continuous sea lev el measur ements was towed by the Patro l Dev a from th e Span ish N avy. Five GPS reference stations were dep loyed on Ibiza island: one in Portinatx, two in San Anton io and two in Ibiza. The marin e geo id has been used to relate the coastal tide gauge data from Ibiza and San An tonio h arbours to off- shore altimetric data. In th e framework of the campaign, the levelling of the Ibiza and San Anton io tide gauges to the r espective GPS mark ers w as p erformed. We present synth esis of the resu lts obtained from Topex/Poseidon and th e first r esults on Jason-1 altimeter calibration using the direct measurements from GPS buoys and the derived marin e geoid. Th e Ibiza results agree relativ ely w ell with resu lts ob tained at Corsica, Harvest and Bass Strait calibration permanen t sites. Moreov er, the geod etic activities (e.g., GPS, levelling) has p ermitted to build a very accurate (few mm) local n etwork link ed to th e European one, w ith a reference frame compatible with th e satellite altimetry missions (ITRF2000). The GPS kinematic data wer e processed using two d ifferen t sof twar es allowing to check th e consistency of the solutions. A perspective of a new Jason-1, in cluding Envisat, Ibiza campaign to be made around 2007 will be pr esen ted. These camp aigns w ere supporte by th e Span ish Ministery of Scien ce and Technology under projects of the N ational Space Program ref : ESP1997-1816-CO4- 03 and ESP2001-4534-PE.Peer ReviewedPostprint (published version

Campañas altimétricas de calibración del Topex y Jason-1 en el Mediterráneo Occidental

Se describen las campañas de calibracion altimétrica realizadas en el Mediterráneo Occidental por la Universidad Politécnica de Cataluña con el soporte del Instituto Cartográfico de Cataluña, el Real Instituto y Observatorio de la Armada y por Puertos del Estado principalmente. Se realizaron tres experiencias en el Cabo de Begur para calibracion altimétrica y mapeo del geoide marino realizadas en 1999, 2000 y 2002. Calibración absoluta directa estimando el bias del Alt‐B del Topex fue realizada durante el overflight del satelite usando boyas GPS. Una contribución española a las experiencias de calibración ha sido el diseño de las Boyas y Catamarán GPS teniendo en cuenta diseños previos de la Universidad de Boulder en Colorado y las de Senetosa/Capraia. Una campaña mas fue realizada en Junio de 2003 en el area de la Isla de Ibiza. Se utilizaron cinco estaciones GPS de referencia localizadas en Ibiza, San Antonio y Portinax, y por dos mareógrafos georeferenciados situados en los puertos de Ibiza y San Antonio. Una calibración directa adicional fue realizada el 14 de Junio. Otro objetivo importante era obtener el perfil de la Superficie Media Marina a lo largo de las trazas del T/P o Jason‐1 con boyas/catamarán GPS. Mapear la superficie marina para la calibración altimetrica indirecta tiene la ventaja de permitir la calibración de cualquier radar que cruce el area estudiada pero, en cambio, la desventaja es reduce la precision de la estimación del bias. Se tiene prevista una nueva campaña a realizar en la misma zona aproximadamente siguiendo las trazas de los atélites Jason‐2 y Altika con lanzamiento previsto en 2011 que permitirá obtener datos altimétricos en zonas róximas a la costa. Three Begur Cape experiences on radar altimeter calibration and marine geoid mapping made on 1999, 2000 and 2002 are overviewed. One campaign has also been made in June 2003 at the Ibiza island area. Direct absolute calibration estimating the Topex Alt‐B bias was performed during the satellite overflight by using GPS buoys. The advantage of that method is that neither geoid modelling nor tidal error is needed. Other main objective was to map the profile of the Mean Sea Surface (mss) along the closest T/P and Jason‐1 groundtrack. Mapping the marine surface for indirect altimeter calibration has de advantage of allowing the calibration of any radar sensor that crosses the studedarea but, in turn, the disadvantage is that the method requires ocean tide and geoid knowledge, which reduces the accuracy of the bias estimate by a factor of 2. A technical Spanish contribution to the calibration experience has been the design of GPS buoys and GPS catamaran taking in account the University of Colorado at Boulder and Senetosa/Capraia. For the mapping of the extended calibration areas centered on satellite ground tracks, the catamaran was tracked by the Patrol Deva, from the Spanish Navy. An additional absolute altimeter direct calibration was performed on June 14. Complementary data came from five GPS reference stations deployed at Ibiza , San Antonio and Portinatx, and from vertically‐referenced tide gauges located at Ibiza and San Antonio. We present first results on Jason‐1 altimeter calibration using the marine geoid derived from data collected during the campaign. Moreover, the geodetic activities (e.g., GPS, leveling) has permitted to build a very accurate (few mm) local network linked to the european one,s (ITRF2000).Postprint (published version

JASON-1 CALVAL experiences in Cape of Begur and Ibiza island

The direct and indirect calibration experiences made at the Cape of Begur area in 1999, 2000 and 2002, for Topex/Poseidon and at the Ibiza island in 2003 have contributed to the international campaigns made at Harvest (USA), Corsica (France) and Bass (Australia). The main objective of IBIZA 2003 campaign has been the determination of the instantaneous sea surface/marine geoid gradient along Jason-1 tracks using a GPS catamaran and a network of GPS located in Portinatx and Ibiza and San Antonio harbours. The marine geoid will be used to relate the tide gauge coastal data with the altimeter data. We present the first results obtained with static and kinematic analysis of the data using different softwares.Peer ReviewedPostprint (published version

GENESIS: Co-location of Geodetic Techniques in Space

Improving and homogenizing time and space reference systems on Earth and, more directly, realizing the Terrestrial Reference Frame (TRF) with an accuracy of 1mm and a long-term stability of 0.1mm/year are relevant for many scientific and societal endeavors. The knowledge of the TRF is fundamental for Earth and navigation sciences. For instance, quantifying sea level change strongly depends on an accurate determination of the geocenter motion but also of the positions of continental and island reference stations, as well as the ground stations of tracking networks. Also, numerous applications in geophysics require absolute millimeter precision from the reference frame, as for example monitoring tectonic motion or crustal deformation for predicting natural hazards. The TRF accuracy to be achieved represents the consensus of various authorities which has enunciated geodesy requirements for Earth sciences. Today we are still far from these ambitious accuracy and stability goals for the realization of the TRF. However, a combination and co-location of all four space geodetic techniques on one satellite platform can significantly contribute to achieving these goals. This is the purpose of the GENESIS mission, proposed as a component of the FutureNAV program of the European Space Agency. The GENESIS platform will be a dynamic space geodetic observatory carrying all the geodetic instruments referenced to one another through carefully calibrated space ties. The co-location of the techniques in space will solve the inconsistencies and biases between the different geodetic techniques in order to reach the TRF accuracy and stability goals endorsed by the various international authorities and the scientific community. The purpose of this white paper is to review the state-of-the-art and explain the benefits of the GENESIS mission in Earth sciences, navigation sciences and metrology.Comment: 31 pages, 9 figures, submitted to Earth, Planets and Space (EPS

A common variant near TGFBR3 is associated with primary open angle glaucoma

Primary open angle glaucoma (POAG), a major cause of blindness worldwide, is a complex disease with a significant genetic contribution. We performed Exome Array (Illumina) analysis on 3504 POAG cases and 9746 controls with replication of the most significant findings in 9173 POAG cases and 26 780 controls across 18 collections of Asian, African and European descent. Apart from confirming strong evidence of association at CDKN2B-AS1 (rs2157719 [G], odds ratio [OR] = 0.71, P = 2.81 × 10−33), we observed one SNP showing significant association to POAG (CDC7–TGFBR3 rs1192415, ORG-allele = 1.13, Pmeta = 1.60 × 10−8). This particular SNP has previously been shown to be strongly associated with optic disc area and vertical cup-to-disc ratio, which are regarded as glaucoma-related quantitative traits. Our study now extends this by directly implicating it in POAG disease pathogenesis

Altimetry for the future: Building on 25 years of progress

In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology. The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the ‘‘Green” Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instruments’ development and satellite missions’ evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion

Agroforesterie et services écosystémiques en zone tropicale

Respectueux de l’environnement et garantissant une sécurité alimentaire soutenue par la diversification des productions et des revenus qu’ils procurent, les systèmes agroforestiers apparaissent comme un modèle prometteur d’agriculture durable dans les pays du Sud les plus vulnérables aux changements globaux. Cependant, ces systèmes agroforestiers ne peuvent être optimisés qu’à condition de mieux comprendre et de mieux maîtriser les facteurs de leurs productions. L’ouvrage présente un ensemble de connaissances récentes sur les mécanismes biophysiques et socio-économiques qui sous-tendent le fonctionnement et la dynamique des systèmes agroforestiers. Il concerne, d’une part les systèmes agroforestiers à base de cultures pérennes, telles que cacaoyers et caféiers, de régions tropicales humides en Amérique du Sud, en Afrique de l’Est et du Centre, d’autre part les parcs arborés et arbustifs à base de cultures vivrières, principalement de céréales, de la région semi-aride subsaharienne d’Afrique de l’Ouest. Il synthétise les dernières avancées acquises grâce à plusieurs projets associant le Cirad, l’IRD et leurs partenaires du Sud qui ont été conduits entre 2012 et 2016 dans ces régions. L’ensemble de ces projets s’articulent autour des dynamiques des systèmes agroforestiers et des compromis entre les services de production et les autres services socio-écosystémiques que ces systèmes fournissent

Altimetry for the future: building on 25 years of progress

In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology. The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the “Green” Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instruments’ development and satellite missions’ evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion

Méthode géométrique de trajectographie par arcs courts

Geometrical short-arc techniqueL’objectif des méthodes géométriques présentées dans cette thèse est de calculer l'orbite d'un satellite artificiel sur une courte période de temps (10-20 mn) avec la plus grande exactitude possible. L'application de ces méthodes dans le cadre des missions d'océanographie spatiale consiste à donner un sens exact (à quelques centimètres) au calcul du niveau de la mer dans l'espace et dans le temps pour accéder ensuite à la surface topographique moyenne de la mer puis au géoïde terrestre. L’utilisation de la méthode de trajectographie par arcs courts au niveau du bassin méditerranéen et lors des expériences de calibration des altimètres du satellite Topex/Poseidon à Lampedusa et Harvest a d'abord permis d'effectuer de façon indépendante une validation des différentes méthodes de détermination d'orbites précises. La précision et l'exactitude atteinte grâce à la méthode d'arcs courts est de l'ordre de 2 cm sur la position radiale du satellite. Aussi, la détermination de la surface moyenne de la mer à partir de ce calcul d'orbite et des mesures altimétriques de Topex/Poseidon atteint une précision de l'ordre de 2 cm, et l'erreur à craindre sur la position moyenne de cette surface est sub-centimétrique. Ainsi, l'évolution saisonnière du niveau moyen de la Méditerranée a été mise en évidence avec une précision au moins centimétrique. Cette analyse a aussi permis de mettre en évidence les zones de variabilités localisées, liées à des phénomènes océanographiques (courants, zones tourbillonnaires). Enfin, l'utilisation combinée des données altimétriques de Topex/Poseidon et ERS-1, contrôlée par les méthodes géométriques a permis de déterminer une surface moyenne mixte dont la résolution (75 km) permet la mise en évidence de structures fines, à caractère géophysique, avec une précision de l'ordre de 5 cm.