The Baleares 2013 Calibration Campaign of Jason-2 and Saral Altimeters

The 2013 Balearic campaign GNSS position analysis of the 2013 will be performed with different softwares by different groups (similarly as it is being done in the International GNSS Service for their different products), in order improve the high demanded accuracy for JASON2 and SARAL altimeters precise calibration. In particular JPL GIPSY-OASIS software will be used, with the undifferenced PPP ambiguity fixing strategy. In order to improve the results accuracy, two similar networks are being processed. The first network includes the deployed GNSS receivers and the reference stations. The second one is a control network, defined by using the permanent receivers in the California dense network with a similar distribution as the main altimeter campaign network. In this case, the position of the receivers plying the role of buoys are being processed in the same kinematic way than the actual buoys, in order to compare them with the very accurate positions obtained with GIPSY-OASIS static processing.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

Continuou GPS station deployment in the Topo-Iberia Project framework

GÁRATE, J. "Despliegue de estaciones GPS permanentes en el marco del proyecto Topo-Iberia". En: 6ª Asamblea Hispano Portuguesa de Geodesia e Geofísica, (Tomar, 11-14 de febrero de 2008)Topo-Iberia is the short name of a Spanish Research Council funded project. lts main objective is to understand interactions among deep, shallow and atmospheric processes, integrating geological, geophysical, geodetic and geotechnological researching activities. Knowledge of topographic changes and their causes are needed in order to assess natural hazards. It is also important to take them into account when evaluating the climatic change impact. The project will be focused in three main areas of interest, located in the Iberian Peninsula: Northern and Southern borders of the lberian micro-plate, as well as its central core. However, the Southern border does not imply that the Northern Moroccan behaviour is not taken into account. This paper will show the preliminary steps that the Topo-Iberia GPS working group is undergoing in order lo deploy a new Continuous GPS Network at Spain and Morocco. We are trying to complement the airead y existing and functioning CGPS Networks (e.g. ROA, ERGPS) by increasing the spatial coverage across Spain and Northern Morocco. While the purchasing procedures have beenfollowed, the places for the new locations have been chosen. A set of available CGPS data files has been downloaded from different institutional servers. A preliminary data analysis has been performed as a maller of geodetic quality control. Since some of the existing CGPS stations have been installed without fol/owing strict lGS/EUREF procedures for the stability of the monumenls, we are investigating their performance through the time series analysis, in order to decide whether to include them as complementing stations to the Topo-Iberia network.Peer reviewe

Altimetric calibration experiences in the Western Mediterranean

Since many years, space borne radar altimeters have brought a powerful contribution in monitoring the dynamic sea surface topography, and in understanding better the ocean circulation and its impact on the earth system. Today, altimetric satellites are observing the whole oceans, measuring the sea surface height with a rms precision of 3-4 cm at 1 Hz sampling, as demonstrated by TOPEX/POSEIDON, launched in 1992, by Jason-1, launched in 2001 and by ENVISAT, launched in 2002. Such a high level error budget was achieved thanks to the tremendous improvements which have been obtained in radar performances as well as in precise orbit determination. Indeed, applications of altimetry in oceanography and geodesy requires very precise measurements of the satellite-sea level range, along with appropriate environmental corrections, but also an accurate knowledge of the satellite position with respect to the Earth reference. One campaign has also been made in June 2003 at the Ibiza island area (Martinez-Benjamin et al., 2003). The marine geoid has been used to relate the coastal tide gauge data from Ibiza and San Antonio harbours to off-shore altimetric data. 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 designs. We present a synthesis of the sea level results results obtained from the altimeter calibration campaign at Ibiza island on June 2003 using the direct measurements from GPS buoys and the derived marine geoid. The main objective of the marine campaign was to check the value of Ibiza Island as a permanent calibration site in the western Mediterranean Sea, to complement the Corsica site in the network of altimeter calibration sites.Peer reviewe

Calibration Altimeter Sites at Cape of Begur and Ibiza Island

The three Begur experiments have been conducted on March, 16-19, 1999, which was the first altimeter calibration ever developed in Spain and the first Alt-B altimeter calibration made in the Mediterranean Sea; on July, 4-7, 2000, and on August, 25-28, 2002. Direct absolute altimeter calibration, estimating the TOPEX Alt-B bias, was made from direct overflights using GPS buoys. This method does not require any modelling of geoid and tidal error. Other main objective of the campaigns was to map with GPS buoys the Mean Sea Surface, MSS, along an ascending T/P groundtrack about 15-20 km from the coast, using coastal tide gauge measurements. This method requires geographical mapping of geoid and ocean tides which reduces the accuracy of the bias estimate by a factor of two. Indirect absolute altimeter calibration is possible for any satellite crossing the MSS, with the only requirement that tide gauges are operational during the overflight. In the framework of the JASON-1 CNES/NASA mission, a campaign was conducted on June 9-17, 2003, in the Absolute Calibration Site of the Island of Ibiza. The objective was to determine the local marine geoid slope under the ascending (187) and descending (248) Jason-1 ground tracks, in order to allow a better extrapolation of the open-ocean altimetric data with on-shore tide gauge locations, and thereby improve the overall precision of the calibration process. We present preliminary results on Jason-1 altimeter calibration using the derived marine geoid: from this analysis the altimeter bias is estimated to be 120 ± 5 mm.These campaigns have been supported by the Spanish Government, Comisión Interministerial de Ciencia y Tecnología CICYT R+D Projects in Space Research Ref.: ESP97-1816-CO4 and ESP2001-4534-PE. GPS (SANB) and tide gauge data from Ibiza and San Antonio were obtained also within the framework of the ESEAS-RI EU project under contract EVR1-CT-2002-40025.Peer reviewe

Baleares 2013 Calibration Campaign for Jason-2 and Saral/AltiKa

A Baleares calibration campaign in Spanish-French cooperation is being prepared for mid September 2013 for the altimeters of Jason-2 and Saral/AltiKa in the Ibiza island area. A similar Spanish/French experience with Jason-1 was made in June 2003 in this geographical area under IBIZA 2003 campaign. In this local/regional campaign focusing in bias, we foresee to calibrate the altimeter of Jason-2 and Saral satellites by means of GPS buoys. 4 buoys will be used near a node from Jason-2 (September 15 about 9:38 in ascending track) and Saral (September 15 about 7:30 in ascending track) satellites to get the slope of the sea in along track and cross track directions, what is necessary to interpolate the exact nadir point of the satellite. It will be used Argos floating transmitters from CLS to be tied to the buoys with a long rope. We have thought over different configurations. The crossover point between Jason-2 and Saral North of Ibiza (around 40 nm) and West of Mallorca island seems to be optimal in order to have a comparable layout of buoys at the same place for both satellites, of couse at one day interval. This would allow moreover cross calibration between Jason2 and Saral. The GPS receivers will be at 1Hz. It will be used the CGPS at Ibiza harbour from Puertos del Estado. A description of the actual geodetic infrastructure of Ibiza site will be presented. This campaign Baleares 2013 is founded from the Ministerio de Ciencia e Innovacion of Spain under National Project I+D+i ref:CGL2009-13435/CLI.Postprint (published version

Baleares 2013 Calibration Campaign for Jason-2 and Saral/AltiKa

A Baleares calibration campaign in Spanish-French cooperation is being prepared for mid September 2013 for the altimeters of Jason-2 and Saral/AltiKa in the Ibiza island area. A similar Spanish/French experience with Jason-1 was made in June 2003 in this geographical area under IBIZA 2003 campaign. In this local/regional campaign focusing in bias, we foresee to calibrate the altimeter of Jason-2 and Saral satellites by means of GPS buoys. 4 buoys will be used near a node from Jason-2 (September 15 about 9:38 in ascending track) and Saral (September 15 about 7:30 in ascending track) satellites to get the slope of the sea in along track and cross track directions, what is necessary to interpolate the exact nadir point of the satellite. It will be used Argos floating transmitters from CLS to be tied to the buoys with a long rope. We have thought over different configurations. The crossover point between Jason-2 and Saral North of Ibiza (around 40 nm) and West of Mallorca island seems to be optimal in order to have a comparable layout of buoys at the same place for both satellites, of couse at one day interval. This would allow moreover cross calibration between Jason2 and Saral. The GPS receivers will be at 1Hz. It will be used the CGPS at Ibiza harbour from Puertos del Estado. A description of the actual geodetic infrastructure of Ibiza site will be presented. This campaign Baleares 2013 is founded from the Ministerio de Ciencia e Innovacion of Spain under National Project I+D+i ref:CGL2009-13435/CLI

The Baleares 2013 Calibration Campaign of Jason-2 and Saral Altimeters

The 2013 Balearic campaign GNSS position analysis of the 2013 will be performed with different softwares by different groups (similarly as it is being done in the International GNSS Service for their different products), in order improve the high demanded accuracy for JASON2 and SARAL altimeters precise calibration. In particular JPL GIPSY-OASIS software will be used, with the undifferenced PPP ambiguity fixing strategy. In order to improve the results accuracy, two similar networks are being processed. The first network includes the deployed GNSS receivers and the reference stations. The second one is a control network, defined by using the permanent receivers in the California dense network with a similar distribution as the main altimeter campaign network. In this case, the position of the receivers plying the role of buoys are being processed in the same kinematic way than the actual buoys, in order to compare them with the very accurate positions obtained with GIPSY-OASIS static processing

The 2013 Ibiza calibration campaign of Jason-2 and Saral altimeters

This study presents the results of the 2013 Ibiza (Western Mediterranean) calibration campaign of Jason-2 and SARAL altimeters. It took place from 14 to 16 September 2013 and was composed of two phases: the calibration of the GNSS (Global Navigation Satellite System) buoys to estimate the antenna height of each of them and absolute calibration to estimate the altimeter bias (i.e., the difference of sea level measured by radar altimetry and GNSS). The first one was achieved in the Ibiza harbor at a close vicinity of the Ibiza tide gauge and the second one was at ˜ 40 km at the northwest of Ibiza Island at a crossover point of Jason-2 and SARAL nominal groundtracks. Five buoys were used to delineate the crossover region and their measurements interpolated at the exact location of each overflight. The overflights occurred two consecutive days: 15 and 16 September 2013 for Jason-2 and SARAL respectively. The GNSS data were processed using precise point positioning technique. The biases found are of (-0.1 ± 0.9) and (-3.1 ± 1.5) cm for Jason-2 and SARAL respectively.Peer ReviewedPreprin

The 2013 Ibiza calibration campaign of Jason-2 and Saral altimeters

This study presents the results of the 2013 Ibiza (Western Mediterranean) calibration campaign of Jason-2 and SARAL altimeters. It took place from 14 to 16 September 2013 and was composed of two phases: the calibration of the GNSS (Global Navigation Satellite System) buoys to estimate the antenna height of each of them and absolute calibration to estimate the altimeter bias (i.e., the difference of sea level measured by radar altimetry and GNSS). The first one was achieved in the Ibiza harbor at a close vicinity of the Ibiza tide gauge and the second one was at ˜ 40 km at the northwest of Ibiza Island at a crossover point of Jason-2 and SARAL nominal groundtracks. Five buoys were used to delineate the crossover region and their measurements interpolated at the exact location of each overflight. The overflights occurred two consecutive days: 15 and 16 September 2013 for Jason-2 and SARAL respectively. The GNSS data were processed using precise point positioning technique. The biases found are of (-0.1 ± 0.9) and (-3.1 ± 1.5) cm for Jason-2 and SARAL respectively.Peer Reviewe