Showing papers by "Royal Institute and Observatory of the Spanish Navy published in 2015"

The 2013 Ibiza Calibration Campaign of Jason-2 and SARAL Altimeters

Abstract: 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 comprised two phases: the calibration of the GNSS (Global Navigation Satellite System) buoys to estimate the antenna height of each of them and the 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 performed 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.

The Time Validation Facility (TVF): An all-new key element of the Galileo operational phase

Abstract: In the Galileo FOC phase (Full Operational Capability), GMV is the prime contractor for the Time and Geodetic Validation Facility (TGVF), a contract of the European Space Agency (ESA). Within the TGVF, the Time Validation Facility (TVF) is the subsystem in charge of steering Galileo System Time (GST) to UTC, among other duties. The new TVF is operated at GMV headquarters near Madrid, Spain. TVF operations rely on the contribution of five European timing laboratories, located at INRiM, OP, PTB, ROA, and SP. This paper provides a general description of the TVF element and its related activities for the FOC phase, and presents the main results and findings of the TVF operation until now.

Use of two traveling GPS receivers for a relative calibration campaign among European laboratories

Abstract: We report about a GPS receiver relative calibration campaign, which took place between five European National Metrology Institutes or Designated Institutes: LNE-SYRTE in Observatoire de Paris (Paris, France), where the reference receiver of the campaign was located, ROA (San Fernando, Spain), SP (Boras, Sweden), PTB (Braunschweig, Germany) and INRIM (Torino, Italy). We used as traveling equipment two main units, both connected to a single antenna, and we kept track of the offset between both traveling units in all the visited sites. An external validation of the resulting hardware delays is provided against the time scale differences derived from the UTC - UTC(k) data published by BIPM in its monthly Circular T. Thanks to a very good stability of the traveling equipment, we obtained expanded uncertainty estimates within 2.0 ns (k = 2) for the hardware delays.

A new proposal to improve the description of astronomical resources: The case of historical star catalogues

Abstract: Purpose – The purpose of this paper is to show that some important astronomical information is still not taken into account in the documental description of historical star catalogues. Design/methodology/approach – A sample of 28 historical star catalogues (eighteenth, nineteenth and twentieth centuries) from the Royal Institute and Observatory of the Spanish Navy was selected in order to analyse their structure and to identify information patterns. Findings – The analysis shows that there are a number of technical parameters which are not present in the cataloguing standards and which should be taken into account in the bibliographic descriptions of these specialised documents since they are of great interest to astronomers and astrophysicists. On the other hand, star catalogues provide some cartographic information which can be described by these standards but whose corresponding fields are not widely used by cataloguers. Originality/value – A proposal of new technical parameters is given in order to tr...

GPS time link calibrations in the frame of EURAMET Project 1156

Abstract: Since 2010 ROA has supported the coordination of the EURAMET Technical Committee for Time and Frequency (TC-TF) Project 1156, a response from EURAMET TC-TF to Recommendation 2 of CCTF 2009: to study the characterization of GNSS equipment in use for establishing the time links between institutes contributing with their clocks to TAI. Starting that year, a GPS calibration campaign was organized between three contributing laboratories: ROA (Spain), PTB (Germany) and INRIM (Italy). The time transfer results were achieved by using the P3 method, and also carrier phase PPP comparison techniques. These results were also used to re-calibrate the TWSTFT (Two-Way Satellite Time and Frequency Transfer, TW for short) links between labs, with an uncertainty slightly higher than that of the GPS links. During 2011 and 2012, the campaign was repeated, and in 2012 two other laboratories were included in the calibration trip: NPL (United Kingdom) and OP (France). In this paper we report the calibration results, with a focus on the long term stabilities of the GPS and TW links between the visited labs.