Statistical characterization of equatorial plasma bubbles over East Africa
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Space weather presents a threat to human activities such as Global Navigation Satellite System (GNSS) positioning and timing, power systems, radio communications and transpolar aviation. Nowcasts and forecasts of the ionosphere could help mitigate some of these damaging effects. In this thesis, state-of-the-art ionospheric specification techniques are assessed in a long-term study. That study shows that Global Positioning System (GPS) derived tomographic images specify monthly median ionospheric Total Electron Content (TEC) accurately in Europe and North America throughout the twelve-year test period. Following this assessment, developments are presented in three key areas. The resolution of horizontal structures in ionospheric images over Africa is assessed. The accuracy gains from adding receivers are quantified using a simulation approach, showing that an extended GPS network reduces Root-Mean-Square (RMS) error from 9.5 TEC units for the currently operational network to 4.5 TEC units. A fictional, ideal network is demonstrated to produce images with RMS errors of 3.0 TEC units. Images of the vertical electron density distribution, vital for High Frequency (HF) radio operators, are greatly improved by adding observations of the ionospheric vertical profile to an imaging algorithm that relies on GPS observations. The peak electron density is resolved to an RMS accuracy of 0.5 x 1011 electrons/m3, compared to an RMS accuracy of 1.0 x 1011 electrons/m3 for the standard approach. A novel experimental method is employed to show that forecasts of ionospheric storms could benefit significantly from accurate specification of the initial neutral composition, in particular the ratio of O to N2 . A theoretical experiment shows that an ideal assimilation of the thermospheric composition can improve storm-time forecasts by at least 10% for over 19 hours, whilst an ideal ionospheric assimilation improves forecasts for less than four hours. This finding will aid the development of a coupled thermosphere ionosphere forecast system.
Space Weather
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Orbit (dynamics)
Orbit Determination
Medium Earth orbit
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Precise Point Positioning
GNSS augmentation
Quasi-Zenith Satellite System
Galileo (satellite navigation)
Satellite Tracking
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Galileo (satellite navigation)
Deformation monitoring
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The temporal and spatial redistribution of the environmental masses deform the surface of the Earth. These deformations are observable by space geodetic techniques such as GNSS. Since highly accurate IGS satellite and clock data are available and sophisticated algorithms have been developped, the integer fixed ambiguity Precise Point Positioning (iPPP) method opened a new era for the Global Navigation Satellite System (GNSS) analysis and its application in geophysical studies. This work is among the first studies to investigate the different loading effects using iPPP time series, particularly using the GINS-PC software and the new, reprocessed REPRO2 orbit and clock products of GRGS (GR2). We aim to exploit the sub-daily iPPP time series to study various Earth deformation effects at different time scales, from sub-daily to seasonal and annual periods. Our goal is to contribute to the validation of geophysical models, to the observation of the various non-tidal phenomena, as well as the presentation of the performance of the iPPP mode and the GINS-PC package that is a powerful tool for geodynamical applications, and to investigate the influence of the loading effects on geodetic time series interpretation. After an overview of the main deformations of the Earth's surface, we present the geodetic techniques that already demonstrated their potential in deformation analysis, in particular in loading deformation studies. We then review the GNSS technique and the iPPP processing mode as it was our choice for the data analysis. We then demonstrate two regional studies. The first one investigates the influence of the loading effects on GNSS campaign to determine tectonic velocities in the Pyrenees mountain chain. The second case study attempts to track the spatial and temporal evolution of an extreme storm event, the Xynthia windstorm that occured in France, in 2010. This study also tries to identify the ocean's response to the fast moving low pressure system using sub-daily iPPP time series. Finally we go towards a global study which gives base for future research.
Precise Point Positioning
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GLONASS
Real Time Kinematic
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Very-long-baseline interferometry
GLONASS
Satellite laser ranging
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One of the very active inter-disciplines in space geodesy and space science is to model the global and regional TEC GNSS technique. Ionospheric TEC along the track from detector to target radio source can be obtained accurately from the simultaneous observable at two different frequencies for these quickly developing space geodetic techniques, i.e., GPS, Satellite altimetry, integrated Doppler, VLBI. In China, we use the continue observation of a regional GPS network and a Shanghai local network to estimate 2D TEC distribution, After removing the instrumental effects successfully. The obtained model is validated by using IGS GIM TEC model and by using other independent observation. Systematic biases between them have been noticed, for example, the seasonal and annual periodical difference in temporal variation; the zonal like difference in spatial distribution. The reliability and effectiveness of the model has been proven by a recent space tracking experiments of VLBI. The regional RIM is developed for precise tracking of Chinese and Japanese lunar missions, as well as for the future deep space missions.
Very-long-baseline interferometry
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Satellites equipped with retroreflectors have been tracked by laser systems since 1964. Satellite laser ranging supports a variety of geodetic, earth sensing, navigation, and space science applications. This poster will show the history of satellite laser ranging from the late 1960‘s through the present and will include retro-equipped satellites on the horizon. Satellite Tracking History Initial laser ranges to a satellite in Earth orbit took place in 1964 with the launch of Beacon Explorer-B (BE-B), the first satellite equipped with laser retroreflectors. Since that time, the global network of laser ranging sites has tracked over eighty satellites including arrays placed on the Moon. Satellite and Lunar laser ranging continue to make important contributions to scientific investigations into solid Earth, atmosphere, and ocean processes. SLR also provides Precise Orbit Determination (POD) for several Earth sensing missions (e.g., altimetry, etc.), leading to more accurate measurements of ocean surface, land, and ice topography. Several of these missions have relied on SLR when other radiometric tracking systems have failed (e.g., GPS and DORIS on TOPEX/Poseidon, PRARE on ERS-1, GPS on METEOR-3M and GFO1) making SLR the only method for providing the POD required for instrument data products. A list of satellites equipped with retroreflectors (past, current, and future) and tracked by SLR is shown in Table 1. The table summarizes the data yield (approximate through fall 2008) and includes a list of any co-located instrumentation (e.g., GNSS, DORIS, or PRARE). Figure 1 shows this rich history in graphical format, as well as future plans, from mid-1960 through 2015. The satellite missions supported by laser ranging are shown in four categories: geodetic, Earth sensing, navigation, and space science or engineering applications. The data generated by the laser ranging stations tracking these satellites, as well as products derived from these data, are available from the Crustal Dynamics Data Information System (CDDIS, http://cddis.nasa.gov). The CDDIS is NASA‘s active archive and information service of space geodesy data and products and currently serves as a key global data center for the ILRS. For over 25 years, the CDDIS has provided continuous, long term, public access to the data and product sets required for many interdisciplinary studies of the global Earth Science community, Proceedings of the 16th International Workshop on Laser Ranging 568 Table 1. ILRS Satellite Tracking Information Satellite Start Date End Date Number of Years Number of Passes Co-Located Instrument? Current and Past Satellites ADEOS-1 Oct-1996 Aug-1997 2 750 ADEOS-2 Dec-2002 Jan-2003 2 180 Ajisai Aug-1986 --23 152,260 ALOS Aug-2006 Aug-2006 1 90 ANDERR-Active Jan-2007 Dec-2007 1 430 ANDERR-Passive Jan-2007 May-2008 2 650 BE-C Jan-1976 --21 66,790 CHAMP Jul-2000 --9 13,650 GNSS DIADEM-1C Apr-1997 Nov-1997 1 2,350 DIADEM-1D Apr-1997 Nov-1997 1 2,590 Envisat Apr-2002 --7 34,820 DORIS ERS-1 Jul-1991 Mar-2000 9 26,080 PRARE* ERS-2 Apr-1995 --14 66,620 GNSS Etalon-1 Jan-1989 --20 15,890 Etalon-2 Jul-1989 --20 15,720 ETS-8 Mar-2007 --2 390 FIZEAU Jun-1995 Oct-1998 4 4,790 GEOS-3 Oct-1998 May-1999 2 2,130 GFO-1 Apr-1998 Aug-2008 11 43,070 GNSS* GFZ-1 Apr-1995 Jun-1999 5 5,140 GIOVE-A May-2006 --3 1,590 GNSS GIOVE-B May-2008 --1 140 GNSS GLONASS (31 sats.) Oct-1994 --15 47,980 GNSS GP-B Jul-2004 Jun-2006 3 2,910 GNSS GPS-35 Oct-1993 --16 7,440 GNSS GPS-36 Apr-1994 --15 6,500 GNSS GRACE-A Mar-2002 --7 12,550 GNSS GRACE-B Mar-2002 --7 11,860 GNSS ICESat Mar-2003 --6 5,320 GNSS Jason-1 Dec-2001 --8 48,110 GNSS, DORIS Jason-2 Jun-2008 --1 990 GNSS, DORIS LAGEOS-1 May-1976 --33 152,350 LAGEOS-2 Oct-1992 --17 88,750 LARETS Nov-2003 Aug-2008 6 19,740 LRE Dec-2001 Mar-2002 2 40 METEOR-3 Jan-1994 Nov-1995 2 6,280 PRARE* METEOR-3M Dec-2001 Mar-2006 6 1,800 GNSS* MOON Jun-1996 --13 1,210 MSTI-2 Jun-1994 Oct-1994 1 60 OICETS Apr-2006 --1 120 Reflector Dec-2001 Aug-2004 4 3,620 RESURS Dec-1995 Oct-1998 4 2,020 Starlette Jan-1976 --33 123,160 STARSHINE-3 Oct-2001 Jun-2003 3 50 Stella Sep-1993 --16 62,990 SUNSAT May-1999 May-2001 3 1,800 TerraSAR-X Jun-2007 --2 3,070 GNSS TiPS Jun-1996 Oct-1997 2 1,680 TOPEX Jan-1992 Dec-2005 14 105,060 GNSS*, DORIS* WESTPAC Jul-1998 Jan-2002 5 5,480 ZEIA Mar-1997 Jul-1997 1 150 Proceedings of the 16th International Workshop on Laser Ranging 569 Table 1. ILRS Satellite Tracking Information (continued)
Satellite laser ranging
Retroreflector
Ranging
Doris (gastropod)
Orbit Determination
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