Very long baseline interferometry as a tool to probe the ionosphere
|
|
- Elfrieda Chapman
- 5 years ago
- Views:
Transcription
1 RADIO SCIENCE, VOL. 41,, doi: /2005rs003297, 2006 Very long baseline interferometry as a tool to probe the ionosphere T. Hobiger, 1,2 T. Kondo, 2 and H. Schuh 1 Received 10 June 2005; revised 10 August 2005; accepted 17 November 2005; published 11 February [1] In geodetic very long baseline interferometry (VLBI), the observations are performed at two distinct frequencies (2.3 and 8.4 GHz) in order to determine ionospheric delay corrections. This allows information to be obtained from the VLBI observables about the sum of electrons per area unit (total electron content) along the ray path through the ionosphere. Because of the fact that VLBI is a differential technique, the calculated ionospheric corrections depend on the differences of the propagation media over the stations. Additionally, an instrumental delay offset per station causes a bias of the ionospheric measurements. This paper presents a method to estimate ionospheric parameters, that is, values of vertical total electron content from VLBI data, and compares the outcomes to results from other space geodetic techniques. As VLBI observations cover more than two complete solar cycles, the relation to space weather indices on long-term timescales can be shown. Citation: Hobiger, T., T. Kondo, and H. Schuh (2006), Very long baseline interferometry as a tool to probe the ionosphere, Radio Sci., 41,, doi: /2005rs Introduction [2] Since its development in the late 1960s (described by, e.g., Clark et al. [1985]) the geodetic very long baseline interferometry (VLBI) technique has achieved a great improvement in precision and accuracy. As the first observations were carried out at single frequencies, ionospheric corrections could only be made by using external measurements. In the 1980s, stations were equipped with dual-frequency receiving systems and the ionospheric influence on the observed group delays could be measured directly and applied in astronomical, astrometric, or geodetic analyses. The routine analysis of GPS observations starting in the mid 1990s allowed the determination of ionospheric parameters all over the world. Since 2003, the International GNSS Service, formerly the International GNNS Service (IGS), has presented an official ionospheric product in the form of global two-dimensional maps of vertical total electron content (VTEC) values. Additionally, many other local, regional, and global solutions, tomographic inversions, high-rate observations, and satellite occultations using 1 Institute of Geodesy and Geophysics, Vienna University of Technology, Vienna, Austria. 2 Kashima Space Research Center, National Institute of Information and Communications Technology, Kashima, Japan. Copyright 2006 by the American Geophysical Union /06/2005RS GPS have been investigated in the last years to determine ionospheric parameters. So far, the ionospheric correction that can be obtained from routine VLBI observations has not been included in any model of the ionosphere or investigated further. Except for one paper [Kondo, 1991], no group has focused how to gain ionospheric information from dual-frequency VLBI measurements. VLBI is only sensitive to the differences of the ionospheric influences at each station pair of a network; it is not a continuous observing technique and does not have as dense a distribution of stations as GPS. Nevertheless, VLBI provides capabilities to probe the ionosphere in an absolute sense, as will be described in this paper. 2. Ionospheric Information From VLBI Observations 2.1. Ionospheric Impact on VLBI Measurements [3] Geodetic VLBI sessions are carried out at 2.3 GHz (S band) and 8.4 GHz (X band) in order to compensate for dispersive delays caused by the ionosphere. Higherorder ionospheric terms can still be neglected to get millimeter accuracy as discussed by Sovers and Jacobs [1996] and recently confirmed by Hawarey et al. [2005]. We will start our derivation from a station-based model equivalent to that one used in GPS and then form differences to get VLBI observables. The delay d i,j of the received signal at one station i on frequency j consists 1of10
2 of a nondispersive part d i, a contribution q i from the ionosphere depending on the observation frequency f j, and a constant instrumental delay G i,j caused by the receiving system. For stations 1 and 2, observing at X and S bands, we obtain the following system of equations: d 1;X ¼ d 1 þ q 1 2 þ G 1;X d 1;S ¼ d 1 þ q 1 fs 2 þ G 1;S d 2;X ¼ d 2 þ q 2 2 þ G 2;X d 2;S ¼ d 2 þ q 2 fs 2 þ G 2;S ð1þ ð2þ ð3þ ð4þ As VLBI observes delay differences t X = d 2,X d 1,X and t S = d 2,S d 1,S, equations (1) (4) yield the VLBI measurements with and t X ¼ t þ Dq 2 þ DG X t S ¼ t þ Dq fs 2 þ DG S ð5þ ð6þ t ¼ d 2 d 1 Dq ¼ q 2 q 1 ð7þ DG X ¼ G 2;X G 1;X ; DG S ¼ G 2;S G 1;S ð8þ Geodetic analysts are interested in an ionosphere-free delay which can be obtained by solving for the q term in equations (5) and (6) and equating them with each other: t ¼ f 2 X f 2 X f 2 S þ f 2 X f 2 X f 2 S t X þ f S 2 fs 2 f X 2 t S DG X þ f S 2 fs 2 f X 2 DG S ð9þ Equation (9) is a linear combination of the delays (t X and t S ) obtained at X and S bands, whereas the last two terms represent constant values and shift the ionosphere-free observable by an unknown constant offset, which is in geodetic parameter estimation absorbed by the clock model [Ray and Corey, 1991]. Reconstruction of the ionospheric delay (t X t) yields after doing some algebra t X t ¼ Dq 2 þ G 2;X G 1;X ð10þ Equation (10) represents the ionospheric delay as stored in VLBI databases [e.g., Noll, 2003]. The first term contains information about the ionosphere, whereas the last two terms represent the constant instrumental effects at station i caused by instrumental delays in X band. These instrumental delays are contained in X band ionospheric corrections t i;inst ¼ G i;x ð11þ which makes equation (10) better readable. Therefore we get t X t ¼ Dq 2 þ t 2;inst t 1;inst ð12þ As the left side of equation (10) represents a measured quantity, the parameters Dq, that is, the difference of the ionospheric contributions at stations 1 and 2 (see equation (7)) and t i,inst, will become the parameters to be solved for. The value of q used in equations (1) (4) and (7) is directly related to the sum of electrons along the ray path and is assigned as slant total electron content (STEC i ) q i ¼ ¼ Z 1: fk 2 N e;i ds 1: fk 2 STEC i ð13þ Using a thin shell approximation of the ionosphere [Schaer, 1999] and an appropriate mapping function MF(e i ), equation (13) can be written in terms of vertical total electron content VTEC q i ¼ whereas MF(e i ) is defined by MFðe i Þ ¼ 1: fk 2 MFðe i ÞVTEC i 1 sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi R 2 e 1 R e þ H cos e i ð14þ ð15þ R e represents the radius of the Earth, H is the height of the ionospheric layer, and e i is the elevation angle. 2of10
3 Figure 1. Relation between VTEC at the observing station and at the intersection point. H is usually located around the height of the F 2 peak of electron density [Schaer, 1999]. For our investigations a height of 450 km was chosen to be consistent with the heights used in ionospheric models from GPS measurements (see section 3.1). On the basis of equations (12), (14), and (15), a method was developed to estimate absolute values of vertical total electrons above each VLBI site. In section 2.2 we will discuss how such values can be derived and which simplifications have to be made in order to obtain absolute values Model Assumptions [4] First, equation (12) is rewritten using equation (14), which shows the relation between the observables and unknown target parameters, that is, the vertical total electron content and instrumental offsets 1: t X t ¼ 2 ðmfðe 2 ÞVTEC 2 * MFðe 1 Þ VTEC 1 *Þþt 2;inst t 1;inst ð16þ VTEC 1 * and VTEC 2 * denote the values of the vertical total electron content at the intersection points of the ray paths with the (infinitesimally thin) shell for stations 1 and 2, respectively. The distance between the station and the intersection point is directly related to the elevation angle and can reach up to more than 1600 km for an elevation angle of 5 and an assumed height of the ionospheric Figure 2. Map of VLBI stations for which VTEC time series were computed. 3of10
4 layer of 450 km. By setting up a model that explains the relation between vertical total content above the station and at the intersection point, we were able to solve for station dependent values by an adjustment process, taking into account that spatially separated antennas will observe under different elevation angles when pointing to the same radio source. For the following considerations, we use (l i, f i ) as geographical coordinates of station i and (l* i, f* i ) as the location of the intersection point (see Figure 1). As a first step, it is taken into account that the diurnal variation of the ionosphere is mainly correlated with the position of the Sun. This leads us to the first assumption, that the thin shell representing values of vertical total electron content is following the apparent motion of the Sun. Or, in other words, it is assumed that the value VTEC* 1 observed at time t* on longitude l* will be the same, when it passes the meridian of the station, which means VTEC* 1 can be observed at (l i, f* i ) at time t* +(l* i l i )/15. This first step is illustrated in Figure 1. The main task is now to determine the vertical total electron content above the station from the VTEC value at the rotated point. By applying the rough assumption of a linear north-south gradient c i, which is constant within the whole session, VTECðl i ; f i ; tþ ¼ ð1 þ c i Df i ÞVTEC* l*; i f*; i t* ð17þ t ¼ t* þ ðl* i l i Þ=15 Df i ¼ f* i f i ð18þ station-dependent values can be obtained from information taken at the intersection points. The coefficients c i can be estimated for each station together with the other parameters, as described in section Estimation of Values of Vertical Total Electron Content (VTEC) [5] The left side of equation (16) represents the measured ionospheric influence on a baseline formed by stations 1 and 2, whereas the right side shows the unknown target parameters, that is, values of vertical total electron content above the stations (by using relationships (17) and (18)) and instrumental offsets assigned to each site. The time-dependent variable behavior of the ionosphere is taken into account by setting up a piecewise linear function model VTEC i ðþ¼a t i þ ðt 1 t 0 Þb i;1 þ ðt 2 t 1 Þb i;2 þ......þ ðt k tþb i;k t t k ð19þ for station i. The time intervals between the VLBI scans vary according to geometry, slewing times of the antennas, flux densities of radio sources, and other reasons. Thus the time steps denoted in equation (19) should be set such that a given number n of observations defines the length of each interval. In our analysis, a value of n = 8 observations, contributing to the estimation of one interval, was chosen which corresponds to an average temporal resolution of the outcomes of about 30 min. This value also sets the lower limit of the detectable ionospheric periods. Changing the value n to a lower number of observations increases time resolution but decreases the redundancy of the estimation process and weakens the stability of the matrices used in the adjustment. [6] The objective function tries to minimize the differences between the data and modeled values. Equation (20) aims at minimizing the vector of residuals by adjusting the unknowns #x, using a linearized model represented by matrix A and a vector #Y containing the values by means of observed minus calculated. Matrix A can be obtained easily as all model assumptions are already linear and iteration, caused by the neglect of higher order derivatives, will not be necessary. Minimizing the squared sum of the weighted residuals v = A#x #Y, using the stochastic (weight) matrix P of the observations yields 0 min #x vt Pv ¼ T A T PA #x fflffl{zfflffl} #x H 2 fflfflfflffl{zfflfflfflffl} A T P#Y #x þ #Y fflfflfflfflfflfflffl{zfflfflfflfflfflffl} T P#YA ¼ min #x f T const>0 1 2 #xt H#x þ f T #x 1 ð20þ Finding then the minimum of equation (20) by setting the derivative to #x to zero would be equal to the Gauss- Markov model [Koch, 1997] used in classical geodetic adjustments. But we will let equation (20) remain unchanged and will find another condition which has to be fulfilled, too. Because of the physical nature of the ionosphere negative values of vertical total electron content are not possible. This knowledge can be added to the estimation algorithm by applying an in equation (expressed by equation (21)) to the vector of improvement, and as linearity of the model parameters is already given, matrices B and C can be set up easily [Hobiger and Schuh [2004]: BDx C ð21þ Solving equation (20) under condition (21) is carried out by a reflective Newton method [Coleman and Li, 1996; Gill et al., 1981] and is implemented in such mathematical analysis software as, for example, Matlab 1. Before equations (20) and (21) can be solved, singularity of the 4of10
5 Figure 3. VTEC values for station Wettzell, Germany, from (top) VLBI and (bottom) IGS-GIM. A matrix, caused by the constant terms of the instrumental offsets (last two terms in equation (16)), has to be eliminated. One method to overcome this problem is to set the instrumental offset at one station within the network to zero and obtain the other values relative to that one. Another approach, equivalent to the first one, sets the sum of all offsets within a network of N stations to zero [Sekido et al., 2003]: X N i¼1 t i;inst ¼ 0 ð22þ One has to be careful not to overparameterize the stationdependent VTEC models. Let the number of model intervals, set up for station i, beint i ; then the redundancy R, using n obs observations and N stations, is given by R ¼ n obs 3N þ XN i¼1 int i!þ 1 ð23þ The last term in equation (23) results from the effect, that one artificial observation (equation (22)) increases the number of observations by 1. As the number of observations carried out by VLBI within one session is rather small compared to global GPS measurements, redundancy should be high enough to be able to detect outliers within the data. 3. Results and Comparison With Other Space Geodetic Techniques [7] Applying the algorithms described in section 2 to VLBI databases of dual-frequency observations, let us estimate values of vertical total electron content and instrumental offsets together with their formal errors at each station. As VLBI is not observing every day and network stations change between the sessions, the outcomes cannot be provided on regularly time-spaced intervals. This has to be taken into account when doing frequency analysis VLBI Results and Their Comparison With GPS Data [8] Using the whole available database of the International VLBI Service for Geodesy and Astrometry (International VLBI Service for Geodesy and Astrometry Web page, time series for 143 network stations plotted in Figure 2 were created. These 5of10
6 Figure 4. Histogram of differences between VLBI and GPS for station Wettzell, Germany. The bias VLBI minus GPS is at 1.95 TECU, the RMS at ±6 TECU. series are of unequal lengths, as stations were constructed and dismantled at different epochs in time. Furthermore, some antennas contributed less than others, as they are not mainly dedicated to astrometric/geodetic observations and/or are not equipped permanently with dual-frequency receivers. As an example, the results for station Wettzell, Germany (20 m dish), shown in Figure 3 (top), will be discussed, as this station has a long history of observations going back to This long time span will become important when investigating long-term trends of the ionosphere. One can see clearly that the solar cycle dominates the overall shape of the total electron content results for this station, but an annual signal of which the amplitude is modulated by the long periodic variation can be found, too. For a cross-technique comparison we used results from a worldwide GPS station network. The International GPS Service (IGS) provides Global Ionospheric Models (GIM) of VTEC values on a geographical grid (Dl = 5, Df = 2.5 ) with a time resolution of 2 hours (International GNSS Service (IGS) Web page, Using a proper interpolation method suggested by Schaer et al. [1998], values of VTEC were obtained for each VLBI station. When this paper was written, the availability of the official IGS files ranged back to the year 1998, which enables us to compare data on a rather short time span of only 6 years. Therefore we have chosen to use GIMs from the Astronomical Institute of Berne, Switzerland, which are also stored in ionospheric exchange (IONEX) format. As these data are provided back to the year 1995, comparison could be done for all observations after this date. Figure 3 (bottom) shows VTEC values for station Wettzell gained from GIM data. VLBI results contain some outliers after the year 2002, but in general, the agreement between both techniques is rather good. Interpolating VTEC values from GIM data to the epoch of each VLBI data point enables us to do descriptive statistics. Figure 4 shows a histogram of the differences between VLBI and GPS at station Wettzell. GPS seems to provide slightly higher values with a bias of 1.95 TECU and a standard deviation of about ±6 TECU. Figure 5 shows the differences between VLBI and GPS for all IVS network stations again displayed by a histogram. The overall mean difference between both techniques is about 2.8 TECU, whereas standard deviation is in the range of ±10 TECU. According to information on the accuracy of IGS products (see 6of10
7 Figure 5. Histogram of differences between VLBI and GPS taken at all IVS stations. The bias VLBI minus GPS is at 2.8 TECU, the RMS at ±10 TECU. nasa.gov/), the GIM errors are within the range of ±2 to ±8 TECU. As the average formal error of the VLBI results is at about ±3 TECU, it can be concluded that both techniques agree well. [9] As VLBI is not observing every day and data gaps might vary according to scheduling, dedication, maintenance, or budgets, the gained time series are not equally sampled. This has to be taken into account when computing the frequency spectra of the VLBI results. Two suitable algorithms that are able to treat unequally sampled data are mentioned by Foster [1996a, 1996b]. We have applied the CLEAN algorithm according to Baisch and Bokelmann [1999] to the data Spectral Analysis [10] CLEANed spectra of the VLBI outcomes were derived, using the algorithm described in section 3.1, and compared to GPS results. Furthermore, values of solar radio flux at 10.7 cm (F 10.7 ) back to 1 January 1984 were downloaded from the World Data Center for Solar- Terrestrial Physics, Chilton, and were analyzed, too. Again, results for station Wettzell will be presented here, as this site can provide the longest time series. As values 7of10 of F 10.7 contain some data gaps, the CLEAN algorithm had also to be applied to this time series. Finally, all outcomes were normalized by the biggest amplitudes in order to compare TECU numbers to F Figure 6 shows the gained spectra from VLBI, GPS, and F Only VLBI and F 10.7 show a sharp peak which can be assigned to the main solar cycle. The maximum amplitude from VLBI results is found at 10.5 years, which is identical to the maximum from F As also expressed by Figure 6, we see that GPS and VLBI have the same amplitudes for the diurnal, semiannual, and annual periods. As expected, GPS cannot detect longer periods than about 5 years in the ionosphere as time series are not long enough. The same series from VLBI and GPS were taken and wavelet spectrograms were obtained, as described, for example, by Foster [1996c] or Schmidt [2000]. The results are plotted in Figure 7. For our comparison we focused mainly on annual signals. The influence of the last two solar cycles can be seen clearly in the VLBI scalograms as the amplitude of the annual signal corresponds to the long-term variations of the activity of the Sun. Scalograms from GPS results confirm this variation in the annual period domain; both
8 Figure 6. CLEANed spectra of VLBI and GPS (both Wettzell, Germany) and F techniques differ less than half a day from the expected 365 day period. 4. Discussion [11] As described in the previous sections, the ionosphere, expressed by values of vertical total electron content, can be monitored by VLBI in an absolute sense. For the first time, VTEC values can be gained from VLBI without any external information using the algorithms presented here. Therefore VLBI can be used as a tool to study the ionosphere, but as VLBI is not a continuously observing technique, its preferable use with respect to ionospheric research will be to contribute to long-term studies or to validate theoretical or measurement-based local, regional, and global ionospheric models rather than providing results for routine monitoring of the ionosphere. At the moment, the combined IGS global ionospheric model which is derived from the results of five different GPS analysis centers is cross validated against Jason and/or Envisat measurements on a routine basis [Hernandez-Pajares, 2004], which shows an absolute bias of less than 1 TECU in most of the cases and a standard deviation of about ±5 TECU. We think that VLBI can be taken as a third independent technique for validation of IGS GIMs. As VLBI is the only technique which is covering more than two solar cycles, it is able to provide important input for theoretical models of the ionosphere and for modeling long-term trends. [12] The final goal of ionospheric modeling using space geodesy should be the development of a global four-dimensional model of the ionosphere, assimilating several independent space techniques, obtaining the most robust and reliable solution of electron densities values. How VLBI can contribute to such a model depends not only on data quality and the number of observations but also on the ability to process the observations in near real time and to provide the measurements and/or ionospheric parameters as soon as possible to combination centers. 5. Conclusions [13] We have presented a method to gain ionospheric parameters in terms of vertical total electron content in an absolute sense without any external information from geodetic VLBI measurements. The necessary model assumptions for the estimation of these parameters from differential measurements were presented. The results 8of10
9 Figure 7. Wavelet spectra of VLBI and GPS (both Wettzell, Germany). from VLBI agree well with GPS in the time and frequency domain. For globally distributed VLBI stations, the biases to GIMs are less than 3 TECU; the standard deviation is less than 10 TECU. Long-term trends in the results were compared to values of solar flux at 10.7 cm; for the last two solar cycles, the periods and intensity variations agree very well. [14] Acknowledgments. We are very grateful to the Austrian Science Fund (FWF), which funded the research project P16136-N06 Investigation of the ionosphere by geodetic VLBI. Furthermore, the first author wants to thank the Japanese Society for the Promotion of Science (JSPS) (project PE 04023) and Kashima Space Research Center (NICT) for supporting his research and enabling him to get the necessary knowledge of VLBI technology. The International VLBI Service for Geodesy and Astrometry (IVS) and the International GPS Service (IGS) are acknowledged for providing data. References Baisch, S., and G. H. R. Bokelmann (1999), Spectral analysis with incomplete time series: An example from seismology, Comput. Geosci., 25(7), Clark, T. A., et al. (1985), Precision geodesy using the Mark-III very long baseline interferometer system, IEEE Trans. Geosci. Remote Sens., 23, Coleman, T. F., and Y. Li (1996), A reflective Newton method for minimizing a quadratic function subject to bounds on some of the variables, SIAM J. Control Optim., 6(4), Foster, G. (1996a), Time series analysis by projection. I. Statistical properties of Fourier analysis, Astron. J., 111(1), Foster, G. (1996b), Time series analysis by projection. II. Tensor methods for time series analysis, Astron. J., 111(1), Foster, G. (1996c), Wavelets for period analysis of unevenly sampled time series, Astron. J., 112(4), Gill, P. E., W. Murray, and M. H. Wright (1981), Practical Optimization, Elsevier, New York. Koch, K.-R. (1997), Parameter Estimation and Hypothesis Testing in Linear Models, Springer, New York. Kondo, T. (1991), Application of VLBI data to measurements of ionospheric total electron content, J. Commun. Res. Lab., 38(3), Hawarey, M., T. Hobiger, and H. Schuh (2005), Effects of the 2nd order ionospheric terms on VLBI measurements, Geophys. Res. Lett., 32, L11304, doi: / 2005GL Hernandez-Pajares, M. (2004), IGS ionosphere WG status report: Performance of IGS ionosphere TEC maps, in Celebrating a Decade of the International GPS Service: 9of10
10 Workshop and Symposium 2004, edited by M. Meindl, pp , Astron. Inst., Univ. of Bern, Bern, Switzerland. Hobiger, T., and H. Schuh (2004), How VLBI contributes to ionospheric research, in International VLBI Service for Geodesy and Astrometry 2004 General Meeting Proceedings, edited by N. R. Vandenberg and K. D. Baver, NASA Conf. Publ. CP , Noll, C. (2003), CDDIS Data Center summary for the 2003 IVS annual report, in International VLBI Service for Geodesy and Astrometry 2003 Annual Report, edited by N. R. Vandenberg and K. D. Baver, NASA Tech. Publ. TP , Ray, J. R., and B. E. Corey (1991), Current precision of VLBI multi-band delay observables, in Proceedings of the Chapman Conference on Geodetic VLBI: Monitoring Global Change, NOAA Tech. Rep. NOS 137, NGS 49, pp , NOAA, Silver Spring, Md. Schaer, S. (1999), Mapping and predicting the Earth s ionosphere using the Global Positioning System, Ph.D. dissertation, Univ. Bern, Bern, Switzerland. Schaer, S., W. Gurtner, and J. Feltens (1998), IONEX: The IONosphere Map EXchange format version 1 0,February 25, 1998, paper presented at 1998 IGS Analysis Centers Workshop, Eur. Space Oper. Cent., Darmstadt, Germany. Schmidt, M. (2000), Wavelet analysis of stochastic signals, in High Frequency to Subseasonal Variations in Earth Rotation, IERS Tech. Note 28, edited by B. Kolaczek, H. Schuh, and D. Gambis, pp , Int. Earth Rotation and Ref. Syst. Serv., Paris. Sekido, M., T. Kondo, and E. Kawai (2003), Evaluation of GPS-based ionospheric TEC map by comparing with VLBI data, Radio Sci., 38(4), 1069, doi: / 2000RS Sovers, O. J., and C. S. Jacobs (1996), Observation model and parameter partials for the JPL VLBI parameter estimation software MODEST -1996, JPL Publ , Jet Propul. Lab., Pasadena, Calif. T. Hobiger and H. Schuh, Institute of Geodesy and Geophysics, Vienna University of Technology, Gusshausstrasse 27 29, A-1040 Vienna, Austria. (thobiger@mars.hg.tuwien. ac.at; harald.schuh@tuwien.ac.at) T. Kondo, Kashima Space Research Center, National Institute of Information and Communications Technology, Hirai, Kashima, Ibaraki , Japan. (kondo@nict. go.jp) 10 of 10
Combined global models of the ionosphere
Combined global models of the ionosphere S. Todorova (1), T. Hobiger (2), H. Schuh (1) (1) Institute of Geodesy and Geophysics (IGG), Vienna University of Technology (2) Space-Time Standards Group, Kashima
More informationIGS Products for the Ionosphere
1 IGS Products for the Ionosphere J. Feltens 1 and S. Schaer 2 1. EDS at Flight Dynamics Division, ESA, European Space Operations Centre, Robert-Bosch-Str. 5, D-64293 Darmstadt, Germany 2. Astronomical
More informationSpace geodetic techniques for remote sensing the ionosphere
Space geodetic techniques for remote sensing the ionosphere Harald Schuh 1,2, Mahdi Alizadeh 1, Jens Wickert 2, Christina Arras 2 1. Institute of Geodesy and Geoinformation Science, Technische Universität
More informationDetection of Abnormal Ionospheric Activity from the EPN and Impact on Kinematic GPS positioning
Detection of Abnormal Ionospheric Activity from the EPN and Impact on Kinematic GPS positioning N. Bergeot, C. Bruyninx, E. Pottiaux, S. Pireaux, P. Defraigne, J. Legrand Royal Observatory of Belgium Introduction
More informationEstimation Method of Ionospheric TEC Distribution using Single Frequency Measurements of GPS Signals
Estimation Method of Ionospheric TEC Distribution using Single Frequency Measurements of GPS Signals Win Zaw Hein #, Yoshitaka Goto #, Yoshiya Kasahara # # Division of Electrical Engineering and Computer
More informationGPS interfrequency biases and total electron content errors in ionospheric imaging over Europe
RADIO SCIENCE, VOL. 41,, doi:10.1029/2005rs003269, 2006 GPS interfrequency biases and total electron content errors in ionospheric imaging over Europe Richard M. Dear 1 and Cathryn N. Mitchell 1 Received
More informationTo Estimate The Regional Ionospheric TEC From GEONET Observation
To Estimate The Regional Ionospheric TEC From GEONET Observation Jinsong Ping(Email: jsping@miz.nao.ac.jp) 1,2, Nobuyuki Kawano 2,3, Mamoru Sekido 4 1. Dept. Astronomy, Beijing Normal University, Haidian,
More informationAtmospheric propagation
Atmospheric propagation Johannes Böhm EGU and IVS Training School on VLBI for Geodesy and Astrometry Aalto University, Finland March 2-5, 2013 Outline Part I. Ionospheric effects on microwave signals (1)
More informationThe impact of low-latency DORIS data on near real-time VTEC modeling
The impact of low-latency DORIS data on near real-time VTEC modeling Eren Erdogan, Denise Dettmering, Michael Schmidt, Andreas Goss 2018 IDS Workshop Ponta Delgada (Azores Archipelago), Portugal, 24-26
More informationIonospheric Range Error Correction Models
www.dlr.de Folie 1 >Ionospheric Range Error Correction Models> N. Jakowski and M.M. Hoque 27/06/2012 Ionospheric Range Error Correction Models N. Jakowski and M.M. Hoque Institute of Communications and
More informationUPC VTEC FORECAST MODEL BASED ON IGS GIMS
The International Beacon Satellite Symposium BSS2010 P. Doherty, M. Hernández-Pajares, J.M. Juan, J. Sanz and A. Aragon-Angel (Eds) Campus Nord UPC, Barcelona, 2010 UPC VTEC FORECAST MODEL BASED ON IGS
More informationThe impact of tropospheric mapping functions based on numerical weather models on the determination of geodetic parameters
The impact of tropospheric mapping functions based on numerical weather models on the determination of geodetic parameters J. Boehm, P.J. Mendes Cerveira, H. Schuh Institute of Geodesy and Geophysics,
More informationPresent and future IGS Ionospheric products
Present and future IGS Ionospheric products Andrzej Krankowski, Manuel Hernández-Pajares, Joachim Feltens, Attila Komjathy, Stefan Schaer, Alberto García-Rigo, Pawel Wielgosz Outline Introduction IGS IONO
More informationIONEX: The IONosphere Map EXchange Format Version 1.1
IONEX: The IONosphere Map EXchange Format Version 1.1 Stefan Schaer, Werner Gurtner Astronomical Institute, University of Berne, Switzerland stefan.schaer@aiub.unibe.ch Joachim Feltens ESA/ESOC, Darmstadt,
More informationCharacterizing Atmospheric Turbulence and Instrumental Noise Using Two Simultaneously Operating Microwave Radiometers
Characterizing Atmospheric Turbulence and Instrumental Noise Using Two Simultaneously Operating Microwave Radiometers Tobias Nilsson, Gunnar Elgered, and Lubomir Gradinarsky Onsala Space Observatory Chalmers
More informationMonitoring the 3 Dimensional Ionospheric Electron Distribution based on GPS Measurements
Monitoring the 3 Dimensional Ionospheric Electron Distribution based on GPS Measurements Stefan Schlüter 1, Claudia Stolle 2, Norbert Jakowski 1, and Christoph Jacobi 2 1 DLR Institute of Communications
More informationIonospheric Tomography with GPS Data from CHAMP and SAC-C
Ionospheric Tomography with GPS Data from CHAMP and SAC-C Miquel García-Fernández 1, Angela Aragón 1, Manuel Hernandez-Pajares 1, Jose Miguel Juan 1, Jaume Sanz 1, and Victor Rios 2 1 gage/upc, Mod C3
More informationGeneration of Klobuchar Coefficients for Ionospheric Error Simulation
Research Paper J. Astron. Space Sci. 27(2), 11722 () DOI:.14/JASS..27.2.117 Generation of Klobuchar Coefficients for Ionospheric Error Simulation Chang-Moon Lee 1, Kwan-Dong Park 1, Jihyun Ha 2, and Sanguk
More informationGPS Based Ionosphere Mapping Using PPP Method
Salih ALCAY, Cemal Ozer YIGIT, Cevat INAL, Turkey Key words: GIMs, IGS, Ionosphere mapping, PPP SUMMARY Mapping of the ionosphere is a very interesting subject within the scientific community due to its
More informationImprovement GPS Time Link in Asia with All in View
Improvement GPS Time Link in Asia with All in View Tadahiro Gotoh National Institute of Information and Communications Technology 1, Nukui-kita, Koganei, Tokyo 18 8795 Japan tara@nict.go.jp Abstract GPS
More informationAtmospheric Delay Reduction Using KARAT for GPS Analysis and Implications for VLBI
Atmospheric Delay Reduction Using KARAT for GPS Analysis and Implications for VLBI ICHIKAWA Ryuichi 2, Thomas HOBIGER 1, KOYAMA Yasuhiro 1, KONDO Tetsuro 2 1) Kashima Space Research Center, National Institute
More informationA study of the ionospheric effect on GBAS (Ground-Based Augmentation System) using the nation-wide GPS network data in Japan
A study of the ionospheric effect on GBAS (Ground-Based Augmentation System) using the nation-wide GPS network data in Japan Takayuki Yoshihara, Electronic Navigation Research Institute (ENRI) Naoki Fujii,
More informationDATA AND PRODUCT EXCHANGE IN THE CONTEXT OF WIS. ITU discussions on ionospheric products and formats. (Submitted by the WMO Secretariat)
WORLD METEOROLOGICAL ORGANIZATION COMMISSION FOR BASIC SYSTEMS COMMISSION FOR AERONAUTICAL METEOROLOGY INTER-PROGRAMME COORDINATION TEAM ON SPACE WEATHER ICTSW-5/Doc. 6.2 (28.X.2014) ITEM: 6.2 FIFTH SESSION
More informationIonospheric Estimation using Extended Kriging for a low latitude SBAS
Ionospheric Estimation using Extended Kriging for a low latitude SBAS Juan Blanch, odd Walter, Per Enge, Stanford University ABSRAC he ionosphere causes the most difficult error to mitigate in Satellite
More informationExperiments on the Ionospheric Models in GNSS
Experiments on the Ionospheric Models in GNSS La The Vinh, Phuong Xuan Quang, and Alberto García-Rigo, Adrià Rovira-Garcia, Deimos Ibáñez-Segura NAVIS Centre, Hanoi University of Science and Technology,
More informationNAVIGATION SYSTEMS PANEL (NSP) NSP Working Group meetings. Impact of ionospheric effects on SBAS L1 operations. Montreal, Canada, October, 2006
NAVIGATION SYSTEMS PANEL (NSP) NSP Working Group meetings Agenda Item 2b: Impact of ionospheric effects on SBAS L1 operations Montreal, Canada, October, 26 WORKING PAPER CHARACTERISATION OF IONOSPHERE
More informationSpace Weather influence on satellite based navigation and precise positioning
Space Weather influence on satellite based navigation and precise positioning R. Warnant, S. Lejeune, M. Bavier Royal Observatory of Belgium Avenue Circulaire, 3 B-1180 Brussels (Belgium) What this talk
More informationEFFECTS OF IONOSPHERIC SMALL-SCALE STRUCTURES ON GNSS
EFFECTS OF IONOSPHERIC SMALL-SCALE STRUCTURES ON GNSS G. Wautelet, S. Lejeune, R. Warnant Royal Meteorological Institute of Belgium, Avenue Circulaire 3 B-8 Brussels (Belgium) e-mail: gilles.wautelet@oma.be
More informationConstrained simultaneous algebraic reconstruction technique (C-SART) a new and simple algorithm applied to ionospheric tomography
Earth Planets Space, 60, 727 735, 2008 Constrained simultaneous algebraic reconstruction technique (C-SART) a new and simple algorithm applied to ionospheric tomography Thomas Hobiger, Tetsuro Kondo, and
More informationAutomated daily processing of more than 1000 ground-based GPS receivers for studying intense ionospheric storms
RADIO SCIENCE, VOL. 40,, doi:10.1029/2005rs003279, 2005 Automated daily processing of more than 1000 ground-based GPS receivers for studying intense ionospheric storms Attila Komjathy, Lawrence Sparks,
More informationimaging of the ionosphere and its applications to radio propagation Fundamentals of tomographic Ionospheric Tomography I: Ionospheric Tomography I:
Ionospheric Tomography I: Ionospheric Tomography I: Fundamentals of tomographic imaging of the ionosphere and its applications to radio propagation Summary Introduction to tomography Introduction to tomography
More informationJohannes Böhm, Paulo Jorge Mendes Cerveira, Harald Schuh, and Paul Tregoning
Johannes Böhm, Paulo Jorge Mendes Cerveira, Harald Schuh, and Paul Tregoning The impact of mapping functions for the neutral atmosphere based on numerical weather models in GPS data analysis IAG Symposium
More informationOn the GNSS integer ambiguity success rate
On the GNSS integer ambiguity success rate P.J.G. Teunissen Mathematical Geodesy and Positioning Faculty of Civil Engineering and Geosciences Introduction Global Navigation Satellite System (GNSS) ambiguity
More informationEvaluation of Potential Systematic Bias in GNSS Orbital Solutions
Evaluation of Potential Systematic Bias in GNSS Orbital Solutions Graham M. Appleby Space Geodesy Facility, Natural Environment Research Council Monks Wood, Abbots Ripton, Huntingdon PE28 2LE, UK Toshimichi
More informationTrimble Business Center:
Trimble Business Center: Modernized Approaches for GNSS Baseline Processing Trimble s industry-leading software includes a new dedicated processor for static baselines. The software features dynamic selection
More informationPerformances of Modernized GPS and Galileo in Relative Positioning with weighted ionosphere Delays
Agence Spatiale Algérienne Centre des Techniques Spatiales Agence Spatiale Algérienne Centre des Techniques Spatiales الوكالة الفضائية الجزائرية مركز للتقنيات الفضائية Performances of Modernized GPS and
More informationA PIM-aided Kalman Filter for GPS Tomography of the Ionospheric Electron Content
A PIM-aided Kalman Filter for GPS Tomography of the Ionospheric Electron Content G. Ruffini, L. Cucurull, A. Flores, and A. Rius Institut d Estudis Espacials de Catalunya, CSIC Research Unit, Edif. Nexus-204,
More informationMONITORING SEA LEVEL USING GPS
38 MONITORING SEA LEVEL USING GPS Hasanuddin Z. Abidin* Abstract GPS (Global Positioning System) is a passive, all-weather satellite-based navigation and positioning system, which is designed to provide
More informationThe Near Real Time Ionospheric Model of Latvia
IOP Conference Series: Materials Science and Engineering PAPER OPEN ACCESS The Near Real Time Ionospheric Model of Latvia To cite this article: M Kainka et al 2015 IOP Conf. Ser.: Mater. Sci. Eng. 96 012042
More informationPropagation effects (tropospheric and ionospheric phase calibration)
Propagation effects (tropospheric and ionospheric phase calibration) Prof. Steven Tingay Curtin University of Technology Perth, Australia With thanks to Alan Roy (MPIfR), James Anderson (JIVE), Tasso Tzioumis
More informationSubdaily station motions from Kalman filtering VLBI data
Subdaily station motions from Kalman filtering VLBI data Benedikt Soja, Maria Karbon, Tobias Nilsson, Kyriakos Balidakis, Susanne Glaser*, Zhiguo Deng, Robert Heinkelmann, Harald Schuh bsoja@gfz-potsdam.de
More informationActivities of the JPL Ionosphere Group
Activities of the JPL Ionosphere Group On-going GIM wor Submit rapid and final GIM TEC maps for IGS combined ionosphere products FAA WAAS & SBAS analysis Error bounds for Brazilian sector, increasing availability
More informationTable of Contents. Frequently Used Abbreviation... xvii
GPS Satellite Surveying, 2 nd Edition Alfred Leick Department of Surveying Engineering, University of Maine John Wiley & Sons, Inc. 1995 (Navtech order #1028) Table of Contents Preface... xiii Frequently
More informationIAG School on Reference Systems June 7 June 12, 2010 Aegean University, Department of Geography Mytilene, Lesvos Island, Greece SCHOOL PROGRAM
IAG School on Reference Systems June 7 June 12, 2010 Aegean University, Department of Geography Mytilene, Lesvos Island, Greece SCHOOL PROGRAM Monday June 7 8:00-9:00 Registration 9:00-10:00 Opening Session
More informationAn Assessment of Mapping Functions for VTEC Estimation using Measurements of Low Latitude Dual Frequency GPS Receiver
An Assessment of Mapping Functions for VTEC Estimation using Measurements of Low Latitude Dual Frequency GPS Receiver Mrs. K. Durga Rao 1 Asst. Prof. Dr. L.B.College of Engg. for Women, Visakhapatnam,
More informationLocal GPS tropospheric tomography
LETTER Earth Planets Space, 52, 935 939, 2000 Local GPS tropospheric tomography Kazuro Hirahara Graduate School of Sciences, Nagoya University, Nagoya 464-8602, Japan (Received December 31, 1999; Revised
More informationAccuracy Assessment of GPS Slant-Path Determinations
Accuracy Assessment of GPS Slant-Path Determinations Pedro ELOSEGUI * and James DAVIS Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA Abtract We have assessed the accuracy of GPS for determining
More informationApril - 1 May, GNSS Derived TEC Data Calibration
2333-44 Workshop on Science Applications of GNSS in Developing Countries (11-27 April), followed by the: Seminar on Development and Use of the Ionospheric NeQuick Model (30 April-1 May) 11 April - 1 May,
More informationTREATMENT OF DIFFRACTION EFFECTS CAUSED BY MOUNTAIN RIDGES
TREATMENT OF DIFFRACTION EFFECTS CAUSED BY MOUNTAIN RIDGES Rainer Klostius, Andreas Wieser, Fritz K. Brunner Institute of Engineering Geodesy and Measurement Systems, Graz University of Technology, Steyrergasse
More informationJames M Anderson. in collaboration with Jan Noordam and Oleg Smirnov. MPIfR, Bonn, 2006 Dec 07
Ionospheric Calibration for Long-Baseline, Low-Frequency Interferometry in collaboration with Jan Noordam and Oleg Smirnov Page 1/36 Outline The challenge for radioastronomy Introduction to the ionosphere
More informationAn Improvement of Retrieval Techniques for Ionospheric Radio Occultations
An Improvement of Retrieval Techniques for Ionospheric Radio Occultations Miquel García-Fernández, Manuel Hernandez-Pajares, Jose Miguel Juan-Zornoza, and Jaume Sanz-Subirana Astronomy and Geomatics Research
More informationEVGA Meeting March 7 th 2013
Current release and plans for the future Johannes Böhm Sigrid Böhm Hana Krásná Tobias Nilsson Lucia Plank Claudia Tierno Ros Jing Sun Kamil Teke EVGA Meeting March 7 th 2013 1 / 24 (VieVS) VLBI data software
More informationInteger Ambiguity Resolution for Precise Point Positioning Patrick Henkel
Integer Ambiguity Resolution for Precise Point Positioning Patrick Henkel Overview Introduction Sequential Best-Integer Equivariant Estimation Multi-frequency code carrier linear combinations Galileo:
More informationGlobal ionosphere maps based on GNSS, satellite altimetry, radio occultation and DORIS
GPS Solut (2017) 21:639 650 DOI 10.1007/s10291-016-0554-9 ORIGINAL ARTICLE Global ionosphere maps based on GNSS, satellite altimetry, radio occultation and DORIS Peng Chen 1 Yibin Yao 2,3 Wanqiang Yao
More information(The basics of) VLBI Basics. Pedro Elosegui MIT Haystack Observatory. With big thanks to many of you, here and out there
(The basics of) VLBI Basics Pedro Elosegui MIT Haystack Observatory With big thanks to many of you, here and out there Some of the Points Will Cover Today Geodetic radio telescopes VLBI vs GPS concept
More informationBernese GPS Software 4.2
Bernese GPS Software 4.2 Introduction Signal Processing Geodetic Use Details of modules Bernese GPS Software 4.2 Highest Accuracy GPS Surveys Research and Education Big Permanent GPS arrays Commercial
More informationGNSS: orbits, signals, and methods
Part I GNSS: orbits, signals, and methods 1 GNSS ground and space segments Global Navigation Satellite Systems (GNSS) at the time of writing comprise four systems, two of which are fully operational and
More informationGlobal IGS/GPS Contribution to ITRF
Global IGS/GPS Contribution to ITRF R. Ferland Natural ResourcesCanada, Geodetic Survey Divin 46-61 Booth Street, Ottawa, Ontario, Canada. Tel: 1-613-99-42; Fax: 1-613-99-321. e-mail: ferland@geod.nrcan.gc.ca;
More informationEffiziente Umsetzung der Integration der Elektronendichte innerhalb der Ionosphäre entlang des Signalweges
Effiziente Umsetzung der Integration der Elektronendichte innerhalb der Ionosphäre entlang des Signalweges (DFG-Projekt MuSIK) Marco Limberger 1, Urs Hugentober 1, Michael Schmidt 2, Denise Dettmering
More informationSpatial and Temporal Variations of GPS-Derived TEC over Malaysia from 2003 to 2009
Spatial and Temporal Variations of GPS-Derived TEC over Malaysia from 2003 to 2009 Leong, S. K., Musa, T. A. & Abdullah, K. A. UTM-GNSS & Geodynamics Research Group, Infocomm Research Alliance, Faculty
More informationComparison of GPS receiver DCB estimation methods using a GPS network
Earth Planets Space, 65, 707 711, 2013 Comparison of GPS receiver DCB estimation methods using a GPS network Byung-Kyu Choi 1, Jong-Uk Park 1, Kyoung Min Roh 1, and Sang-Jeong Lee 2 1 Space Science Division,
More informationPrinciples of the Global Positioning System Lecture 19
12.540 Principles of the Global Positioning System Lecture 19 Prof. Thomas Herring http://geoweb.mit.edu/~tah/12.540 GPS Models and processing Summary: Finish up modeling aspects Rank deficiencies Processing
More informationInternational GNSS Service Workshop 2017
International GNSS Service Workshop 2017 The Recent Activities of CAS Ionosphere Analysis Center on GNSS Ionospheric Modeling within IGS CAS: Chinese Academy of Sciences Yunbin Yuan*, Zishen Li, Ningbo
More informationOperational Products of the Space Weather Application Center Ionosphere (SWACI) and capabilities of their use
Operational Products of the Space Weather Application Center Ionosphere (SWACI) and capabilities of their use N. Jakowski, C. Borries, V. Wilken, K.D. Missling, H. Barkmann, M. M. Hoque, M. Tegler, C.
More informationIonospheric bending correction for GNSS radio occultation signals
RADIO SCIENCE, VOL. 46,, doi:10.109/010rs004583, 011 Ionospheric bending correction for GNSS radio occultation signals M. M. Hoque 1 and N. Jakowski 1 Received 30 November 010; revised 1 April 011; accepted
More informationMeasuring Total Electron Content. Investigation of Two Different Techniques
Measuring Total Electron Content with GNSS: Investigation of Two Different Techniques Benoît Bidaine 1 F.R.S. FNRS B.Bidaine@ulg.ac.be Prof. René Warnant 1,2 R.Warnant@oma.be 1 University of Liège (Unit
More informationTHE USE OF GPS/MET DATA FOR IONOSPHERIC STUDIES
THE USE OF GPS/MET DATA FOR IONOSPHERIC STUDIES Christian Rocken GPS/MET Program Office University Corporation for Atmospheric Research Boulder, CO 80301 phone: (303) 497 8012, fax: (303) 449 7857, e-mail:
More informationTEC Estimation Using GNSS. Luigi Ciraolo, ICTP. Kigali, July 9th 2014
TEC Estimation Using GNSS Luigi Ciraolo, ICTP Workshop: African School on Space Science: Related Applications and Awareness for Sustainable Development of the Region Kigali, July 9th 2014 GNSS observables
More informationDesign of leaky coaxial cables with periodic slots
RADIO SCIENCE, VOL. 37, NO. 5, 1069, doi:10.1029/2000rs002534, 2002 Design of leaky coaxial cables with periodic slots Jun Hong Wang 1 and Kenneth K. Mei Department of Electronic Engineering, City University
More informationComparative analysis of the effect of ionospheric delay on user position accuracy using single and dual frequency GPS receivers over Indian region
Indian Journal of Radio & Space Physics Vol. 38, February 2009, pp. 57-61 Comparative analysis of the effect of ionospheric delay on user position accuracy using single and dual frequency GPS receivers
More informationGNSS Ionosphere Analysis at CODE
GNSS Ionosphere Analysis at CODE Stefan Schaer 2004 IGS Workshop Berne, Switzerland March 1-5 Time Series of Global Mean TEC Covering Nearly One Solar Cycle as Generated at CODE 1 Exceptionally High TEC
More informationA PIM-aided Kalman Filter for GPS Tomography of the Ionospheric Electron Content
A PIM-aided Kalman Filter for GPS Tomography of the Ionospheric Electron Content arxiv:physics/9807026v1 [physics.geo-ph] 17 Jul 1998 G. Ruffini, L. Cucurull, A. Flores, A. Rius November 29, 2017 Institut
More informationLow Earth orbit satellite navigation errors and vertical total electron content in single-frequency GPS tracking
RADIO SCIENCE, VOL. 4,, doi:.29/25rs342, 26 Low Earth orbit satellite navigation errors and vertical total electron content in single-frequency GPS tracking Miquel Garcia-Fernàndez and Oliver Montenbruck
More informationThe Promise and Challenges of Accurate Low Latency GNSS for Environmental Monitoring and Response
Technical Seminar Reference Frame in Practice, The Promise and Challenges of Accurate Low Latency GNSS for Environmental Monitoring and Response John LaBrecque Geohazards Focus Area Global Geodetic Observing
More informationHigh Speed Data Transmission and Processing Systems for e-vlbi Observations
High Speed Data Transmission and Processing Systems for e-vlbi Observations Yasuhiro Koyama, Tetsuro Kondo, and Junichi Nakajima Communications Research Laboratory, Kashima Space Research Center 893-1
More informationStudy of the Ionosphere Irregularities Caused by Space Weather Activity on the Base of GNSS Measurements
Study of the Ionosphere Irregularities Caused by Space Weather Activity on the Base of GNSS Measurements Iu. Cherniak 1, I. Zakharenkova 1,2, A. Krankowski 1 1 Space Radio Research Center,, University
More informationUpdates on the neutral atmosphere inversion algorithms at CDAAC
Updates on the neutral atmosphere inversion algorithms at CDAAC S. Sokolovskiy, Z. Zeng, W. Schreiner, D. Hunt, J. Lin, Y.-H. Kuo 8th FORMOSAT-3/COSMIC Data Users' Workshop Boulder, CO, September 30 -
More informationELECTROMAGNETIC PROPAGATION (ALT, TEC)
ELECTROMAGNETIC PROPAGATION (ALT, TEC) N. Picot CNES, 18 Av Ed Belin, 31401 Toulouse, France Email : Nicolas.Picot@cnes.fr ABSTRACT For electromagnetic propagation, the ionosphere plays a key role. This
More informationDetection and Mitigation of Static Multipath in L1 Carrier Phase Measurements Using a Dual- Antenna Approach
Detection and Mitigation of Static Multipath in L1 Carrier Phase Measurements Using a Dual- Antenna Approach M.C. Santos Department of Geodesy and Geomatics Engineering, University of New Brunswick, P.O.
More informationPrinciples of the Global Positioning System Lecture 20" Processing Software" Primary research programs"
12.540 Principles of the Global Positioning System Lecture 20" Prof. Thomas Herring" Room 54-820A; 253-5941" tah@mit.edu" http://geoweb.mit.edu/~tah/12.540 " Processing Software" Examine basic features
More informationFirst assimilations of COSMIC radio occultation data into the Electron Density Assimilative Model (EDAM)
Ann. Geophys., 26, 353 359, 2008 European Geosciences Union 2008 Annales Geophysicae First assimilations of COSMIC radio occultation data into the Electron Density Assimilative Model (EDAM) M. J. Angling
More informationAn experiment of predicting Total Electron Content (TEC) by fuzzy inference systems
Earth Planets Space, 60, 967 972, 2008 An experiment of predicting Total Electron Content (TEC) by fuzzy inference systems O. Akyilmaz 1 and N. Arslan 2 1 Department of Geodesy and Photogrammetry Engineering,
More informationROTI Maps: a new IGS s ionospheric product characterizing the ionospheric irregularities occurrence
3-7 July 2017 ROTI Maps: a new IGS s ionospheric product characterizing the ionospheric irregularities occurrence Iurii Cherniak Andrzej Krankowski Irina Zakharenkova Space Radio-Diagnostic Research Center,
More informationMINIMIZING SELECTIVE AVAILABILITY ERROR ON TOPEX GPS MEASUREMENTS. S. C. Wu*, W. I. Bertiger and J. T. Wu
MINIMIZING SELECTIVE AVAILABILITY ERROR ON TOPEX GPS MEASUREMENTS S. C. Wu*, W. I. Bertiger and J. T. Wu Jet Propulsion Laboratory California Institute of Technology Pasadena, California 9119 Abstract*
More informationIonospheric Corrections for GNSS
Ionospheric Corrections for GNSS The Atmosphere and its Effect on GNSS Systems 14 to 16 April 2008 Santiago, Chile Ing. Roland Lejeune Overview Ionospheric delay corrections Core constellations GPS GALILEO
More informationObserving the APOD satellite with the AuScope VLBI network
10 th IVS General Meeting, June 3-8, 2018, Svalbard, Norway Observing the APOD satellite with the AuScope VLBI network Andreas Hellerschmied Johannes Böhm Technische Universität Wien, Austria Lucia McCallum
More informationTEC Prediction Model using Neural Networks over a Low Latitude GPS Station
ISSN: 223-237, Volume-2, Issue-2, May 2 TEC Prediction Model using Neural Networks over a Low GPS Station D.Venkata.Ratnam, B.Venkata Dinesh, B.Tejaswi, D.Praveen Kumar, T.V.Ritesh, P.S.Brahmanadam, G.Vindhya
More informationImpact of Different Tropospheric Models on GPS Baseline Accuracy: Case Study in Thailand
Journal of Global Positioning Systems (2005) Vol. 4, No. 1-2: 36-40 Impact of Different Tropospheric Models on GPS Baseline Accuracy: Case Study in Thailand Chalermchon Satirapod and Prapod Chalermwattanachai
More informationPolar Ionospheric Imaging at Storm Time
Ms Ping Yin and Dr Cathryn Mitchell Department of Electronic and Electrical Engineering University of Bath BA2 7AY UNITED KINGDOM p.yin@bath.ac.uk / eescnm@bath.ac.uk Dr Gary Bust ARL University of Texas
More informationGNSS zenith delays and gradients in the analysis of VLBI Intensive sessions
GNSS zenith delays and gradients in the analysis of VLBI Intensive sessions Kamil Teke (1), Johannes Böhm (2), Matthias Madzak (2), Younghee Kwak (2), Peter Steigenberger (3) (1) Department of Geomatics
More informationPresented at the FIG Congress 2018, May 6-11, 2018 in Istanbul, Turkey
Presented at the FIG Congress 2018, May 6-11, 2018 in Istanbul, Turkey 2 Improving Hydrographic PPP by Height Constraining Ashraf Abdallah (Egypt) Volker Schwieger, (Germany) ashraf.abdallah@aswu.edu.eg
More informationMethods and other considerations to correct for higher-order ionospheric delay terms in GNSS
Methods and other considerations to correct for higher-order ionospheric delay terms in GNSS M. Hernández-Pajares(1), M.Fritsche(2), M.M. Hoque(3), N. Jakowski (3), J.M. Juan(1), S. Kedar(4), A. Krankowski(5),
More informationTechnology of Precise Orbit Determination
Technology of Precise Orbit Determination V Seiji Katagiri V Yousuke Yamamoto (Manuscript received March 19, 2008) Since 1971, most domestic orbit determination systems have been developed by Fujitsu and
More informationSIRGAS Combination Centre at DGFI Report for the SIRGAS 2009 General Meeting September 1, Buenos Aires, Argentina
September 1, 2009. Buenos Aires, Argentina Laura Sánchez, Wolfgang Seemüller, Manuela Seitz. Deutsches Geodätisches Forschungsinstitut, DGFI Munich, Germany 1. Introduction The densification of the ITRF
More informationAssessment of Nominal Ionosphere Spatial Decorrelation for LAAS
Assessment of Nominal Ionosphere Spatial Decorrelation for LAAS Jiyun Lee, Sam Pullen, Seebany Datta-Barua, and Per Enge Stanford University, Stanford, California 9-8 Abstract The Local Area Augmentation
More informationPlasma effects on transionospheric propagation of radio waves II
Plasma effects on transionospheric propagation of radio waves II R. Leitinger General remarks Reminder on (transionospheric) wave propagation Reminder of propagation effects GPS as a data source Some electron
More informationCOMPARISON OF IONOSPHERIC DELAYS OBTAINED FROM s-x VLBI EXPERIMENTS AND GPS OBSERVATIONS
COMPARISON OF IONOSPHERIC DELAYS OBTAINED FROM s-x VLBI EXPERIMENTS AND GPS OBSERVATIONS E. SARDON (1), A. RIUS (1,2), N. ZARRAOA (1,3) 1 Instituto de Astronomía y Geodesia (CSIC-UCM), Facultad de Ciencias
More informationIonospheric measurement with GPS: Receiver techniques and methods
RADIO SCIENCE, VOL. 43,, doi:10.1029/2007rs003770, 2008 Ionospheric measurement with GPS: Receiver techniques and methods Lars Dyrud, 1 Aleksandar Jovancevic, 1 Andrew Brown, 1 Derek Wilson, 1 and Suman
More informationVLBI and DDOR activities at ESOC
VLBI and DDOR activities at ESOC Claudia Flohrer 1, Mattia Mercolino 2, Erik Schönemann 1, Tim Springer 1, Joachim Feltens 1, René Zandbergen 1, Werner Enderle 1, Trevor Morley 3 1) Navigation Support
More informationGPS STATIC-PPP POSITIONING ACCURACY VARIATION WITH OBSERVATION RECORDING INTERVAL FOR HYDROGRAPHIC APPLICATIONS (ASWAN, EGYPT)
GPS STATIC-PPP POSITIONING ACCURACY VARIATION WITH OBSERVATION RECORDING INTERVAL FOR HYDROGRAPHIC APPLICATIONS (ASWAN, EGYPT) Ashraf Farah Associate Professor,College of Engineering, Aswan University,
More information