tag:blogger.com,1999:blog-59182519470109527632024-03-14T03:10:14.352+01:00GNSS BlogPosiTim GNSS BLOG about GPS, Glonass, Galileo, and other Satellite navigation systemsSpringinhetveldhttp://www.blogger.com/profile/14360127679091995926noreply@blogger.comBlogger36125tag:blogger.com,1999:blog-5918251947010952763.post-69061077567513937982015-04-01T10:06:00.002+02:002015-04-01T10:07:27.842+02:00Busy GNSS Launch weekWow that was a busy week with respect to GNSS launches. The week was started by the GPS system launching its 9th block IIF satellite on March 25. It was followed by the second Galileo FOC launch on March 30. There was quite some anxiety about the Galileo launch as the first FOC launch did put the two GALILEO satellites in a wrong orbit due to an issue with the fregat upper stage. The week was completed by a very secretive BeiDou launch by the Chinese.<br />
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The GPS launch is basically just a continuation of the IIF launches and from that point of view nothing new. But of course very important to keep the GPS constellation alive and kicking.<br />
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The Galileo and BeiDou launch are certainly more interesting. For Galileo although being the second FOC launch it is actually the first as the initial launch resulted in the satellites ending up in the wrong orbits. And although the orbits have been adjusted they are still very far from nominal. So these will be the first Galileo FOC satellites in their nominal orbit.<br />
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The BeiDou satellite, although very little is known about it, seems to be the first satellite of what is called the phase III in the BeiDou programme. This means that the signals of this satellite will be completely different from the previously launched BeiDou satellites. For both the B1 and B2 signals the frequency is now slightly different, i.e., bringing B1 to the same frequency as used by the GPS L1 signals and the Galileo E1 signals. The change of the B2 signal frequency makes it use the identical frequency as the Galileo E5 signal.<br />
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The GPS IIF already started to transmit its first signals and will be included in the products of the International GNSS Service very soon. When the first signals of the other two satellites may be expected is unclear. But if they come they will be much more exiting!<br />
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I am at least very much looking forward to them!<br />
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<br /><div class="blogger-post-footer"><a href="http://www.PosiTim.com/">
PosiTim High Accuracy GNSS
</a></div>Springinhetveldhttp://www.blogger.com/profile/14360127679091995926noreply@blogger.com0tag:blogger.com,1999:blog-5918251947010952763.post-76653619737099853212014-08-24T02:12:00.002+02:002014-08-24T10:12:30.985+02:00Groundtrack of the Galileo SatellitesPurely out of interest I have made a plot of the ground track of the orbits in which the last two Galileo Satellites ended up in. The results is shown in the figure below.
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<div class="separator" style="clear: both; text-align: center;">
<a href="http://1.bp.blogspot.com/-fZO2d_TzOnI/U_ko7GPVt-I/AAAAAAAAADE/uR0fUUMhrT4/s1600/galileo_ground.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://1.bp.blogspot.com/-fZO2d_TzOnI/U_ko7GPVt-I/AAAAAAAAADE/uR0fUUMhrT4/s320/galileo_ground.gif" /></a></div>
The figures shows the ground track of Galileo-101 (E11), one of the older Galileo satellites, and Galileo-201, one of the two new Galileo satellites, over a period of 24 hours for August 23, 2014. A couple of interesting features can be seen from the plot. Firstly the difference in inclination, 56 vs 49 degrees, is clearly visible as the maximum latitude of the Galileo-201 satellite is clearly smaller. Secondly, the orbital revolution period is clearly significantly shorter. The normal Galileo satellites have an orbital period of around 13 hours. This means that in 24 hours, the period used for the plot, they will complete less then two orbital revolutions. The new satellite clearly completes two full revolutions within the 24 hour interval. This nicely shows that the new two satellites will not fit into the Galileo constellation in their current orbit. They will move through the constellation in a very wild way.<br />
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What I find a bit scary is that with the Perigee of these orbits at merely 20000 km these three objects, the two Galileo satellites and the Fregat, are actually moving through the orbital planes of the GPS and GLONASS constellations. This means to sooner or later they will be on a "collision" course with one of those satellites. Fortunately the satellites seems to be in good order so they can be steered but not sure about the Fregat. So GPS and GLONASS may have to do collision avoidance manoeuvres because of this mishap.<br />
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But not all is bad. GNSS scientist have actually concluded a couple of times that different orbits for the different GNSS satellites would be advantegeous for their high accuracy investigations. So at least some of the GNSS scientist might be happy with this situation!<br />
<br /><div class="blogger-post-footer"><a href="http://www.PosiTim.com/">
PosiTim High Accuracy GNSS
</a></div>Springinhetveldhttp://www.blogger.com/profile/14360127679091995926noreply@blogger.com0tag:blogger.com,1999:blog-5918251947010952763.post-8895856925457963042014-08-23T12:02:00.000+02:002014-08-24T10:12:52.272+02:00Galileo Orbit AnomalyIt seems that the Galileo satellites, numbers 5 and 6, launched yesterday (August 22, 2014) have not reached their intended orbit. The intended orbit would have had an altitude of around 23'000 km whereas it is said that the lowest point of the achieved orbit is only 13'000 km, i.e. 10'000 km below the intended orbit. Also the intended inclination of the orbit was not reached with 47 deg versus the planned 55 degrees.
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<a href="http://3.bp.blogspot.com/-pEVtZoL5vjc/U_hlzaDMeXI/AAAAAAAAAC0/O4OAkgpzDrM/s1600/GalileoOHBsats.jpg" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" src="http://3.bp.blogspot.com/-pEVtZoL5vjc/U_hlzaDMeXI/AAAAAAAAAC0/O4OAkgpzDrM/s320/GalileoOHBsats.jpg" /></a></div>
The launch seemed to go picture perfect, I watched it life at the European Space Operations Centre in Darmstadt, Germany. So my guess is that the Fregat upper stage did not perform as expected. I think that the 10'000 km altitude may be corrected but the inclination error may be harder to correct. I would have to do some calcuations but if I remember correctly an inclination manoeuvre is more "expensive" (in terms of fuel consumption) than the altitude correction. So I fear that these satellites are more or less "lost" in terms of being part of the final Galileo constellation. But, as these are brand new satellites, they will serve a very much needed purpose of testing and validating these new birds! So not all is lost.
In any case this is unfortunately an other big blow for the Galileo project. But this is basically just a small technical "hick-up" which does happen in the Space Industry. I am sure the Galileo project will survive this and continue on the path it has set out of brining us a very much needed European Satellite Navigation System.
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For more information here some of the links on this topic (but they do not have too much information yet).
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<a href="http://www.arianespace.com/news-press-release/2014/8-22-2014-orbital-injection.asp" target="_blank">Arianespace</a><br />
<a href="http://www.esa.int/Our_Activities/Navigation/The_future_-_Galileo/Launching_Galileo/Soyuz_Galileo_launch_injection_anomaly" target="_blank">ESA Navigation</a><br />
<a href="http://spaceflightnow.com/soyuz/vs09/140822anomaly/#.U_hjGvl_vxU" target="_blank">Spaceflight Now</a><br />
<a href="http://www.ohb.de/media-relations/pressemitteilungen-detail/items/esa-announcement-soyuz-galileo-launch-injection-anomaly.html" target="_blank">OHB</a><br />
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Small add-on. Just looked up the TLE (two line elements) from NORAD <a href="http://celestrak.com/" target="_blank">(celestrak)</a> and computed the orbits myself. Based on the last set of TLE's the semi-major axis is 26'196 km, the eccentricity 0.23, and the inclination 49.76 degrees. This gives a Perigee (closest distance from Earth) of 20'170 km which is indeed about 10'000 km too low. But it would also mean that the Apogee (furthest distance from Earth) is around 32'000 km. That would be about 3'000 km too much. So seems that the Fregat had enough power but the orbit injection was miscalculated and/or misfired... Not good!<div class="blogger-post-footer"><a href="http://www.PosiTim.com/">
PosiTim High Accuracy GNSS
</a></div>Springinhetveldhttp://www.blogger.com/profile/14360127679091995926noreply@blogger.com0tag:blogger.com,1999:blog-5918251947010952763.post-81167230304498864392011-10-25T07:45:00.000+02:002011-10-25T07:45:56.059+02:00GALILEO IOV Launch SuccessfulThe first two GALILEO In Orbit Validation (IOV) satellites have been launched successfully from the European Space Port in Kourou, French Guyana, on Friday October 21, 2011. This launch was a double success as besides being the very first true GALILEO launch it was also the first launch of a Soyuz rocket from Kourou. Despite all these "firsts", which is always a bit exciting in the aerospace industry, everything worked picture prefect. The satellites were injected into the planned orbits. <br />
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The satellite are now in what is called the Launch and Early Orbit Phase (LEOP). Currently the satellites are slowly drifting towards their orbital positions and therefore also drifting apart. To get their relative positions correct the two satellites will have to be separated by 40 degrees in their argument of latitude. This will take a couple of days of "drifting" to accomplish. After this drifting phase both satellites will make a number of small manoeuvres to get into their nominal orbit position with very high accuracy. Once in their nominal orbits the GALILEO satellites are expected to need at most one station keeping manoeuvre in their nominal life time of 20 years.<br />
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At long last Europe has become one of the players in the GNSS field! Personally I am very much looking forward to working with the first observational data of these brand new satellites which mark a new era for the GNSS industry.<div class="blogger-post-footer"><a href="http://www.PosiTim.com/">
PosiTim High Accuracy GNSS
</a></div>Springinhetveldhttp://www.blogger.com/profile/14360127679091995926noreply@blogger.com0tag:blogger.com,1999:blog-5918251947010952763.post-84479127511650014792011-10-20T11:07:00.000+02:002011-10-20T11:07:03.308+02:00GALILEO IOV Launch delayed....The GALILEO IOV launch has been delayed by 24 hours. No information on the cause if this delay. Will keep you posted!<div class="blogger-post-footer"><a href="http://www.PosiTim.com/">
PosiTim High Accuracy GNSS
</a></div>Springinhetveldhttp://www.blogger.com/profile/14360127679091995926noreply@blogger.com0tag:blogger.com,1999:blog-5918251947010952763.post-82328168443228708002011-10-18T21:18:00.004+02:002011-10-18T21:21:15.286+02:00Upcoming GALILEO IOV Launch<div class="separator" style="text-align: center;"><a href="http://4.bp.blogspot.com/-F4-DA9Z8ORg/Tp3P44Ld9ZI/AAAAAAAAACY/faj1neGPqmY/s1600/Galileo_IOV.jpg" imageanchor="1" style="float:right; margin-left:1em; margin-bottom:1em"><img border="0" height="150" width="200" src="http://4.bp.blogspot.com/-F4-DA9Z8ORg/Tp3P44Ld9ZI/AAAAAAAAACY/faj1neGPqmY/s200/Galileo_IOV.jpg" /></a></div>At long last the launch of the first two real GALILEO satellites is near. This Thursday, October 20, 2011, the first real GALILEO satellites will be launched. This phase of the GALILEO developments is called the "IOV" phase which stands for "In Orbit Validation". <br />
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An interesting feature of this launch is that although it is from Kourou it is not with an Arianne launcher. The launch is with a Soyuz rocket and this is actually the very first Soyuz launch from Kourou. So a number of firsts are coming together, so lets keep our fingers crossed that all goes smooth!<br />
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For detailed information please look at the ESA web-site.<br />
<a href="http://www.esa.int/SPECIALS/Galileo_IOV/">Special ESA IOV website.</a><br />
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Live coverage of launch will be supplied on the <a href="http://www.esa.int">ESA website</a> and a number of other websites, e.g., <a href="http://www.europarl.europa.eu/wps-europarl-internet/frd/live/live-program?language=en">European parlement</a> and <a href="http://www.dlr.de/dlr/desktopdefault.aspx/tabid-10521/869_read-1661/">DLR Oberpfaffenhofen</a><br />
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GALILEO IOV Artist Impression Picture from European Space Agency (ESA)<div class="blogger-post-footer"><a href="http://www.PosiTim.com/">
PosiTim High Accuracy GNSS
</a></div>Springinhetveldhttp://www.blogger.com/profile/14360127679091995926noreply@blogger.com0tag:blogger.com,1999:blog-5918251947010952763.post-81446610868071356552010-09-04T21:40:00.003+02:002010-09-05T14:19:03.951+02:00To GPS or to GNSS that is the questionMany people ask why do we need any other GNSS system in addition to GPS. This question is asked especially in view of the European Galileo related developments but also when looking at the Russian efforts of rebuilding the GLONASS constellation.<br />
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Well “need” may be too big a word but there are very significant benefits of using more than one system. For high accuracy applications, which are our primary focus, there is a significant accuracy benefit. This benefit is especially visible and important in real time usage. The additional satellites of another GNSS do improve the real-time position estimates dramatically.<br />
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To explain this we have done a simple experiment. We have taken a static station, a station that does not move, but estimated the position for each 30 second epoch over a 24 hour period. The repeatability of the epoch estimates gives us a very good measure for the precision of the epoch estimates. Since the station does not move the estimates should be the same for each epoch, well at least if our model for the Earth tides and such is accurate. <br />
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To show the effect of GPS versus GNSS we selected a station that does track both the GPS and the GLONASS satellites. Thus we could generate 3 solutions, a GLONASS-only solution, a GPS-only solution, and a GNSS solution (GPS + GLONASS). The results are given in the bar plot below where the red bars represent the GLONASS solution, green the GPS solution, and blue the GNSS solution. And we distinguished between the East, North and Up component as Up is typically the worst component. <br />
<div class="separator" style="text-align: center;"><a href="http://2.bp.blogspot.com/_hR47tgX21wU/TIKgG88OHsI/AAAAAAAAABs/3Pmi-DCwIyg/s1600/gnss_kin.jpg" imageanchor="1" style="cssfloat: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="251" ox="true" src="http://2.bp.blogspot.com/_hR47tgX21wU/TIKgG88OHsI/AAAAAAAAABs/3Pmi-DCwIyg/s320/gnss_kin.jpg" width="320" /></a></div><br />
The bar plot nicely demonstrates that the GNSS solution (blue) is significantly better then the GPS solution (green), in the East and North directions almost by a factor of two. This is despite the fact that the GLONASS only solution (red) does not perform very well. The quality of the kinematic GNSS position estimates is astonishing with repeatability’s of 5 mm for the horizontal and 15 mm for the vertical components.<br />
The relatively poor performance of the GLONASS solution is caused by the fact that the GLONASS constellation is not complete. Does during the 24 hour period we used for this experiment there is a period where there are less than 4 satellites in view, this severely impacts the quality of the GLONASS only solution but has no negative effect at all on the GNSS solution. This highlights another benefit of GNSS solutions; the larger number of satellites leads to much more reliable and robust estimates. This explains the main reason why especially surveyors and the offshore industry are fully “addicted” to GNSS. Besides being better it is much more robust and reliable.<br />
<div class="separator" style="text-align: center;"><a href="http://1.bp.blogspot.com/_hR47tgX21wU/TIKgVuEu1CI/AAAAAAAAAB0/RhAm36LF7hU/s1600/gnss_kine.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="225" ox="true" src="http://1.bp.blogspot.com/_hR47tgX21wU/TIKgVuEu1CI/AAAAAAAAAB0/RhAm36LF7hU/s320/gnss_kine.jpg" width="320" /></a></div><br />
Last but not least the picture above shows the 30 second position estimates of the GNSS solution. A repeatability of 5 mm for the horizontal and 15 mm for the vertical components for fully kinematic position estimates is quite impressive, is it not!? So regarding the question "to GPS or to GNSS" the answer is a clear <b><i>GNSS</i></b>.<div class="blogger-post-footer"><a href="http://www.PosiTim.com/">
PosiTim High Accuracy GNSS
</a></div>Springinhetveldhttp://www.blogger.com/profile/14360127679091995926noreply@blogger.com0tag:blogger.com,1999:blog-5918251947010952763.post-26073991482070117372010-06-11T08:20:00.002+02:002010-06-11T08:22:31.236+02:00Interesting Article in GPS WorldThis month’s issue, June, of GPS world features an interesting article in its innovation column on true GNSS processing within the International GNSS Service. The authors, one of the authors being a <a href="http://www.PosiTim.com">PosiTim </a>employee working at <a href="http://nng.esoc.esa.de" target=_blank>ESOC OPS-GN</a>, show the significant developments that have taken place in the high accuracy GNSS area over the last two years. These developments have made the GLONASS orbit and clock products significantly better and they are now approaching the GPS orbit and clock quality.<br />
Also the authors are convinced that the IGS analysis centres are all working on getting their GNSS solutions up and running. In fact, already one additional analysis centre, GFZ from Potsdam, Germany, has started to produce very good combined GNSS products. So the GNSS future looks bright!<br />
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So please check out the <a href="http://www.gpsworld.com/gnss-system/glonass/innovation-gps-glonass-and-more-10007" target=_blank>article on the GPS-world web-site</a> or in the paper version if you have it!<div class="blogger-post-footer"><a href="http://www.PosiTim.com/">
PosiTim High Accuracy GNSS
</a></div>Springinhetveldhttp://www.blogger.com/profile/14360127679091995926noreply@blogger.com0tag:blogger.com,1999:blog-5918251947010952763.post-16184985790946277552010-05-18T08:24:00.002+02:002010-05-18T08:26:38.133+02:00First GPS block IIF Satellite set for launch<div class="separator" style="text-align: center;"><a href="http://1.bp.blogspot.com/_hR47tgX21wU/S_IyhXCHD7I/AAAAAAAAABU/BB_JRXw_vA0/s1600/IIF_2.jpg" imageanchor="1" style="cssfloat: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="283" src="http://1.bp.blogspot.com/_hR47tgX21wU/S_IyhXCHD7I/AAAAAAAAABU/BB_JRXw_vA0/s320/IIF_2.jpg" width="320" wt="true" /></a></div>This week is poised to set a new milestone in the GPS history. The launch of the first GPS block IIF satellite is scheduled for Thursday May 20. You may ask "why is this special". Well firstly because this is only the fourth type of GPS satellite to be launched. It all started with the block I test satellite from which only 10 were operated. Those were followed by only 9 block II satellites and 19 block IIA satellites. The block II and IIA were very similar satellites. The current constellation consists mainly out of the 12 block IIR (R for Replenishment) and 8 IIR-M (M for Modernised) satellites which build the third generation of GPS satellites. One of the IIR-M (SVN49/PRN01) is still unhealthy due to the issues with its signal caused by its experimental triple frequency, <a href="http://positimgnss.blogspot.com/2009/06/svn-49-anomaly-revealed.html">see our past reports on this issue</a>.<br />
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The first block IIF (F for Follow-On or Future) we originally supposed to be launched in 2000. However, due to the much longer lifetime of the GPS block II satellites the launch date was moved backwards. In recent year’s problems in the development caused significant additional delays which even impaired the GPS constellation. There were concrete fears that the GPS constellation could drop below the required number of 24 healthy satellites. A successful launch of this first IIF satellite will put an end to these worries and will pave the way for a further shining GPS future.<br />
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As PosiTim we will anxiously await the first triple frequency signals from this satellite in the scope of our work at the navigation support office (<a href="http://nng.esoc.esa.de/">OPS-GN</a>) at the European Space Operations Centre (<a href="http://esoc.esa.int/">ESOC</a>) of the European Space Agency (<a href="http://www.esa.int/">ESA</a>). We hope to analyse this data as soon as they become available from the tracking network of the International GNSS Service (<a href="http://igs.org/">IGS</a>). We hope to be able to report soon on the quality of the signals of this satellite. A second important aspect will be to study the in orbit behaviour of this satellite. As the shape and dimensions are completely different from the previous GPS generation the orbit model may be somewhat different. In order to achieve the highest possible accuracies it will be important to have a very good understanding of the orbit model.<br />
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The additional third frequency on this new GPS satellite generation will open up completely new capabilities in the scientific GNSS world. One interesting example is the application of triple carrier ambiguity resolution (TCAR) which a very promising technique for high accuracy GNSS solutions.<br />
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We hope to be back soon with a very positive report on this new satellite and with that a new era in GPS!<div class="blogger-post-footer"><a href="http://www.PosiTim.com/">
PosiTim High Accuracy GNSS
</a></div>Springinhetveldhttp://www.blogger.com/profile/14360127679091995926noreply@blogger.com3tag:blogger.com,1999:blog-5918251947010952763.post-44227889314742265972010-01-19T12:31:00.001+01:002010-06-15T09:17:29.427+02:00GNSS Picutre GaleryJust a short post this time but an interesting one! Here we provide some links to interesting pictures and videos from different GNSS systems.<br />
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<strong>Galileo info.</strong><br />
<a href="http://news.bbc.co.uk/2/hi/science/nature/8351457.stm" target="_blank">A look at the navigation payloads on the satellites being assembled at EADS Astrium in Portsmouth, England, a video from the BBC.</a><br />
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<strong>Glonass launch from December 14, 2009</strong><br />
<a href="http://www.federalspace.ru/main.php?id=2&nid=8580." target="_blank">Roscosmos has announced the successful launch of the Proton rocket carrying three GLONASS-M satellites (in Russian).</a><br />
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<a href="http://www.spaceflightnow.com/news/n0912/14glonass/" target="_blank">The launch occurred on time at 10:38 UTC, on December 14, 2009.</a><br />
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<a href="http://www.federalspace.ru/main.php?id=2&nid=8582" target="_blank">Pictures of the launch.</a><br />
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<a href="http://rt.com/Sci_Tech/2009-12-14/glonass-proton-launch-satellite.html" target="_blank">Video 1 of the launch from RT (Russia Today).</a><br />
<a href="http://rt.com/Sci_Tech/2009-12-14/glonass-improve-navigation-system.html" target="_blank">Video 2 of the launch from RT (Russia Today).</a><br />
<a href="http://tvroscosmos.ru/frm/kosmostv/vesti/2009/vesti141209.php" target="_blank">Video 3 of the launch from TV Roscosmos.</a><br />
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<strong>Beidou/Compass info</strong><br />
<a href="http://www.beidou.gov.cn/" target="_blank">The Chinese Government opened a Beidou/Compass Web site today at 12:00 local time "to promote greater public participation and understanding of the Compass navigation satellite [system] development, launch, operation and application." The site is presently in Chinese only.</a><br />
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<a href="http://china.huanqiu.com/roll/2010-01/690813.html" target="_blank">Beidou/Compass-G1 was launched at 00:12 Beijing Time on 17 January = 16:12 UTC</a><br />
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<a href="http://space.tv.cctv.com/video/VIDE1263684073836880" target="_blank">China Central Television video of launch:</a> <br />
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Hope you like these!<div class="blogger-post-footer"><a href="http://www.PosiTim.com/">
PosiTim High Accuracy GNSS
</a></div>Springinhetveldhttp://www.blogger.com/profile/14360127679091995926noreply@blogger.com0tag:blogger.com,1999:blog-5918251947010952763.post-2956441360558618012010-01-04T11:29:00.001+01:002010-06-15T09:17:05.637+02:00Galileo IOV ScheduleFirst of all a very happy and prosperous 2010 to all of you!<br />
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In 2009 saw very little concrete progress within the Galileo project. Behind the scenes a lot has happened, e.g., the cooperation between the EU and ESA has been improved and a lot of progress was made in the negotiations for the full orbit constellation (FOC) contracts. However, from a (scientific) user point of view this is not very concrete progress at all.<br />
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A significant issue with the Galileo project is the lack of an open communication principle. In 2009 I was really positively surprised about how open the GPS system has been regarding the issues with SVN-49. This is quite different from the way how the Galileo project is treating things. This is very surprising and even more so if one considers that GPS is still very much a military system whereas Galileo is a civil system. Thus one would expect much more open communications from Galileo!! <br />
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Secondly, also the data policy from the Galileo project is not really transparent. Since 2005 GIOVE-A has been in orbit and ESA has been gathering data from this satellite, and its brother GIOVE-B, using a network of 13 Galileo Experimental Sensor Stations (GESS). In principle this data is available to all ESA "trusted users", a status one can apply for on the <a href="http://www.giove.esa.int/">ESA GIOVE web site.</a> However, I know several institutes that have applied but never received this status. This is really disappointing, especially since a open data policy would most likely lead to much more interest, and consequently investigations and progress, from the scientific community. The currently employed "closed data policy" is very likely more harmful then helpful for the project. Several world leading scientist who would be interested in studying the Galileo, or rather GIOVE, data do not have access to the data. In this sense the Galileo project is very similiar to the Chinese COMPASS project.<br />
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So this brings us to the status of the Galileo IOV phase. In this phase 4 satellites will be launched in two launches. Both launches will be from Kourou using the the Russian Soyuz launcher. The four IOV satellites should, in principle be very similar to the final Galileo satellites. In Summer 2009 the IOV schedule foresaw that launch 1 would take place around September 2010 and launch 2 around February 2011. However, ever since the schedule has been slipping. Of course slipping schedules are quite normal in the space business but the lack of communications around it in the case of the Galileo project are untypical and make people wonder about the reasons for the delays. The latest rumours I have heard, and so far these rumours have always been true, is that launch 1 for the Galielo IOV is now scheduled for May 2011. The reason(s) for this (huge!) delay are completely unclear. But, we can speculate a bit about them.... <br />
<br />
Interesting is that in the FOC negotiations it seems that for building the satellites the consortium around OHB now seems to be winning against the "favourite" <a href="http://www.eads.com/">EADS consortium</a>. The <a href="http://www.ohb-technology.de/">OHB consortium</a> includes <a href="http://www.sstl.co.uk/">Surrey Satelite Technology Ltd</a> which was responsible for the very successful GIOVE-A satellite. GIOVE-A was build on-time and within budget. And that was a truley great performance as time was the most critical factor in that case. The performance of EADS in building GIOVE-B was quite in constrast to the this with very significant delays and huge cost overruns. So if we put 1 and 1 together and start speculating a bit, it could very well be that the EU and ESA are a bit disappointed with the EADS performance both from GIOVE-B as well as now for the IOV satellites and are thus now favouring the OHB consortium for the FOC phase. It can also be just "politics" but the GIOVE-B and IOV satellites projects are certainly not one of the "best" we have seen. So there is some room for speculation here..... <br />
<br />
Of course, in case the OHB consortium wins this will lead to a very inhomogeneous Galileo satellite constellation as the OHB satellites will most likely be quite different from the EADS IOV satellites. Also most likely the FOC constellation will be build in different phase with different generations of satellites. So when Galileo reaches FOC at least 3 different types of satellite will be in orbit.<br />
<br />
In any case these are interesting times but before we see any real Galileo satellites in orbit my bet is that we will have to wait until 2011. So for 2010 the highlights we may expect will come from GPS and GLONASS. The GPS system is going to launch its, long overdue, first Block IIF satellite (currently scheduled for May) whereas the GLONASS system is going to launch its first GLONASS-K satellite (scheduled for the end of 2010). <br />
<br />
Meanwhile I hope the Galileo project will become a bit more open both in its communication policy and, even more importantly, in its data policy.<div class="blogger-post-footer"><a href="http://www.PosiTim.com/">
PosiTim High Accuracy GNSS
</a></div>Springinhetveldhttp://www.blogger.com/profile/14360127679091995926noreply@blogger.com0tag:blogger.com,1999:blog-5918251947010952763.post-76371500932446061342009-12-24T00:53:00.001+01:002010-06-15T09:16:11.233+02:00GNSS Year in Review 2009So what happened in the GNSS world in 2009!?<br />
<br />
Well....not as much as we hoped for but some progress was made. Most progress was made "behind the scenes".<br />
<br />
<h2>GPS</h2>The most exiting and most "visible" was the launch of the GPS satellite SVN-49. This satellite brought new signals to the GPS system as it carries an experimental payload that allows the transmission of the new (future) GPS signals on the L5 band. The L5 experiment was bitterly needed because of the significant delays in getting the GPS IIF (F for Future) satellites ready. Thus the GPS system was at risk of loosing the L5 frequency allocation if they would not get a satellite up and "beeping" on the L5 frequency. The European Galileo system faced, and still faces, a similar challenge for which the launched the Giove-A and Giove-B experimental satellites. Unfortunately, the experimental character of the SVN-49 satellite actually caused some unexpected ill effects on the satellite on which <a href="http://www.positim.com/gnss/2009/05/detailed-look-at-gps-satellite-svn.html">we reported in our BLOG</a>. This is the reason the satellite is still unhealthy although it is planned to turn the satellite healthy soon. However, the satellite will never perform as good as the other GPS satellites due to its anomaly. Besides SVN-49 also SVN-50 was launched marking the last GPS Block IIR-M satellite launch. The next GPS satellite to be launched will be the of the Block IIF type, currently scheduled for May 2010. An other "sad" event in 2009 was that SVN-35 was taken out of service. This satellite was special as it was one of only two GPS satellites that carries a Satellite Laser Ranging reflector array. The loss of this satellite is a grave loss for the scientific world especially because currently no SLR reflector arrays are foreseen on the GPS Block IIF nor on the first batch of the GPS Block III satellites. Hopefully the second batch of GPS Block III satellites will correct this "oversight" of the GPS system.<br />
<br />
<h2>GLONASS</h2>The most solid progress was made by the GLONASS system. Firstly, one of the three satellites launched in December 2008, GLO-729, is carrying a brand new SLR reflector array design which is 1.5 times better then the previous arrays. This is very exiting because it allows daylight tracking of this satellite which is an absolute "first" in the GNSS world. So far GNSS satellites could only be tracked by the SLR stations during the night. Furhtermore, an other successful triplet launch took place on December 14, 2009. However, also the GLONASS system did have its problems this year. One of the new satellites launched in 2008, GLO-726, developed a problem with its signal generator. As the satellites planned for launch in September 2009 used signal generators from the same batch as this faulty satellite the September launched was cancelled in order to check the satellites and replace the signal generators. The satellites are now scheduled for launch in February 2010. Nevertheless, the progress of GLONASS remains remarkable and they have managed to stick to the schedule that was laid out in 2005! In the space business that is an really astonishing accomplishment!<br />
<br />
<h2>Galileo</h2>On the Galileo front things have been very quiet. Giove-A and Giove-B remain to operate which especially for Giove-A is a great accomplishment as it is well past its design life time. However, the schedule of the In Orbit Validation (IOV) seems to remain a "running target". In June the first launch was planned for September 2010. Meanwhile, rumours say the launch has been postponed until May 2011. The reasons for these delays are completely unclear and a more open communication policy would do the project a lot of good. The same holds for the data policy. Since 2005 Giove data has been gathered but the data is only available to ESA "trusted users". Unfortunately, it is practically impossible to obtain a trusted user status with ESA. So the Giove data is only accessible to a very limited number of institutes and thus limits the scientific analysis of the data. Under the surface a lot of things are happening in the Galileo project. The cooperation between ESA and the EU has been improved although it is certainly still not optimal. And a lot of progress has been made for awarding the contracts. The contracts should have been awarded early in 2009 but the process has, not unexpectedly, taken longer then planned. So also for 2010 visibly nothing much will be happening with Galileo. We will have to wait until 2011, at least.<br />
<br />
<h2>Others</h2>Some progress was made for the COMPASS/Beidou system but since no data is publicly available I can not say too much about it. To my understanding there is still only 1 MEO satellite (MEO is the typical GNSS orbit) and a couple of GEO satellites. One additional GEO satellite was launched but also one was lost and was drifting through the GEO orbit causing quite some concerns for other GEO satellite operators (GEO is the orbits used for most telecommunication satellites). A "wild" satellite in this orbit is very dangerous and can cause a lot of damage.<br />
<br />
The Japanese regional QZSS system is making good progress. The signal generator is currently undergoing in space testing as it is being flown on a GEO satellite. The first satellite will be launched in 2010. In principle three satellites are planned but currently funding for only 1 satellite exists. <br />
<br />
The only thing remaing to be said is....<br />
<div style="text-align: center;"><strong><span style="color: red; font-size: x-large;">Merry Christmas</span></strong><br />
</div><div class="blogger-post-footer"><a href="http://www.PosiTim.com/">
PosiTim High Accuracy GNSS
</a></div>Springinhetveldhttp://www.blogger.com/profile/14360127679091995926noreply@blogger.com0tag:blogger.com,1999:blog-5918251947010952763.post-92116614855349634712009-12-02T21:52:00.002+01:002009-12-02T22:02:01.660+01:00GLONASS UpdateSo it is time for an update on GLONASS.<br />
As you may have noticed meanwhile the September has been canceled. There have been all sorts of speculations and it was difficult to get any hard facts. As far as we have been able to figure out the reason for canceling the launch lies in the fact that the GLONASS 726, in orbital slot 22, developed an unexpected problem and has consequently been unhealthy since quite some time. The problem seems to be with the signal generator on board of the satellite. <br />
<br />
Now you may wonder, what does that have to do with the September launch. Well, as it turns out the three satellites scheduled for launch in September make use of the same signal generator. So as it is "better to be save then sorry" it was decided to send the satellites back to the factory to check, or more likely replace, the signal generators in all three satellites.<br />
<br />
We originally thought that this would then also impair the December launch. However, we have been told that the satellites for the December launch used a different version of the signal generator and thus the December launch is "on track". In fact <a href="http://www.iss-reshetnev.com/?cid=news&nid=144&ses=223d5bcc4b16cb3f44d0e">the last of the three Glonass-M navigation spacecraft intended for cluster 41 was delivered to Baikonur on November 27, 2009 by the JSC Academician M.F. Reshetnev Information Satellite Systems</a>. The first two satellites were delivered to the spaceport on 17 and 23 November and are currently in preparation for launch. The launch date is set for December 18. A bit earlier then the normal "Christmas" launches around the 25 and 26 of December.<br />
<br />
The September launch is now scheduled for February 2010.<br />
<a href="http://www.positim.com/gnss/uploaded_images/glonass_status-753516.png" imageanchor="1" style="clear: left; cssfloat: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" er="true" height="271" src="http://www.positim.com/gnss/uploaded_images/glonass_status-753506.png" width="400" /></a>If both of these launches work out as planned GLONASS will get very close to its full operational capabilities (FOC). The picuture gives the current GLONASS status which is already pretty good.<div class="blogger-post-footer"><a href="http://www.PosiTim.com/">
PosiTim High Accuracy GNSS
</a></div>Springinhetveldhttp://www.blogger.com/profile/14360127679091995926noreply@blogger.com0tag:blogger.com,1999:blog-5918251947010952763.post-38698435119888291802009-09-21T07:55:00.007+02:002010-06-15T09:15:41.097+02:00GLONASS Launch Delay*** UPDATE *** UPDATE ***<br />
The GLONASS launched is delayed because of a problem with one of the three GLONASS-M satellites. The new launch data is October 29, 2009.<br />
*** UPDATE *** UPDATE ***<br />
<br />
The preparations for the next triplet GLONASS-M satellites scheduled for September 25, 2009, are progressing. Roscosmos is releasing interesting <a href="http://www.tvroscosmos.ru/frm/video/start54.php">videos</a> and <a href="http://www.roscosmos.ru/NewsDoSele.asp?NEWSID=7368">pictures</a> from the preparations. This is really exciting since this is, according to my knowledge, the first time that pictures like this are released officially by Roscosmos. A very good and positive development!<br />
<br />
Furhtermore, last week the frequencies of two active GLONASS satellites were changed. For the two "antipodal" satellites in plane one, with GLONASS numbers 701 and 728, the frequency channel was changed from 1 to -4. This is an indication that the September launch will put 3 new satellites in plane 1. This is not surprising since it carries the two oldest satellites in the constellation, 701 from December 2003 and 712 from December 2004 with 701 being the first and therefore oldest GLONASS-M satellite. The "modernized" GLONASS satellites that live significantly longer then the first generation GLONASS satellites.<br />
<br />
For those wondering what "antipodal" means. In GLONASS these are two satellites that fly in the same orbital plane but with an 180 degrees angle between them, meaning they are on opposite sides of the world. Several years ago the GLONASS system has been kind enough to have given back half of its frequency allocation because those frequencies were interfering with astronomical observations. However, for the GLONASS system, where the satellites are identified based on having different frequencies, this caused a small problem since there were no longer 24 different frequency channels available. However, since satellites on opposite ends of the Earth will not be observed simultaneously by an Earth bound observed the GLONASS system introduced the concept of using the same frequency channel for "antipodal" satellites.<br />
<br />
Personally I am very much looking forward to the launch at the end this month as it will further improve the GLONASS performance and bring it very close to the GPS performance. In my "high accuracy" work (I deal with millimeters) we can now clearly see the benefit of using GPS and GLONASS compared to using just GPS.<br />
<br />
Happy positioning and timing!<div class="blogger-post-footer"><a href="http://www.PosiTim.com/">
PosiTim High Accuracy GNSS
</a></div>Springinhetveldhttp://www.blogger.com/profile/14360127679091995926noreply@blogger.com2tag:blogger.com,1999:blog-5918251947010952763.post-56545963754572861802009-09-08T07:30:00.006+02:002010-06-15T09:15:25.600+02:00GLONASS Launch PreparationsThis is something really cool so I just had to put this link here for you all to see. <a href="http://www.tvroscosmos.ru/frm/video/start54.php">This link</a> shows the preparation of one of the GLONASS-M satellites that is being prepared for launch. The launch is scheduled for Septermber 25, see <a href="http://gnss.servolux.nl/2009/08/glonass-launch-schedule-update.html">my earlier post</a>.<br />
<br />
This video has been posted on YouTube by Roscosmos, the Russian Space Agency.<br />
<br />
Check it out is is really cool!<br />
<br />
Personally I am very much looking forward to the launch at the end this month as it will further improve the GLONASS performance and bring it very close to the GPS performance. In my "high accuracy" work (I deal with millimeters) we can now clearly see the benefit of using GPS <strong><em>and </em></strong>GLONASS compared to using just GPS.<br />
<br />
The GNSS future looks bright!<div class="blogger-post-footer"><a href="http://www.PosiTim.com/">
PosiTim High Accuracy GNSS
</a></div>Springinhetveldhttp://www.blogger.com/profile/14360127679091995926noreply@blogger.com0tag:blogger.com,1999:blog-5918251947010952763.post-34337948657866150422009-08-26T08:02:00.006+02:002010-06-15T09:15:02.967+02:00GLONASS Launch Schedule UpdateAs in 2008 the GLONASS schedule promises again two triplet launches this year. The first one to take place on September 25, just like in 2008. The second is planned for the meanwhile "traditional" Christmas launch around the end of December. The first satellite for the September launch has been shipped to the Baikonur spacedrome and launch pad in Uzbekhistan. The two other satellites will follow in late August and early September.<br />
<br />
Currently there are 18 healthy dual frequency GLONASS satellites. With the two triplet launches of this year the constellation should reach the "magical" number of 24 satellites which is the amount of satellites needed to reach to so-called "full orbit constellation" (FOC). However, for FOC each of the three orbital planes of the GLONASS system will need 8 satellites. Currently the planes have 5, 5, and 8 respecitively. So most likely the launch in September will be used to populated plane I which has the oldest satellites. The December launch will then repopulate plane II.<br />
<br />
Plane I has two rather old satellites, by GLONASS standards, one from 2003 (SVN-701 in slot 6) and one form 2004 (SVN-712 in slot 7). These might die before the end of this year. The offical planned FOC data is by the end of 2010. In 2010 two more triplet launches are planned again in September and December.<br />
<br />
The really exiting part of that will be the launch of the the new platform, the GLONASS-K satellite. One of the 3 satellites to be launched in December 2010 will be a GLONASS-K satellite. The most important features of this new GLONASS satellite generation are:<br />
<ul><li>Longer life time, design life time of 10 years</li>
<li>Much lighter satellites reducing launch costs and enabling launches with Soyus rather then with the huge and costly Proton launcher</li>
<li>Addition of GPS-like CDMA signals.</li>
</ul><br />
<br />
The addition of CDMA, in paralel to the GLONASS original FDMA signals, will make GLONASS interoperable with GPS (and Galileo). This will enhance the interest and usage of GLONASS even further then its already rapidly spreading usage.<br />
<br />
The GNSS future looks very interesting and very bright!<div class="blogger-post-footer"><a href="http://www.PosiTim.com/">
PosiTim High Accuracy GNSS
</a></div>Springinhetveldhttp://www.blogger.com/profile/14360127679091995926noreply@blogger.com0tag:blogger.com,1999:blog-5918251947010952763.post-39678414983022998862009-08-10T21:33:00.006+02:002010-06-15T09:14:42.439+02:00Last launch of GPS Block IIR SatelliteOn August 17 the last GPS Block IIR satellite will be launched. It will be named SVN50/PRN21. This launch is the end of the aera of the Block IIR, "replenishment", satelites. The next satellite generation to be launched will be the Block IIF, "future", satellites. Of course the lifetime of 10 years will mean that we will use GPS Block IIR satellites for the next decade. <br />
<br />
SVN50 will be placed into orbital plane/slot E3, replacing SVN40, a Block IIA satellite launched in July 1996 that is past its design life but still working well. SVN40 will be moved a little further along the orbital path. Successful launch and activation of the new satellite will bring the constellation to 31 operational satellites, not counting SVN49 which is still set unhealthy due to its signal anomaly.<br />
<br />
Here it is important to note that SVN50 will not have any payload connected to the J2 auxiliary payload port that proved problematical with the L5 demonstration payload on SVN49, and possibly on other Block IIR/IIRMs.<div class="blogger-post-footer"><a href="http://www.PosiTim.com/">
PosiTim High Accuracy GNSS
</a></div>Springinhetveldhttp://www.blogger.com/profile/14360127679091995926noreply@blogger.com0tag:blogger.com,1999:blog-5918251947010952763.post-67587726751433308082009-07-19T20:34:00.004+02:002009-09-24T23:04:35.912+02:00SVN-49 Tip of the icebergAfter publishing the SVN-49 story on <a href="http://www.insidegnss.com/node/1575">InsideGNSS</a> a lot of things have happened. Most of the discoveries and developments you can read about on <a href="http://insidegnss.com/">InsideGNSS</a> and <a href="http://gpsworld.com/">GPS World</a>.<br /><br />However, one very interesting new issue was brought to our attention. We were informed that other GPS block IIR and IIR-M satellites may show similar problems as SVN-49 because they use a similar configuration as SVN-49 but of course for a different signal then the L5 signal. So we took a close look at the residuals of all the GPS and GLONASS satellites and discovered that several other GPS block IIR and IIR-M satellites suffer from a similar, albeit much smaller, signal anomaly as observed for SVN-49. Most pronounced anomalies are observed for SVN-55 and SVN-43.<br /><br />Read more about this in our addition the our InsideGNSS article on <a href="http://www.insidegnss.com/node/1599">InsideGNSS</a><div class="blogger-post-footer"><a href="http://www.PosiTim.com/">
PosiTim High Accuracy GNSS
</a></div>Springinhetveldhttp://www.blogger.com/profile/14360127679091995926noreply@blogger.com0tag:blogger.com,1999:blog-5918251947010952763.post-6572767138876090922009-06-25T10:01:00.005+02:002010-06-15T09:14:22.593+02:00SVN-49 Anomaly RevealedAfter writing my two earlier blog's on this issue I decided to write a full article about this SVN 49 issue and submit it to <a href="http://insidegnss.com/">Inside GNSS</a>. The article will be printed in the July/August 2009 issue but because of its high news value it is <a href="http://www.insidegnss.com/node/1574">available online now</a>.<br />
<br />
Enjoy the reading!<div class="blogger-post-footer"><a href="http://www.PosiTim.com/">
PosiTim High Accuracy GNSS
</a></div>Springinhetveldhttp://www.blogger.com/profile/14360127679091995926noreply@blogger.com0tag:blogger.com,1999:blog-5918251947010952763.post-23959503922180272892009-05-14T00:54:00.011+02:002010-06-15T09:14:10.714+02:00A detailed look at GPS Satellite SVN-49/PRN-01As promised in my post <em>"Problem with new GPS Satellite SVN-49/PRN-01"</em>here some details regarding what we observe when we analyse the data of this satellite.<br />
<br />
Below are two plots. The first one showing the pseudo range residuals of a "normal" GPS satellites. We randomly picked satellite SVN-38/PRN08 for this. The residuals are based on all the observations taken by the stations observing this satellite. The data used was from day 100 in 2009, or in normal date April 10, 2009. The residuals are plotted as a function of the elevation of the satellite above the local horizon of the observing station. That means that at 90 degrees elevation the satellite stands right above the station whereas at 10 degrees elevation the satellite is very low on the horizon. In this figure one can clearly see the increase of the noise of the observations at low elevations which is a well known phenomenon mainly caused by so called "multipath" effects.<br />
<br />
<div class="separator" style="text-align: center;"><a href="http://www.positim.com/gnss/uploaded_images/g08res-773060.bmp" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="http://www.positim.com/gnss/uploaded_images/g08res-773019.bmp" vr="true" width="400" /></a><br />
</div><br />
The second figure shows the same picture but for our the new GPS satellite SVN-49/PRN01. The behavior of the residuals shows a clear signature which is obviously elevation dependent. Interestingly enought the carrier phase observation residuals do not show such a signature. This indicates that the problem is in the pseudo range observations, e.g., in the so called group delay.<br />
<br />
<div class="separator" style="text-align: center;"><a href="http://www.positim.com/gnss/uploaded_images/g01res-784528.bmp" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="http://www.positim.com/gnss/uploaded_images/g01res-784486.bmp" vr="true" width="400" /></a><br />
</div><br />
However, the residuals show that the problem is only at the few meter level. But somehow the GPS operators see much larger problems. How and where the see those is still unclear to me. However, to my understanding it is possible to measure the differences between the observations on board of the satellite. Possilbe the >100 meter effects are observed in such measurments. However, for normal users as us there is only a few meter problem which we could live with, more or less. The really <strong><em>big</em></strong> problem comes from the fact that the GPS system operators are trying to solve this problem by changing the broadcast ephemerides. This becomes clear if we compare an orbit estimated by ourselves with the orbit information broadcasted by the GPS satellites. Note that our estimated orbits have a precission of a few centimeters whereas the broadcast ephemeris is normally at the few meter level. The figure below shows such a orbit comparison of the GPS satellites with PRN 1, 2, 3, 4, and 5. The differences for the "normal" GPS satellites is at the few meter level. For PRN 1 the differences amount up to 60 kilometers!!! This of course makes the satellite completely useless for any processing.<br />
<br />
<div class="separator" style="text-align: center;"><a href="http://www.positim.com/gnss/uploaded_images/g01brdc-747335.bmp" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="290" src="http://www.positim.com/gnss/uploaded_images/g01brdc-747269.bmp" vr="true" width="400" /></a><br />
</div><br />
All in all the problems with this satellite do not seem to be very severe except for the broadcast ephemerides which are truely horrid!<br />
<br />
So whatever you do with GPS do not use the data of the new SVN-49/PRN01 unless you know what you are doing!<br />
<br />
(ps. I appologize for the poor quality of the plots. Have to find a better tool to do these plots...)<div class="blogger-post-footer"><a href="http://www.PosiTim.com/">
PosiTim High Accuracy GNSS
</a></div>Springinhetveldhttp://www.blogger.com/profile/14360127679091995926noreply@blogger.com2tag:blogger.com,1999:blog-5918251947010952763.post-67142309980080342842009-05-11T23:46:00.010+02:002010-06-15T09:13:56.749+02:00Problem with new GPS Satellite SVN-49/PRN-01It looks as if the newest GPS satellite has a significant problem. This is the GPS satellite which also broadcast signals on the new L5 frequency to ensure that frequencies for the GPS system. The L5 signals were planned to be available from the new GPS Block II-F satellites but due to delays in building these satellites it became necessary as kind of an "emergency rescue" of the L5 frequency band to launch launch some other satellite to use the frequency. The "perfect" solution was found to add the L5 capability to one of the Block II-R satellites. So this was done for the SVN-49/PRN-01 satellite that was launched on March 29, 2009.<br />
<br />
However, it seems that something has gone wrong with the signals of this satellite. In my work where we try to get the highest precission out of the GPS system, meaning orbits at the ~20mm level and receiver positions at the ~1mm level, we can see a clear pattern in the pseudo range residuals of this satellite. Now since we typically use the carrier phase observations and not the code this is not really a problem for our type of work. However, the few meter (!!!!) pseudo range residuals are disturbing and they show a clear dependency on elevation.<br />
<br />
However, what is more disturbing is that on the GPS system side they seem to be getting even larger effects then the few meters we see in our work. So far this is something I have not yet been able to understand. It seems the GPS system operators see problems with this satellite at the 100 to 200 meter level!!! A true catastrophy! As work around for this problem they GPS system is applying a <em><strong>huge</strong></em> antenna offset when broadcasting the ephemerides and clock corrections of this satellite. These problems also explain why this satellite is still not declared healthy. In fact there is some speculation that because of the observed problems it may never be set healthy.<br />
<br />
So in summary the facts are: <br />
<ol><li>There is a significant problem difference the code and the phase observations</li>
<li>The phase observations seem to be fine as we can do integer ambiguity resolution without too much problems (but of course one can not use the code observations for aiding the ambiguity resolution)</li>
<li>The observed differences point in the direction of a significant "group delay". This is a delay which effects the code observations but not the phase observations</li>
<li>The GPS system is observing even larger problems (>100m)!? We do not see those problems however!? </li>
</ol>In any case it may be that this GPS satellite will never be set healthy making the L5 experiment a rather costly one...<br />
<br />
As soon as I find out more details I will let you know!<br />
<br />
Cheers,<br />
Springinhetveld<div class="blogger-post-footer"><a href="http://www.PosiTim.com/">
PosiTim High Accuracy GNSS
</a></div>Springinhetveldhttp://www.blogger.com/profile/14360127679091995926noreply@blogger.com0tag:blogger.com,1999:blog-5918251947010952763.post-39433041989143745862009-04-04T21:18:00.006+02:002010-06-15T09:13:33.824+02:00GNNS based personal weather forecast with Google EarthA company we work with <a href="http://www.gps-solutions.com/">GPS Solutions</a> has developed a really cool application which I would like to introduce to you here.<br />
<br />
GPS solutions specialises in high accuracy GPS solutions and applications. Besides accurate positioning there are many other things one can do with GPS. One of these things is using GPS based tropospheric delay estimates to improve numerical weather predictions. So GPS solutions is generating weather predictions based on the more or less standard models and data but in addition includes GPS estimates to improve the weather predictions. The really fun part of this is that they have coupled the weather predictions with Google Earth. Thus you can "click" on any location on the world and get the weather forecast for that location for the next couple of days. I find that a really cool application!<br />
<br />
Just think about you want to go out sometime in the next days. You just go to any point on the Earth using Google Earth, click on the location and up comes the weather forcast for the selected location.<br />
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Want to try it out, <a href="http://clickforweather.com/index.php?lat=53.066092310729374&lon=6.458378434181213&tz=2.0&weather_model=europe&map_type=h&zoom=18&units=metric">just click this link.</a> This links shows you the location of the main <a href="http://gnss.servolux.nl/">Servolux</a> office and the weather forecast for the next couple of days!<br />
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I find this really cool and also very usefull. However, GPS solutions has, so far, been unable to sell this application. If you are interested in this application please let us know or in the least give us some feedback!<br />
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Wishing you nice weather and a good forecast!<div class="blogger-post-footer"><a href="http://www.PosiTim.com/">
PosiTim High Accuracy GNSS
</a></div>Springinhetveldhttp://www.blogger.com/profile/14360127679091995926noreply@blogger.com0tag:blogger.com,1999:blog-5918251947010952763.post-59813643928464056242009-03-25T07:32:00.005+01:002010-06-15T09:13:04.363+02:00Innovative GPS Satellite LaunchedOn March 24, 2009, a next GPS Block IIR-M satellite was succesfully launched. This satellite carries an interesting innovative payload that is capable of sending signals on the new L5 civil frequency. It was launched successfully with a Delta II rocket from Cape Canaveral Air Force Station in Florida.<br />
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Follow-on generations of GPS spacecraft will include an operational L5 signal to improve the accuracy and performance capabilities of the system, in particular for civil users. This new satellite, designated GPS IIR-20(M), will demonstrate this new civil signal located on the L5 frequency (1176.45MHz). The signal will comply with international radio frequency spectrum requirements. <br />
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<a href="http://www.gpsworld.com/">GPS world</a> quotes Don DeGryse, Lockheed Martin's vice president of Navigation Systems “Working closely with our Air Force partner, and building upon the design capabilities of the IIR-M space vehicle, the team has developed an innovative, low-risk, low-cost demonstration payload that will pave the way for the new operational third civil signal. We look forward to a successful demonstration of this critical capability and setting another modernized GPS spacecraft into operations as quickly as possible.”<br />
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The original plan was to demonstrate the new L5 signals on the first Block IIF GPS satellite generation. However, the L5 frequency band was assigned to the GPS system under the condition that it would use the frequency before the end of 2009. Due to significant delays in building the new IIF generation of satellites it became impossible to launch those satellites before 2010. Therefore a special experiment was designed and implemented on this block IIR satellite. <br />
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So on this satellite the L5 signals are only an experiment and, to my understanding, the L5 experimental transmitter will only be on "occasonaly" and not permanently. Furthermore, it is unclear whether there are any receivers capable of tracking these new signals when they are transmitted. So although a very interesting innovation it is not something that will widely be used. However, if any L5 data from these satellites becomes available it will be very interesting to have a detailed look at it just as at the Giove-A and Giove-B signals.<br />
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Let us wait and see when we get the first L5 "beebs".<div class="blogger-post-footer"><a href="http://www.PosiTim.com/">
PosiTim High Accuracy GNSS
</a></div>Springinhetveldhttp://www.blogger.com/profile/14360127679091995926noreply@blogger.com0tag:blogger.com,1999:blog-5918251947010952763.post-15385389799768587872009-01-19T12:26:00.006+01:002009-10-16T23:46:22.045+02:00COMPASS/BeiDou StatusAccording to Chinese officials China plans to launch 10 Compass satellites during the next two years using the Long-March 3 rocket launcher. After the launch of the first test satellite in April 2007, called COMPASS-M1, this would be the real start of <a href="http://gnss.servolux.nl/compass_overview.html">this interesting GNSS system.</a> <br />
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China plans to establish an independent global satellite navigation system, called COMPASS/BeiDou-2, by launching 30 satellites before 2015. The system will make China independent from foreign systems like GPS, GLONASS, and Galileo. The 2015 time frame is similar to the current European Galileo time schedule, so it will be an interesting "battle" who will have the system fully operational first! European officials have been surprised to learn that the first Compass/Beidou medium Earth satellite, COMPASS-M1 launched on April 14, 2007, is providing substantially better atomic-clock timing precision than was expected. China had purchased atomic clocks from a Swiss company, but these were said at the time to be an older technology.<br />
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If the Chinese are serious about launching 10 Long-March 3 rockets with Compass satellites there should be a launch soon! Actually a launch was expected in December 2008 but that did not take place. So lets wait and see what happens!<div class="blogger-post-footer"><a href="http://www.PosiTim.com/">
PosiTim High Accuracy GNSS
</a></div>Springinhetveldhttp://www.blogger.com/profile/14360127679091995926noreply@blogger.com8tag:blogger.com,1999:blog-5918251947010952763.post-74147750140215016202008-12-25T15:57:00.011+01:002010-06-15T09:12:34.582+02:00Successfull GLONASS Launch<div class="separator" style="text-align: center;"><a href="http://www.positim.com/gnss/uploaded_images/Glonass-launch-20081225-706131.jpg" imageanchor="1" style="cssfloat: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="320" src="http://www.positim.com/gnss/uploaded_images/Glonass-launch-20081225-706130.jpg" vr="true" width="208" /></a><br />
</div>The GLONASS launch planned for today, December 25, 2008, was successfull! Launches around Christmas are by now a tradition for GLONASS. Since several years the Christmas time is used to make "triplet" launches. This launch was the second triplet launch this year and will bring the number of active GLONASS satelites to 20!<br />
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A very nice Christmas present from Russia to the GNSS world! These satellites further enhance the GLONASS constellation and bring it yet again a step closer to completion. More interestingly, the combination of GPS and GLONASS is also profiting from a ever increasing GLONASS constellation. <br />
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According to the <a href="http://www.orbiter-forum.com/showthread.php?p=70022">orbiter-forum </a>the spacecrafts have been given the designations Melchior-2447, Gaspar-2448 and Baltasar-2449. <br />
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Last but not least I wish all my readers that they will find their direction(s) in 2009!<div class="blogger-post-footer"><a href="http://www.PosiTim.com/">
PosiTim High Accuracy GNSS
</a></div>Springinhetveldhttp://www.blogger.com/profile/14360127679091995926noreply@blogger.com0