Wow 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.

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.

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.

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.

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!

I am at least very much looking forward to them!

Labels: BeiDou, Galileo, GNSS, GPS, Launch

Purely 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.
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.

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.

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!

Labels: Galileo, GNSS, Orbit Anomaly

It 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.
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.

For more information here some of the links on this topic (but they do not have too much information yet).
Arianespace
ESA Navigation
Spaceflight Now
OHB

Small add-on. Just looked up the TLE (two line elements) from NORAD (celestrak) 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!

Labels: ESA, ESOC, Galileo, GNSS, Orbit Anomaly

The 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.

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.

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.

Labels: Galileo, GNSS, IOV, Launch

Many 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.

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.

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.

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.

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.
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.

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 GNSS.

Labels: Accuracy, GLONASS, GNSS, GPS, Kinematic

This 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 PosiTim employee working at ESOC OPS-GN, 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.
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!

So please check out the article on the GPS-world web-site or in the paper version if you have it!

Labels: ESOC, GNSS, GPS World, OPS-GN

Just a short post this time but an interesting one! Here we provide some links to interesting pictures and videos from different GNSS systems.

Galileo info.
A look at the navigation payloads on the satellites being assembled at EADS Astrium in Portsmouth, England, a video from the BBC.

Glonass launch from December 14, 2009
Roscosmos has announced the successful launch of the Proton rocket carrying three GLONASS-M satellites (in Russian).

The launch occurred on time at 10:38 UTC, on December 14, 2009.

Pictures of the launch.


Video 1 of the launch from RT (Russia Today).
Video 2 of the launch from RT (Russia Today).
Video 3 of the launch from TV Roscosmos.

Beidou/Compass info
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.

Beidou/Compass-G1 was launched at 00:12 Beijing Time on 17 January = 16:12 UTC

 
China Central Television video of launch:

Hope you like these!

Labels: GNSS, pictures, videos

A company we work with GPS Solutions has developed a really cool application which I would like to introduce to you here.

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!

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.

Want to try it out, just click this link. This links shows you the location of the main Servolux office and the weather forecast for the next couple of days!

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!

Wishing you nice weather and a good forecast!

Labels: GNSS, Google Earth, GPS, weather forecast

On 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.

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.

GPS world 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.”

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.

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.

Let us wait and see when we get the first L5 "beebs".

Labels: GNSS, GPS, L5, launch schedule

According 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 this interesting GNSS system.

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.

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!

Labels: BeiDou, Compass, GNSS, Status

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!

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.

According to the orbiter-forum the spacecrafts have been given the designations Melchior-2447, Gaspar-2448 and Baltasar-2449.

Last but not least I wish all my readers that they will find their direction(s) in 2009!

Labels: GLONASS, GNSS, launch schedule

Since my earlier post this year several things have changed so it is time for a short GNSS launch update.

Galileo

Galileo has kept its "promise" and successfully launched the Giove-B satellite on April 27, 2008. The real special of this satellite is its extremely stable on board clock, a hydrogen maser clock. This is the first time a clock like that is flown on a GNSS satellite and it seems to be performing really well. The next step in the Galileo project will be the IOV phase (In Orbit Validation). For the IOV 4 satellites will be launched in a constellation that will allow the simultaneous visibility of all 4 satellites for a limited amount of time each day. This is similar to what was done with GPS in its early days. The IOV phase is currently scheduled for 2010, but with this project one never knows. Galileo FOC (Full Orbit Constellation) is scheduled for 2014 although it would be saver to say 201x (if not 20xx).

GPS

There were four GPS launches planned for 2008; in March, June, August, and September. The launch in March took place, GPS-48 (PRN07), a Block IIRM (2R-19)satellite, was launched successfully. The launch from June (2R-20) has been postponed and is now scheduled for November 7. The launch of the first Block IIF, (Future) satellite which was planned for August, has been moved to 2009. The third launch (2R-21) is currently TBD (to be determined) sometime in 2009. Although this slippage of the launch schedule looks bad it is not. There are currently 30 active satellites so there is no dire need for fresh new satellites. Unfortunately, GPS-35 (PRN05) is at its end because all its clocks have gone bad. It is one of only two GPS satellites that were equipped with special Satellite Laser Ranging (SLR) refelectors. Currently, none of the future GPS satellites are scheduled to carry such an equipment which is really a big loss for the scientific community. Fortunately, all GLONASS and Galileo satellites will carry SLR reflectors!

GLONASS

The GLONASS schedule promises two triplet launches this year. The first one no September 27, the second on December 25. Currently there are 16 GLONASS satellites although only 14 have been usable in the last weeks. If we assume that all the GLONASS satellites launched before 2005 are decomissioned the GLONASS constellation will still grow to 17 active satellites. Since we can savely assume that some of the 2003 and 2004 satellites will remain active we should see a GLONASS constellation of more then 18 satellites. That would be a very good achievement for the GLONASS system and will make it really usable! The next big step for GLONASS will be the new platform, the GLONASS-K satellites. That will increase the lifetime of the satellites and, more importantly, should move GLONASS from the FDMA technique to the CDMA technique used by GPS and Galileo. That would make all three systems interoperable and will keep the end-user equipment simple and therefore cheap!

Stay on track!

Labels: Galileo, GLONASS, GNSS, GPS, launch schedule

So it has been a while since my last post... Just too busy at work to get any new BLOG entry. However, on the GNSS front several things have happened.

First of all yet another GPS satellite has been launched successfully on March 15. Meanwhile this satelite, GPS-48 with PRN number 07, is already transmitting its signals. It is still set unhealty so most navigation devices will not yet use it but the International GNSS Service (http://igs.org) is producing accurate orbits and clocks for this satellite. The launch of first GPS IIF is no longer planned for 2008 but shifted to 2009. However, the next GPS satellite due for launch, in June 2008, will be able to transmit on three frequencies. This as proof of concept for the GPS IIF satellites. This will be really exiting since it will bring us a complete new set of signals.

GLONASS now has 16 active satellites. Unfortunately the global tracking network still has many gabs and several of the receivers still have problems tracking the satellites with zero and/or negative frequency numbers. Nevertheless, GLONASS is in a much better state then ever in the last decade. With 6 more satellites scheduled for launch this year the future really looks bright. Hopefully the tracking equipment will improve. This will be a important task for Trimble, TPS, JPS, and Co. Also the global tracking network should improve. This is an important task for the IGS.

Last but not least GALILEO. GIOVE-B is getting ready for launch. ESA has set up a special web site for this major event GIOVE-B launch . The launch is scheduled for April 27, less then 1 month from now! As I wrote in my previous BLOG the exiting thing of GIOVE-B is the extremly stable clock, the Hydrogen Maser. This should improve the clock quality for the navigation and other real-time users. For the high accuracy domain it should enable a very significant reduction of the number of estimated clock parameters. This should give an accuracy improvemente comparable, if not more, to integer ambiguity resolution. Furthermore, with GIOVE-A and GIOVE-B in orbit at the same time it will give to opportunity to study how well integer ambiguity resolution may be performed when using the Galileo signals! I am really looking forward of working with the GIOVE-A and B data and especially looking forward at exploiting all the opportunities offered by the new signals and the H-Maser.

Please feel free to comment on this text and join me next time on this BLOG!

Labels: Galileo, Giove, GLONASS, GNSS, GPS

The year 2008 promises to become a very interesting year for the Global Navigation Satellite Systemss (GNSS). You say why? Well let me explain.

Lets first have look at the dominating global satellite navigation system, the American NAVSTAR GPS (Global Positioning System). What makes 2008 special for 2008!? Well there are four launches planned. Most of them are really needed to ensure that the system remains complete. Currently there are 32 GPS satellite operational. This is actually the maximum number of PRN codes that were originally envisioned for GPS. However, from the 32 satellites 14 are relatively old Block IIA satellites. Most (if not all) of them have passed their design life time and thus they may fail any day. Therefore launching new satellites is not really a luxury but actually a most. The interesting part is that with the new launches the L2C capacity in orbit is enhanced and will allow a thorough use of it. Thus it will allow us to evaluate how much this signal can help to improve the quality of using GPS. The real highlight is that one of the launches will be the launch of the new GPS Block IIF satellite. This will be really interesting since it will be the first GPS satellite which emits signals on three frequencies. This will open up a whole new "world" to the users of the GPS constellation. I am really looking forward to working with the first data from this satellite and analyse the quality of the new signalis. The triple frequency will offer an exiting field for new usage of the GPS signal. The launch of this satellite is currently scheduled for August 2008. The other GPS launches are planned for March, June, and September.

Now to the Russian based system GLONASS. By the way the abreviation GLONASS comes from the Russion "Global'naya Navigatsionnaya Sputnikovaya Sistema" which may be translated as "Global Navigation Satellite System". Also for GLONASS 2008 holds quite some promise. After the two successful "triplet" launches in October and December 2007 the GLONASS system currently has 16 active satellites. The launch schedule for 2008 is not 100% clear (it is still difficult to get reliable information out of Russia). However, at least one additional triplet launch is planned but there are also indication that there will be two. The first triplet launch is scheduled for September. The second may be, as is almost a GLONASS tradition, around Christmas 2008. The most interesting fact for GLONASS is the planned launch of the first new GLONASS-K satellites. The GLONASS-K, is an entirely new model based on the non-pressurized platform, standardized to the specifications of the previous models' platform, Express-1000. Its main difference with the previous GLONASS satellites is that is much lighter (about half the weight!). This allows them to be launched (two at a time) with the Soyuz launcher which is much cheaper than the Proton launcher currently used (even if it launches three satellites at the same time). Furhtermore the design lifetime of the GLONASS-K satellites is much longer. There are rumours that the GLONASS-K will also transmit on three frequencies. But this is not very clear at the moment. In any case it will be interesting to see if Russia can keep up with their very ambitious plan of restoring GLONASS to full orbit constellation (FOC) by 2009. So far they have been doing very well and I am convinced that they will manage this. The only real threath to this goal would be significant politcal changes is Russia. Given the fact that Putin seems to have all well under control this threath does not seem to be very large. In any case it will be very interesting to receive the first GNSS data from this completely new satellite and see how both the data and the satellite will behave.

Next to GPS and GLONASS there are also developments on the European "front". As you may know Europe is in the process of building up its own Global Satellite Navigation System, called Galileo. A first test satellite, called GIOVE-A, is in orbit since two years and performing very well. In 2008 its "larger brother", called GIOVE-B, is scheduled for launch in April. The real "special" GIOVE-B offers is its on board clock. The on-board clock is the single most important instrument of any GNSS satellite. Therefore, all GNSS satellite use atomic clocks since those are the only ones which offer the required clock stability. And since the clock is so imporant typically 3 or 4 clocks are on-board for redundancy purposes. The new thing on GIOVE-B is that besides atomic clocks it will also have what is called a Hydrogen Maser on board. A H-maser on the long term is not as stable as an atomic clock but on the short term (12-48 hours) it is extremely stable. Thus the behavior of a H-maser clock can be predicted much betten than an atomic clock. And since the navigation messages as broadcasted by all GNSS systems are based on predictions the use of H-masers offers a significant accuracy improvement for the end-users (e.g. you and me with our cars navigation systems). So it will be very thrilling to see the behaviour of the H-maser in orbit. This is the first time such a clock is flown on a GNSS satellite! Furthermore, it will be very interesting to observe the GIOVE-B signals and validate if they can uphold the European Galileo promise of much improved signal quality compare to GPS and GLONASS. Furhtermore, there is also some rumour that the GIOVE-A2, a copy of the GIOVE-A, will be launched in November 2008. However, I believe that this will only happen if the GIOVE-B fails.

Furthermore, 2008 will certainly also show some new developments on the Chinese side of the GNSS world. The Chinese are quickly expanding their Beidou/Compass system. Currently I have very little knowledge on this system. I will dig into that during the year and "blog" about that later.

So I hope that you agree with me that 2008 holds a lot of GNSS promises! Maybe not all promises will be kept, but nevertheless even if 1 or 2 of these exiting events will come true the year will be very interesting!!

More on GNSS next month (or sooner if I can find the time).

Labels: GNSS, GNSS BLOG, launch schedule

So the new year, 2008, is there and I start this year with my first BLOG site. The idea is to write things about GNSS on this BLOG. I have a very modest aim of writing one article each month on this site. So I should manage to write 12 articles this year but not counting this one! I will set the end of the month as deadline for my montly articles.

However, in this first article I would like to inform you about two recent GNSS launch events. One GPS launch and one GLONASS launch.

The GPS launch took place on 20-December 2007 at 20:04 GMT a Delta II rocket holding the newest GPS satellite, IIR-18(M) was launched successfully from Cape Canaveral, FL. This GPS satellite, IIR-18(M), is planned to be stationed in GPS orbital slot C1. This satellite has been assigned the Space Vehicle Number 57 (SVN-57) and it will use the Pseudo Random Noise code 29 (PRN-29). This new GPS satellite is expected to be set healthy for use in early January 2008.

Click here for detailed information on the GPS constellation status.

The GLONASS launch took place on 25-December-2007 three more GLONASS satellites were launched successfully. This second successful launch in 2007 will bring the GLONASS constellation up to 16 satellites. With this the GLONASS system remains well on track to reach full orbit constellation and full availability in 2009.

Click here for more information regarding the GLONASS launch.

Click here for detailed information on the GLONASS constellation status.

Labels: GNSS, GNSS BLOG, launch schedule