Thursday, 24 December 2009
So what happened in the GNSS world in 2009!?
Well....not as much as we hoped for but some progress was made. Most progress was made "behind the scenes".
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 we reported in our BLOG
. 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.
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!
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.
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.
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.
The only thing remaing to be said is....
Labels: Compass, Galileo, GLONASS, GPS, QZSS, SLR, SVN-49 anomaly
Wednesday, 2 December 2009
So it is time for an update on GLONASS.
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.
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.
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 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
. 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.
The September launch is now scheduled for February 2010.
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.
Labels: GLONASS, launch schedule
Monday, 21 September 2009
*** UPDATE *** UPDATE ***
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.
*** UPDATE *** UPDATE ***
The preparations for the next triplet GLONASS-M satellites scheduled for September 25, 2009, are progressing. Roscosmos is releasing interesting videos
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!
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.
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.
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.
Happy positioning and timing!
Labels: antipodal, Frequency channels, GLONASS, launch schedule
Tuesday, 8 September 2009
This is something really cool so I just had to put this link here for you all to see. This link
shows the preparation of one of the GLONASS-M satellites that is being prepared for launch. The launch is scheduled for Septermber 25, see my earlier post
This video has been posted on YouTube by Roscosmos, the Russian Space Agency.
Check it out is is really cool!
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.
The GNSS future looks bright!
Labels: GLONASS, launch schedule
Wednesday, 26 August 2009
As 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.
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.
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.
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:
- Longer life time, design life time of 10 years
- Much lighter satellites reducing launch costs and enabling launches with Soyus rather then with the huge and costly Proton launcher
- Addition of GPS-like CDMA signals.
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.
The GNSS future looks very interesting and very bright!
Labels: cdma, FDMA, GLONASS, launch schedule
Thursday, 25 December 2008
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
Wednesday, 17 December 2008
The GLONASS schedule promised two triplet launches this year. The first one took place on September 25. The second is planned for December 25.
All three satellites of the September launch were succesfully taken into serve, in fact in record time! Unfortunately some older GLONASS satellites were decomissioned in the September/October timeframe. So the current GLONASS constellation consists out of 16 active and healthy GLONASS satellites.
The launch in December should bring to total number of satellites up to 19. With the oldest satellites being from 2004. This great number of satellites together with the ever growing size of the GNSS station tracking network makes GLONASS a very interesting addition, and even independent alternative, to GPS. Within the International GNSS Service
there are two Analysis Centres that do a full fledged GNSS analysis, i.e., a processing of the combination of GPS and GLONASS observations to estimate the satellite orbits but also Earth Orientation parameters, station coordinates, and atmospheric influences. These two Analysis Centres should start seeing a significant benefit from the combination of the two systems (but more on that in a next post).
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 will make all three systems interoperable and will keep the end-user equipment simple and therefore cheap!
Last but not least: Merry Christmas!
Labels: GLONASS, launch schedule
Thursday, 18 September 2008
Since my earlier post
this year several things have changed so it is time for a short GNSS launch update.
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).
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!
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
Saturday, 29 March 2008
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