GNSS Satellite (GIOVE-A)


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Monday, 10 August 2009

Last launch of GPS Block IIR Satellite

On 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.

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.

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.

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Monday, 19 January 2009

COMPASS/BeiDou Status

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!

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Saturday, 22 November 2008

Galileo Status

Short update on the Galileo, or rather Giove, status. Both Giove-A and Giove-B are in good health and cycling the Earth. The 13 Galileo Experimental Sensor Stations (GESS) are tracking the satellite signals. The GESS track Giove-A using 2 channels and Giove-B using 5 channels. This is due to the limit of 7 Galileo (Giove) tracking channels in the GESS hardware, these are truly experimental receivers.

Giove-A, launched in December 2005, is meanwhile passed its design lifetime but still going strong. Giove-B is performing very well. Especially its on-board passive hydrogen maser (PHM) is performing extremly well. Even much better then its specifications. This is a very important result for two reasons. First of all this is the first time such a clock is flown in space. Secondly, this type of clocks holds a promise of significantly improving the navigation quality of the GNSS systems. The main limiting factor today in GNSS navigation solutions is the quality of the predicted clocks. This PHM will allow clock predictions that may be one order of magnitude better than todays atomic clocks. A real break trought for GNSS!

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