GNSS Satellite (GIOVE-A)

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Tuesday, 18 May 2010

First GPS block IIF Satellite set for launch

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, see our past reports on this issue.

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.

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 (OPS-GN) at the European Space Operations Centre (ESOC) of the European Space Agency (ESA). We hope to analyse this data as soon as they become available from the tracking network of the International GNSS Service (IGS). 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.

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.

We hope to be back soon with a very positive report on this new satellite and with that a new era in GPS!

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Blogger Unknown said...

Is this going to have any impact on existing GPS systems? Specifically, am I going to get more precise GPS readings on my smartphone in Ecuador? I assume that I have a sirfstarIII chip in my phone, although it doesn't reveal that information.

25 May 2010 at 18:37

Blogger Springinhetveld said...

Hi MiG,
On your current smartphone it will have no effect as the chip in your phone will (most likely) not be able to track these signals.

Currently all cheap GPS devices use only one single frequency which is the L1 frequency. One way to get (much!!) more precise solutions would be to use two frequencies. However, the current GPS constellation only partially offers civil signals on two frequencies (L2C). This is because only the block IIR-M satellites had this functionality. With this new block IIF satellite generation a third civil signal is added. So L2C remains and a third code on the L5 frequency is added. This brings the GPS constellation to 9 satellites with L2C and one with L5C (not sure if L5C is the proper name). So until L2C becomes really usable we will need about 15 more satellites and for L5C to become usable we need 23 more satellites. How soon we will have 15 new satellites to complete L2C mainly depends on how long the currently active satellites remain operational. Only when a full L2C constellation is available we may expect cheap dual frequency GPS chips on the market and thus in your car navigation system and your smart phone. This may be a couple of more years.....

29 May 2010 at 15:37

Blogger Springinhetveld said...

Small add-on.

The first of the GPS Block IIF satellites was successfully launched on May 28. Liftoff occurred at 03:00 UTC.

Launch details and photos are available on the Spaceflight Now website:

29 May 2010 at 15:41


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