Joined: 20/08/2002 11:51:57 Posts: 3831 Location: Essex, UK
Posted: Mon Jul 30, 2012 3:32 pm Post subject: Last Galileo In-Orbit Validation GPS Satellite is Retired
Earlier this month we reported on the final retirement of GIOVE-A, now it it the turn of GIOVE-B to be deactivated and retired. The two GIOVE spacecraft were designed and deployed to test the technology for the European GPS system known as Galileo.
The GIOVE (Galileo In-Orbit Validation Element) project was designed to test and prove various technology elements of the new navigation satellite constellation. The main component for navigation is precise timing and this was one feature of the GIOVE spacecraft. There were two timing devices being tested in the satellites: a rubidium clock and hydrogen maser clock, both atomic clocks.
The rubidium clock is accurate to 3 seconds in a million years, whilst the hydrogen maser clock is quoted at losing only one second in three million years. These are critical to the overall accuracy of the GPS location as your position is determined by the amount of time it take for the various satellite signals to reach your location. These combined with the knowledge of the satellite locations provide your location on the surface of the planet. The more accurate the timing is the more precise your position is.
The original design life of the GIOVE satellites was 27 months and they have successfully been in operation for more than twice that amount of time.
GIOVE-B was lofted 30km above it's operational orbit last week and will be lifted a further 600km in the next few weeks over three more burns. This will leave it in a 'graveyard orbit' of 23,822km above Earth.
Joined: Feb 27, 2006 Posts: 30 Location: Thurnby, Leicestershire
Posted: Tue Jul 31, 2012 12:57 pm Post subject: Re: Last Galileo In-Orbit Validation GPS Satellite is Retire
News Team wrote:
The rubidium clock is accurate to 3 seconds in a million years, whilst the hydrogen maser clock is quoted at losing only one second in three million years.
I wonder if the clocks are calibrated for use in space unlike the current gps system. Clocks in space run at a different speed to those on the ground (Einsteins theory of relativity) and the current clocks have to be manually adjusted every day.
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