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Darren
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Location: Hampshire, UK
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 Posted: Thu Mar 06, 2008 1:36 pm Post subject: ESA Space Tug Ready for 9th March launch |
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 The European Space Agency's new Automated Transfer Vehicle (ATV) named Jules Verne is on target for its first mission to the International Space Station (ISS) on Sunday. The ATV is a 20-tonne unmanned automated cargo vehicle which is designed to take over the resupply from the Space Shuttle which is soon to retire.
All fascinating stuff I can hear you thinking, but what has this to do with GPS? Well the most interesting aspect of the design is that it is fully autonomous, capable of holding orbit and docking with the ISS automatically. It is this automatic docking capability that is of particular interest as it uses a sophisticated GPS system to acquire and approach the station.
Because the ISS occupies a relatively low orbit at about 340km above the earth GPS still works effectively (GPS Satellites orbit at about 20,000km). From 30km out the ATV will switch to GPS to allow it to close in on the ISS. It continues to use GPS data until it is 240m away. At this point it switches to a different system using lasers fired at reflectors on the station.
There is no mention of a TMC capability, Text To Speech etc and athermic windscreens won't be a problem as there are a number of external antennas positioned around the circumference of the craft. Let's hope that the system does not need a reboot in orbit, as it is unmanned there will be nobody around to insert the stylus into the reset hole!
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Darren Griffin |
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GPS_fan
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Joined: Jan 04, 2007
Posts: 2789
Location: Hampshire, UK
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| Posted: Thu Mar 06, 2008 2:10 pm Post subject: |
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| Darren wrote: | | There is no mention of a TMC capability, Text To Speech etc and athermic windscreens won't be a problem as there are a number of external antennas positioned around the circumference of the craft. |
What constitutes a traffic jam at this altitude? Two martians and a tractor?
...more importantly, is it compatible with the PGPSW database? Will the next sponsorship deal be a PGPSW car sticker in the window of ISS?
On a more serious note, this unmanned docking ability can't be bad for GPS development, but is sensitivity of devices not governed more by the satellite than simply the GPS? I would suspect that military devices are more sensitive than our everyday devices and this is controlled through what the US military will let us utilise from their satellites is it not?
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Andy
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Darren
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Joined: 11/07/2002 14:36:40
Posts: 23848
Location: Hampshire, UK
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| Posted: Thu Mar 06, 2008 2:36 pm Post subject: |
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| GPS_fan wrote: | | but is sensitivity of devices not governed more by the satellite than simply the GPS? I would suspect that military devices are more sensitive than our everyday devices and this is controlled through what the US military will let us utilise from their satellites is it not? |
Well ESA is European but Selective Availability which degraded signal quality for commercial receivers was removed many years ago. You just need a high-end survey grade receiver and perhaps augmentation using WAAS or EGNOS.
Having said that, with off the shelf receivers having +/- 10m accuracy that would be more than enough to get close enough to the ISS for the auto docking to take over.
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