6.5 Ton to GEO, that is a big baby.
American comms specialist ViaSat is set to put the world's most powerful communications satellite into orbit on Thursday afternoon atop an Ariane rocket. The launch – scheduled for 1645 PDT (Friday 2345 UTC) from the Guiana Space Centre in French Guiana – will see the 6,418kg (14,149lb) Boeing-built ViaSat 2 sent up into …
Friday 2nd June 2017 08:22 GMT MyffyW
Friday 2nd June 2017 08:49 GMT Daniel Garcia 2
Friday 2nd June 2017 10:47 GMT Mike Dimmick
Re: Mixture of Chemical and Xenon?
The xenon gas is the medium in the ion drive (ViaSat refer to it as electric propulsion). The long-term purpose is for station-keeping, keeping the satellite exactly above 69.9°E longitude on the equator.
The chemical thrusters will be used to circularise the satellite's orbit. The launch has only put it into a Geosynchronous Transfer Orbit, an elliptical orbit that is near the final altitude at the furthest point (apogee) but still barely above the Earth's atmosphere at the closest (perigee). It typically needs around 1500 metres per second delta-V to circularise - bring the perigee up to the target altitude - and change the inclination to equatorial. The orbit that the booster left it in is inclined by about the same amount as the latitude of the launch site, so for Ariane around 5°.
ViaSat state that they have enough chemical fuel (probably UMDH/N2O4) to circularise, but electric propulsion will be used to change inclination. Source: https://www.viasat.com/news/what-happens-after-viasat-2-launches-step-1-orbit-raising
Friday 2nd June 2017 08:51 GMT Bronek Kozicki
"Smaller satellites spend a lot of time over parts of the earth that don't have demand and they can't reallocate that capacity to other areas,"
... these smaller satellites are also much close to the ground, offering much better latency. For a sufficiently large constellation it should be even possible to beat latency of intercontinental fibre connection, which opens up a whole new attractive market sector.
Friday 2nd June 2017 09:17 GMT Anonymous Coward
The BBC article on the satellite says that it will boost WiFi on planes.
Well if 'The Donald' has his way, we won't be able to take any electronic devices into the cabin. His motley crew of so called experts are already trying to get anything larger than a Phablet banned. I'm sure that it won't be long before someone says that even a phone or an iPod Mini can pack enough Cemtex etc to bring down a plane and as a result all electronics needs to be banned.
Naturally it won't apply to the people proposing the move as they all that their own private jets.
No electronics will mean an awful lot of people won't fly. LEss Aircraft in the air means more air space for their LearJets.... Simple really.
A good few airlines will go to the wall if this move covers the world as the US people want.
Well, that's one way of removing CO2. Less Jet-A burnt means less CO2.
Friday 2nd June 2017 09:59 GMT phuzz
Re: Redundant already?
As much fun as it is to blame trump for everything, they're considering banning laptops because the intelligence services think some scrote has worked out how to hide a bomb in one that is unlikely to be picked up by normal screening.
Not really the orange idiot's fault, (although I'm sure he'll find a way to screw things up worse anyway).
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Friday 2nd June 2017 12:15 GMT Dr Who
To all space comms experts
I've set up a satellite dish for fixed domestic satellite Internet. It's a bit of a pig, to say the least, to get the alignment spot on and the signal can easily be disrupted by stupid things like leaves growing on a nearby tree.
My question then is how does a mobile terminal such as an individual sat-phone or an aircraft moving at several hundred miles per hour acquire and maintain a high bandwidth connection to either a geostationary or LEO satellite?
Saturday 3rd June 2017 17:02 GMT JeffyPoooh
Saturday 3rd June 2017 17:27 GMT JeffyPoooh
Re: To all space comms experts
Allow me to expand further.
L-band systems, around 1.6 GHz, such as Iridium and Inmarsat, can provide low bandwidth satcom using low gain antennas that do not require aiming. When I use the word low, I mean REALLY low bandwidth. 5% of dial-up speeds. Just enough for heavily compressed voice or short messages.
Higher data rates (0.4Mbps) on L-band need medium antenna gain which implies steerable antenna systems. There are some very cute little antenna systems, one using a quad array of end-fed helical elements. Little motors aim it, but aiming is not very critical at L-band. Floodlight, not laser.
Higher ka- and ku-bands are where all the high bandwidth action is these days. The aircraft typically need a small dish with precision aiming capabilities. It's very critical because mis-aiming could interfere with the satellite in the next orbital slot, only 2 or 3 degrees away.
Unlike manually aiming a dish, these are fully automatic. They can slew into alignment in seconds.
One thing to consider is 2-axis mounts can get into lockup. So 3-axis mounts might be better.
Electronic beam steering can be mentioned, but last time I checked it wasn't quite ready for prime time. Might be by now.
Friday 2nd June 2017 14:32 GMT W4YBO