Gyro failure fingered for sending Earth-gazing Digital Globe sat TITSUP (That's a total inability to snap usual pics) An Earth-imaging satellite that generated $85m in revenue last year for Maxar Technologies' Digital Globe business went TITSUP: a total inability to snap usual photographs. On Monday, the orbiting bird's owners announced that their WorldView-4 satellite had suffered a gyroscope failure. The “control moment” gyros are needed …
a trade-off between risk / reward,
Which (unless they can fix it) the designers have got expensively wrong. Certainly is far from the first gryo failure on a satellite - some apparently better designed ones have been recoverable, such as the Maxar operated Radarsat 2.
Other press reports state that Maxar plan to try and claim the full $183m insured value from insurers. Whether they get that, and whether the insurers then have recourse to the makers will presumably be viciously fought through the courts. But if Radarsat 2 could be recovered, clearly the design of Digital Globe was an intentional high risk - you'd have thought that the insurers would have a good case for saying that they aren't there to cover reasonably forseeable failures caused by by cheapskate design?
When building spacecraft, adding a backup means increasing weight
On top of which, my understanding is that satellites have rigid weight budgets imposed by the desired orbit and the capabilities of the launch platform. If your camera comes in 2kg over what you'd planned for, you don't just write a check for the weight overage. You cut weight elsewhere. Perhaps the planned backup gyro has to go.
@Terje, are you thinking of navigation gyros? as in everything that wants to know how its moving from mobile phones to jetliners.
Control Moment Gyros are big beasts that are used instead of propellant based thrusters to rotate the satellite. They are spun using electricity generated from solar panels and have to be a non trivial % of the all up weight to produce a useful amount of 'thrust' as per Newtonian rules.
On one of its satellites. They had backup gyros so they were able to recover it the next day and I think were able to get the original one working again too. It seems like a reasonable precaution when you have satellites in orbit that are generating $85 million a year in revenue!
Some LEO satellites have used magnetic coils to torque the satellite against the Earth's magnetic field.
Others have booms with weights extending down to make use of the differential gravity to keep the satellite pointed in the right direction (i.e. down); but no control as such. That wouldn't be ideal for a satellite with cameras (boom protruding into the camera's field of view), so perhaps they could use a helium balloon on the other side. ;-)
"Others have booms with weights extending down to make use of the differential gravity to keep the satellite pointed in the right direction"
Why not put the boom up? All in all, it's just the same. Isn't it?
Call the dead weight satelite and call the satelite boom. So to speak.
Altouth would be harder to point the camera at the right direction
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