• Pons_Aelius@kbin.social
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    1 year ago

    Did you watch the video?

    The tracking problems Hubble would have imaging the earth surface are a direct guide to what differences the design would be.

    • teft@startrek.website
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      1 year ago

      Did you finish the video where they essentially say what I said in my first comment? Hubble and spy satellites share a lot of the same technologies. I wasn’t aware of the speed issue but other than that they are similar like I said.

        • mkwt@lemmy.world
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          1 year ago

          And the angular momentum is conserved.

          Your choices are basically RCS thrusters or reaction wheels. Thrusters burn limited fuel. Reaction wheels are flywheels inside the satellite that you spin in the operator opposite direction to where you want to rotate. They are limited by the mass and size of flywheel, and the maximum speed you can spin it up to.

          • yetiftw@lemmy.world
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            1 year ago

            electromagnets also work as the earth has a magnetic field. a pair of reaction wheels can be rotated (which yes, adds complexity) opposite directions along an axis perpendicular to the axles once they have reached saturation, effectively resetting the reaction wheels

          • Madlaine@feddit.de
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            1 year ago

            They have to rotate it fast enough, and hubble is not built to rotate that fast

            • schmidtster@lemmy.world
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              1 year ago

              Is it an actual limitation of the hardware or a software safety limit? The designs are similar it more has to do with limitations put on it.

              They mention they can’t because the gyro vibrates, so it does sound like it’s capable of spinning faster it’s limited for specific reasons. Now are those reasons detrimental to its use or would they just have to get fancier.

              These can’t be answered.

              • Madlaine@feddit.de
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                1 year ago

                The sattelite bus for the KH-11 Spy sattelites (which hubble is based on) uses thrusters for orientation (and has a huge propellant tank) while the Hubble sattelite bus uses several gyroscopes for orientation. They are not as similar as you might think.

                • schmidtster@lemmy.world
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                  1 year ago

                  With reaction wheels/gyros could they not build up momentum over time to achieve the appropriate spin rate to match earths rotation?

                  After that it would just be timing and they could also layer multiple images together to work out details in theory.