Timeline for Using what technology one can keep a spacecraft truly non rotating
Current License: CC BY-SA 3.0
18 events
| when toggle format | what | by | license | comment | |
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| Feb 28, 2021 at 6:39 | vote | accept | zephyr0110 | ||
| Dec 18, 2018 at 0:33 | answer | added | Steve Linton | timeline score: 1 | |
| Dec 17, 2018 at 10:10 | comment | added | Steve Linton | Gravity Probe B en.wikipedia.org/wiki/Gravity_Probe_B sensed its attitude relative to IM Pegasi (whose own absolute position was measured relative to distant quasars by Earth-based radio astronomy). More details einstein.stanford.edu/TECH/technology1.html#telescope. Pointing accuracy was < 0.1 milliarcseconds (about 0.5 nanoradians). | |
| Dec 17, 2018 at 4:51 | answer | added | uhoh | timeline score: 0 | |
| Apr 18, 2018 at 13:34 | answer | added | uhoh | timeline score: 4 | |
| Apr 9, 2018 at 3:26 | history | tweeted | twitter.com/StackSpaceExp/status/983184260415844355 | ||
| Apr 9, 2018 at 2:48 | answer | added | David Hammen | timeline score: 7 | |
| Apr 9, 2018 at 1:06 | history | edited | zephyr0110 | CC BY-SA 3.0 |
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| Apr 9, 2018 at 1:05 | comment | added | zephyr0110 | But, I just put that as an example that why would someone want this high degree accuracy. I shall research a bit on high bandwidth optical communication. Though, still the core issue remains same, the misalignment measured by conventional attitude sensors are poor for such endeavor spare the hubble I guess. | |
| Apr 8, 2018 at 23:47 | comment | added | uhoh | So I'm just suggesting that it might be better to completely separate one question about precision attitude control from another question about sub-arcsec pointing of optical communication. | |
| Apr 8, 2018 at 23:45 | comment | added | uhoh | @Prakhar a small unit placed at the focal plane can contain both a light emitter (fiber pigtail attached to a laser diode+modulator) and a CCD monitoring positions of stars, planets, or other objects within a degree or so of the target which may be invisible. A computer + ephemeris will know the orientation of one with respect to the other, and be able to do the light time and other corrections. If image processing detects a misalignment, tiny MEMS actuators can move the FP unit, or just the fiber by microns in order to compensate. No need to change the attitude of the whole spacecraft. | |
| Apr 8, 2018 at 21:38 | comment | added | zephyr0110 | But in order to steer the optical component one needs the knowledge of where to steer. How can that be possibly done without attitude knowledge? | |
| Apr 8, 2018 at 20:15 | comment | added | uhoh | This is because light is really quite slow, and in space everything is moving, and correcting the direction of a beam of light can be done with small optical components much more easily and precisely than trying to control the attitude of the entire spacecraft, since it's not really a rigid body at all at this level | |
| Apr 8, 2018 at 18:58 | comment | added | uhoh | Rigid body rotation with respect to a hypothetical absolutely inertial frame is one question, generating an optical wave front that will maximize signal strength when it is ultimately received at a distant location is quite another. Both have general relativity implications but the second one is best done without thinking about the first. If you really want to ask about pointing a sub-arcsec resolving optical system to maximized a distance received signal strength, it's better to ask that without bringing up anything about spacecraft attitude or inertial frames. | |
| Apr 8, 2018 at 17:13 | history | edited | zephyr0110 | CC BY-SA 3.0 |
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| Apr 8, 2018 at 16:22 | comment | added | zephyr0110 | That is exactly my question. Even if one considers star as reference in a different galaxy. One simply does not have enough accurate sensor to get the attitude of the star as of now. Now, I want to make an object truly non-rotating. Probably, aligning it to perfect attitude would be next level of challenge. | |
| Apr 8, 2018 at 16:11 | comment | added | fred_dot_u | when considering a rotation, one has a reference datum. In your question, what is the reference point? A remote star would provide a reference point at a galactic level, wouldn't it? The galaxy rotates too! | |
| Apr 8, 2018 at 15:32 | history | asked | zephyr0110 | CC BY-SA 3.0 |