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From what I know, to communicate with Earth, a space probe locates signals sent from Earth and then sends data (in that direction). For probes that are several light hours away (Voyagers, New Horizons), however, the Earth will rotate (and with it, the locations of the DSN arrays will change).

Is the spot size of these communication signals large enough to compensate for this movement? Or does the probe need to calculate where the next available array will be, and make small adjustments?


marked as duplicate by 1337joe, mins, TildalWave Aug 5 '15 at 19:54

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    $\begingroup$ 'The planet will rotate', heck the planet will MOVE! At about 30 km/s, or 108 000 km every hour. $\endgroup$ – NPSF3000 Aug 5 '15 at 9:16
  • $\begingroup$ I recently saw a figure of 0.3 degrees beam width for the 2 metre dish of the New Horizons probe. (Sorry, can't find the source right now. It's highly dependent on the dish design, size and frequency.) I understand that, for distant probes they just point at Earth and that's good enough... (The big Earth-based DSN dishes have to steer of course.) $\endgroup$ – Andy Aug 5 '15 at 13:58