4 ms·

what speed is the spacecraft going? is the doppler effect an issue?

• Qantourisc 11y ago
  Hardly, all you have to do is listen to a slightly lower or higher frequency. To be exact: 58536 km/h (spacecraft) divided by 1079252848.8km/h(speed of light) -> So that's frequency shift of 0.0054% (If I am wrong please correct me.)
  • nraynaud 11y ago
    Yeah, I might have been stupid. It has nothing to do with the carrier frequency (I was thinking low frequency vs high spacecraft speed, instead of propagation speed vs aircraft speed).
• rootbear 11y ago
  The Doppler shift is tracked, as it tells them how fast (in radial terms) the spacecraft is going. Some years back, I watched the live coverage on NASA TV of the Cassini spacecraft going into orbit around Saturn. When they went into orbit, they didn't announce it with some Hollywood dialog like "Saturn orbit confirmed!" No, what they said was, "The Doppler curve has flattened!" and the room went wild! It was wonderful.
  • david-given 11y ago
    ...they actually forgot to account for Doppler shift when deploying the Huygens probe to Titan: as planned, the 5.5km/s velocity change as Huygens reentered Titan would have caused Cassini's receiver to lose lock on the signal (due to a timing change, rather than a frequency shift, IIRC). As Huygens had no storage and ran on batteries this would cause a total loss of mission. The problem was discovered after launch, and corrected for --- not by reprogramming the receiver, but by changing Cassini's flight profile to reduce the Doppler shift: http://www.thespacereview.com/article/306/1 http://www.thespacereview.com/article/306/1