What is a light-day? The milestone Voyager 1 is closing in on

(science.nasa.gov)

28 points | by geox 1 hour ago

4 comments

  • robotresearcher 9 minutes ago
    > the spacecraft, in flight since 1977, is cruising at nearly 38,000 mph (61,000 kph) through the vacuum of space,

    The page takes great pains to explain things, but omits a frame of reference for this speed. I’m guessing it’s sun-relative, but it could be relative to its take-off on Earth. Does anyone know?

  • polalavik 38 minutes ago
    Free space pathloss for rf signals is proportional to 1/r^2, absolutely bonkers we can get anything from voyager.
    • rnhmjoj 10 minutes ago
      1/r² is for an isotropic radiator, but Voyager 1 mounts (thankfully) a high gain directional antenna. The gains seem to be 36dBi or 48dBi, depending on the frequency [1]. This means that when pointed towards Earth, the signal power is actually between 4000 to 63000 times stronger than what that formula would give you. It's still tiny, but not as bad as that would suggest.

      [1]: https://space.stackexchange.com/questions/65801/what-are-the...

    • freedomben 26 minutes ago
      And with 50 year old tech! I do wonder if humanity will get to a point where we can retrieve the spacecraft at some point in the future (cue Star Trek fantasies)
      • deadnomore 6 minutes ago
        I would prefer they just maintain it as long as possible and maybe deploy a proxy for earth that trails behind it indefinitely once it’s finally out of range. Let’s set an unbreakable record.
      • bonzini 18 minutes ago
        Technically, the receivers need not use 50 years old tech. I am saying that not to be annoying but because I wonder how much that matters.
        • robotresearcher 4 minutes ago
          It’s a very convenient property that we have time to improve the receiver tech as the vehicle recedes.

          I don’t know if this was ever done with Voyager, but theoretically we could also change the software on the sending side as we improve coding methods.

  • zomtorg 18 minutes ago
    And the closest known galaxy to the Milky Way, Canis Major Dwarf Galaxy, is just 25,000 light-years away - it's almost incomprehensible how vast the universe is!
  • soniman 23 minutes ago
    So it is traveling 1/18250 the speed of light. That is pretty fast.