How did cameras track space launches?

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  • griffb
    griffb Posts: 168 Forumite
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    The launch sequences are mightily impressive, but the one that always gets me is the lift-off of the lunar module from Apollo 17, a command sent manually from Earth to trigger a tilt and zoom routine on the camera on the lunar rover at the exact moment of ignition


    https://io9.gizmodo.com/how-nasa-captured-this-iconic-footage-of-apollo-17-leav-1671650186
  • googler
    googler Posts: 16,103 Forumite
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    griffb wrote: »
    The launch sequences are mightily impressive, but the one that always gets me is the lift-off of the lunar module from Apollo 17, a command sent manually from Earth to trigger a tilt and zoom routine on the camera on the lunar rover at the exact moment of ignition

    The point being that the command had to be sent a few seconds before to anticipate the moment of ignition, of course...
  • Manxman_in_exile
    Manxman_in_exile Posts: 8,380 Forumite
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    Yes - thank you both.


    I watched the last two episodes of "Chasing the Moon" on BBC4 earlier tonight and had forgotten how impressive the shots of the LEM lifting off the moon were.


    So somebody 220,000 miles away on earth had to press a button to start the film sequence some seconds before the engine fired up - astonishing. (Can't be bothered doing the maths, but I think on the documentary it mentioned a 12 (?) second delay in communications - would it be as long as that?)


    Great stuff.
  • googler
    googler Posts: 16,103 Forumite
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    edited 19 July 2019 at 8:26AM
    Manxman_in_exile wrote: »
    Yes - thank you both.


    I watched the last two episodes of "Chasing the Moon" on BBC4 earlier tonight and had forgotten how impressive the shots of the LEM lifting off the moon were.


    So somebody 220,000 miles away on earth had to press a button to start the film sequence some seconds before the engine fired up - astonishing. (Can't be bothered doing the maths, but I think on the documentary it mentioned a 12 (?) second delay in communications - would it be as long as that?)

    Doing the calcs on the direct radio signal between Earth and Moon is the easy part - determining the routing delays ON Earth less so, considering the comms were going through radio telescopes outwith the US some of the time...


    Great stuff.

    He had two practice runs on Apollo 15 and 16 which didn't work out so well, but nailed it on 17.

    Long wait between practice sessions, though ...

    Computing the radio signal time between Earth and Moon is the easy bit. When you consider the delays in routing the signal to and from mission control to the radio telescope(s), which were sometimes outwith the US ...
  • Undervalued
    Undervalued Posts: 8,844 Forumite
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    Manxman_in_exile wrote: »
    Yes - thank you both.


    I watched the last two episodes of "Chasing the Moon" on BBC4 earlier tonight and had forgotten how impressive the shots of the LEM lifting off the moon were.


    So somebody 220,000 miles away on earth had to press a button to start the film sequence some seconds before the engine fired up - astonishing. (Can't be bothered doing the maths, but I think on the documentary it mentioned a 12 (?) second delay in communications - would it be as long as that?)


    Great stuff.

    No, more like 1.2 seconds each way. Say about a 2.5 sec lag in a two way voice conversation.
  • worried_jim
    worried_jim Posts: 11,631 Forumite
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    Can I recommend the excellent Apollo 11 documentary that is in cinemas now, the footage is so good (a lot of 70mm film) and even if you think you know the story inside out there are some very revealing moments like repairing the rocket on the launch pad with 30 mins to go- a couple of guys with spanners!

    https://www.imdb.com/title/tt8760684/
  • googler
    googler Posts: 16,103 Forumite
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    worried_jim wrote: »
    Can I recommend the excellent Apollo 11 documentary that is in cinemas now, the footage is so good (a lot of 70mm film) and even if you think you know the story inside out there are some very revealing moments like repairing the rocket on the launch pad with 30 mins to go- a couple of guys with spanners!

    https://www.imdb.com/title/tt8760684/

    Superb when seen at an IMAX ...
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