Ranging and Pioneer

In article ,
George Dishman writes:
The transmitter can be switched off and on but
after switching on it can take a long time to
lock on.

Don't think about switching the transmitter on and off. Instead
command the spacecraft to continuously downlink the contents of some
memory location. Now send a command to change the contents of that
location, and see how long it takes for the new value to be received
in downlink. As Craig wrote, a more sophisticated equivalent of this
is how ranging to more modern spacecraft is done.

Apparently the Pioneer hardware and software don't allow this
procedure to give a useful range. Without knowing spacecraft
details, it's impossible to say exactly why, but I see no reason to
disbelieve the experts. I wouldn't be surprised, though, if signal
strength is the major issue: how many bits/s can Pioneer send back
now? That is certainly one fundamental limitation.

--
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
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