Ranging and Pioneer

"George Dishman" wrote in message
...

.. a better approach is to consider the switch
off transition. Once the uplink and downlink have
been locked, there should be a clear indication
if the downlink is switched off. One problem is
that the downlink keeps lock by using a very
narrow bandwidth, probably less than 1 Hz so the
response time may be more than a second. Another
problem is how it is achieved. For normal
operational purposes, they probably had software
that would switch the transmitter off and on at
specified times to match the ground station
schedules. Using that requires an accurate clock
on the craft and synchronisation becomes
significant. ..

[[Mod. note -- In practice, I think a major issue is that power cycling
(and thus thermal cycling) any hardware carries some risks of it breaking.
When you've spent 30+ years getting the hardware where it is, you do
_not_ want to do anything which would endanger it.
-- jt]]

Agreed, but if it had to go off for the ConScan
manoeuvres anyway then timing the transitions
would be no extra risk. However I was merely
trying to point out some of the engineering
reasons why using on/off transitions was not
really practical.

There were times when the uplink was swept across
the anticipated receive frequency to help achieve
lock and I wondered whether they could be used to
get a range reading but it looks as though the
frequency settling time was too long. Craig has
talked of many seconds to achieve lock but in at
least one case I picked at random the acquisition
time was several minutes.

George