QUESTION:
At the longest distance between Earth and Mars, assume that the transmission
time is six minutes. If the Pathfinder transmits only five minutes of data
to Earth and suddenly breaks down, will the data reach the Earth station?

ANSWER from David Mittman on September 2, 1997:
Maybe. As soon as the spacecraft's transmitter comes on, you can expect that
the signal will reach Earth exactly one one-way light time (OWLT) later. If
the spacecraft's transmitter turns off just a few seconds after turning on,
then only a little blip of signal will reach Earth and we probably wouldn't
be able to detect it unless we were properly prepared.

In order to receive digital data, the transmitter must usually be on for at
least 5 minutes or so. If the transmitter were on for only five minutes,
then we might not get any digital data even if the spacecraft were
transmitting at 8295 bits per second.