Re: Mars Lander to Rover QRP

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From: Stephan Greene (sgreene@washsq.com)
Date: Mon Jul 14 1997 - 08:38:30 EDT


On Sun, 13 Jul 1997, William K Hibbert wrote:

> >Just heard an interesting comment on Headline News Network about the
> communications >from the Mars Lander to the Rover being a modified Radio
> Shack Business "Radio" >(Family or Business HT on 450? Maybe even some
> sort of packet controller?). Leave it to >a Ham! Anyone got big ears
> other than Paul, NA5N. Might be some interesting listening.

Doubt they're using business band or anything from Rat Shack, but a UHF FM
link running 9600 bps G3RUH packet is a good possibility. Read on... And
while the lander-earth link is a bit too Qrpppppp....ppppp for amateurs,
there WAS a successful test involving amateurs of the radio links during
Pathfinder's trip to Mars, see Amsat Journal for the write-up.

> >From what was said on NPR's "Talk of the Nation, Science Friday", the
> rover "talks" to the lander using a DARPA-developed data format called
> "X-25", at 9600 bits/second. "Time" this last week stated that the rover
> runs data at a very slow 9600 BpS...
>
> Sounds like a 450 Mhz UHF HT, and a Paccom "PicoPacket" at 9K6 packet, or
> similar, to me.

I do not KNOW for CERTAIN, but I can make an educated guess that the
Rover-Lander link *IS* 9600 bps G3RUH-style packet. Several years ago, I
was associated with the company that built the Eyesat-1/AO-27 satellite.
I recall that we had lengthy discussions with JPL about building a pair of
high-efficiency UHF fixed-frequency FM transmitters and receivers suitable
for 9600 baud FM. The transmitters would have likely been based on
the flight-proven design used in the AMSAT Microsats. I don't
recall what we planned to do about the receivers, if we were going to do
them at all. Nothing ultimately came of it (pity), but it was an
interesting tangent to the main satellite effort.

JPL wanted something with some flight history behind it that was
inexpensive by NASA standards and WORKED. While 9600 bps AX.25 is too
slow for video, it is plenty fast for digitized stills and telemetry data
(just think - no competition for the channel, no interference from pagers,
and a nice line-of-sight path).

My assumption is that JPL either did it themselves or bought/ruggedized
comemrcial hardware. I'm hoping the info will eventually show up on the
Mars Pathfinder web site.

And as I told my wife when JPL experienced the initial comm link problems
between the lander and rover, if things had worked out differently, the
July 4th weekend would have been VERY hectic for us!

72 & 73, Steve KA1LM

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Stephan A. Greene sgreene@washsq.com
PGP Public Key 0xB96717F5 1996/10/01 at http://ww2.washsq.com/~sgreene/
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