From: gat@forsight2.jpl.nasa.gov (Erann Gat)
Newsgroups: comp.robotics
Subject: Re: How to Explore Mars
Date: 12 Jan 1993 19:32:55 GMT
Organization: Jet Propulsion Laboratory
NNTP-Posting-Host: forsight2.jpl.nasa.gov

In article <GERRY.93Jan11231754@onion.cmu.edu> gerry@cmu.edu (Gerry Roston) writes:
>[As Erann and Gerry cross verbal swords...]
>
>In his post, Erann brought up one important fact: what are you really
>trying to accomplish with a mission.  If all you are trying to to is
>to determine if there is water at the surface at some point
>(literally) on the surface of Mars, the cornet cube concept may be the
>appropriate solution.  However, this is a fairly meaningless mission.

What?  Determining the existence of water on the surface of Mars is
meaningless?   This is an outrageous claim, especially with no support.
It may not be the scientific discovery of the millenium, but it's certainly
not meaningless.  (My source: Dr. Arthur Lane, a senior JPL planetary
scientist, personal communication, 11:00 AM PST, 12 January 1993.)

[Stuff deleted]

>The biggest drawback with "micro" rovers is their inability to
>accomodate components that do not scale in size, for instance
>scientific instruments and telemetry systems.  For example, SDIO has
>developed a number of imaging sensors.  These are (to the best of my
>unclassified world knowledge) the smallest, space qualified imaging
>sensors in existance.  For example, a wide field of view camera for
>350 grams and about 5 watts of power.  However, when Erann speaks of
>"micro rovers" (and Erann, PLEASE correct my impresion if I'm wrong),
>he is thinking in terms of machines that mass less than 5 kg.i

That's about right.

>  Thus, to have only one imaging device consumes 7% of the total available
>landed mass!  

Yes?  So what?

>Now, to do a survey of the type I identified, a suite of
>instruments are required.  Okay, I hear the chourus shouting, send
>many "micro" rovers, each with one instrument in to the same area.
>Bzzt!  How do you register the data returned by one rover with the
>data returned by another?  This is a very difficult problem. 

Here again you give an argument of the form: I do not know the answer
to this problem, therefore no answer exists.  This is an invalid argument.
(Also, the word Bzzt is not a very effective rhetorical device.)

Without getting into detail, I would just like to point out that a
microrover with functioning scientific instruments has been built.
Rocky IV has a camera, a near-IR spectrometer, a chipping tool, and a
seismometer, and masses about 7kg.  Not only is it possible to build
a useful microrover, IT'S BEEN DONE.

[More arguments why microrovers are impossible deleted.]

>  Of course, the biggest problem with "micro" rovers is this:
>Because of the lack of scaling, the mass fraction of a micro rover
>that can be used for scientific purposes will be quite limited.  Let
>us say, giving them the benefit of the doubt, that 25% can be thus
>allocated.  Having many micro rovers does not change this mass
>fraction.  We (FRC) are currently working on the Ambler's successor, a
>combined lander/rover that can deliver approximately 50% of the landed
>mass as scientific payload.  

If we look at the CURRENTLY AVAILABLE DATA, and not speculations about
the future, then microrovers are by far and away the winners on available
payload.  (And there are theoretical reasons why this should be the case
having to do with increased strength ratios as one scales down.)  Even
if FRC succeeds in building Ambler2, before one can draw conclusions one
would need to conduct a control experiment where the same amount of money
was sunk into a microrover development effort.

>Now, let me lastly address one of Erann's comments, specifically,
             ^^^^^^
[Stuff deleted]

>As a final note about the corner cube concept.  Let us assume that a
      ^^^^^^^^^^
[Stuff deleted]

>Finally, lets deal with reality.  There are only a fixed number of
 ^^^^^^^
[More stuff deleted]

>Now, in conclusion (finally!), am I saying that making robots the
      ^^^^^^^^^^^^^^^^^^^^^^^^
[Still more stuff deleted]

Jerry, you would make a fine politician.

Erann Gat
gat@robotics.jpl.nasa.gov


Newsgroups: comp.robotics