From: Amara Graps (Amara.Graps@mpi-hd.mpg.de)
Date: Tue May 22 2001 - 11:42:01 MDT
From: Max More (max@maxmore.com),Fri May 18 2001
>Cassini *should* have a Webcam so that we can see the vantage point of "We
>are transhumans" as the Extropic Art Manifesto recedes ever-farther into
>space.
First: do you care where it points? If not, then Great. Your next
problem would be data-rate. if yes, then Not-so-Great. Welcome to the
world of Spacecraft Observations Planning, which, for Cassini, is
especially difficult since the spacecraft is crippled in its pointing
capabilities.
Unlike some other spacecraft like Galileo and Ulysses, where the
instruments are mounted on a rotating portion of the spacecraft, so
that *all* instruments have 360-degree viewing (with the occassional
magnetometer boom obstructing some of the FOV), Cassini has none.
This lack of a rotating portion was a NASA cost-saving measure some 10
years (?) ago. Therefore, if any instrument on Cassini wants to look
in a particular direction, then it has to compete with the other dozen
instruments. Mission planning is generally done years in advance, with
a huge (and ongoing) effort by members of the instrument teams: they
must submit their observational requirements in detail, in a
particular format by a particular date, then meetings and meetings are
held with key managers, and the merits of each scientific goal are
discussed and somehow one or several instruments are given priority
over another for that time slot. The large bandwidth instruments like
the imaging system often win over the others because of its good PR.
Our group's Cassini CDA dust instrument is low-requirement, low
bandwidth instrument with respect to some of the others and sometimes
we really need to fight to have our observations. At Saturn, probably
even more fighting will be required: For example: If we want to look
at the dust in Saturn's E-ring, and the Imaging system wants to look
at the dust in Saturn's E-ring, what then? The two instruments are
located about 120-degrees apart in Cassini's viewing boresight.
Regarding Cassini's datarate.. there are currently two downlinks per
week (100 kilobit/s ?) which currently wouldn't make a webcam possible
(unless you would be happy with a static picture for half of the
week). So then I suppose this problem might be addressed by Eugene's
notice of that Interplanetary Internet protocal.
(http://www.lucifer.com/exi-lists/extropians/2711.html)
Amara
--
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Amara Graps | Max-Planck-Institut fuer Kernphysik
Interplanetary Dust Group | Saupfercheckweg 1
+49-6221-516-543 | 69117 Heidelberg, GERMANY
Amara.Graps@mpi-hd.mpg.de * http://galileo.mpi-hd.mpg.de/~graps
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"Never fight an inanimate object." - P. J. O'Rourke
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