From: szabo@techbook.com (Nick Szabo)
Subject: Re: NEAR asteroid mission (but wait! There's more!)
Organization: TECHbooks --- Public Access UNIX --- (503) 220-0636
Date: Sun, 27 Sep 1992 00:42:12 GMT

In article <1992Sep24.081212.1@fnala.fnal.gov> higgins@fnala.fnal.gov (Bill Higgins-- Beam Jockey) writes:
>
>Let's talk about the New, Improved NASA, with Secret Ingredient FCB!
>Prime target is a 1998 launch to 4660 Nereus, an asteroid with an
>orbit similar to Earth's, requiring a delta-V of 1.165 km/sec.

Nice delta-v.  Significantly less than landing on the moon.  Does
anybody have the original designation of this asteroid (it was
renamed after _Asteroids II_ came out)?  Has it been given a
type (C,S,M, etc.)?  Anything else known about its composition?

>The Announcement of Opportunity is due about a year from now, but the
>strawman payload includes visible imager, gamma-ray spectrometer,
>imaging spectrograph (I presume seeing deep into the infrared),
>magnetometer, and laser altimeter. 

Very nice.  Now, where is the upper stage going?  Any chance we
can ping the asteroid with the upper stage and get imaging and
spectroscopy on the resulting dust cloud and crater?

>The fixed 1.5 m X-band dish allows (at 1 AU from Earth) 20.8 kbits/sec
>using DSN's 34-meter ground stations, 83.8 kb/sec with the 70-m
>dishes.  Solid-state data recorder would  hold 5E5 bits. (Now that I
>look at my notes, that seems a bit small! Maybe I transcribed it
>incorrectly.  Think that 5 coulda been an 8?)

Indeed, they'd be pulling a Magellan. :-)  Unlike Magellan, they might
not have the clout to get tons of DSN time, and would lose the data
instead.  'Tis not a good thing to skimp on storage, especially in
an era of many small missions, all competing for DSN time.

>Dry mass would be 400 kg, experiments taking up 60 kg of that, and
>there would be 300 kg of propellants.  A bipropellant propulsion
>system has a big 450-N (100-pound) thruster and twelve 22-N thrusters.

Hmmm.  If this was a bigger payload and an electric rocket were available,
I'd want to use that.  Even for this small a delta-v.  (It's still
a bigger delta-v than comsats, which can also benefit from electric
for the GTO to GEO run).  I'd want to look at how much thrust is
needed for maneuvering around the asteroid, though.  After the Neried
rendesvous, it would greatly increase the flexibility of the rest of
the mission.  Not that Farquar is doing so bad himself!

>Now for the fun part.  You say you want to visit more than one
>asteroid? There's one on the way, 2019 Van Albada, and for an extra 16
>m/sec of delta-V NEAR can see it.  1.7 AU perihelion, 2.61 AU
>aphelion, inclined 4.0 degrees, 17 km diameter. 

This one seems to be unclassified, as well. There's a small possibility 
of ice in that kind of orbit, though it would be well-hidden beneath the
regolith.  My guess of the best search space for more accessible ice is 
perihelion 1-2 AU, aphelion 3-4 AU, classification type C,P,D, or comet.

>...2003 sailing past Comet Encke!

The comet closest to the Sun: perihelion 0.33 AU (!), aphelion 4.09 AU.

>Or! Do three swingbys of Earth, an Encke flyby, then return for two
>Earth swingbys, and you can go on to the asteroid Eros on 18 August
>2005.  

Naah, Eros is a boring silicate-dominated, like Gaspra.  

>Instead of Eros, you could go to comet Tempel-1 or another I wrote
>down as S.W.3.

That would be P/Schwassman-Wachman 3, in the top ten of known accessible
Jupiter-family comets.  Quite nice!  P/Tempel-1 is almost as good.

>...major asteroid Vesta with three Earth swingbys! 

Scientifically interesting, since it may match a unique set of meteoric
material.  Not a good prospecting prospect; it's basaltic and too
far out in the belt.

>This would
>give you a "small-body grand tour" for a total delta-V cost of 158
>meters per second beyond the Nereus-orbit budget.

Farquar is incredible.  Does he have some software we could borrow?


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