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10/10/2007
Space Probes - Old and New
Perhaps I should feel somewhat guilty writing about scientific
and technological advances whilst using computer software and
hardware that have been declared obsolete. For example, I am
typing this column on a Dell Inspiron 2500 laptop that has been
either hacked or corrupted. I can no longer visit secure sites or
post the column on the stocksandnews.com Web site. What I do
is to save the column on an obsolete medium known as a “floppy
disc”. Hopefully, a few of you will recognize the term. To post
the column, I transfer the floppy into an ancient Dell Latitude
laptop with Windows 95 software, which thankfully still works
even though Microsoft hasn’t supported it for years. (Both
laptops are hand-me-downs from our Editor, Brian Trumbore.)
Last week, spurred by reflections on obsolete stuff, I looked up
an old Bell Labs Technical memorandum, dated March 1981,
that I wrote with colleagues James Auborn and Shelie Granstaff.
The memo described the hardware and software we used to cycle
our rechargeable lithium batteries. I was quite proud of our
home-programmed software, which was capable of cycling up to
255 batteries with individually controllable cycle regimes,
alarms, cut-offs, etc. This with a Hewlett-Packard 9825S
computer with just 23 kilobytes (not megabytes or gigabytes!) of
memory, later upgraded to a bountiful 62 kilobytes. The HP9825
computer had a one-line LED display and no hard drive, any
storage of data taking place on 8-inch discs in a separate
machine. The computer language was the beautifully simple
HPL, an abbreviated form of BASIC, that even I could
understand and program. I was devastated when it was rendered
obsolete.
Why all this reminiscing about ancient history? This year marks
the 30th anniversary of the launching of Voyagers 1 and 2, those
two pioneering space probes that were only slated for 5-year
missions. Yet, 30 years later, they are still radioing back data
from over 9 billion miles from Earth. This is fantastic, so what’s
the problem? Well, according to an item by Bethany Halford in
the Newscripts section of the September 24 issue of Chemical
and Engineering News (C&EN), it’s much the same problem I
would have if I tried to resurrect my old battery cycling system
today. The computer guys and gals of today probably have never
heard of HPL, let alone think anything useful could be
accomplished with only a few kilobytes!
To communicate with the Voyagers, the spacecraft tracking
station in Tidbinbilla, Australia has to maintain a bank of those
1977 computers to talk to what the C&EN article calls
“electronic dinosaurs”. I’m amazed that the Voyagers are
expected to continue transmitting until about 2020. The
unexpectedly long-lived probes have put a premium on the
experienced old-timers at Tidbinbilla (love those Australian
names). For example, 40-year veteran John Murray finds
himself teaching the younger employees at the tracking station
how to maintain and find parts for computers that are older than
the youngsters themselves.
A much more recent probe is sending back some disappointing
news from Mars. Last year you may remember that the Mars
Global Surveyor orbiting Mars sent back a picture that made
quite a splash in the media. When compared to a previous
picture of the same spot on Mars’ surface, there was a new bright
spot in a gully. Excitement was rampant, with the possibility
advanced that the new feature was the result of a recent gush of
water. However, in five papers by an international host of
authors in the September 21 issue of Science, the gushing water
is shown to be unlikely. The Mars Reconnaissance Orbiter
(MRO) is a more sophisticated probe compared to the Global
Surveyor. Instruments on board the MRO can resolve features as
small as a boulder only a couple of feet in size.
The MRO data indicate that the bright spots are not due to water,
but to dry landslides. Not only that, but large channels thought
to be formed by rushing water in the distant past have been found
to be filled with lava. Other areas thought earlier to be the sites
of ancient seas are littered with boulders, not the snow or sandy
residues from ancient oceans. All in all, it seems that the MRO
has provided data that indicate Mars has never been the warm
and wet place that earlier results have suggested. Furthermore, it
appears that any members of a manned Mars mission hoping to
find a source of water on Mars will have to be very choosy about
their selection of a landing spot.
It does appear that the polar regions of Mars offer the presence of
H2O in some abundance. One of the five papers in Science
reports measurements of density of layered deposits in the South
Polar regions. The densities are calculated from gravity data
from radio tracking of MRO and various other Mars orbiters.
The density is consistent with a mixture of water ice with about
15 percent dust. The water ice is thought to be covered by dust
and carbon dioxide ice. The CO2 ice is denser than water ice
and, if I interpret the paper correctly, there may be layers of
fairly pure water ice covered with layers of dust and CO2 ice
about 1 to 10 meters thick. Astronauts might have to drill or dig
through a CO2 layer to get their water although the layer may
have a kind of Swiss cheese structure with holes penetrating
down to or near the underlying water ice.
Well, it’s time to save this column to my floppy disc. At least I
know I have company working with outdated technology down
in Tidbinbilla.
Allen F. Bortrum
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