parachute but, in fact, the
probe actually revolved the
wrong way due to an
unforeseen aerodynamic effect of part of the structure. In
fact, I also worked on analyzing some of the data from
accelerometers and tilt sensors on the probe, to understand
the degree of turbulence in the atmosphere.
I was aided in this effort by data from parachute-borne
instrumentation on Earth — using a BASIC Stamp and other
microcontrollers with ADXL202 accelerometers and similar
hobby-grade sensors, just to get familiar with the kind of
readings one sees for different kinds of motion. I even put
that same instrumentation on a Frisbee to measure its
aerodynamic characteristics (see Frisbee Black Box;
February 2004 issue of Nuts & Volts)
The broad picture from the probe showed a desert
landscape, yet one that had signs that liquid had flowed in
the past. Like the arroyos in desert Arizona (where I was
living at the time of Huygens ‘landing’), these liquid-cut
scars on the landscape are a poor guide of the ‘average’
climate. It need only rain once in a while to form gulleys,
canyons, and cobbles like those seen in post-landing images
(Figure 5).
(While we had no right to expect any images from the
surface after landing — the probe could have just crashed,
or toppled over blocking its radio antenna, or the parachute
might have fallen on the camera! — in fact, we continued
to get data from Huygens until 72 minutes after landing, at
which point the probe was still working fine; the Cassini
SERVO 05.2015 45
Figure 5. Titan's low latitude
surface as seen from the Huygens
probe, which survived impact to
operate for more than an hour. This
knee-high perspective shows
cobbles 15 cm across, rounded by
tumbling in a methane stream. The
grayscale image has been tinted
with real color information from
Huygens' spectrometers.
Figure 6. Titan's seas, as mapped by Cassini's radar instrument. Titan is tidally locked to Saturn, so
Saturn defines the prime meridian and hovers in the same part of Titan's sky, but shows phases like our
moon. Saturn is visible (dimly) from Kraken (K), but is below the horizon seen from the other two seas,
Punga and Ligeia (P and L).
