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Space Topics: SaturnTitan: Data from the Huygens Landing SiteOne of the main purposes of the Huygens probe mission was to provide a set of in situ measurements of Titan's atmosphere and surface that could be used to "ground truth" the remote observations made from the Voyager and Cassini spacecraft. The visible and infrared radiation that an orbiter detects from the surface of Titan is strongly affected by the properties of the atmosphere that lies between the orbiter's sensors and the moon's surface. With the Huygens data set, Titan scientists may eventually be able to correct the orbiter's data for the effects of the atmosphere -- or, at a minimum, understand how the atmosphere is likely to bias the remote data. Therefore, comparing the orbiter and probe data sets is one of the most important activities of the Cassini-Huygens mission. » Photos of the Landing Site from Cassini Cassini Orbiter Views of the Huygens Landing Site
Imaging Science Subsystem: Predicted location of the Huygens
landing site
Data from the Huygens Descent Imager / Spectral
Radiometer (DISR):
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Source:
ESA / NASA / JPL / University of Arizona / USGS
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Matching the DISR panorama to the RADAR images
Mosaic of Huygens DISR images
overlaid on a Cassini orbiter RADAR image taken on October 28, 2005. The landing
site, marked by a red "X", is located at 192.3 degrees west, 10.3 degrees
south. Note that two "cat scratches" were visible in several of the
highest-altitude DISR images.
Credit: ESA / NASA / JPL / University of Arizona
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Matching the DISR panoramas to the RADAR images
A comparison of the
Huygens DISR panoramas captured at different altitudes to the Cassini RADAR
imagery captured on October 28, 2005.
Credit: ESA / NASA / JPL / University of Arizona / René Pascal
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Large amateur-produced surface mosaic of Titan
This mosaic was stitched by amateur image processor René Pascal from the
Huygens DISR data. The mosaic is mostly composed of Medium Resolution Imager
data, supplemented with some High Resolution Imager and some Side Looking Imager
data.
Credit: ESA / NASA / JPL / University of Arizona
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DISR mosaic: 35 kilometers altitude
This was the panorama of Titan visible to Huygens from an altitude of about
35 kilometers (22 miles), just below the cloud deck. There was still a lot
of haze at this altitude, and the view near the horizon is very fuzzy. But
directly below the probe you
can already see the sharp boundary between bright highland to the north and
west and dark lowland to the south and east. This image has been updated from
a previous version (below) through the addition of many Side-Looking Imager
frames. At this altitude the Side-Looking Imager is gazing through a thick
pile of atmosphere, but there is enough detail in the images to resolve two
parallel linear features that were also seen from orbit by the Cassini RADAR
instrument. This mosaic allowed the Huygens and Cassini teams to determine
the location of the Huygens landing site at last.
Credit: ESA / NASA / JPL / University of Arizona
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DISR mosaic: 35 kilometers altitude
This was the panorama of Titan visible to Huygens from an altitude of about
35 kilometers (22 miles), just below the cloud deck. There was still a lot
of haze at this altitude, and the view near the horizon is very fuzzy. But
directly below the probe -- the area marked by the faint gray circle -- you
can already see the sharp boundary between bright highland to the north and
west and dark lowland to the south and east. The white dots on the image
are Huygens' ground track, and the numbers are Huygens' altitude in kilometers
as it flew over each point on the ground. The next image zooms in on the
area bounded by the gray circle.
Credit: ESA / NASA / JPL / University of Arizona
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DISR mosaic: 8 kilometers altitude
Huygens' view of Titan an altitude of 8 kilometers (5 miles) is much clearer
than a higher-elevation view. Huygens' ground track marches inexorably to
the east, though the descent is much steeper than it was earlier in the mission.
To the left (east) we can see the "alien landing strip," the straight,
broad channel with stubby tributaries. To the north we can see the drainage
channels that so shocked the scientists when they were first spotted in Huygens'
images on January 15. To the Pasadena, California-based management team of
Cassini-Huygens, this set of channels debouching into the ocean-like dark
lowlands were reminiscent of the Los Angeles River's terminus at Long Beach,
California. The gray circle at the center of this image marks the boundary
of the next mosaic.
Credit: ESA / NASA / JPL / University of Arizona
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DISR mosaic: 1.2 kilometers altitude
A mosaic representing Huygens' view of Titan from 1.2 kilometers (4000 feet).
The component images are fuzzy because the landscape is very dark, lacking
contrast, and the available light quite dim. Still, Huygens made out what
looks like a ridge dissected by channels. Probably the oddest thing in this
image is the ground track. It continues from west to east, but suddenly,
below an elevation of 9.3 kilometers (5.8 miles), Huygens' eastward motion
stalled. The probe descended, took a hairpin turn, and traveled back in the
direction that it had come from!
Credit: ESA / NASA / JPL / University of Arizona
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DISR mosaic: 800 meters altitude
This mosaic is made from 17 of the highest-resolution views of Huygens' landing
site. During the final part of the descent, Huygens stopped capturing images,
and never got a high-resolution image of the point at which it touched down.
That point is marked with the white cross at the center of this mosaic.
Source:
ESA / NASA / JPL / University of Arizona / USGS
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Topographic model of dark plains on Titan
This perspective view of an area
on Titan was generated from two DISR images (inset). The left image was acquired
from 8 miles (12.2 kilometers) above the surface with the high resolution imager;
the right from 4 miles (6.9 kilometers) altitude with the medium resolution
imager. The two images differed in their "look angle" by about six
degrees, allowing scientists at the USGS to generate a topographic model of
the terrain. The ridges in the center of the view are about 50 meters high;
the area covered is about 2.5 kilometers (1.6 miles) square. Return
to top
Source:
ESA / NASA / JPL / University of Arizona / USGS
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Topographic model of dissected terrain on Titan
This perspective view of an area
on Titan was generated from two DISR images (inset). The left image was acquired
from 14.8 kilometers (9 miles) above the surface with the high resolution imager;
the right from 6.7 kilometers (4 miles) altitude with the medium resolution
imager. The two images differed in their "look angle" by about
15 degrees, allowing scientists at the USGS to generate a topographic model
of the terrain. The total relief in the view is about 150 meters, and the
area covered in the view is about 1 by 3 kilometers (0.6 by 2 miles). Return
to top
Credit: ESA / NASA / JPL / University of Arizona
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Titan's topography as seen by Huygens (movie)
This animation is based upon a terrain model derived from the Huygens photographs
of Titan's surface. The region pictured is approximately 1.5 by 3.5 kilometers
(1 by 2 miles) and displays a maximum relief of approximately 150 to 200
meters. There is no vertical exaggeration. The magnitude of the topographic
relief could be off by as much as a factor of two, but the relative relief
will be correct regardless of future reinterpretation of the images. A smoothly
animated version (.AVI format) can be downloaded from the University
of Arizona website (skip to the bottom of the page).
Data from the Huygens Descent Imager
/ Spectral Radiometer (DISR):
Panoramic Views
An initial 360-degree panorama of the Titanian landscape captured by Huygens
during its January 14, 2005 descent. The images were taken from an altitude
of about 8 kilometers. Credit: ESA / NASA / JPL / University of Arizona
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The same panorama, edited by René Pascal.
Credit: ESA / NASA / University of Arizona / René Pascal |
Panorama of the channels at the Huygens landing site
Credit: ESA / NASA / University of Arizona |
Similar panorama, edited by René Pascal.
Credit: ESA / NASA / JPL / University of Arizona / René Pascal |
Pictures and Data from the Surface and Impact
HASI recorded the impact instant to be 11:38:11 UTC (T0 plus 2 hours, 27 minutes, 49.840 seconds). Huygens transmitted data from the surface of Titan to Cassini until 12:50:24. During that time, the view remained constant: a boulder-strewn plain. The last signal sent from Huygens that was received on Earth was sent at about 14:53 UTC. Analysis of the probe telemetry data suggests that it probably survived only another 17 minutes after that, at which point the batteries would have been exhausted.
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| The leftmost image is unprocessed, taken
by the Huygens DISR from Huygens' position on Titan's surface. The camera
was only 40 centimeters (17 inches) off the ground, which made the rounded,
icy rocks look a lot bigger than they are. The second image gives the
proper sense of scale. The third image (Click
to enlarge) was colorized based on the
scant color information returned from the "spectral radiometer" aboard
Huygens: one color was applied as a wash to the sky and another as a
wash to the ground surface. To make this image, six Side-Looking
Imager images captured on the surface of Titan were chosen for their
relatively low compression ratio and optimum exposure time. They were
sharpened, and they were colored with a hue that averaged 22.5 and varied
over the angles covered by the image as determined by the Downward-Looking
Visible Spectrometer on the DISR instrument. The fourth image (Click
to enlarge) is a
mosaic of two images from the Huygens DISR medium-resolution and side-looking
imagers. All images credit ESA / NASA / JPL / University of Arizona. Return
to top |
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Credit: ESA / ASI / UPD / OU
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The HASI instrument's accelerometers recorded the signature of the probe
impact
HASI's accelerometer recorded the signature of the probe's impact. The
accelerometer had three axes: X, Y, and Z. The X axis (blue line on graph)
was aligned in the direction of the probe's symmetry axis, so it was aligned
with the descent direction and recorded the greatest accelerations. HASI recorded
the impact instant to be T0 plus 2 hours, 27 minutes, 49.840 seconds.
Credit: ESA / Open University
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Force profile measured by the Huygens penetrometer upon
Titan impact
The Huygens Surface Science Package included a penetrometer
designed to measure the force of Huygens' impact on Titan's surface. The penetrometer
stuck out of the bottom of Huygens by 55 millimeters (2.2 inches). The Surface
Science package team interpret the force profile to show that Titan's surface
has the consistency (though is not necessarily composed of) lightly packed
snow, tar, or wet sand or clay. The sharp peak at the beginning of the profile
suggests that Huygens first hit one of the icy pebbles visible to the DISR
camera, or perhaps that the surface is covered by a thin, firm crust. Return
to top
Credit: ESA / NASA / University of Arizona
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Spectrum of Titan's surface
The red line is a reflectance spectrum of Titan's
surface obtained after Huygens landed. The visible part of the spectrum is
dark and brownish, and there are absorption features in the infrared part of
the spectrum that match water ice. However, the slope of the spectrum in the
infrared wavelengths matches no existing laboratory measurements. The black
lines show laboratory spectra of two "tholins."
Credit: ESA / NASA / GSFC / ASI / GCMS Team
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Increase in methane observed after impact by GCMS
This graph of data from the Huygens GCMS instrument
shows the increase of nitrogen and methane during the probe descent and
the rapid and important increase in methane at the surface.
Credit: ESA / NASA / GSFC / ASI / GCMS Team
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Mass spectrum of the atmosphere at Titan's surface
Huygens GCMS measured the mass spectrum of the atmosphere
at Titan's surface. The spectrum shows the signatures of many compounds: hydrogen
(H2), methane (CH4), nitrogen (N2), ethane
(C2H6), argon-40 (40Ar), carbon dioxide (CO2),
cyanogen (C2N2), and possibly benzene (C6H6).
Listen to the Sounds of Titan!
Huygens Data on Titan's Winds
Credit: ESA / RIUB / NASA GISS / JPL
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Titan zonal wind height profile from the Doppler Wind Experiment
This wind profile was derived from Doppler tracking of
the signals received from Huygens by the NRAO Robert C. Byrd Green Bank and
CSIRO Parkes radio telescopes in West Virginia and Australia. The minimum in
wind speed between 60 and 100 kilometers altitude was unexpected and remains
unexplained. The Parkes data shows that the winds actually reversed direction
close to Titan's surface. The gap between the Green Bank and Parkes data may
eventually be filled through analysis of data acquired at other radio telescopes.
Credit: ESA / NASA / University of Arizona
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Wind speed on Titan inferred from DISR images
DISR found the wind speed to decrease steadily throughout most of its
descent. At an altitude of 7 kilometers, wind speed dropped to near zero. At
this altitude, the winds also reversed direction and blew westward.
Huygens Data on Titan's Atmospheric Composition
Credit: ESA / NASA / University of Arizona
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Upward-looking spectra from Huygens
These spectra represent the color of Titan's sky
in the direction opposite to the Sun. At the highest altitudes, the spectra are
dark. As Huygens descended, more light-scattering particles brightened the sky.
The wiggles in the spectra will provide constraints on the composition and abundance
of gases and haze particles in the atmosphere.
Return to top
Huygens Descent Timeline
| Activity | Time (h:m:s UTC) |
Mission time, T-T0 (h:m:s) |
|---|---|---|
| Probe power-on | 04:41:18 | -4:29:03 |
| Probe support avionics power-on | 06:50:45 | -2:19:56 |
| Arrival at interface altitude (1,270 km) | 09:05:53 | -0:04:28 |
| T0 (start of descent sequence) | 09:10:21 | 0:00:00 |
| Main parachute deployment | 09:10:23 | 0:00:02 |
| Heat shield separation | 09:10:53 | 0:00:32 |
| Transmitter ON | 09:11:06 | 0:00:45 |
| GCMS inlet cap jettison | 09:11:11 | 0:00:50 |
| GCMS outlet cap jettison | 09:11:19 | 0:00:58 |
| HASI boom deployment (latest) | 09:11:23 | 0:01:02 |
| DISR cover jettison | 09:11:27 | 0:01:06 |
| ACP inlet cap jettison | 09:12:51 | 0:01:30 |
| Stabilizer parachute deployment | 09:25:21 | 0:15:00 |
| Radar altimeter power-on | 09:42:17 | 0:31:56 |
| DISR surface lamp on | 11:36:06 | 2:25:45 |
| Surface impact | 11:38:11 | 2:27:50 |
| End of Cassini-probe link | 12:50:24 | 3:40:03 |
| Probe support avionics power-off | 13:37:32 | 4:27:11 |
| Last channel A carrier signal reception by Earth-based radio telescopes | ~14:53 (16:00 Earth received time) |
~5:43 |
| Probable full discharge of Huygens batteries | ~15:10 | ~6:00 |
| From Jean-Pierre Lebreton et al., "An overview of the descent and landing of the Huygens probe on Titan," DOI:10.1038/nature04347 | ||
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