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Thread: Huygens encounter with Titan

  1. #1141
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    It looks rather red, or orange - which is a rather unlikely but not impossible color for water & organics. Red sandy stuff we are familiar with elsewhere are rich in iron oxide. Sand is also consistent with both the penetrometer and permittivity recorded by Huygens.
    “It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.” ― Arthur Conan Doyle, Sherlock Holmes

  2. #1142
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    How the world watched Huygens

    As Huygens parachuted to the surface of Titan in January 2005, a battery of telescopes around the world were watching or listening.

    The results of those observations are now being collected together and published for the first time. The work gives valuable additional context within which to interpret the 'ground truth' returned by Huygens.
    Everything I need to know I learned through Googling.

  3. #1143
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    New scientific publications on Titan and Huygens

    There were two sets of Titan-related scientific papers published this week. A pair of papers in Nature describes Titanian weather, including clouds and methane drizzle, and a passel of papers in the Journal of Geophysical Research is devoted to the Earth-based campaigns to observe Titan before, during, and after the Huygens mission.
    Everything I need to know I learned through Googling.

  4. #1144
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    ESA: Huygens Scientific Archive Data Set Released

    ESA's Huygens probe successfully descended through the atmosphere of Titan, Saturn's largest moon, and safely landed on its surface on 14 January 2005. An extraordinary new world has been unveiled. The unique data obtained by the six Huygens experiments are now being archived in the ESA planetary Science Archive (PSA). A copy of the archived data set is also available in the NASA Planetary Data System (PDS).
    Looking forward to your analysis, Jerry. (By the way, I'm sure we're all still awaiting your analysis of the Deep Impact PDS data available since January.)
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    Skepticism enables us to distinguish fancy from fact, to test our speculations. --Carl Sagan

  5. #1145
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    Huygens data

    I started playing around with some of the Huygens data now that it is available to the public. The first data I looked at was the Central Accelaration Sensing Unit (CASU). The CASU was responsible for detecting the correct time to begin parachute deployment and thus was critical for the mission. I've plotted the time around maximum deceleration and parachute deploy. You can see that around 09:08 the deceleration starts to build and very quickly reaches the saturation level of the CASU. The parachute arming sequence was initiated on the rising edge of the deceleration profile at 80 m/s2 (~ 8g) and the sequence was triggered on the trailing edge of the profile at 9.484 m/s2 (~ 1g).

    You can see a small bump around 09:10:20. This is the mortar firing that releases the pilot chute. The pilot chute pulls off the backcover of the probe and releases the main parachute. The subsequent large bump is the main chute deploying. About 30 seconds later there is another small bump which is from the release of the heat shield.

    I also plotted the time around impact. You can see a spike right around 11:38:11.

    The final plot I made was for the entire descent and post-landing.

    There were actually 3 CASU on Huygens, but I've only plotted the data for one. The values were so close together that you couldn't see the difference.

  6. #1146
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    Huygens’s second landing anniversary – the surprises continue

    Two years ago, planetary scientists across the world watched as Europe and the US did something amazing. The Huygens descent module drifted down through the hazy atmosphere of Saturn's moon Titan, beaming its data back to Earth via the Cassini mothership. Today, Huygens's data are still continuing to surprise researchers.
    Everything I need to know I learned through Googling.

  7. #1147
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    Quote Originally Posted by 01101001 View Post
    Looking forward to your analysis, Jerry. (By the way, I'm sure we're all still awaiting your analysis of the Deep Impact PDS data available since January.)
    Still waiting. After a year.
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    Skepticism enables us to distinguish fancy from fact, to test our speculations. --Carl Sagan

  8. #1148
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    NASA: Mission News: Fasten Your Seat Belts, Turbulence Ahead - Lessons From Titan

    Ever spilled your drink on an airline due to turbulence? Researchers on both sides of the Atlantic are finding new ways to understand the phenomenon - both in Earth's atmosphere and in that of Saturn's moon, Titan, aided by Huygens probe data. The study of one is helping the other.
    [...]
    The Surface Science Package onboard Huygens included a set of tilt sensors, which measured motions of the probe during its descent. These tilt sensors acted much like a drink in a glass, using a small slug of liquid to measure tilt angle.

    As the probe plummeted under the parachute through Titan's atmosphere, there was a lot of buffeting, even though the atmosphere itself was fairly still. Knowing the signature of cloud-induced turbulence in Harrison's balloon data from Earth inspired Lorenz to look for a similar effect in the Huygens data using the tilt sensor.
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    Skepticism enables us to distinguish fancy from fact, to test our speculations. --Carl Sagan

  9. #1149
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    Cool ESA article

    http://www.esa.int/SPECIALS/Cassini-...EM9RR1F_0.html

    Quote Originally Posted by ESA
    The team combined temperature and pressure measurements from the Huygens Atmosphere Structure Instrument (HASI) with other measurements from the Surface Science Package (SSP), the Gas Chromatograph and Mass Spectrometer (GCMS), Descent Imager/Spectral Radiometer (DISR) and the Doppler Wind Experiment (DWE) to arrive at their trajectory.

    The success of this effort is particularly significant because the combination of Titan’s dense and cold atmosphere, together with the operational challenges posed by the satellite’s enormous distance from Earth, makes the Huygens trajectory reconstruction unique. “We realised that we could not always apply the standard techniques on Titan; we had to bring in new methods and ideas and start from scratch,” says Kazeminejad.

    The final test was whether the defined reconstruction methodology and its implementation could actually provide an accurate landing site location. This was checked against other estimates, such as those from DISR images and the radar measurements from the Cassini orbiter.

    All methods showed a remarkably strong agreement as to where Huygens landed. This increases the project’s confidence in that they know exactly how their probe behaved. “Everything converges to the same location,” says Kazeminejad, “All the years of work have paid off.”
    Well, not exactly. In fact not even close, as you can read in the PDS qualifications in the final release of the Huygens data:

    http://atmos.nmsu.edu/PDS/data/hphk_0001/AAREADME.TXT

    Quote Originally Posted by PDS Huygens Data
    Warnings: It should be pointed out that the reconstruction of descent trajectory of the Huygens probe is not coherent with the altitude profile retrieved from the Huygens radar altimeter.

    Different approaches/methods for descent trajectory reconstruction
    resulted in altitude and velocity profiles that show discrepancy,
    not consistent with uncertainty range relevant to models and measurements.

    The reason for this discrepancy is at present still under investigation. Results of future analysis could imply the need to reconsolidate the trajectory.
    We also read:

    http://starbrite.jpl.nasa.gov/pds/vi...-HK-2%2F3-V1.0


    Quote Originally Posted by Huygens PDS Data

    Radar calibration
    =================

    The digital data have been affected by a hardware bug, which caused the upper bits of the digital 15-bit altitude word to change their logical state in a seemingly random fashion. In addition, due to the 15-bit limitation of the digital altitude word, any radar data above 32767 m are affected by a register overflow.
    Any expert in digital engineering will tell you that if you do not know the values of your most significant bits, you don't know jack. The way this is worded it sounds like the problem is limited to altitudes above 32767 km, but this is actually where the problems starts. They write the "most significant bits" plural meaning at least two bits, meaning that there cannot be accurate data above 8 km.

    And from unpublished Huygens documents:
    IMPORTANT: DUE TO AMBIGUITIES IN THE RADAR ALTIMETER UNIT (RAU)
    DATA CALIBRATION PROCESS, BOTH DATA SETS WERE NOT TAKEN INTO
    ACCOUNT FOR THE DESCENT PHASE RECONSTRUCTION.

    THE ALTITUDE PROFILE FROM THE SSP ACOUSTIC SOUNDER (SSP-APIS)
    WAS NOT USED AS INPUT FOR THE DESCENT PHASE RECONSTRUCTION.
    THE SSP-APIS ALTITUDE MEASUREMENTS (AND DERIVED DESCENT
    SPEED) ARE HOWEVER CONSISTENT WITH THE DTWG DESCENT TRAJECTORY
    They did not use either the altimeter data or the acoustic sounder data in the reconstruction! They were winging it! Now an article is published stating that all of their analysis converges, but they don't mention that the four tools that were designed specifically for this analysis: The DWE*, the altimeters, the sonar and the radial accelerometers* are not used in the determination of the descent trajectory! That is bad astronomy!

    *The doppler wind experiment was lost when channel A probe data was not recieved by Cassini, the accelerometers did not record any meaningful data after the first ~20 minutes of the descent; the official reason is that the probe was 'rotating backwards', although vanes in Huygens construction precluded this possibility.

    http://atmos.nmsu.edu/PDS/data/hphk_...LYSIS_2006.PDF

    Because of the amplitude of the DDB Spin change, together with the relatively high average spin value (and therefore good measurement accuracy), it is strongly believed that the feature evidenced in Fig.18 [!Backwards! rotation of the probe, relative to the vane design] corresponds to real Probe spin changes. At that time no explanation to this behaviour is given.
    “It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.” ― Arthur Conan Doyle, Sherlock Holmes

  10. #1150
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    Quote Originally Posted by Jerry View Post
    http://www.esa.int/SPECIALS/Cassini-...EM9RR1F_0.html


    Well, not exactly. In fact not even close, as you can read in the PDS qualifications in the final release of the Huygens data:

    http://atmos.nmsu.edu/PDS/data/hphk_0001/AAREADME.TXT



    We also read:

    http://starbrite.jpl.nasa.gov/pds/vi...-HK-2%2F3-V1.0



    Any expert in digital engineering will tell you that if you do not know the values of your most significant bits, you don't know jack. The way this is worded it sounds like the problem is limited to altitudes above 32767 km, but this is actually where the problems starts. They write the "most significant bits" plural meaning at least two bits, meaning that there cannot be accurate data above 8 km.

    And from unpublished Huygens documents:

    They did not use either the altimeter data or the acoustic sounder data in the reconstruction! They were winging it! Now an article is published stating that all of their analysis converges, but they don't mention that the four tools that were designed specifically for this analysis: The DWE*, the altimeters, the sonar and the radial accelerometers* are not used in the determination of the descent trajectory! That is bad astronomy!

    *The doppler wind experiment was lost when channel A probe data was not recieved by Cassini, the accelerometers did not record any meaningful data after the first ~20 minutes of the descent; the official reason is that the probe was 'rotating backwards', although vanes in Huygens construction precluded this possibility.

    http://atmos.nmsu.edu/PDS/data/hphk_...LYSIS_2006.PDF
    Is there a point to this, or are you just rambling?

  11. #1151
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    Absolutely.

    I staked my career upon the results of the Huygens mission. When I flail my arms and talk about how different the observational results were from the prior expectations, all I see is confusion and incredibility, because the ESA has been releasing articles about the success of the mission and not even mentioning that there were at least four primary instruments that did not return data consistent with the published descent profile.

    This major error-of omission is only one breath short of...but what's the point? In any other field, if the calibrated instruments failed to provide the expected answers, there would not be attempts to devine the velocity and altitude from pressure, temperature, poorly sampled radio doppler and other convoluted, uncalibrated and unproven signal analysis and reconstruction techniques.

    Instead of throwing the altimeter readings out, they should examine the possibility that the readings are correct. Also the possibility that the probe did not 'reverse rotation' after ~20 minutes (a totally unphysical reconstruction, given the design of Huygens' vanes,) but that it actually hit the ground.

    Just as importantly from my prospective, I can go on about this until hell freezes over and it will not mean a thing, unless someone else dives into the data reduction processes used by the Huygens team and says ;hey! you can't make these kinds of assumptions! , I don't have a snowballs chance in hell of being heard.

    Ralph Lorenz assumes that the temperature started increase just seconds after 'landing' because of the loss of aerodynamic cooling once the probe hit the ground. But Huygens switched-on a fairly powerful surface light just seconds before 'the landing'. He omits this detail from his analysis. Isn't this a more likely reason that the temperature of some (but definitely not all) of the thermol sensors increased?
    “It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.” ― Arthur Conan Doyle, Sherlock Holmes

  12. #1152
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    Quote Originally Posted by 01101001 View Post
    Still waiting. After a year.
    It's 2 years. Did I miss your analysis of the Huygens Entry, Descent and Landing? I don't see it in this thread. Or have you just given up on the data?

    (And, where did the Deep Impact analysis get posted?)
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  13. #1153
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    Quote Originally Posted by 01101001 View Post
    It's 2 years. Did I miss your analysis of the Huygens Entry, Descent and Landing? I don't see it in this thread. Or have you just given up on the data?

    (And, where did the Deep Impact analysis get posted?)
    Did you read my last post? Or the one before it?

    Quote Originally Posted by jerry
    I staked my career upon the results of the Huygens mission.
    In other words, I am no longer funded to do fundamental scientific research.

    Quote Originally Posted by jerry
    Just as importantly from my prospective, I can go on about this until hell freezes over and it will not mean a thing, unless someone else dives into the data reduction processes used by the Huygens team and says ;hey! you can't make these kinds of assumptions! , I don't have a snowballs chance in hell of being heard.
    I can't change that - the ESA has to step forward and actually say: 'Like the Doppler wind experiment, our radar, sonar and accelerometer data are not in order'; instead of: “We realised that we could not always apply the standard techniques on Titan; we had to bring in new methods and ideas and start from scratch.” This is not a valid approach to mission data, either what is observed agrees with prior expectations or it does not. If it does not, you must then decide whether it is telling you something you did not expect to learn, or if the data is invalid. If you are starting from scratch, start by throwing out your preconceptions of what the results of the mission should be; not by throwing out the tools that were designed for analysis and inventing new, unproven, uncalibrated techniques.

    That said, I am presenting a paper in September that centers around the Huygens mission and what we have observed about Titan and Saturn. I'll put something on the internet -somewhere- after that presentation.
    Last edited by Jerry; 2008-Aug-04 at 03:03 AM. Reason: omitted word (unproven)
    “It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.” ― Arthur Conan Doyle, Sherlock Holmes

  14. #1154
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    Quote Originally Posted by Jerry View Post
    That said, I am presenting a paper in September that centers around the Huygens mission
    Not at Europlanet is it?

    Doug

  15. #1155
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    Quote Originally Posted by Jerry View Post
    In other words, I am no longer funded to do fundamental scientific research.
    That's unfortunate. Is it a permanent condition?

    Will you and your readers be appreciative of further reminders if you still haven't presented the many analyses that would have supported your claims?

    Or have you at this point given up on supporting those claims forever?
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  16. #1156
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    Nothing gained flogging a dead horse

    Quote Originally Posted by 01101001 View Post
    That's unfortunate. Is it a permanent condition?
    Pretty much, but it doesn't mean I am not doing something I don't enjoy. Applied science, applied research, has always been my forte anyway.

    Quote Originally Posted by 01101001
    Will you and your readers be appreciative of further reminders if you still haven't presented the many analyses that would have supported your claims?

    Or have you at this point given up on supporting those claims forever?
    I will continue to point out that the ESA miss-represented the performance of several key instruments, and relied upon data reduction techniques that are invalid in their presentations of Huygens data, as I delineated above. The problem is, there is also hard data - the time stamps on the pressure and temperature data that are inconsistent with my opinion of when the probe actually landed. The ESA would have to retract these data for my own analysis of Huygens descent to carry any weight. I don't see that happening.

    I hope you can see my quandry: Space exploration is important to me. I will be the harshest critic up to the point that my opinions encourage critical analysis and are not harmful to the public dialogue. So I am focusing my attention on the Messinger mission and other evidence that may eventually be vindicating. Let's figure out what Titan is made out of, and whether Iapetus is white on black or black on white. Why is there iron all over the surface of Phoebe? There is much to learn.
    “It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.” ― Arthur Conan Doyle, Sherlock Holmes

  17. #1157
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    I don't remember seeing this posted yet.

    A View from Huygens - Jan. 14, 2005

    This movie was built with data collected during the 147-minute plunge through Titan's thick orange-brown atmosphere to a soft sandy riverbed by the European Space Agency's Huygens Descent Imager/Spectral Radiometer on Jan. 14, 2005,
    In 4 minutes and 40 seconds, the movie shows what the probe 'saw' within the few hours of the descent and the landing.

  18. #1158
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    Quote Originally Posted by Cassini weekly log
    Tuesday, Sept. 14 (DOY 257)

    At the Mission Planning Forum today the topic was the Titan-70 (T70) post flyby attitude control results and corresponding atmospheric density estimate. The T70 flyby on June 20, 2010, was the lowest altitude flyby of Titan ever performed by the Cassini spacecraft. The predicted set of two Z-facing thrusters had the highest activity among the thrusters, as expected. However, the duty cycles of these two thrusters were higher than expected, although well within available margins. Further analysis of the T70 data to explain the reason for the higher-than-expected thruster activities is still ongoing.
    Not Titan shattering news, but it fits the general pattern: Every time Cassini gets closer to Titan, the thrusters in the Z plane react more-than-predicted.
    “It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.” ― Arthur Conan Doyle, Sherlock Holmes

  19. #1159
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    Jerry

    Do not bring your ATM claims into this forum. You know the rules and routine.

    Thank You
    Rules For Posting To This Board
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  20. #1160
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    Quote Originally Posted by Jerry View Post
    Not Titan shattering news, but it fits the general pattern: Every time Cassini gets closer to Titan, the thrusters in the Z plane react more-than-predicted.
    It seems to me that the closer Cassini comes to Titan, the more spacecraft would encounter atmospheric drag and unexpected gravitational effects, such as MASCONs that affect the orbit of lunar probes. So, what is unusual about the thrusters reacting more than predicted?

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