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I Dawn dead in Ceres orbit, ran out of fuel Oct 2018

  1. Jan 5, 2016 #821

    marcus

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    Since we just turned a page I'll bring forward some stuff as a reminder of some of what we are watching:
    ==quote post#806==
    http://dawnblog.jpl.nasa.gov/2015/12/31/dawn-journal-december-31/

    DECEMBER DAWN JOURNAL IS OUT!

    This journal entry is unusually visually rich with many stunning and fascinating images of Ceres' surface. Do check it out!
    But it also has this about the GRaND data being taken:
    ==quote Rayman==
    ...
    With the spacecraft this close to the ground, it can measure two kinds of nuclear radiation that come from as much as a yard (meter) deep. The radiation carries the signatures of the atoms there, allowing scientists to inventory some of the key chemical elements of geological interest. One component of this radiation is gamma ray photons, a high energy form of electromagnetic radiation with a frequency beyond visible light, beyond ultraviolet, even beyond X-rays. Neutrons in the radiation are entirely different from gamma rays. They are particles usually found in the nuclei of atoms (for those of you who happen to look there). Indeed, outweighing protons, and outnumbering them in most kinds of atoms, they constitute most of the mass of atoms other than hydrogen in Ceres (and everywhere else in the universe, including in your correspondent).

    To tell us what members of the periodic table of the elements are present, Dawn’s gamma ray and neutron detector (GRaND) does more than detect those two kinds of radiation. Despite its name, GRaND is not at all pretentious, but its capabilities are quite impressive. Consisting of 21 sensors, the device measures the energy of each gamma ray photon and of each neutron. (That doesn’t lend itself to as engaging an acronym.) It is these gamma ray spectra and neutron spectra that reveal the identities of the atomic species in the ground.

    Some of the gamma rays are produced by radioactive elements, but most of them and the neutrons are generated as byproducts of cosmic rays impinging on Ceres. Space is pervaded by cosmic radiation, composed of a variety of subatomic particles that originate outside our solar system. Earth’s atmosphere and magnetic field protect the surface (and those who dwell there) from cosmic rays, but Ceres lacks such defenses. The cosmic rays interact with nuclei of atoms, and some of the gamma rays and neutrons that are released escape back into space where they are intercepted by GRaND on the orbiting Dawn.
    ==endquote==

    It also has the latest word on the BRIGHT SPOTS on some of the crater floors. They are not pure white, many have a slight blueish tinge. The best known, the Occator crater spots, have a faint reddish tinge. It might take an instrument more sensitive than the human eye to detect this--we might say it was just some tone of white. But the variation in color gives clues as to what salts are there. Rayman discusses this and how the spots might have formed. Magnesium sulfate (a compound somewhat akin to "epsom salts") is considered as a likely candidate.

    Rayman also discussed the indicated presence of AMMONIA-BEARING minerals on Ceres' surface. Ammoniated clays---this was not expected and is very interesting. Also an important advantage is Ceres ever becomes a site for habitation and chemical industry.

    Things seem to be going OK. This is a great mission! The targets (especially Ceres) and the solar powered ion propulsion technology were forward looking. I was worried Dawn might not make it down to this final nearest orbit and am very glad it seems so far to be operating as planned.
    ==endquote==

    There is an interesting interactive page of graphics that explains in part how the GRaND instrument aboard Dawn is able to give numerical estimates or in some cases lower limits on the abundances of a dozen or so elements in Ceres surface material. This was discussed some in post#801, which gave a link.
     
    Last edited: Jan 5, 2016
  2. Jan 8, 2016 #822

    marcus

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    New update from Marc Rayman
    ==quote==
    January 8, 2016 -Dawn to Perform Small Orbit Maintenance Maneuvers

    After devoting much of the week to observing Ceres, Dawn will execute a pair of burns with its ion engine today to modify its orbit. Starting a little after 1:00 PM, the ship will thrust for less than two hours, wait about six hours as it continues to revolve around Ceres and then thrust again for less than two hours, finishing around 11:00 PM. With its uniquely efficient and gentle ion engine, these small orbit maintenance maneuvers will keep the explorers' orbital motion aligned with the plan the flight team has devised for systematically studying the alien world from this low orbital altitude of 240 miles (385 kilometers). Dawn will spend most of the weekend sending its pictures and other data to Earth. When it has finished on the morning of Jan. 10, it will begin collecting still more data.
    ==endquote==
    Here's the interactive graphic you get (after a brief animation) when you click on
    http://www.jpl.nasa.gov/dawn/swf/GRAND/Grand_animation.swf
    SSGRanD.png
    There are 10 or more pop-up explanatory messages (little essays) you get
    e.g by hovering over any of the green text:
    Fast neutrons
    Thermal and epithermal...
    Gamma rays
    or e.g. from the numbered blue dots 1 thru 5:
    Natural radioactivity
    Moderation
    Neutron capture
    Inelastic collision
    or by clicking on one of the yellow dots:
    Overview
    dot #6
    dot #7
    But what I put here is not interactive, it is just a screen shot of what you see when you click on the above link.
    ===================
    Going by Rayman's update the orbit adjustment maneuver was completed 11PM pacific on 8 Jan. Then data transmission, to be completed by morning of 10 Jan, when the probe resumes observation.
     
    Last edited: Jan 9, 2016
  3. Jan 12, 2016 #823

    marcus

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    January 11, 2016 -Dawn Hard at Work Observing Ceres

    After completing its orbit maintenance maneuver on Jan. 8, Dawn spent much of the weekend with its main antenna aimed at Earth as it revolved around Ceres, beaming its latest data to NASA's Deep Space Network. Then around 9:00 AM PST on Jan. 10, the spacecraft turned to point its science instruments at the ground beneath it and resumed its program of observations of the dwarf planet. It will continue until 7:00 PM PST on Jan. 13, when it is scheduled once again to start transmitting the precious measurements stored in its memory.
     
  4. Jan 15, 2016 #824

    marcus

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    Good news about the reaction wheels and hydrazine usage!

    ==quote==
    January 15, 2016 -Dawn Maintaining its Productive Pace

    Dawn used its main antenna for about 26 hours on Jan. 13 and 14 to transmit a wealth of data to Earth. Now the spacecraft is taking more photographs and other scientific measurements while orbiting about 240 miles (385 kilometers) above Ceres’ surface.

    Dawn is healthy and continuing to operate smoothly. The two reaction wheels that were activated on Dec. 14 have been functioning well, and the consumption of hydrazine propellant (used in combination with the reaction wheels to control the probe's orientation) is very good.
    ==endquote==
    http://dawn.jpl.nasa.gov/mission/status.html

    Simview seems to have started up again

    [EDIT: for example
    19 Jan 17:51 UTC 42º to Npole, 360.16 km
    19 Jan 18:15 UTC 10º to Npole, 356.72 km
    20 Jan 21:08 UTC 42º to Npole, 359.31 km
    20 Jan 21:32 UTC 12º to Npole, 356.46 km
    20 Jan 21:56 UTC 16º from Npole, 357.01 km
    21 Jan 02:41 UTC 40º to Npole, 357.53 km]
     
    Last edited: Jan 20, 2016
  5. Jan 16, 2016 #825
    Still no news about Occator?
     
  6. Jan 16, 2016 #826

    marcus

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    A consensus seems to have developed that the bright spots in the crater floors are salt (not, for example, ice).
    Based on optical and IR spectroscopy one prominent guess is magnesium sulfate.
    There are differences in the spectra imperceptible to human eye---e.g. two spots might look white to us, or the same gray tone, but one have a slight reddish tinge and the other a bluish tinge which the instrument could detect.

    Occator bright spots are faintly reddish while many of the others are bluish.

    I would say there has been no news since the Dawn Journal of 31 December. And the chemical composition (and origin) of the bright spots are unsolved puzzles.
    About all people agree on, for now, is salt .

    Significantly, a lot of GRaND data has been taken and transmitted (gammaray and neutron spectral data) but so far no preliminary report on this released.
    http://dawnblog.jpl.nasa.gov/2015/12/31/dawn-journal-december-31/
     
  7. Jan 19, 2016 #827

    marcus

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    http://dawn.jpl.nasa.gov/mission/status.html
    ==quote==
    January 19, 2016 -Dawn About to Resume Observing Ceres

    The spacecraft spent the weekend filling its computer memory with more Ceres data, and it has been sending those findings to NASA's Deep Space Network since yesterday morning. Shortly after noon PST today, it will resume its observations.

    Meanwhile, the flight team is using the latest navigational measurements to determine Dawn's orbit very accurately and calculate what it will be for the next few weeks. Based on these and other analyses, the mission director will decide tomorrow whether Dawn should perform an orbit maintenance maneuver. If so, mission planners already have windows in Dawn's intricate schedule on Jan. 23-24 and Jan. 31-Feb. 1. (Orbit maintenance maneuvers in this low altitude orbit are always done in pairs separated by about eight days.)
    ==endquote==
     
    Last edited: Jan 20, 2016
  8. Jan 21, 2016 #828

    marcus

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    a new status update
    ==quote==
    January 21, 2016 -Dawn Collecting Data with Good Orbital Accuracy

    Dawn remains healthy and productive, taking photos and spectra of Ceres. It will continue doing so until Jan. 22, when it is scheduled to transmit more of its precious data to Earth.

    The spacecraft's orbit around the dwarf planet is close enough to what mission planners had specified for this period that it is not necessary to perform the pair of orbit maintenance maneuvers described in the Jan. 19 mission status update. Instead, the spacecraft will continue pointing its sensors at Ceres during the windows that were scheduled for the maneuvers. The next decision on whether to perform orbit maintenance maneuvers will be in three weeks.
    ==endquote==

    Incidental check on the simulation:
    [22 Jan 00:50 UTC, 12º to N pole, 356.50 km
    22 Jan 17:38 UTC, 16º from N pole, 358.71 km]
    Checking at DSN as of 22 Jan 10am pacific, the data transmission planned for today hasn't started yet,
    so far just the usual 10 bit per second tracking signal (to Madrid#55)
     
    Last edited: Jan 22, 2016
  9. Jan 26, 2016 #829

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    ==Rayman seems to be in a mood to take stock==
    January 25, 2016 -Dawn's High Resolution Observations Continue

    After concluding its telecommunications session on Jan. 23, Dawn brought Ceres back into its sights. It has been collecting more data since then as it circles the dwarf planet at an average altitude of 240 miles (385 kilometers).

    One year ago today, the spacecraft was 147,000 miles (237,000 kilometers) from Ceres, using its ion engine to approach the alien world. Later in the day, it took its second set of pictures to navigate to the uncharted destination. Those were its photos to surpass the resolution provided by the Hubble Space Telescope. Now Dawn's sharp pictures show about 830 times the detail that Hubble's images revealed. The Jan. 29, 2015, Dawn Journal described the navigation pictures and even looked ahead to the improvement we would achieve in the current low altitude orbit. The last year has been a fantastic period of discovery.
    ==endquote==

    Data transmission seems to proceed, roughly speaking, on a 4 and 1/2 day cycle. For instance the 21 Jan update mentioned:
    "... taking photos and spectra of Ceres. It will continue doing so until Jan. 22, when it is scheduled to transmit more of its precious data to Earth."
    Transmission takes about 26 hours so would have lasted for a fair chunk of 22 and 23 Jan. We can guess the next telecommunication session is happening some 4 and 1/2 days later--- 27 Jan which is today. I just checked DSN and it showed Dawn transmitting to Goldstone at 125 kilobit per second. (2:45 pm pacific)

    [Update: as of 12:20 pm pacific 28 Jan, still transmitting data---62.5 kilobit per second.]
    [Update: as of 6:50 pm pacific 28 Jan, no transmission.]
     
    Last edited: Jan 28, 2016
  10. Jan 29, 2016 #830
    Still Occator is strangely neglected (although the bright spots are one of the strangest features encountered in the Solar System, so far).
     
  11. Feb 1, 2016 #831

    marcus

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  12. Feb 1, 2016 #832

    OmCheeto

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    I made a prediction about a month ago, regarding when we would see the new images of Occator:

    Unfortunately, I didn't start following Dawn until it was approaching Ceres, and missed the entire Vesta portion of the adventure, and wasn't aware of the ratio of image collection time to data transmission time. I was going to ask Marc about it, but decided he would think I was just being lazy, not wanting to go over the Vesta era journals.

    But in his typical; "I wonder what OmCheeto is going to ask me next" fashion, he answered both of my questions:

    Now, my "15 days" may not look very close to Dr. Rayman's "six weeks", but I left out the fact that "15 days" would be "best case", for impatient people, like me and you.

    Marcus, is it my imagination, or was it not the original plan that Dawn would do 3 complete surveys over six months?
     
  13. Feb 1, 2016 #833

    mfb

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    The new Dawn journal has a new animation of Occator.

    There is no guarantee that we get close-up images as soon as they are available. The scientists involved in the mission have a strong interest in publications about it - before anyone else writes them. If the images show something really surprising, we'll probably have to wait a bit.
     
  14. Feb 2, 2016 #834

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    nothing special, it seems
    ===status update for 1 Feb===

    February 1, 2016 -Dawn Mapping Proceeds Flawlessly

    Dawn continues to operate flawlessly in its final mapping orbit around Ceres. The spacecraft is pointing its main antenna at Earth today, transmitting its latest pictures and other data. It will resume its observations tomorrow shortly before 10:00 AM PST.

    The latest Dawn Journal describes some of the measurements Dawn is making to reveal the nature of the first dwarf planet discovered.

    ==endquote==
    just business as usual.

    It would be great to get some preliminary results from the GRaND instrument package on the chemistry of surface material. I can't believe they don't have some results already, that they could share.

    This may relate to what Mfb just said. Observations, whether imagery (revealing geological and surface history) or gammaray spectroscopy (revealing chemical composition) may not be published immediately so as to first give scientists time to study them and draw conclusions.
     
    Last edited: Feb 2, 2016
  15. Feb 3, 2016 #835
    So NASA is holding back information in order for scientists to publish their findings. Well, I'm tired of waiting for them to upload images of the spots. As I have already noticed, they have heavily photoshopped Occator imagery, and I think that in the process something went wrong and they erased important portions of the images. Now they are in LAMO but not a single photo of Occator has emerged so far. Well, someday someone will find out what has really happened.
     
  16. Feb 3, 2016 #836

    mfb

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    I would phrase it differently: they do not release all their raw data to the public immediately. Which is completely sensible. Raw data needs to be analyzed properly for scientific conclusions.
     
  17. Feb 5, 2016 #837

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    Rayman nicely addressed some of our concerns (which may well be more widespread.)
    ==new status update==
    February 5, 2016 -Dawn Seeing More and More of Ceres

    Dawn is gathering more Ceres data, circling the dwarf planet every 5.4 hours with its combined gamma ray and neutron detector, infrared mapping spectrometer and camera pointed at the landscapes beneath it. Meanwhile, it is transmitting a broad radio signal through one of its auxiliary antennas so we can track its orbital motion to improve measurements of Ceres' gravity field. Shortly after 9:00 PM PST today, the spacecraft will begin sending its results through its main antenna to Earth.

    Dawn has photographed about 90% of Ceres from this low altitude orbit. Many people who share our fascination with that distant alien world ask about new pictures of the famous bright area (or famously bright area) at the center of Occator crater, but Dawn has not observed it yet. That is just the way the orbit has worked out. Mission planners did not design the orbit or the schedule of observations and telecommunications to view any specific targets. Rather, as mentioned in the January Dawn Journal, the team designed them so that over the course of six weeks, the probe would see most of the surface. As we will see in the February Dawn Journal, the first few weeks of LAMO don't contribute to this pattern, so the beginning of the six week period was January 10. By simple coincidence, Dawn will not have the opportunity to see Occator until the very end of that period. Therefore, we all wait patiently. After Occator is photographed, the standard process for releasing images will be followed. The need for accuracy and scientific review of the data sometimes slows the release of some products, but all of the data are released to the public after the science team has performed the necessary analysis and interpretation for scientific publication. It will be worth the wait!
    ==endquote==

    "I think that in the process something went wrong and they erased important portions of the images."
    I haven't noticed. Not sure I understand, could you give examples? It's easy to attach images to a post, which would show what you mean.

    I did see that the the large bright spots became more "spotty" as the pixel size shrank down. To be expected. Also as they adjusted the contrast this changes the upper limit of gray-tone levels that "pin the needle" and go over the top---i.e. can no longer register as a gray tone and has to come across as blank white. So the big blank blobs broke up into a more complex pattern of small pixels.

    This seems straightforward, please correct me if I'm misinterpreting or wrong about some of this.
     
    Last edited: Feb 5, 2016
  18. Feb 5, 2016 #838

    OmCheeto

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    I'm actually more interested in seeing Ahuna Mons.
    I should send Marc a nasty email about that, asking what they are hiding..... :biggrin::oldwink:
     
  19. Feb 8, 2016 #839

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    ==Marc replied in a dignified and not especially informative manner==

    February 8, 2016 -Dawn Continuing to Study Ceres

    Aiming its suite of sophisticated sensors at the ground below, Dawn is orbiting closer to Ceres than the International Space Station is to Earth. The explorer is healthy and continuing to perform all of its duties.
    ==endquote==

    I guess we should be thankful the probe is continuing taking all its readings according to plan. For me, this close-in final orbit is what it's all about and I just hope it can keep it up for several more months.
     
  20. Feb 21, 2016 #840

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    ===new update from Rayman===
    February 19, 2016 -Dawn Maintaining Productive Pace of Operations

    Dawn has been collecting more data on Ceres this week with its camera and spectrometers, and all systems are working well. It will begin transmitting the results to Earth shortly before 1:00 PM PST today. The probe will resume observing Ceres a little after 4:00 PM tomorrow.
    =====
    So regular observations resumed 4 PM on 20 Feb. Sometime later when convenient I checked DSN (deep space network) and data transmission had ended. Dawn was transmitting a simple tracking signal, 10 bits per second. (for comparison, Dawn's data usually comes in around 125 kilobits per second)
     
    Last edited: Feb 21, 2016
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