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ISEE-3

ISEE-3 Is Not Exactly Where NASA Thought It Was

By Keith Cowing
NASA Watch
May 25, 2014
Filed under

ISEE-3 Reboot Project: Updates From the Front at Arecibo, Dennis Wingo
“The error in position has just elevated the concern level greatly. We know approximately what the offset error is from the existing ephemeris but we don’t have enough information yet to plot a new course and generate a new ephemeris file. This has become extremely important as there is a solid statistical chance that the spacecraft could impact the moon or even be off course enough to threaten other spacecraft in Earth orbit.”
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NASA Watch founder, Explorers Club Fellow, ex-NASA, Away Teams, Journalist, Space & Astrobiology, Lapsed climber.

10 responses to “ISEE-3 Is Not Exactly Where NASA Thought It Was”

  1. Todd Austin says:
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    What’s the lesson to be learned about the 250K-mile discrepancy?

    Any quick-and-dirty guesses as to possible causes?

    • Denniswingo says:
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      It is astonishing that it is ONLY 250,000 km. You have to understand that the last time a propulsive maneuver was done with this spacecraft was in 1986, a full 28 years ago.

      To me it is a testament to the abilities of the people involved that the error is as small as it is after that amount of time.

      The error is just slightly over 1 km/hour. That is a very good deal that far in the past… That is an error of about 0.005%

      We would not have even known the magnitude of the error without being here at Arecibo with its incredibly narrow beam width.

    • Hug Doug ✓ᵛᵉʳᶦᶠᶦᵉᵈ says:
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      the discrepancy is likely due primarily to the Yarkovsky effect and radiation pressure from the sun gently pushing on the probe. drag from the solar wind / interplanetary medium may also be a contributor.

      these three forces are difficult to model, so makes their effects on the orbits of objects in space very difficult to predict.

      as noted by Denniswingo, the accuracy of the predicted location of the probe is very, very good given the cumulative effect of 28 years of these forces.

    • Michael Spencer says:
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      At current distance just how wide is the beam? Did the guys have to fish around looking for the spacecraft? I suppose it was located with radar?

      Arecibo is a national treasure for sure.

      • Denniswingo says:
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        The beam width of the Arecibo radar is 2 arc minutes.

        🙂

        It was not too far off as it was still in the beam of the 21 meter dish at Morehead State University.

        Arecibo is a national treasure, but one that is in danger of being lost through inattention. The NSF should fully fund it as well as money is needed to maintain and upgrade the site. We are leaving equipment here as a donation for this fabulous place…

  2. Hug Doug ✓ᵛᵉʳᶦᶠᶦᵉᵈ says:
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    what the ISEE-3Reboot project has done so far alone is worth it. learning the current trajectory is definitely important if it might interfere with other satellites.

    keep up the good work, guys 🙂

  3. kcowing says:
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    Where the ISEE-3 spacecraft is right now has nothing whatsoever to do with what ISEE-3 Reboot Project has done. However, we are the only ones who can alter its trajectory.

  4. AgingWatcher says:
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    Best wishes for the project’s success! The team offered no guarantees of success — only that they’d make a good-faith, competent effort to revive the old satellite with the goal of making it available to the broader science community. However this turns out, it will have been worth the investment of time and donated funds.

  5. Denniswingo says:
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    Yep, lets us speed up the process by having the money to pay for it!

  6. Denniswingo says:
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    You need to do a bit of research. There was a tremendous amount of data that came from both cometary flybys. We are not proposing to send it back to one, but to return it to the task of looking at solar wind and the earth’s magnetosphere. If there are other satellites out there doing this already, why is NASA preparing three to do this in 2015 and another one at L1 that same year. Obviously there are not enough out there doing it now, and we have a plan to put the spacecraft into a very interesting place, where it will have much scientific value.

    Also, this will not be a PI led mission but one where all of the data will be open for students to process and evaluate…