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Thread: Double Asteroid Redirection Test : How much will the impact alter the orbit of Dimorphos?!

  1. #1 Double Asteroid Redirection Test : How much will the impact alter the orbit of Dimorphos?! 
    Forum Ph.D. Double Helix's Avatar
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    The DART mission has blasted off, sending an "impact spacecraft" to a binary asteroid system (1). The mission is designed to determine if we can alter the movements of an asteroid, at least those large enough to cause severe damage to earth.

    The target, Dimorphos, itself orbits a larger asteroid, Didymos, with a period of about 12 hours. That is the reason this particular target was chosen, since ground-based telescopes should be able to measure any significant change in the target's orbital period.

    According to The Johns Hopkins University Applied Physics Laboratory website (2), the DART impactor will be hitting Dimorphos head-on at a speed of ca. 6.6 km/s (15,000 mph). The impactor weighs about 550 kg, and the target weighs in at about 4.8 billion kg (3). This is quite a significant difference, but the impact is expected to decrease the orbital period of Dimorphos by about 10 minutes.

    Any asteroid-physics freaks out there who might care to guess about the accuracy of such an estimate? Is it possible that the magnitude of any change in the orbit may depend in part on the nature of the target? A pile of rubble, or a really hard target, might result in a different change in orbital time. It would seem that ejecta (more or less) from the impact could cause a variance to the orbital dynamics as momentum from the impact imparted to the target would be different.

    In any event, the predicted result seems like a bit of a WAG, at least to some of us.


    "Nasa Dart asteroid spacecraft: Mission to smash into Dimorphos space rock launches"

    (1) https://www.bbc.com/news/science-environment-59327293


    "Impactor Spacecraft"

    (2) https://dart.jhuapl.edu/Mission/Impactor-Spacecraft.php


    "Double Asteroid Redirection Test "

    (3) https://nssdc.gsfc.nasa.gov/nmc/spac...action?id=DART


    Last edited by Double Helix; November 25th, 2021 at 11:37 AM.
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    Time Lord Paleoichneum's Avatar
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    Just a random thought, could you please work on providing much more concise short post titles? As they currently are, there often is very little way to tell what the topic is since its cut off by the character display max


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    Forum Ph.D. Double Helix's Avatar
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    Quote Originally Posted by Paleoichneum View Post
    Just a random thought, could you please work on providing much more concise short post titles? As they currently are, there often is very little way to tell what the topic is since its cut off by the character display max

    The topics are often specific and the titles provide an immediate point to the thread. Concise responses to the issues posted is the main reason.

    Will try my best at your suggestion of brevity.

    Commentary beyond the titles would also be appreciated.
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  5. #4  
    Forum Ph.D. Double Helix's Avatar
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    The impact spacecraft for the DART mission is going to hit Dimorphos soon.

    See the details below on BBC's Sky at Night Magazine.


    "NASA's DART: The mission to crash into an asteroid"

    https://www.skyatnightmagazine.com/s...-dart-mission/
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  6. #5  
    Forum Ph.D. Double Helix's Avatar
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    The DART impact is today - 26 September, 2022 at ca. 7:14 p.m. EDT.

    Johns Hopkins University has a website where you can follow the impact event live*.




    "Double Asteroid Redirection Test"

    * https://dart.jhuapl.edu/
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    Forum Ph.D. Double Helix's Avatar
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    Various telescopes have provided images of the impact of the DART spacecraft with an asteroid. Two sets from the Hubble and Webb instruments are shown in two links below (1,2).

    A "motion picture" was captured by an ATLAS telescope, providing a dynamic view of the impact, which is quite impressive (3). Hopefully we will get more detailed videos of this from larger telescopes.



    "Space telescopes capture asteroid slam with striking clarity"

    1. https://apnews.com/article/nasa-aste...3f93a941701e03


    "Webb, Hubble Capture Detailed Views of DART Impact"

    2. https://www.nasa.gov/feature/goddard...of-dart-impact


    "Atlas telescope captures Dart asteroid crash"

    3. https://www.bbc.com/news/av/science-...nment-63053138
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    Since the purpose of the crash was to see if the orbit of even a miniscule planetary body can be altered in that way, when is the data regarding success or failure expected, do you have any information?
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    Moderator Moderator Janus's Avatar
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    Quote Originally Posted by Guitarist View Post
    Since the purpose of the crash was to see if the orbit of even a miniscule planetary body can be altered in that way, when is the data regarding success or failure expected, do you have any information?
    My understanding Is that they will observe the pair with telescopes for about a week. This is enough time to view multiple orbits of the smaller body and determine how much its orbital period has changed, which, in turn, will show how much of an effect the impact had.
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    Forum Ph.D. Double Helix's Avatar
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    Quote Originally Posted by Janus View Post
    Quote Originally Posted by Guitarist View Post
    Since the purpose of the crash was to see if the orbit of even a miniscule planetary body can be altered in that way, when is the data regarding success or failure expected, do you have any information?
    My understanding Is that they will observe the pair with telescopes for about a week. This is enough time to view multiple orbits of the smaller body and determine how much its orbital period has changed, which, in turn, will show how much of an effect the impact had.
    The impact is expected to slow Dimorphos enough for it to adopt a shorter orbital period around Didymos. This is best described in the first BBC article in this thread*.

    Scroll down to the illustration showing the details of the double asteroid system, and how the impact will change the target's orbit.

    Quoting from that article:

    "A binary is the perfect natural laboratory for such a test. The impact should change Dimorphos' orbit around Didymos by roughly 1%, a change that can be detected by ground telescopes in weeks or months."

    end quote

    Judging from the plume of ejecta, there should be a significant enough change in the orbital period to determine the effectiveness of the impact. It is expected to decrease the period by 15-30 minutes, or so. The text in that article provides more details for this aspect of the impact.



    "Nasa Dart asteroid spacecraft: Mission to smash into Dimorphos space rock launches"

    * https://www.bbc.com/news/science-environment-59327293
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    Thankyou both. I wonder if, knowing 1) the momentum of this craft, 2) the momentum of this asteroid and 3) the orbital deviation acheived, one could calculate the size of a craft that could literally save the planet from something larger than this toddler.
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  12. #11  
    Forum Ph.D. Double Helix's Avatar
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    NASA has confirmed that the orbit of Dimorphos has been modified by the DART impactor (1). Using various Earth and space-based telescopes, the orbit of the target was changed from 11 hours and 55 minutes to 11 hours and 23 minutes. The decrease of 32 minutes is quite significant, and was within the range of that predicted - 10-35 minutes.

    So this little spacecraft had a significant impact, so to say, on the orbital period of the target. Some believe this technology will eventually save Earth from a killer asteroid or comet. But of course that will depend on how big it is, its speed, and how much advance warning we will have. If it is a near-earth asteroid not yet found, it might provide enough time to build the appropriate vehicle and launch it to prevent an impact. But if it is a long-period comet, like Hale-Bopp, which was ca. 60 km in diameter, it is very unlikely that humans could do anything to prevent our demise.

    It is significant to appreciate that nobody is going to build a standby system since it makes no sense to construct one until the size and speed of the object is well established. Despite the success of this mission, stopping a significant body from hitting Earth seems like a bit of a long shot. Fortunately the odds are against a major impact which could wipe us out any time soon (2). However, it is very likely to happen at some time in the future, assuming humans haven't done the job on themselves in the interim. And they are feverishly working away at it right now.


    "Nasa's Dart spacecraft 'changed path of asteroid'"

    1. https://www.bbc.com/news/science-environment-63221577


    "Impact: Earth - Killer Asteroids"

    2. https://www.killerasteroids.org/impact.php
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