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The NASA spacecraft DART will impact the small companion of asteroid 65803 Didymos at 23:14 UTC on Monday, 2022 September 26. The spacecraft mass is around 550kg and it will hit the target at 6.6 km/s. The mass of the companion, Dimorphos, is around 5 x 10^9 kg so the change in velocity will be around 1 mm/s. This should change the moon’s orbital period around Didymos by an amount which should be detectable over time. Not quite Bruce Willis though.
At the time of the impact the asteroid will be high in the sky as seen from Australia so the NASA DSN station at Canberra, ACT, and the ESA DSA station at New Norcia, WA, will be receiving the stream of images from the DRACO camera on DART. These should be decoded in real time as they arrive on the earth. The distance from earth at impact is 11.3 million km so the one-way light time is only 38s.
There is a nice write-up of the ESA contribution here:
It is unlikely that the impact will be detectable from earth but a number of telescopes will be looking.
NASA TV will be presenting live coverage from 6pm Eastern U.S time, which (I think) equates to 11pm BST.
Amateur and professional astronomers in the southern hemisphere have been asked to obtain photometry of the Didymos+Dimorphos system
https://groups.io/g/IOTAoccultations/message/72575
Alex.
That was fun to watch last night and the last image few images showed a huge amount of detail on Dimorphos. It looks like quite a few people, including some using small telescopes, detected the impact flash and subsequent dust cloud. I’m quite surprised how prominent the impact was from Earth although a quick calculation shows that the spacecraft kinetic energy was around 12GJ, so approx. the equivalent of 3t of TNT.
We almost take for granted the amazing guidance and control systems required to hit a celestial bullseye at those high velocities – and that the camera will be set to the correct ‘shutter speed and f-stop’.
https://www.nasa.gov/feature/dart-s-final-images-prior-to-impact
Looking forward to seeing the images from the CubeSat which was also monitoring the impact!
Alex.
It was fun to watch and some of those observing from the ground did quite well too…
https://twitter.com/fallingstarIfA/status/1574583529731670021?s=20&t=bSNlZJgGJmZCFPEEcFqEvA
3 tonnes of TNT appears to have made a pretty impressive cloud of debris.
It was fun to watch and some of those observing from the ground did quite well too…
https://twitter.com/fallingstarIfA/status/1574583529731670021?s=20&t=bSNlZJgGJmZCFPEEcFqEvA
3 tonnes of TNT appears to have made a pretty impressive cloud of debris.
Well, it is (or was) a loosely bound rubble pile according to the images returned so perhaps it is not too surprising that a lot of rubble was thrown out.
It is interesting that the velocity change is larger than would be expected and it appears that much of the momentum change came from ejecta rather than the spacecraft. That is something specific to rubble-pile objects I guess. A solid object would produce far less ejecta.
Hi Nick,
Yes, it’s likely that a body with higher density or cohesive strength would be far less affected. The NASA news release says:
“The recoil from this blast of debris substantially enhanced DART’s push against Dimorphos – a little like a jet of air streaming out of a balloon sends the balloon in the opposite direction. To successfully understand the effect of the recoil from the ejecta, more information on of the asteroid’s physical properties, such as the characteristics of its surface, and how strong or weak it is, is needed. These issues are still being investigated.”
We still need to wear our tin hats…
Alex.
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