Shape model of asteroid Didymos and its moon or satellite called Dimorphos. Tonight, the NASA DART spacecraft will attempt to slam into Dimorphos to slightly alter the satellite's orbit in the first test to deflect the orbit of an asteroid. If this test is successful, this will be provide information on the best way to deflect a larger asteroid that may impact Earth sometime in the future. (Image Sources: NASA, Wikipedia.org, By NASA/Naidu et al., AIDA Workshop, 2016 - https://www.nasa.gov/planetarydefense/darthttps://www.nasa.gov/sites/default/files/thumbnails/image/screen_shot_2017-06-30_at_12.03.56_pm.png, Public Domain, https://commons.wikimedia.org/w/index.php?curid=90615158)
By Glenn A. Walsh
Reporting for SpaceWatchtower
Tonight (2022 September 26), a NASA spacecraft named DART will make the first attempt to alter the orbit of a small asteroid. This attempt, which will be live-streamed by NASA, if successful, could lead to information on how to deflect a larger asteroid that could possibly hit the Earth sometime in the future.
The asteroid to be deflected in this test, actually a moon or satellite of a larger asteroid, is named Dimorphos. Neither Dimorphos, nor the larger asteroid Didymos, has any risk of hitting the Earth in the future.
NASA will provide live-stream coverage of this deflection test, on NASA-TV, tonight beginning at 5:30 p.m. Eastern Daylight Saving Time (EDT) / 21:30 Coordinated Universal Time (UTC), Friday Evening, 2022 September 26; the actual deflection test is expected to take place at 7:14 p.m. EDT / 23:14 UTC.
This coverage includes a news briefing that evening, from the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland, at 6:00 p.m. EDT / 22:00 UTC. Another media briefing will occur shortly after the asteroid impact occurs, at September 26, 8:00 p.m. EDT / September 27, 0:00 UTC. During the hour before impact occurs, DART will send images back to Earth at a rate of one image per second, “as Dimorphos grows from a point of light to an object that fills the entire camera frame”, according to a news release issued by The Planetary Society.
Internet link to LIVE-STREAM coverage of this event on NASA-TV can be found near the end of this blog-post.
NASA's DART spacecraft, which is an acronym for Double Asteroid Redirection Test, was launched from Earth, using a SpaceX Falcon 9 rocket, on 2021 November 24. It will slam into Dimorphos at a speed of about 14,000 miles-per-hour / 22,500 kilometers-per-hour. It is expected that the impact of DART on Dimorphos will slightly alter the orbit of Dimorphos around Didymos.
DART's sole instrument on-board is the Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO), which will only be used for coverage of the impact. The weight of this spacecraft: 1,345 pounds / 610 kilograms at launch and 1,210 pounds / 550 kilograms pounds at time of impact.
According to NASA, the mission of DART: “This test will show a spacecraft can autonomously navigate to a target asteroid and intentionally collide with it to change the asteroid’s motion in a way that can be measured using ground-based telescopes. DART will provide important data to help better prepare for an asteroid that might pose an impact hazard to Earth, should one ever be discovered.”
According to the mission overview, regarding proposed relevance to a larger asteroid heading for a collision with the Earth, by the Johns Hopkins University Applied Physics Laboratory, "Mostly, what we're looking to do is change the speed of the incoming object by a centimeter per second or so. That's not very fast, but if you do it enough seconds in advance, you can cause it to miss the Earth entirely."
This technique, to influence the orbit of a celestial object, is known as "deflection by kinetic impactor.
There are several ways to confirm a successful mission.
Several astronomical observatories around the world will train their telescopes to determine the outcome of the impact event. This includes the Lowell Discovery Telescope in Arizona, the Las Campanas Observatory in Chile, the Las Cumbres Observatory global network, and the Magdalena Ridge Observatory in New Mexico.
A CubeSat, a miniature satellite deployed by DART before the impact event, will also observe the event and send data back to NASA regarding the result. Called LICIACUBE (Light Italian CubeSat for Imaging of Asteroids), it was deployed from DART about 10 days ago. From a distance of about 31 statute miles / 50 kilometers, LICIACUBE will be looking for the actual impact of DART on Dimorphos, the plume the impact generates, and possibly the impact crater. LICIACUBE can only communicate with Earth using slow data rates, so it could be days or weeks before scientists get the chance to view LICIACUBE images.
In 2026, the European Space Agency (ESA) space probe, Hera, will visit the Didymos / Dimorphos asteroid system to evaluate the type of crater created when DART hit Dimorphos. To be launched in 2024, Hera will evaluate the impact using a laser altimeter that will create 3-D maps and an infrared camera to determine the asteroid’s temperature and surface properties. Hera will deploy two of its own CubeSats, as well as Hera landing on Dimorphos and, possibly, Didymos.
One way scientists will evaluate the impact will be determining any change in the revolution time of Dimorphos around Didymos. Presently, it takes about 11.9 hours for Dimorphos to complete one orbit around Didymos; Scientists expect that this revolution time should be reduced to 11.8 hours by the DART impact. Also, Dimorphos should end-up a little closer to Didymos after the impact. If this happens, this will be one strong piece of evidence showing that the deflection test was a success.
NASA's Planetary Defense Program spent $324.5 million on DART. This includes $308 million for the spacecraft, $68.8 million for launch services, and $16.5 million on operations and data analysis.
LIVE-STREAM Internet Coverage of DART Mission, from NASA-TV:
Link >>> https://www.nasa.gov/nasalive
Internet Links to Additional Information ---
Link 1 >>> https://www.nasa.gov/planetarydefense/dart/dart-news
Link 2 >>> https://www.planetary.org/articles/dart-impact-what-to-expect
Link 3 >>> https://en.wikipedia.org/wiki/Double_Asteroid_Redirection_Test
Link 4 >>> https://www.cnet.com/science/nasa-will-crash-the-dart-probe-into-an-asteroid-on-monday-what-to-know/
Dimorphos: Link >>> https://en.wikipedia.org/wiki/Dimorphos
Didymos: Link >>> https://en.wikipedia.org/wiki/65803_Didymos
Related Blog-Post ---
"Scientists Plan for Asteroid Deflection Mission." Mon., 2013 April 15.
Link >>> http://spacewatchtower.blogspot.com/2013/04/scientists-plan-for-asteroid-deflection.html
Source: Glenn A. Walsh Reporting for SpaceWatchtower, a project of Friends of the Zeiss
Monday, 2022 September 26.
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