With Its Single 'Eye,' NASA's DART Returns First Images From Space (phys.org) 7
Just two weeks after launching from Vandenberg Space Force Base in California, NASA's Double Asteroid Redirection Test (DART) spacecraft has opened its "eye" and returned its first images from space -- a major operational milestone for the spacecraft and DART team. Phys.Org reports: After the violent vibrations of launch and the extreme temperature shift to minus 80 degrees C in space, scientists and engineers at the mission operations center at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, held their breath in anticipation. Because components of the spacecraft's telescopic instrument are sensitive to movements as small as 5 millionths of a meter, even a tiny shift of something in the instrument could be very serious. On Tuesday, Dec. 7, the spacecraft popped open the circular door covering the aperture of its DRACO telescopic camera and, to everyone's glee, streamed back the first image of its surrounding environment. Taken about 2 million miles (11 light seconds) from Earth -- very close, astronomically speaking -- the image shows about a dozen stars, crystal-clear and sharp against the black backdrop of space, near where the constellations Perseus, Aries and Taurus intersect.
The DART navigation team at NASA's Jet Propulsion Laboratory in California used the stars in the image to determine precisely how DRACO was oriented, providing the first measurements of how the camera is pointed relative to the spacecraft. With those measurements in hand, the DART team could accurately move the spacecraft to point DRACO at objects of interest, such as Messier 38 (M38), also known as the Starfish Cluster, that DART captured in another image on Dec. 10. Located in the constellation Auriga, the cluster of stars lies some 4,200 light years from Earth. Intentionally capturing images with many stars like M38 helps the team characterize optical imperfections in the images as well as calibrate how absolutely bright an object is -- all important details for accurate measurements when DRACO starts imaging the spacecraft's destination, the binary asteroid system Didymos.
The DART navigation team at NASA's Jet Propulsion Laboratory in California used the stars in the image to determine precisely how DRACO was oriented, providing the first measurements of how the camera is pointed relative to the spacecraft. With those measurements in hand, the DART team could accurately move the spacecraft to point DRACO at objects of interest, such as Messier 38 (M38), also known as the Starfish Cluster, that DART captured in another image on Dec. 10. Located in the constellation Auriga, the cluster of stars lies some 4,200 light years from Earth. Intentionally capturing images with many stars like M38 helps the team characterize optical imperfections in the images as well as calibrate how absolutely bright an object is -- all important details for accurate measurements when DRACO starts imaging the spacecraft's destination, the binary asteroid system Didymos.
Bug on the windsheild (Score:2)
DART - hitting a 4.8 billion kg asteroid with a 500 kg satellite moving at 6.6 km/s to see if it will wobble. It will be interesting to see if the orbit changes over time.
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If you believe everything you read, you shouldn't read.
Re: (Score:3)
"bug on a windshield" is a bad analogy because this is space where nothing is pushing off of anything.
A better analogy would be a bowling ball falling out of the sky (without any friction) and seeing if shooting it with a BB gun will change where it impacts. If the impact is even a micrometer different then it's a success.
Re: Bug on the windsheild (Score:5, Informative)
For a numerical reference, I'm calculating Dimorphos' orbital velocity to be 0.17 m/s, and with a mass of 5e9 kg, that's a momentum of 8.7e8 kg-m/s. Dart's velocity on impact will be 6600 m/s, with a mass of 500 kg, so a momentum of 3.3e6 kg-m/s. Assuming full momentum transfer and Dimorphos stays intact, thats a momentum change of ~0.4%. Not huge but more than a bug on a windshield (if a bug on your windshield changed your momentum by 0.4% at highway speed, I suspect you'd need a new windshield). Incidentally the kinetic energy of Dimorphos is 73 MJ while the kinetic energy of Dart is 11,000 MJ.
Estimates are that the velocity of Dimorphos will change by 0.4 mm/s. Thats 12 km in a year. That said, if a truly serious asteroid threat we're headed towards earth, it would be bigger than Dimorphos, and we'd want to deflect it more than 12 km. But the technology demonstrated here would hopefully be scalable to handle a larger asteroid.
Re: (Score:2)
Worst case for scaling up, there's always the obvious and expensive scaling method of sending multiple impactors. If you can't whack it hard enough all at once, try hitting it repeatedly. But we'd need to know how many and how fast they should be going for maximum momentum transfer, and that's the kind of data we're hoping to see soon. I suspect it may be wise to employ this tactic in an Armageddon situation, because of the risk that a given impact may occur in a place that's unexpectedly soft. The more you
Re: Bug on the windsheild (Score:2)
Agreed about the ability to scale up. Fortunately the ability to shift orbit is directly proportional to asteroid mass. So an asteroid that is 10x more massive only needs 10x more "Darts" for the same effect.
Re: (Score:2)
Once they're got observations it'll be easy to determine. Dimorphus orbits every 11 hours 55 minutes right now. Each time it passes between a scope and Didymos there's a change in brightness which is easy to detect. After impact the orbital period of Dimorphus will be around 11 hours 30 minutes. Get a few measurements of that and then we can determine exactly how much we changed its speed even without directly looking at Dimorphus or trying to measure its velocity.