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After a two-year journey, a NASA spacecraft arrives at its target asteroid Link to The Verge article
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Today, one of NASA’s deep-space probes, OSIRIS-REx, arrived at the space rock it’s been traveling toward for the last two years, an asteroid named Bennu. At noon ET, OSIRIS-REx came within about 12 miles (20 kilometers) of the asteroid, which is closer than ever before. The arrival means that OSIRIS-REx is now starting a new phase of its mission that entails extensively mapping the surface of the asteroid to find the best place to grab a sample of material.
I think it is always interesting that we very rarely get a space background any more.
One of the things I like to do sometimes is to take a NASA photo and to check out whether they have masked out the background. For this one, the image below which I have processed, shows red where they have masked out the background with pure black. In practice, the background is never pure black - even in space because the camera always captures some light, even if it appears black to us, the values of the greys in the picture are very low. (As you can see, the area around the ball-shaped asteroid is fuzzy which means it has been masked out from the background.)
I just wonder why anyone would bother to do that if it was not necessary?
I was struck by the similarity to the Ryugu asteroid being visited by the Hayabusa 2. The equatorial bulge must be a feature of certain classes of rubble-pile asteroids.
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I think it is always interesting that we very rarely get a space background any more.
Have we ever? I don't see a mystery here. The exposure time needed to display stars is significantly longer than the exposure time for an asteroid image. To show the background they would need to overexpose the asteroid, and then what's the point? They're there to image the asteroid. Showing a space background often requires overlaying images from different shots.
I was struck by the similarity to the Ryugu asteroid being visited by the Hayabusa 2. The equatorial bulge must be a feature of certain classes of rubble-pile asteroids.
Have we ever? I don't see a mystery here. The exposure time needed to display stars is significantly longer than the exposure time for an asteroid image. To show the background they would need to overexpose the asteroid, and then what's the point? They're there to image the asteroid. Showing a space background often requires overlaying images from different shots.
I understand the explanation about the stars not showing in the background.
I agree, they are there to image the asteroid and the background is incidental. These days, cameras are so good you would have thought they could give us a better image of the asteroid too. I suspect they will be taking pin-sharp images so they can decide which area to scrape the surface for the sample return experiment. Do you think we will get to see those pin-sharp images in due course?
As I said before, why go to the trouble of bothering to blank out the background if there is nothing there anyway?
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