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A tumbling 1,100-foot-wide asteroid

Nereus tumbling on December 10th close approach
Click for full image.

Using the Goldstone radio antenna in California, scientists have been able to take some of the highest resolution radar images of the 1,100-foot-wide asteroid Nereus during its close approach to Earth on December 10, 2021.

The montage to the right, cropped to post here, shows twelve images from the 39-image sequence, which can also be viewed as an animation here.

During the asteroid’s close approach, an image resolution of about 12.3 feet (3.75 meters) per pixel was possible, revealing surface features such as potential boulders and craters, plus ridges and other topography. Asteroid Nereus’ previous approach in 2002 was near enough to Earth to reveal the asteroid’s size and overall shape, but too distant to show surface features. The new observations will also help scientists better understand the asteroid’s shape and rotation while providing them new data to further refine its orbital path around the Sun.

The asteroid will not make a similar close-approach again until 2060.

Genesis cover

On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.

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  • Lee Stevenson

    I have a question for those who understand radio astronomy better than myself.
    Would these images be captured “radar” style, by actively bouncing radio waves of the astroid?
    I actually don’t really understand imaging by radio astronomy in general, any reference to a good text based source where I can educate myself would be appreciated.

  • Jay

    Correct, this is Radar Astronomy. Places like the former Aericebo, Goldstone, and other radar sites, like the Deep Space Network, would transmit transmit anywhere from a few hundred kilowatts to over one Megawatt at microwave frequencies. The signal would hit the object, reflect the signal back, the same dish would receive the weak signal, the signal would go into preamps and signal processing to be outputted on a display. The computer does all the work. Here is a good introduction to Radar Astronomy.

    I am into ham radio, so working satellites and weak signal processing can be done by anyone. A lot of the equipment can be bought off the shelf for under $100, like I said the computer is doing all the work. Of course that is radio astronomy, you are only receiving radio signals. If you want to do radar astronomy, you need a lot of money for equipment and the power bill.

  • Lee S

    Thank you Jay!
    Unfortunately I cannot get the link to open, I’d be very pleased to have a read if you could post it again please.

  • Jay

    Sorry Lee,
    My bad, here is site again from National Academies Press:

    Also here is another one that describes both radio and radar astronomy:
    It is a dated document but the theories are still true.

  • Lee S

    Thank you Jay…. After a quick scan I’ve got some interesting Sunday reading!

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