Slashdot Mirror


World's Largest Digital Camera Project Passes Critical Milestone

An anonymous reader writes in with a link about the progress of one of the coolest astronomy projects around. "A 3.2 billion-pixel digital camera designed by SLAC National Accelerator Laboratory is now one step closer to reality. The Large Synoptic Survey Telescope camera, which will capture the widest, fastest and deepest view of the night sky ever observed, has received 'Critical Decision 1' approval by the U.S. Department of Energy (DOE) to move into the next stage of the project. The Large Synoptic Survey Telescope (LSST) will survey the entire visible sky every week, creating an unprecedented public archive of data – about 6 million gigabytes per year, the equivalent of shooting roughly 800,000 images with a regular eight-megapixel digital camera every night, but of much higher quality and scientific value. Its deep and frequent cosmic vistas will help answer critical questions about the nature of dark energy and dark matter and aid studies of near-Earth asteroids, Kuiper belt objects, the structure of our galaxy and many other areas of astronomy and fundamental physics."

73 comments

  1. Sad for NASA by treeves · · Score: 4, Insightful

    that DOE is doing this and not NASA.

    --
    ...the future crusty old bastards are already drinking the Kool-Aid.
    1. Re:Sad for NASA by Anonymous Coward · · Score: 0

      NASA doesn't need a picture of submitter's mom.

    2. Re:Sad for NASA by Jeng · · Score: 5, Informative

      It is politically beneficial it for politicians to cut NASA's funding, but other agencies want these projects done so they do it because they actually have the funding to do it.

      So yea, it is sad for NASA, but it's not NASA's fault.

      --
      Don't know something? Look it up. Still don't know? Then ask.
    3. Re:Sad for NASA by ArsonSmith · · Score: 1, Flamebait

      NASA's to worried about global warming and reducing energy usage for the US.

      --
      Paying taxes to buy civilization is like paying a hooker to buy love.
    4. Re:Sad for NASA by Bam_Thwok · · Score: 1

      Not sure why you think they're "to" worried about those things. NASA's whole job is developing technology and processes for a long-term human presence in space, and environmental science and sustainability are crucial elements of that goal.

    5. Re:Sad for NASA by Dishevel · · Score: 0

      I thought they were spending all their time now making Muslims feel better about themselves.

      --
      Why is it so hard to only have politicians for a few years, then have them go away?
    6. Re:Sad for NASA by the_other_chewey · · Score: 1

      Sad for NASA that DOE is doing this and not NASA.

      It's a ground-based telescope. Where exactly would NASA come in?

      Also: Don't start your sentences in the subject field, it's bloody annoying.

    7. Re:Sad for NASA by Anonymous Coward · · Score: 0

      NASA is not "doing" ground based telescopes, NOAO is.
      And guess what, NOAO members are actively involved in LSST.

      SLAC is involved, "besides" the camera, because the amount of data to be generated
      by the LSST is in the range of modern high energy physics experiments. SLAC has a
      lot of experience dealing with similar amounts of data while the "astronomers" (an
      overgeneralization of the LSST users group) mostly don't.

      Disclaimer: anonymous coward very distantely involved in LSST.

    8. Re:Sad for NASA by treeves · · Score: 1

      Makes sense. I figured that NASA is not really the right organization for this project, but their decline, and the fact they don't get much positive attention nowadays, is still saddening to me.

      --
      ...the future crusty old bastards are already drinking the Kool-Aid.
    9. Re:Sad for NASA by Impy+the+Impiuos+Imp · · Score: 1

      Well, at .003 million megapixels, they've got a long way to go to catch up to the 5 million megapixel cameras for sale at Best Buy, according to the illiterate, innumerate salespeople.

      --
      (-1: Post disagrees with my already-settled worldview) is not a valid mod option.
  2. WOW by Anonymous Coward · · Score: 0

    'nuff said

    1. Re:WOW by jellomizer · · Score: 1, Funny

      It will probably come standard on the iPhone 6. The Android people will say they have it now.

      --
      If something is so important that you feel the need to post it on the internet... It probably isn't that important.
    2. Re:WOW by Anonymous Coward · · Score: 0

      Yep. I downloaded the app to my Galaxy Nexus this afternoon.

    3. Re:WOW by cayenne8 · · Score: 1
      No shit.

      I'm getting ready to pull the trigger to buy one of the new Canon 5D Mark III's soon....and thought I'd have quite a camera.

      I guess this one wins the megapixel wars hands down.

      ;)

      With that many MP's though...I wonder how their ISO levels are?

      --
      Light travels faster than sound. This is why some people appear bright until you hear them speak.........
    4. Re:WOW by Savantissimo · · Score: 3, Informative

      More to be said - here's the scientific FAQ: http://www.lsst.org/lsst/faq-science
      Choice bits:

      ...That combination is unique: wide field of view (10 square degrees), short exposures (pairs of 15-second exposures), and sensitive camera (24th magnitude single images, 27th magnitude stacked). ...
      The etendue of LSST is 320 square meters square degrees. A primary mirror diameter of 8.4 m (effective aperture 6.7 m due to obscuration) is the minimum diameter that simultaneously satisfies the depth (24.5 mag depth per single visit and 27.5 mag for coadded depth) and cadence (revisit time of 3-4 days, with 30 seconds per visit) constraints....
      The nominal high-SNR sample defined by i25 for point sources) will include four billion galaxies (55 per square arcminute) with the mean photometric redshift accuracy of 1-2% (relative error for 1+z), and with only 10% of the sample with errors larger than 4%. The median redshift for this sample will be z=1.2, with the third quartile at z=2. ...

      Q: Will the full resolution, full depth image data be available to download?

      A: Yes. There will be a range of data products and download portals. The LSST data system is being designed to enable as wide a range of science as possible. Standard data products, including calibrated images and catalogs of detected objects and their attributes, will be provided both for individual exposures and the deep incremental data coaddition. For the "static" sky, there will be yearly database releases listing many attributes for billions of objects. This database will grow in size to about 30 PB and about 20 billion objects.
      As in the SDSS, we expect a power law of user interactions with the data. At one end of this distribution are simple lookup queries or color jpeg cutout downloads. At the other end are huge statistical calculations over the entire database, and image operation scripts on billions of objects. The data management system is budgeted to handle most but not all of that distribution. Institutions joining LSST early, and members of the LSST Science Collaborations, will have the customary advantage of deep familiarity with the LSST system and survey.

      --
      "Is life so dear, or peace so sweet, as to be purchased at the price of chains and slavery?" - Patrick Henry
    5. Re:WOW by Savantissimo · · Score: 1

      Follow up -"etendue" is effectively a measure of optical throughput which correlates with how many objects can be detected per unit of time. It is the product of the effective area of the primary mirror (m^2) times the effective area of the sky that is covered (degrees^2). The LSST's sensors do not cover quite the full field of view, which likely accounts for the difference between the calculated value of 347 and the claimed value of 320.

      From the Pan-STARRS site is this comparison on etendues:
      USAF Linear 1.5
      SDSS 6.0
      CFHT 8.0
      SUBARU 8.8
      Pan-STARRS 60
      (It lists LSST as 190, which is wrong.)

      --
      "Is life so dear, or peace so sweet, as to be purchased at the price of chains and slavery?" - Patrick Henry
    6. Re:WOW by pgpalmer · · Score: 1

      "It's full of stars!"
      "No, John, that's just a grainy image."
      "Oh. What about this one? Stars?"
      "Grain again."
      "... They're ALL grainy! These images are useless!"
      "True, but we have MEGAPIXELS!"

  3. In LOC, please by Overzeetop · · Score: 4, Insightful

    I hate when articles can't use standard units. Are petabytes, exabytes, zettabytes not really usable yet?

    --
    Is it just my observation, or are there way too many stupid people in the world?
    1. Re:In LOC, please by Anonymous Coward · · Score: 0

      I second this!
      Personally, I'm just not quite visualizing the size of the sensors. How many, edge to edge, would it take to run the length of a football field?

    2. Re:In LOC, please by RenderSeven · · Score: 5, Funny

      Most people think that 'petabytes' is somehow related to child pornography, 'exabytes' is a skin disease, and 'zettabytes' is a video game character.

    3. Re:In LOC, please by Anonymous Coward · · Score: 1

      Authors should assume they can use any prefix that is currently available for civilian hard drives. "6 thousand terabytes per year" is somewhat workable. A better term would be "500 terabytes each month."

      Also, 3.2 gigapixels!

    4. Re:In LOC, please by Anonymous Coward · · Score: 0

      The problem is, that peta, exa, and zetta have different
      meanings depending on the country you're in (akin to billion)

      Of course I'm kidding...

    5. Re:In LOC, please by Anonymous Coward · · Score: 0

      News for nerds ... Could fix it in the summary at least.

    6. Re:In LOC, please by HapSlappy_2222 · · Score: 3, Funny

      Zettabyte goes north.
      Zettabyte goes north.
      Zettabyte sees entrance to Cave of Ominous Petabytes.
      Zettabyte enters Cave of Ominous Petabytes.
      Zettabyte contracts Exabytes! Also, his sword broke!

    7. Re:In LOC, please by HapSlappy_2222 · · Score: 2

      I often create canvas prints of family photos. Mainstream 3.2 gigapixel pics means I'll be photoshopping another 1.1 gigapixels of zits, fat, and moles OUT, another 1.1 gigapixels of hair, tanned skin, and white teeth IN, and just plain giving up on the remaining gigapixel (meh, it's probably just the dog or grandma anyway).

      God it's hard to make people prettier than they are in real life; exponentially so when they're high-rez people. Maybe I'll ONLY make canvas prints out of LSST space photos. Uh.... 3. Profit?

  4. Who stole the international metric system? by Anonymous Coward · · Score: 1

    I thought we had terabytes and above for "zillions of gigabytes"?

    1. Re:Who stole the international metric system? by BlackThorne_DK · · Score: 1

      But then again.. Who do you know, that uses Gg or Giga Gram, instead of 'Thousand Tons'?

    2. Re:Who stole the international metric system? by voidphoenix · · Score: 1

      Kiloton? Even megaton is fairly mainstream. I know the mainstream use is for imperial tons of TNT, but there is such a thing as a metric ton.

  5. Spotting Solar system object by DadLeopard · · Score: 4, Insightful

    I would think that it would also help track down just about everything in the Solar system, when using successive pictures of the same portion of the sky in a "Blinker" box or whatever they use in place of that now. Dark matter is all fine and dandy, but the location and trajectory of Asteroids and comets are of a different degree of importance!

    1. Re:Spotting Solar system object by Jeng · · Score: 5, Funny

      The problem is that even with this camera, if what you are looking at is not illuminated then it will not be visible (think asteroid in shadow of moon).

      So basically the worlds largest digital camera needs the worlds largest camera flash. I would suggest using a low yield nuclear warhead, but there would be a few issues with that.

      --
      Don't know something? Look it up. Still don't know? Then ask.
    2. Re:Spotting Solar system object by Anonymous Coward · · Score: 0

      That's how they sell it to the public and how they sold pan starrs to the public. However, both pan starrs and the lsst are primarily for cosmology. A telescope used for searching asteroids wouldn't use narrow filters since it defeats the purpose of having a large mirror.

    3. Re:Spotting Solar system object by formfeed · · Score: 2

      So basically the worlds largest digital camera needs the worlds largest camera flash. I would suggest using a low yield nuclear warhead, but there would be a few issues with that.

      Make that two nuclear warheads to avoid red eye.

    4. Re:Spotting Solar system object by ks*nut · · Score: 1

      Yes, they're doing asteroid searches, too. But what, at this moment, appeals to the lowest common denominator scientifically uninformed American mind?

    5. Re:Spotting Solar system object by dietdew7 · · Score: 1

      If they took pictures during the day they wouldn't need a flash. The Sun has a lot more output than any terrestrial bomb flash.

    6. Re:Spotting Solar system object by DadLeopard · · Score: 1

      I'm Pretty sure that most of the objects in the Solar System are not in the shadow of another object more than a minuscule portion of the time! So what didn't show on the first pic will show on the next, unless time between pics coincidently coincides with the orbital periodicity of the object, the probablitity of this continuing for a long period of time is vanishingly small! Now a very low albedo on the other hand, will make it hard to see some things!

  6. Precursor Google Galaxy: Aliens watch ur rooftops by youn · · Score: 2

    any unauthorized spaceships, doomsday stars and other prohibited devices should not be left in orbit without at least cloaking :p

    --
    Never antropomorphize computers, they do not like that :p
  7. Opening the JPEG takes Eternity by retroworks · · Score: 2

    And don't even ask about the amount of hard drive space to Photoshop the cosmos.

    --
    Gently reply
    1. Re:Opening the JPEG takes Eternity by mj1856 · · Score: 2

      "To the cloud!"

    2. Re:Opening the JPEG takes Eternity by almitydave · · Score: 1

      Quick, buy stock in HDD manufacturers! 6 million gigabytes (by which I assume they mean 5.7 petabytes) per year comes out to roughly 113 terabytes per week. I hope they get volume discounts on drives!

      Seriously, though, this is cool. I can't wait to see what sort of time-lapse videos they can make from this. Has anyone worked out what the pixels-per-arc-second resolution would be?

      --
      my, your, his/her/its, our, your, their
      I'm, you're, he's/she's/it's, we're, you're, they're
    3. Re:Opening the JPEG takes Eternity by FrankSchwab · · Score: 1

      which comes out to roughly 30 (4 TB) hard drives a week, or maybe $6000. I don't think that's going to bankrupt a federal agency.

      Sure, you've got to double or triple that to pay for backups and replication, but let's be real - disk storage is cheap these days.

      --
      And the worms ate into his brain.
    4. Re:Opening the JPEG takes Eternity by almitydave · · Score: 2

      Has anyone worked out what the pixels-per-arc-second resolution would be?

      OK, if my math is correct, assuming a single image encompasses the entire sky, this is 167 square arc-seconds per pixel, or about 13 linear arc-seconds per pixel. This would mean the moon would be 645 pixels across, Venus would be (currently) about 3 pixels across, and Jupiter at its closest would be about 4.

      --
      my, your, his/her/its, our, your, their
      I'm, you're, he's/she's/it's, we're, you're, they're
    5. Re:Opening the JPEG takes Eternity by MetricT · · Score: 4, Informative

      I'm with the group at Vanderbilt developing the storage filesystem for LSST, and it has some interesting challenges.

      1. It requires redundancy at the server, rack, and site level. 2. Both data and metadata have to scale both in volume and in throughput (GB/sec or transactions/sec) separately of each other.
      3. It has to work on the WAN level (GPFS & Lustre don't scale beyond the LAN yet).
      4. It should optionally have HSM functionality so you can offload stuff to tape.
      5. The data must be maintained in perpetuity so researchers years/decades from now can use it.
      6. It must be portable across operating systems so Windows/Mac/Linux/etc users can all access the data.
      7. All of this should be completely transparent to the user.
      8. And it has to be done on the cheap (scientists definition of cheap, not CIO's definition).

      Yeah, it can be (and is) being done. We're already using our filesystem to store 2+PB of data for the CERN CMS-HI experiment on commodity hardware. But I can tell you it is a substantially harder problem than you think.

    6. Re:Opening the JPEG takes Eternity by Mt._Honkey · · Score: 1

      assuming a single image encompasses the entire sky

      That assumption is quite false: it takes an exposure every 20 seconds and takes days to form an all-sky survey. The pixel size is 0.2", so Jupiter at its closest would be 250 pixels wide, not 4.

      --

      Don't Bogart the fish sticks
    7. Re:Opening the JPEG takes Eternity by Savantissimo · · Score: 1

      The camera covers a little less than 9.7 square degrees, not the whole sky. (It's not a square image but an array of sensor chips, the array is missing corners to more closely follow a circular image shape.)

      The page http://www.lsst.org/lsst/science/concept_camera lists the sampling resolution as "better than 0.2 arcseconds" (with 6 color bands per pixel 300nm-1200nm). That would make the moon 9000 pixels wide (assuming 0.5 degree width - it varies a little).

      --
      "Is life so dear, or peace so sweet, as to be purchased at the price of chains and slavery?" - Patrick Henry
    8. Re:Opening the JPEG takes Eternity by Savantissimo · · Score: 1

      More - each pixel samples each of the six colors, (u-g-r-i-z-y, roughly 300-400-500-600-700-800-900-1000-1100nm) using filters. Each exposure is a bit less than 2.5s, for a total of 15s. The sequence is then repeated before the telescope is moved to the next patch of sky.

      --
      "Is life so dear, or peace so sweet, as to be purchased at the price of chains and slavery?" - Patrick Henry
    9. Re:Opening the JPEG takes Eternity by belthize · · Score: 1

      I assume you guys are familiar with the Lustre WAN work being done for the 2.x branch. For example:
      http://www.teragridforum.org/mediawiki/index.php?title=JWAN:_lustre-wan_advanced_features_testing

      Not implying it does or will necessarily scale, in fact I'd be a bit surprised if you guys weren't following it but figured I'd toss it out there in case you weren't.

      Interesting project, I do same thing with radio telescope data but a much smaller scale (1/10th or so) without the added complexity of transparent access to OS of the month. I assume you also have to support VAO hooks (Virtual Astronomical Observatory) or is that at a different layer than the storage portion.

    10. Re:Opening the JPEG takes Eternity by jd2112 · · Score: 1

      Unless the storage array has the letters E, M, and C along with the number 2 in which case it's more like $60,000.

      --
      Any insufficiently advanced magic is indistinguishable from technology.
    11. Re:Opening the JPEG takes Eternity by formfeed · · Score: 1

      And once NASA sends it over to Target for printing, they'd probably downsize it anyhow.

    12. Re:Opening the JPEG takes Eternity by NemoinSpace · · Score: 1

      newsflash... We ARE bankrupt.

    13. Re:Opening the JPEG takes Eternity by almitydave · · Score: 1

      Well that's significantly cooler. I did read TFA, but didn't click through to the LSST site itself. Thanks for the details, and obviously you can't image the whole sky at once from the Earth. This would allow planetary surface details to be studied over time (although rotation means you won't see the same side in every image).

      --
      my, your, his/her/its, our, your, their
      I'm, you're, he's/she's/it's, we're, you're, they're
    14. Re:Opening the JPEG takes Eternity by Whip · · Score: 1

      Don't suppose you have a paper/website/whatever talking about your filesystem development work for this?

  8. All those pixels... by Reasonable+Facsimile · · Score: 5, Funny

    ... just waiting to be dumbed-down with an instagram filter.

    1. Re:All those pixels... by Anonymous Coward · · Score: 0

      "Either I've been looking at these too long, or I found something."
      "What, where?"
      "I don't know, but over here in Libra, I'll zoom in for a better view."
      "That looks somewhat like a new nebula, but there's no way a nebula that large and bright could happen overnight."
      "Let me just boost the brightness on it a little to get a better idea of what we're looking at.... do you see that?"
      "Yes, yes I do."
      "We've been trolled. Check the backups from Tuesday and try to find the original copies, I want to know if we have a clean copy of this data."

  9. Good news by GodGell · · Score: 2

    This is great news. Remember the scene in Star Wars where Obi-Wan uses that 3D star map, projecting from a crystal ball?
    With this, if the weekly image is public, we could actually create such real-time maps.

    --
    [SHOW SOME LENIENCY TOWARDS ... I mean, FUCK BETA] Eat. Survive. Reproduce. GOTO 10
    1. Re:Good news by MisterSquid · · Score: 1

      Remember the scene in Star Wars where Obi-Wan uses that 3D star map, projecting from a crystal ball?

      No.

      --
      blog
    2. Re:Good news by MisterSquid · · Score: 2

      I see. You actually meant a scene from Episode II, not Episode IV.

      --
      blog
  10. Dark matter... lulz by Anonymous Coward · · Score: 0, Interesting

    Amazing the lengths people will go to discount the huge role of electricity in space.

  11. Not that much storage by dak664 · · Score: 1

    The first image would compress a factor of 2-5 depending on how good the S/N. Each image after that x100 using delta compression, unless there is something really funky going on in our neck of the woods

    1. Re:Not that much storage by rlseaman · · Score: 1

      Astronomical data are background limited. The noise is as interesting as the signal, and many sources lie beneath the noise and are only visible through coadding. The gain and read-noise of LSST's detectors will be tuned similarly to other astronomical cameras because these parameters are governed by the experimental design.

      Lossless Rice compression should be around R of 2-2.5 (http://arxiv.org/pdf/0903.2140.pdf) with lossy compression of reduced data products falling between R of 3 to 5 depending on the quantization selected (http://arxiv.org/pdf/1007.1179.pdf).

      There will be no delta frame advantage since the compression is governed entirely by the noise (i.e., entropy) due to the sparse signal in astronomical data and the noise is a combination of gaussian and poisson (shot noise) sources that varies from exposure to exposure.

      In fact, a key goal of the project is precisely to look for differences between each frame and a baseline static sky so the differences must be preserved in great detail.

  12. Or they could just ... by PPH · · Score: 1

    ... turn a KH-12 satellite around.

    --
    Have gnu, will travel.
  13. when you put it that way... by kanoalani · · Score: 1

    Comparing a hypothetical science instrument to an old grade of consumer device is poor hype. A better comparison is the 1.4 billion pixel camera on Pan Starrs that has been on the sky for two years now or the 340 megapixel CFHT-Megacam that has been on the sky for over nine years. If LSST is delayed much longer, a 3.4 billion pixel astronomy camera will sound like 8 megapixels in an SLR does today: obsolete.

  14. Re:Precursor Google Galaxy: Aliens watch ur roofto by Anonymous Coward · · Score: 0

    And that's why Starfleet should have invested in cloaking devices for the Enterprises. I believe that NCC 1701 and NCC-1701E both would have benefited from them at different point, and the HMS Bouty demonstrated its utility.

    But, then, the plot points would have been harder to achieve.

  15. Re:Precursor Google Galaxy: Aliens watch ur roofto by UnknownSoldier · · Score: 1

    Somehow I doubt the governments of the world would even have the tech to try to enforce the "unauthorized" part on "spaceships, doomsday stars and other prohibited devices" =)

  16. another funding cut is coming. by Anonymous Coward · · Score: 0

    "I've personally been working on this since 2003, and it is tremendously satisfying to finally see this move forward to the point when we can begin to carry out the project. "

    you've been milking this for 9 years and just couldn't keep quiet till after the election could you?
    Boy is your boss gonna be pissed.!

    p.s. captcha is "voters" this is scary.

    1. Re:another funding cut is coming. by NemoinSpace · · Score: 1

      Maybe he wants the bosses job.

  17. Puhhhhleaseeee.... by Anonymous Coward · · Score: 0

    like dey ain't gonna turn dat big bitch downwards b lookin' at sum shiznit going down

  18. Actually Arthur C. Clarke (as usual) proposed this by wisebabo · · Score: 3, Interesting

    In one of his short stories, (I believe) after a near miss by an earth grazing asteroid (sliced through the upper atmosphere over a major city), a very large (gigaton) bomb is detonated in earth's orbit in a position diametrically opposed to the earth. The resulting "flash" resulted in a radar pulse (remember that was Clarke's early training in WWII) that was used to illuminate all the objects in the solar system. This was recorded and catalogued.

    Decades later, an extra-terrestrial signal is recorded from another star system. After a quick calculation, it is apparent that the aliens, upon detecting the flash of this giga-bomb, quickly responded with a reply aimed at our solar system.

  19. Compression? by wisebabo · · Score: 1

    Hi there- I know that the scientists are loath to use any form of lossy compression on what could be priceless scientific data but I just wanted to ask if you are using any compression. I mean, images of this sort should be ideally suited to some forms of compression (a simplistic example would be RLE); after all, there is a lot of "space" (yuk yuk :).

    I used to work in digital cinema during the early trials and very prominent movie directors would often walk up to the projection screen, inches fom their face, looking for compression artifacts that could be caused by our servers (we used wavelets). They passed and now digital cinemas are everywhere in the world.

  20. Won't get funded by dutchwhizzman · · Score: 1

    Unless the members of congress can point it at the bedroom of the hot girl that lives across the street.

    --
    I was promised a flying car. Where is my flying car?
  21. The important question is... by Tastecicles · · Score: 1

    ...when is Samsung going to launch the SHDTV with the 3.2GP "lookback" feature?

    --
    Operation Guillotine is in effect.
  22. DOE did it because of the military applications by Anonymous Coward · · Score: 0

    This is for tracking objects in orbit like spy satellites, and the occasional meteor. the science benefit is secondary. The people that want this don't care if it is NASA, DOE, or the Dept. of Agriculture. they wanted it and got funding by the path of least resistance.

  23. That had to hurt by Muad'Dave · · Score: 1

    World's Largest Digital Camera Project Passes Critical Milestone

    I've passed a tiny 1mm stone - a milestone must've been sheer agony.

    --
    Tiller's Rule: Never use a word in written form that you've only heard and never read. You will end up looking foolish.
  24. Re:Actually Arthur C. Clarke (as usual) proposed t by DerekLyons · · Score: 1

    Sir Arthur may have proposed it, but he got the science badly wrong.

    Not only would such a bomb not produce a flash (the flash is a product of the bomb's reactions with the atmosphere) or a radar pulse of any kind, but even if it did - it would have to be in the tens or hundreds of gigatons to exceed the illumination available from the sun, and would only be useful for 1 AU or so from the bomb.