9 ms·

There certainly is a real concern for astronomers, but the photo illustrations used in the article are selected to make things seem worse than they really are.

There certainly is a real concern for astronomers, but the photo illustrations used in the article are selected to make things seem worse than they really are. They're wide field of view, long-duration exposures. That used to be the way astronomers imaged space, with film systems a century ago. But these days astronomical telescopes tend to have much narrower fields of view (like tiny soda straws peering into one particular spot in space) and use image stacking, a technique where many individual images are processed to form the final image (very simplistic overview: https://www.skyatnightmagazine.com/astrophotography/astrophoto-tips/a-guide-to-astrophotography-stacking https://www.skyatnightmagazine.com/astrophotography/astropho... .) Using image stacking and armed with accurate catalogs that predict precisely where every satellite will be at any time, enables the removal of satellites during the image stacking process. Or they can just use that information for better scheduling: wait a minute or two to image a particular spot, so there won't be satellites in the field of view. The article definitely gets this part right: > “Some astronomers see this as a true ‘hair on fire’ emergency, heralding irretrievable losses to space science; others present a more sanguine face, depicting this as yet another challenge to be surmounted in surveying a decreasingly pristine sky,” Koplow remarks. Being involved in both space and astronomy plants me squarely in the latter camp. It takes a bit more work and software, but having so many satellites in space is a surmountable challenge for terrestrial astronomers. (Not to mention, these days some of the best astronomy is performed by telescopes in space, so astronomy overall benefits by having easier access to space.)

shadowgovt 2y ago
Forget satellites; you can't do raw long-exposure for "serious" terrestrial-based astronomy anymore because you'll get planes in the way.
gammarator 2y ago
> They're wide field of view, long-duration exposures. That used to be the way astronomers imaged space, Sorry, but one of the two example images (https://noirlab.edu/public/images/iotw1946a/ https://noirlab.edu/public/images/iotw1946a/) is a single 333-second exposure with a modern survey camera, the Dark Energy Camera. This is not particularly long nor does it represent some outmoded observational strategy. Large, wide-field imaging sky surveys (such as the upcoming Rubin Observatory) are among the highest-profile ground-based astronomy projects today. Masking and stacking can mitigate the problem but it does not of course compensate for the lost area and sensitivity. And the brightest satellites (like BlueWalker) saturate the readout electronics and spoil the whole exposure. Narrow field instruments (such as spectrographs) have less geometric chance of seeing a satellite but tend to take longer exposures (tens of minutes), so there is a greater loss of telescope time when a streak does happen. Even space telescopes are affected by streaks (https://www.space.com/hubble-images-spoiled-starlink-satellite-steaks https://www.space.com/hubble-images-spoiled-starlink-satelli...). > It takes a bit more work and software Equivalently, it takes more money and time. That just means less science, given flat to declining funding from Congress.
- nomel 2y ago
  > Masking and stacking can mitigate the problem but it does not of course compensate for the lost area and sensitivity. And the brightest satellites (like BlueWalker) saturate the readout electronics and spoil the whole exposure. Is this only a problem in systems that aren't aware of where the satellites will be? I naively assume that, if the system knew, it could start exposing in the next clear window. I naively assume that the window is almost always clear, especially for an individual sensor.
  - hedora 2y ago
    Even if they don’t know where the satellites will be, a simple motion detection algorithm in the stacker would delete the streak caused by the satellite. A given pixel will only be impacted for a few exposures, so just grab 5% more images. I’d guess terrestrial light pollution is a much bigger problem.
    - schiffern 2y ago
      >so just grab 5% more images. You say it like major observatory telescopes are sitting idle, but they're not. In practice what actually happens is you lose 5% of your scientific data return. >terrestrial light pollution Problem is that it's global vs local, so our normal solution for terrestrial light pollution (build telescopes in a remotely populated area) doesn't work.
      - labcomputer 2y ago
        So just write all grant proposals with an extra 5% slop.
        dexwiz 2y ago
        Why would they not already be trying to maximize grant size?
        schiffern 2y ago
dheera 2y ago
> the photo illustrations used in the article are selected to make things seem worse than they really are Exactly. I do a LOT of astrophotography and satellite trails are actually very easy to get rid of. Even the stupidest, most naive outlier rejection techniques, such as taking a stack of tracked images, finding their mean and standard deviation, throwing out any data points outside of 2 standard deviations, and then re-averaging, will get rid of the satellites very cleanly. You can go to more advanced techniques such as doing linear fits and RANSAC and whatnot, but you get the idea. NOT doing any outlier rejection, just taking the mean of all the images will show the satellite tracks, but very dimly. The people who are trying to make noise on social media deliberately and disingenuously take the max() instead of the mean() to make the problem seem worse than it is. That said -- in all of my imaging sessions, aircraft are a much, much, much bigger problem than satellites, and still easy to deal with. Yet nobody makes any noise about aircraft.
- malfist 2y ago
  Seriously, any time you have >3 images to stack satellites and planes are a complete non issue. The median pixel value is always going to exclude those. Five images is enough to eliminate any trails even if they overlap between images.
  - nullc 2y ago
    You're not imaging with cryogenic CCDs --- satellite trail can blow out whole rows.
    - rblatz 2y ago
      Just do it in space and avoid the whole atmosphere and ground based light pollution. Space is cheaper than ever now, this is a problem for amateur astronomers, and hobbyists shouldn’t hold back progress.
      - nullc 2y ago
        Space imposes extraordinary costs and limitations which heavily precludes exploratory research. Instruments are built for space to achieve specific tasks which we know will be successful. Instrument development has to first occur on earth-- including the research that lets us know which things will yield results deployed in space. Astronomy aside, fleets of satellites once they turn to junk may eventually make further launching problematic.
thayne 2y ago
If you are looking for short period events, losing a single frame can mean losing critical data. > Or they can just use that information for better scheduling: wait a minute or two to image a particular spot, so there won't be satellites in the field of view. Which means more time and effort, and ultimately money needs to be spent on scheduling observations to avoid the thousands of these satellites. And sometimes it isn't an option. What if a GRB happens in the same field of view as one of these satellites and you want to observe it as soon as possible? Now there are some types of observations that won't be impacted that much. If you can tolerate scheduling around it, or throwing away some of your frames it is just a minor annoyance. But a lot of observations are also more sensitive to such disruptions.
- serial_dev 2y ago
  > What if a GRB happens Yeah, what if? I mean, you probably missed the GRB, sure, but apart from that, you'll be fine and you can wait for the next one, or find a data from somewhere else.
- lifeisstillgood 2y ago
  GRB - Gamma Ray Burst (I am guessing)
  - thayne 2y ago
    Yes
whoopdedo 2y ago
> these days some of the best astronomy is performed by telescopes in space, so astronomy overall benefits by having easier access to space. Public access satellites. The FCC requires broadcast licensees to demonstrate that they're acting "in the public interest". Should private rocket launches have to give a minimum amount of their payload to research and non-profit purposes?
- labcomputer 2y ago
  Sure, why not? A Hubble-sized telescope is only about 12 tons, which is only about 70% the mass of what a Falcon 9 can deliver to low earth orbit, and SpaceX does that 100x per year (it's only May and they've launched 47 so far this year). For reference, Spitzer is 1 ton and Chandra is 6 tons. The elephant in the room is that launching one Hubble per year to a Hubble-like orbit only uses about 1% of SpaceX's current annual demonstrated launch capacity, and the actual reason people are upset has little to do with the actual impact on astronomy and more do with wanting to punish a certain CEO. One new space telescope every year would completely revolutionize the field, yet he'd barely notice. Better think of something else.
  - deleted 2y ago
    [deleted]
  - ghaff 2y ago
    The upset is also because urban people or people in many denser areas generally don’t really benefit from Starlink etc. You can bet if those types of satellites were the only readable way for them to get internet, astronomy would suddenly fall way down on their list of priorities.
  - WithinReason 2y ago
    Fun fact: in 2012 the Department of Defense donated 2 Hubble-class telescopes to NASA it had lying around and didn't need: https://en.wikipedia.org/wiki/2012_National_Reconnaissance_Office_space_telescope_donation_to_NASA https://en.wikipedia.org/wiki/2012_National_Reconnaissance_O...
  - 2y ago
sitkack 2y ago
You ignore the entirety of the LSST which will take more image data in its first year than all of humanity. It is wide field, and these constellations cannot just be stacked out. You think you are more informed than you are.
- fecal_henge 2y ago
  Why is stacking not possible in this case?
  - sitkack 2y ago
    The objects are so bright and so numerous that they corrupt an entire imagers data for the entire exposure. In a CCD rows and columns can become saturated and hot pixels can spill over into neighboring pixels (blooming). When the imagers for the LSST were being designed, it was not anticipated that they would have to deal with tens of thousands of hot fast moving objects. https://www.lsst.org/content/lsst-statement-regarding-increased-deployment-satellite-constellations https://www.lsst.org/content/lsst-statement-regarding-increa...
sitkack 2y ago
You ignore the entirety of the LSST which will take more image data in its first year than all of humanity. It is wide field, and these constellations cannot just be stacked out. You think you are more informed than you are.
- malfist 2y ago
  OP is not wrong, there is no satellite constellation that can't be "stacked out" That's precisely what stacking does. Trust me, I'm an astrophotographer, you can check my website in my profile, I know what I'm talking about here.
  - was_a_dev 2y ago
    There's a bit of difference between the aims of astrophotography and professional astronomy. Ones getting a subjectively good image where the other is getting an objectively good quantitative measurement. Do the software "tricks" really translate that well. If they did, these terrestrial telescopes wouldn't engineered to the tune of billions.
    - malfist 2y ago
      Stacking isn't a "trick". It's mathematics. I agree my aim is to make pretty pictures, and professional astronomy is to take accurate imagery, but up until I'm making subjective calls about colors, they're not too far apart before the image is stretched to a non linear histogram. After all, I can't build pretty pictures on crappy data. Astrophotography is a heck of a lot of math
WithinReason 2y ago
Not to mention this only happens at dusk and dawn when the satellites are in sunlight.

shadowgovt 2y ago

Forget satellites; you can't do raw long-exposure for "serious" terrestrial-based astronomy anymore because you'll get planes in the way.

gammarator 2y ago

> They're wide field of view, long-duration exposures. That used to be the way astronomers imaged space, Sorry, but one of the two example images (https://noirlab.edu/public/images/iotw1946a/ https://noirlab.edu/public/images/iotw1946a/) is a single 333-second exposure with a modern survey camera, the Dark Energy Camera. This is not particularly long nor does it represent some outmoded observational strategy. Large, wide-field imaging sky surveys (such as the upcoming Rubin Observatory) are among the highest-profile ground-based astronomy projects today. Masking and stacking can mitigate the problem but it does not of course compensate for the lost area and sensitivity. And the brightest satellites (like BlueWalker) saturate the readout electronics and spoil the whole exposure. Narrow field instruments (such as spectrographs) have less geometric chance of seeing a satellite but tend to take longer exposures (tens of minutes), so there is a greater loss of telescope time when a streak does happen. Even space telescopes are affected by streaks (https://www.space.com/hubble-images-spoiled-starlink-satellite-steaks https://www.space.com/hubble-images-spoiled-starlink-satelli...). > It takes a bit more work and software Equivalently, it takes more money and time. That just means less science, given flat to declining funding from Congress.

nomel 2y ago
> Masking and stacking can mitigate the problem but it does not of course compensate for the lost area and sensitivity. And the brightest satellites (like BlueWalker) saturate the readout electronics and spoil the whole exposure. Is this only a problem in systems that aren't aware of where the satellites will be? I naively assume that, if the system knew, it could start exposing in the next clear window. I naively assume that the window is almost always clear, especially for an individual sensor.
- hedora 2y ago
  Even if they don’t know where the satellites will be, a simple motion detection algorithm in the stacker would delete the streak caused by the satellite. A given pixel will only be impacted for a few exposures, so just grab 5% more images. I’d guess terrestrial light pollution is a much bigger problem.
  - schiffern 2y ago
    >so just grab 5% more images. You say it like major observatory telescopes are sitting idle, but they're not. In practice what actually happens is you lose 5% of your scientific data return. >terrestrial light pollution Problem is that it's global vs local, so our normal solution for terrestrial light pollution (build telescopes in a remotely populated area) doesn't work.
    - labcomputer 2y ago
      So just write all grant proposals with an extra 5% slop.
      - dexwiz 2y ago
        Why would they not already be trying to maximize grant size?
      - schiffern 2y ago

dheera 2y ago

> the photo illustrations used in the article are selected to make things seem worse than they really are Exactly. I do a LOT of astrophotography and satellite trails are actually very easy to get rid of. Even the stupidest, most naive outlier rejection techniques, such as taking a stack of tracked images, finding their mean and standard deviation, throwing out any data points outside of 2 standard deviations, and then re-averaging, will get rid of the satellites very cleanly. You can go to more advanced techniques such as doing linear fits and RANSAC and whatnot, but you get the idea. NOT doing any outlier rejection, just taking the mean of all the images will show the satellite tracks, but very dimly. The people who are trying to make noise on social media deliberately and disingenuously take the max() instead of the mean() to make the problem seem worse than it is. That said -- in all of my imaging sessions, aircraft are a much, much, much bigger problem than satellites, and still easy to deal with. Yet nobody makes any noise about aircraft.

malfist 2y ago
Seriously, any time you have >3 images to stack satellites and planes are a complete non issue. The median pixel value is always going to exclude those. Five images is enough to eliminate any trails even if they overlap between images.
- nullc 2y ago
  You're not imaging with cryogenic CCDs --- satellite trail can blow out whole rows.
  - rblatz 2y ago
    Just do it in space and avoid the whole atmosphere and ground based light pollution. Space is cheaper than ever now, this is a problem for amateur astronomers, and hobbyists shouldn’t hold back progress.
    - nullc 2y ago
      Space imposes extraordinary costs and limitations which heavily precludes exploratory research. Instruments are built for space to achieve specific tasks which we know will be successful. Instrument development has to first occur on earth-- including the research that lets us know which things will yield results deployed in space. Astronomy aside, fleets of satellites once they turn to junk may eventually make further launching problematic.

thayne 2y ago

If you are looking for short period events, losing a single frame can mean losing critical data. > Or they can just use that information for better scheduling: wait a minute or two to image a particular spot, so there won't be satellites in the field of view. Which means more time and effort, and ultimately money needs to be spent on scheduling observations to avoid the thousands of these satellites. And sometimes it isn't an option. What if a GRB happens in the same field of view as one of these satellites and you want to observe it as soon as possible? Now there are some types of observations that won't be impacted that much. If you can tolerate scheduling around it, or throwing away some of your frames it is just a minor annoyance. But a lot of observations are also more sensitive to such disruptions.

serial_dev 2y ago
> What if a GRB happens Yeah, what if? I mean, you probably missed the GRB, sure, but apart from that, you'll be fine and you can wait for the next one, or find a data from somewhere else.
lifeisstillgood 2y ago
GRB - Gamma Ray Burst (I am guessing)
- thayne 2y ago
  Yes

whoopdedo 2y ago

> these days some of the best astronomy is performed by telescopes in space, so astronomy overall benefits by having easier access to space. Public access satellites. The FCC requires broadcast licensees to demonstrate that they're acting "in the public interest". Should private rocket launches have to give a minimum amount of their payload to research and non-profit purposes?

labcomputer 2y ago
Sure, why not? A Hubble-sized telescope is only about 12 tons, which is only about 70% the mass of what a Falcon 9 can deliver to low earth orbit, and SpaceX does that 100x per year (it's only May and they've launched 47 so far this year). For reference, Spitzer is 1 ton and Chandra is 6 tons. The elephant in the room is that launching one Hubble per year to a Hubble-like orbit only uses about 1% of SpaceX's current annual demonstrated launch capacity, and the actual reason people are upset has little to do with the actual impact on astronomy and more do with wanting to punish a certain CEO. One new space telescope every year would completely revolutionize the field, yet he'd barely notice. Better think of something else.
- deleted 2y ago
  [deleted]
- ghaff 2y ago
  The upset is also because urban people or people in many denser areas generally don’t really benefit from Starlink etc. You can bet if those types of satellites were the only readable way for them to get internet, astronomy would suddenly fall way down on their list of priorities.
- WithinReason 2y ago
  Fun fact: in 2012 the Department of Defense donated 2 Hubble-class telescopes to NASA it had lying around and didn't need: https://en.wikipedia.org/wiki/2012_National_Reconnaissance_Office_space_telescope_donation_to_NASA https://en.wikipedia.org/wiki/2012_National_Reconnaissance_O...
- 2y ago

sitkack 2y ago

You ignore the entirety of the LSST which will take more image data in its first year than all of humanity. It is wide field, and these constellations cannot just be stacked out. You think you are more informed than you are.

fecal_henge 2y ago
Why is stacking not possible in this case?
- sitkack 2y ago
  The objects are so bright and so numerous that they corrupt an entire imagers data for the entire exposure. In a CCD rows and columns can become saturated and hot pixels can spill over into neighboring pixels (blooming). When the imagers for the LSST were being designed, it was not anticipated that they would have to deal with tens of thousands of hot fast moving objects. https://www.lsst.org/content/lsst-statement-regarding-increased-deployment-satellite-constellations https://www.lsst.org/content/lsst-statement-regarding-increa...

sitkack 2y ago

malfist 2y ago
OP is not wrong, there is no satellite constellation that can't be "stacked out" That's precisely what stacking does. Trust me, I'm an astrophotographer, you can check my website in my profile, I know what I'm talking about here.
- was_a_dev 2y ago
  There's a bit of difference between the aims of astrophotography and professional astronomy. Ones getting a subjectively good image where the other is getting an objectively good quantitative measurement. Do the software "tricks" really translate that well. If they did, these terrestrial telescopes wouldn't engineered to the tune of billions.
  - malfist 2y ago
    Stacking isn't a "trick". It's mathematics. I agree my aim is to make pretty pictures, and professional astronomy is to take accurate imagery, but up until I'm making subjective calls about colors, they're not too far apart before the image is stretched to a non linear histogram. After all, I can't build pretty pictures on crappy data. Astrophotography is a heck of a lot of math

WithinReason 2y ago

Not to mention this only happens at dusk and dawn when the satellites are in sunlight.