[HN Gopher] SpaceX tests black satellite to reduce 'megaconstell...
___________________________________________________________________
SpaceX tests black satellite to reduce 'megaconstellation' threat
to astronomy
Author : pseudolus
Score : 154 points
Date : 2020-01-16 16:39 UTC (6 hours ago)
(HTM) web link (www.nature.com)
(TXT) w3m dump (www.nature.com)
| a-wu wrote:
| I have no experience in astronomy or satellites, but here's my
| naive idea. The article suggested erasing trails from the images
| using software. If SpaceX made an open API that detailed the
| precise location of every satellite at every point in time, could
| the imaging software use this to know that at this location in
| the image there is definitively a satellite that can be erased?
| I'm not sure what kind of sensors these telescopes use, and it
| probably wouldn't solve the issue of the bright spot messing up
| the exposure, but at least you could get rid of the trails?
| cgriswald wrote:
| I've mostly dealt with amateur and semi-pro equipment and I'm
| not certain what the state-of-the-art is so someone else might
| be able to answer this better than me.
|
| These telescopes essentially work by capturing photon counts on
| a sensor. The individual pixels on the sensor have a limit to
| the number of photons they can count. You could theoretically
| subtract the satellite pixel-count values from the photon
| counts to get rid of the trails. The two problems I see are: 1)
| You don't know the correct counts for the satellites and I'm
| not sure how you could get them. 2) The trails will probably
| saturate the pixels anyway (which can also cause bleeding into
| other pixels), in which case you just don't have the data of
| what's 'behind' the trails.
| Groxx wrote:
| could they put an LCD in front of it, and block the relevant
| pixels as a satellite passes?
| redisman wrote:
| That would limit your resolution to the resolution of a LCD
| panel. Also just not how cameras work
| petschge wrote:
| Tl;dr: Perfect subtraction is impossible due to physics.
|
| Problem is: With photon count the uncertainty in the number
| of photons also goes up (the relative error goes down). So
| even if you know that you should have received 100 photons
| from the satellite (and have not reached the overflow of 256
| in this example yet), Poisson statistics means you will
| actually get anything between 90 and 110 photons. So if you
| subtract 100 you have an uncertainty of plus or minus 10
| photons left. That is deadly if you astronomical source only
| gave you 2 photons in that pixel in that time.
| hackinthebochs wrote:
| Are the sensors recording a timestamp with the photon counts?
| If so, it should be trivial to filter out bright fast moving
| objects with zero impact on image fidelity.
| petschge wrote:
| Photons are not individually time tagged (that is much
| harder and reduces quantum efficiency due to dead times),
| but rather are collected for some exposure time (think 30
| seconds) and then their count is read.
| HorstG wrote:
| one gets time signals from photomultipliers, but those
| are too bulky for traditional pixel sensors. And
| something as bright as a satellite flare might fry them
| at an unexpected moment. They are usually built and tuned
| to be able to observe few to single photons.
| modeless wrote:
| SpaceX is publishing the precise location of each satellite
| continuously. It's really cool actually; most satellite
| operators don't do this. The raw data is available at Celestrak
| here: https://celestrak.com/NORAD/elements/supplemental/
|
| I'm using this data to power my site that shows when you can
| see Starlink yourself:
| https://james.darpinian.com/satellites/?special=starlink-lat...
| a-wu wrote:
| This is really cool
| pugworthy wrote:
| That "where" feature based on street view is really nice
| dgritsko wrote:
| This site is awesome! Have you thought about extending it to
| check for the position of the ISS? I would assume that
| information is probably readily available, as well.
| modeless wrote:
| Thanks! Yes, it can track most of the other bright
| satellites in the sky as well, try the base page link:
| https://james.darpinian.com/satellites/
| keenmaster wrote:
| The overlay on a nearby Streetview showing where the
| satellite will likely appear, with a timeline-based
| trajectory, is especially impressive.
| xingped wrote:
| That's a really cool piece of software dude! Will definitely
| use this in the future to show some friends the starlink
| satellites.
| Rebelgecko wrote:
| What's the difference between the SpaceX supplied TLEs and
| ones derived from other sources? More accurate? Updated more
| often?
| modeless wrote:
| > More accurate? Updated more often?
|
| Yes. There's only one other (public) source, https://space-
| track.org/ which publishes tracking results from US
| military radars. But the tracking results aren't as
| accurate as the satellites' own telemetry data.
| king07828 wrote:
| Going further, put a small space facing camera on each
| satellite. The images can be stiched together to improve
| resolution and maintain continuous observation of space at all
| angles. Image downloads can be limited to save bandwidth.
| jaywalk wrote:
| Are you joking?
| redisman wrote:
| Probably not. I see a lot of ridiculous "startup-hacks" for
| a hard science problem in this thread.
| rtkwe wrote:
| Telescope images are usually long exposures so that won't work.
| AFAIK there's no method of selectively dumping or damping the
| pixels only ass the Starlink satellites pass through the frame.
|
| To do it you'd need a screen in front of the sensor that could
| occlude the pixels that the Starlink sats were passing over..
| skybrian wrote:
| If you're doing image stacking, could you dump some frames
| that were ruined? It would take a bit longer to collect
| enough frames.
| petschge wrote:
| During twilight our section of EVERY frame would be ruined.
| Massively reducing the useful observation time during
| twilight. And keep in might that some sources are only
| visible to some telescopes during those hours. And we have
| neither the money to build arbitrarily many new telescope,
| nor the suitable locations with good conditions.
| tropo wrote:
| Astronomers do put a screen in front of the sensor to occlude
| pixels. This is to block the light of natural space objects
| that get troublesome.
| rtkwe wrote:
| Those are static though right? For starlink you'd need to
| have it moving.
| orbital-decay wrote:
| Nearly every object in orbit is already tracked and any
| specific object of interest can be tracked even more precisely,
| so no need for an additional API. That won't work as they use
| multiple hour exposures that accumulate the light, you can't
| "erase" something, as most of the info is already discarded,
| unless it's a deep stack. You can try recording the video of
| the same field of view with a smaller auxiliary telescope,
| accounting for the satellites that crossed the view of the big
| instrument in the resulting exposure. But that's still
| artifact-prone, and won't work in many cases (saturated pixels,
| very faint objects etc). You have to pause the exposure for
| every satellite that crosses the view, if that's possible at
| all.
| namibj wrote:
| It's possible with a shutter. Not easy, but feasible.
| orbital-decay wrote:
| I mostly meant observational possibility, not a technical
| one. Astronomers rarely have photons to waste.
| deegles wrote:
| SpaceX could provide a handful of at-cost launches for astronomy
| projects per year. It wouldn't fix anything for the ground
| telescopes but could be a bit of an olive branch for the
| community.
| SiempreViernes wrote:
| Even if they were _free launches_ that wouldn 't rank above a
| taunt: most of the satellite cost is in the development and
| construction anyway.
| saterHater wrote:
| I wonder how much it would cost to get a decent camera on one
| of those Starlink launch missions just so it would beam down
| some distortion free, high-resolution pictures to the masses.
|
| Although I doubt that would provide meaningful data to
| professional astronomer.
| desireco42 wrote:
| You have to give credit to SpaceX for tackling this thing head
| on. If someone else was in question, I don't think they would be
| as responsive.
|
| We are also coming to a point where we have to acknowledge that
| sky is changing and astronomy or where we place telescopes should
| change. Depending on what is being observed.
| biomcgary wrote:
| A couple years ago I moved near Lowell Observatory and our city,
| Flagstaff, has a number of Dark Sky ordinances, which are great.
| I've seen so many more stars than ever in my life. We just bought
| our kids a Newtonian reflector telescope.
|
| Most things have trade-offs. Hopefully, the reduced cost of
| access to space will allow launching of more space-based
| telescopes, which don't have problems with atmosphere. Any
| astronomers here that care to explain what only ground-based
| observatories can do?
| Rebelgecko wrote:
| Not an astronomer but things you can do on the ground:
|
| 1. Bigass telescopes. Some radio telescopes are 100 or even
| 1000 feet across. You can't put something like that easily in a
| rocket fairing. JWST has a _20 foot_ mirror and they probably
| spent hundreds of millions of dollars figuring out how to fit
| that thing in an Arianne 5.
|
| 2. Easy maintenance and upgrades. There are 80 year old
| telescopes still doing useful science since you can make
| incremental upgrades over the years. (shoutout to Hubble: at 30
| I think it's probably the longest lived space telescope, even
| if it's getting a bit long in the tooth)
|
| 3. Interferometry. This would potentially be really cool to do
| in space, since you could theoretically make a telescope whose
| diameter is tens of thousands of miles. However, interferometry
| requires you to be able to position yourself really accurately
| (amount of accuracy you need depends on wavelength and a few
| other factors, but potentially at the micro-meter level).
| That's really hard to do in space.
|
| 4. You can build a bunch of ground based observatories for the
| cost of a single space one.
|
| 5. Data downlink. Some telescopes generate a lot of data. It's
| not easy to get a terabit per second of data down to the
| ground.
| _verandaguy wrote:
| Not an astronomer, but ease of maintenance comes to mind. If a
| mirror is defective on a ground-based telescope, it's easier to
| build a replacement and install it. Hubble had a defective
| mirror which required an essentially dedicated Shuttle mission
| in the mid 90s.
| petschge wrote:
| Mounting new detectors, fixing broken things, swapping out
| (optical) filters and shear mirror size are all a big problem
| for satellites. No atmosphere is nice for IR, but current
| optical telescopes are 10 meters and up, much larger than even
| a Falcon 9 heavy can fit.
| tropo wrote:
| 10 meters should be doable. You'd need a custom fairing.
|
| Probably you'd want a fairing that holds the mirror on edge,
| so that it travels edge first as if looking to the side
| during launch. This would save on air resistance during
| launch.
| _verandaguy wrote:
| Spoken like someone who's spent a bit too much time in KSP
| :)
|
| There are more issues than just sheer mirror size in this
| case.
|
| - Resistance to vibrations is a _major_ issue if the mirror
| is monolithic (as with HST) as opposed to segmented (as
| with JWST).
|
| - The mirror also has to either be very resistant to
| extreme temperature changes (and the contraction that comes
| with it), or must be cooled before launch. For extremely
| large mirrors, the cooling assembly would add _tons_ of
| extra weight, since this would most likely be
| active/liquefied gas cooling, and the weight of the cooling
| medium alone would be significant in this case.
|
| - Using a shape that's close to being a cylinder is great
| for cooling too, because cylinders have a very good surface
| area-to-volume ratio, which matters when you have to
| account for heat exchange. If memory serves, only
| ellipsoids are better (with spheroids being a better than
| ellipsoids, and spheres being ideal).
|
| - The support structure for the mirror (the satellite
| fuselage proper) would probably have to fit in there too,
| at least for the first launch. That's not small, even
| though it can be made collapsible.
|
| - All of the optical elements have to stay outstandingly
| precisely positioned within insanely tight tolerances. Any
| shifting could result in a lack of clarity, chromatic
| aberrations, or other issues, even if the mirror(s) aren't
| directly warped or damaged.
|
| Even accounting for that, a fairing that's irregular around
| the long axis of the rocket is often undesirable. While it
| reduces (compared to the alternative), it can cause issues
| with rolling after launch, and introduces additional
| complexity.
| NikolaeVarius wrote:
| You can make really really really big mirrors,. Space
| telescopes mirrors are limited by Fairing size, so barr folding
| mirrors ala James Webb, there is a fairly hard limit.
|
| https://en.wikipedia.org/wiki/Extremely_Large_Telescope
| modeless wrote:
| That's one of the reasons I'm excited about SpaceX's
| Starship. It has a large diameter, so space telescope mirrors
| can be much bigger with less folding.
| C14L wrote:
| And it will (hopefully) be able to fly to the moon "for
| cheap" and put large, land-based telescopes in the best
| location there is for telescopes.
| marvin wrote:
| Do you know anything about development work that's been made
| regarding manufacturing mirrors in space? I'm not thinking
| assembling them from pieces, I'm thinking more about melting
| some raw material and using some physical process to create
| in space something larger.
| clmul wrote:
| The manufacturing tolerances for large mirrors are very
| small, and it seems unlikely that we would be able to do
| this - note that barely any manufacturing has been done in
| space.
|
| Assembling from pieces on the other hand, is more doable.
| ceejayoz wrote:
| I wonder if something akin to glassblowing would work in
| zero-G.
| HorstG wrote:
| Gravity is an issue for mirror production. But it is far
| less of an issue than tension and deformation during the
| months- to years-long cooling of the substrate. The
| temperature and environment control to do that is
| challenging on earth, fairly impossible in space. Except
| with maybe a really really huge spacestation as a thermal
| sink, which we won't get for the next few hundred years I'd
| guess...
| LargoLasskhyfv wrote:
| I've read a novel from Daniel Suarez titled Delta-v.
| Chapter 31, Alchemist beginning on page 175 and ending on
| 177 changed my assumptions about that. With not that much
| suspension of disbelief. It's about chemical vapor
| deposition at large scale, the chapter, not the whole
| book. _That_ is about near term asteroid mining.
|
| edit: book -> novel
| m4rtink wrote:
| Aren't the terrestrial mirrors so thick due to the need
| to survive all the tilting under the strong terrestrial
| gravity ?
|
| I would assume a micro gravity only mirror could be much
| thinner & thus easier to cool down. Or possible
| alternative techniques could be used to get the needed
| reflective surface geometry if it does not need to take
| gravity and atmosphere into account.
| HorstG wrote:
| Yes, but stability against vibration and thermally
| induced warping is also important. So you could make the
| mirror thinner than on the ground, but not really thin.
| petschge wrote:
| You also need a minimum thickness and stability if you
| ever want to turn the mirror to point elsewhere.
| njarboe wrote:
| Aren't the newest and biggest ground based telescopes made up
| of many mirrors that have millions of actuators on them to
| correct for atmospheric distortion? I don't see why you
| couldn't make similar multi-mirror telescopes in space. Here
| is a link to an article[1] that shows three of the biggest
| telescopes that have 7, 798 and 492 individual mirrors
| respectively. The biggest one has the most mirrors.
|
| [1]https://www.space.com/22505-worlds-largest-telescopes-
| explai...
| NikolaeVarius wrote:
| Yes. You still have to fit it in.
| ISL wrote:
| Physics does not exclude such an instrument. Budget does.
|
| Shipping complicated physical hardware to space requires
| that it absolutely must work on the first try, and never
| require maintenance for the lifetime of the instrument. In
| contrast, the large earth-based telescopes can be regularly
| updated, maintained, and debugged. Access for such
| activities costs as much as a plane ticket to Chile,
| instead of a dedicated mission to space.
| Filligree wrote:
| That limit won't exist forever. Sooner or later we'll get
| space-based industry, and I'd rather that be sooner.
|
| I'm as much a fan of astronomy as anyone, but I'm not willing
| to let it block the best chance we currently have of becoming
| a space-faring species. The comm satellites aren't important,
| but the launch capacity scaling is.
| m4rtink wrote:
| Exactly, eventually you should be able to build much bigger
| telescopes than what can be reasonably built on Earth
| thanks to the lack of gravity, no horizon and no atmosphere
| to trash your giant scope with a storm.
|
| Many kilometers in diameter in circumference should be
| possible and likely much more. The whole thing would at the
| same time be likely really really light, just thin
| stabilized foil, as it does not need to fight gravity or
| survive launch loads. Could be quite a sight. :)
| orbital-decay wrote:
| _> eventually you should be able to build much bigger
| telescopes than what can be reasonably built on Earth
| thanks to the lack of gravity
|
| >Many kilometers in diameter in circumference should be
| possible and likely much more._
|
| This is a misconception. There is plenty of "gravity".
| The mirror has to keep a very precise shape and attitude,
| which severely limits the possible size, considering it
| has to be light and is a subject to gravitational
| perturbations. Large and thin constructions in space
| (solar panels, antennas etc) are mechanically non-trivial
| on their own, and for telescope-quality mirrors it seems
| downright impossible.
| K0SM0S wrote:
| I'd say it may envisioned _theoretically_ (better
| materials, new photo-sensor processus, you-tell-me,
| physics say we have a much higher bound).
|
| But in the short-medium term, the cheapest course that
| delivers is to use normal telescopes and interferometry
| (say on some orbit between Venus and Mars). I'm pretty
| sure it's also a domain where narrow AI may help because
| finding "anomalies" in space is a lot like finding
| anomalies on X-rays to find malignant tumors -- something
| AI apparently can do well. Both problems fit incredibly
| large datasets + ultra low resolution of said anomalous
| blobs, and discrepancy with normal ones barely
| statistically significant (well below what human eyes may
| spot).
|
| This is how I see the immediate future of space-based
| observation: lots of small things that cooperate
| extremely (increasingly) well with each other, "networks"
| more than "giants", much like down here on the ground.
|
| It's just easier, cheaper, and lets you grab a lot of
| low-hanging fruits. Meanwhile, space-based fabrication
| can kick off and take the time to reach 'self-sustaining'
| velocity.
| clmul wrote:
| But why would you want that we become a space-faring
| species, at all costs? There is not much interesting to
| find in space, compared to what we have on Earth
| (especially not close to us, and I do not see us getting
| out of the solar system for a long time). Perhaps you could
| argue that we might do asteroid mining at some point, but
| at the moment that's very far out of reach.
| short_sells_poo wrote:
| Because we are limited in every conceivable way down here
| on Earth. Transportation is expensive, resource
| extraction is expensive, resources are limited, space is
| limited, pollution is a problem, energy generation runs
| into geopolitical, geographical and efficiency issues.
| And so on.
|
| Never mind the problem of us being one asteroid strike or
| supervolcano away from a cataclysm, and that's not an if
| but a when.
|
| I have a feeling that for humans to transcend the
| proverbial great filter, we have to tap into the vast
| quantities of resources and energy in the solar system,
| but more importantly rekindle the pioneering era that
| last ended with the industrial revolution.
|
| The expensive part of the space industry is lifting
| infrastructure from ground to space. Moving within the
| solar system is comparatively cheap if we avoid
| descending into the gravity well of other planets.
| Luckily, this is unnecessary for most asteroid mining.
|
| Humankind experienced incredible advances with the
| toppling of every transportational frontier. The wheel,
| seafaring, motorized transport and flight all resulted in
| expansions lasting a hundred years each.
|
| The next frontier is the solar system. We don't know if
| we'll be able to ever leave it, but that's irrelevant
| because it can be our home for the next billion years.
| Our best shot at actually preserving the habitability of
| Earth is exploiting resources out in space.
| outworlder wrote:
| Exactly. We need a backup. Right now, the Earth is a
| single point of failure.
| K0SM0S wrote:
| I have no idea who downvotes such a wonderfully worded
| and inspiring comment, but surely, those willing to
| follow the space path and those willing to remain here on
| Earth should neither deny the other side of their dream
| nor enact "rules" that forbid it.
|
| In fact, I'm pretty sure both "sides" would benefit
| greatly from cooperating. It might even be that these
| aren't "sides" but just different cousins of the family
| with different outlooks on _their own_ life, and we need
| a little bit of everything, and everyone, to make a
| world.
| vidarh wrote:
| It's all always going to remain out of reach for a long
| time if we don't try.
| m4rtink wrote:
| There is also the possibility that we miss an open window
| of opportunity. This might be a key resource running out,
| a plague or global war or even an asteroid impact.
|
| That might close the window of opportunity and not give
| us a second chance. So better not risk it. :-)
| EthanHeilman wrote:
| I'd bet you a coffee that, barring a collapse or decline
| of our present global society, we will have launched a
| probe to another star before 2100 with a planned arrival
| before 2150.
| HorstG wrote:
| Launch capacity scaling isn't only possible through useless
| comsats.
|
| And astronomy is still an extremely important component for
| becoming space-faring. No use in going somewhere blindly
| when you can have a look first. But if there is no-one
| looking because nothing to see, funding dried up,
| scientists demotivated,...
| zekrioca wrote:
| Astronomers are already criticizing such ideas, and have already
| created an international appeal by professional astronomers open
| for subscription to ask for an intervention from institutions and
| governments. See: https://astronomersappeal.wordpress.com/
| audunw wrote:
| Question: If SpaceX is successful in developing the Starship,
| couldn't they launch huge space telescopes for a very low cost?
| I'd imagine that SpaceXs efforts will be a net positive for
| astronomers in the end. If the satellite problems becomes too
| big, maybe they should offer discounts for launching space
| telescopes.
|
| Another question.. if you are building a radio telescope in
| space, could you just use a thin foil that folds out like origami
| for the reflector?
| dr_orpheus wrote:
| > If SpaceX is successful in developing the Starship, couldn't
| they launch huge space telescopes for a very low cost?
|
| If the BFR (the rocket behind the starship) is successful then
| yes it could mean the ability to launch very large telescopes
| in to space. The scientific community would be very exited
| about this possibility. However, this doesn't necessarily make
| it very low cost. One launch of the BFR would still likely be
| much more than an a Falcon Heavy launch.
|
| > if you are building a radio telescope in space, could you
| just use a thin foil that folds out like origami for the
| reflector?
|
| Yes! This technology already exists and it is really pretty
| amazing to see in action. Right now most of them are used on
| communications satellites or for synthetic aperture radar
| satellites. See the videos below:
|
| Animation of the radar antenna on SMAP:
|
| https://smap.jpl.nasa.gov/resources/83/smap-antenna-deployme...
|
| Actual video of a large communcations antenna (12m diameter)
| being deployed. Skip ahead to ~2:15 for the actual unfurling.
|
| https://www.youtube.com/watch?v=_mFnNDzxKFk&feature=emb_titl...
| itp wrote:
| Couple quick clarifications:
|
| BFR isn't a name that's still in use. Poster you're
| responding to was correct in calling it Starship: "SpaceX's
| Starship spacecraft and Super Heavy rocket (collectively
| referred to as Starship)" (from
| https://www.spacex.com/starship).
|
| Starship projects to be significantly less expensive than
| Falcon Heavy _or_ Falcon 9. With total reusability of both
| stages and a construction built toward little to no refurbish
| or rehab, the cost per launch is nearly completely dictated
| (order of magnitude) by fuel costs, and project to be ~$2
| million. This is an order of magnitude reduction in $/kg over
| the Falcon 9.
|
| https://www.space.com/spacex-starship-flight-passenger-
| cost-...
|
| https://www.thespacereview.com/article/3740/1
| dr_orpheus wrote:
| The article you pointed to said that is would be $2 million
| that SpaceX would have to spend on each launch. That would
| not be the amount for someone to purchase a launch with
| that rocket. Considering Elon estimated that development
| would cost $5 billion to $10 billion [1], the cost of
| launch would likely be much higher based on recouping the
| intial development and manufacturing costs.
|
| As a side note, I don't really believe the $2 million price
| tag either based on my own experiences. Mission specific
| planning/services/verification tend to push prices of
| launches 10s of millions of dollars above the "sticker
| prices" that SpaceX puts on their website.
|
| Nothing against SpaceX, I am a fan of everything they have
| done to decrease launch costs. They have significantly
| changed the game in terms of lowering launch costs. But it
| is really hard to take Elon's wild numbers that he gives
| the press at face value.
|
| [1] https://www.theverge.com/2018/9/18/17873332/spacex-
| elon-musk...
| Rebelgecko wrote:
| Launch costs are a relatively small part of the cost of space
| telescopes. Pretty much always less than 10%, sometimes as low
| as 2% of the program's cost. The expensive part is building
| something that can run for years at a time with no maintenance.
| Things that are relatively easy on the ground (keeping some
| parts at cryogenic temperatures, having enough electricity) get
| significantly more complicated (and expensive) in space.
| jcims wrote:
| But if launch costs go from $400M to $4M maybe it's ok to put
| stuff up with dramatically shortened mission expectations.
|
| What really needs to happen is the ability to build mirrors
| in LEO so they don't have to be built to survive the launch.
| SiempreViernes wrote:
| Saving 8% of the total budget will not make it easier to
| make reliable cooling systems, nor easer to get the
| remaining 80% of needed funds.
| jjaredsimpson wrote:
| How much of the leading edge of astronomy is ground based, vs
| space based? Are they complementary or is space based going to
| eventually assume any and all roles ground based could?
| petschge wrote:
| That depends on the wave length regime.
|
| Radio is firmly ground based, because you need huge dishes and
| potentially many (thousands) of them, at very precisely known
| distances.
|
| IR is mostly space based (with SOFIA and ALMA the notable
| exception) because of atmospheric absorption.
|
| Optical is firmly ground based, due to much lower cost for
| large telescopes. (See https://doi.org/10.1117/1.2031216 for
| the factors that affect cost). The notable exceptions are
| Hubble and satellites monitoring the sun such as Stereo and
| SDO.
|
| X-Ray is space based again due to atmosphere.
|
| Gamma-ray telescopes are an interesting mix between ground
| based air cherenkov telescopes (IACTs such as Hess, Magic and
| Veritas) and water cherenkov detektors such as HAWK and space
| based Fermi (with relatively poor sensitivity and low upper
| energy cut off, but very wide field of view).
|
| Neutrino detectors are firmly ground based because the need
| huge detectors (the cubic kilometer of icecube is basically the
| lower limit).
|
| So they are very much complementary. And some things will
| probably never moved to space, even if launch was free.
| penagwin wrote:
| Slightly off topic but I love the fact that (over
| simplifying) some of our most advanced technology - for
| detecting neutrino - is a cubic km of ice.
| petschge wrote:
| It is very clean ice, with is shielded by another 1.5 km of
| ice on top and that is filled with more than 5000
| photomultipliers.
| m4rtink wrote:
| For radio telescopes, some Very Long Baseline Interferometry
| experiments have a space based component:
|
| https://en.wikipedia.org/wiki/Very-long-
| baseline_interferome...
| SiempreViernes wrote:
| RIP Radio Astron :(
|
| http://www.asc.rssi.ru/radioastron/news/newsl/en/newsl_36_e
| n...
| clmul wrote:
| If we are talking about visual light astronomy (the wavelengths
| where black satellites could help), a majority of astronomy is
| ground based. There exists just a single capable space
| observatory in visual light, the Hubble telescope, which will
| be going out of service in a few years. There's some metrics
| here[1] which show that about 10% of the most cited papers use
| Hubble data, which is still quite impressive. This is dated
| though, it could very well be that Hubble is becoming less
| relevant with recent advances in technology.
|
| [1]
| http://www.stsci.edu/%7Ewebdocs/STScINewsletter/2003/spring_...
| WhompingWindows wrote:
| Let's think about this rationally...is there a cost-benefit
| analysis for global internet access vs higher fidelity astronomy?
| Can astronomers use software and API's to minimize the downsides?
| Are the upsides for human inter-connectivity as great as claimed?
| ramraj07 wrote:
| My initial reaction was NO, but then saner minds prevailed and
| you might have a point - to be able to get unrestricted
| internet in China or Iran or India (didn't realize how bad
| censorship was even here. And satellite internet is a criminal
| offense) would be amazing. We might still not get it though,
| since it's not just receiving but also transmitting, so
| surreptitiously using SpaceX internet might not be possible in
| those places.
|
| If you can't solve that problem, then I don't think it's worth
| it just so some first world folks can YouTube when camping.
| C14L wrote:
| Accessing those satellites from China or Iran or North Korea
| and many other countries (though, why did you mention India?)
| will probably still be illegal.
|
| But there are many poor countries with rural areas that have
| almost no Internet access and would greatly profit from it.
| Starlink seems to be especially useful for people in those
| areas.
| SiempreViernes wrote:
| _Are_ there that many poor rural areas that could use and
| pay for internet? It seems necessary that they have both
| electricity _and_ digital devices, which isn 't really
| something you see in what I would consider _poor_ rural
| area on a global scale. You might be thinking of a poor
| _urban_ area instead, the poor rural areas in sub-sahara
| africa rarely have built up _stoves_ , so requiring
| electricity is pretty far fetched.
| chr1 wrote:
| Starlink is important not simply because it gives faster
| internet, but because it creates steady demand for space
| launches. The only way we can get cheap and reliable rockets
| is using them for something, and at this point rockets do not
| have many other uses. So if spacex gets "first world folks"
| spend their money on improving rockets, it's good for
| everyone!
| cma wrote:
| I would think Space X isn't even going to transmit to the
| ground in China.
| C14L wrote:
| It will be very interesting to see how China will react to
| this. Will they use the Tesla investment in the country to
| "convince" Musk to disable the signal when the satellites
| are over China? Or will they simply make the satellite
| receivers illegal and not care about the few who use them
| anyways?
| SiempreViernes wrote:
| The will undoubtedly apply financial pressure, regardless
| of what other actions they take.
| Traster wrote:
| Rationally the company that was founded by a guy who thinks we
| need to start seriously considering space travel probably
| shouldn't be fucking up our primary way of studying space.
| AWildC182 wrote:
| NRO already does this. "Stealth" satellites are a big area of
| interest right now.
|
| https://en.wikipedia.org/wiki/Misty_(satellite)
| rtkwe wrote:
| NRO is willing to spend much more than SpaceX is on these and
| they're (probably) much larger giving them more volume to deal
| with the additional heat accumulation that comes with a darker
| satellite.
| reaperducer wrote:
| I find this interesting considering that when the threat to
| astronomy from these swarms of thousands of satellites from
| dozens, maybe eventually hundreds, of different companies was
| first brought up on HN, there was a massive outcry from the
| technosphere saying it was a non-issue and saying that satellite
| internet is far more important than being able to see a natural
| sky.
|
| At least SpaceX seems to be taking these concerns a little
| seriously.
|
| Also, wasn't there a sci-fi TV show not that long ago that was
| popular on HN that had a theme song along the lines of "They
| can't take the sky from me?" I guess the lyricist was wrong.
| petschge wrote:
| Yeah it is interesting that people are more willing to
| sacrifice the night sky then exert political pressure to get
| the horrible internet situation in the US fixed.
|
| Also interesting how people who could not find the big dipper
| think that removing the streaks is "just basic image
| processing" without knowing anything how modern astronomy is
| done. Never mind that professional astronomers are complaining.
| Oh and of course you get suggestions like "you can just fill a
| 30 km bubble with gas in space and use that". As another
| commenter put it nicely "everything is trivial when it is
| somebody else problem".
| reaperducer wrote:
| A lot of arguments in this HN discussion boil down to "It's
| not that bad and it doesn't matter because this will earn
| Saint Elon enough money will fix it!"
|
| That's like saying "Sure, let the giant industrial
| conglomerate dump toxins in the drinking water. That way it
| can earn enough money to build a machine to clean the water
| up and sell it back to us and everyone will be happy!"
|
| Why not just not pollute the water in the first place?
| bscphil wrote:
| > A lot of arguments in this HN discussion boil down to
| "It's not that bad and it doesn't matter because this will
| earn Saint Elon enough money will fix it!"
|
| This is a forum for engineers (for a broad sense of
| engineer). We like to talk about technology. We like to
| speculate about the future and about politics. Starlink is
| a _cool_ idea, so it 's not surprising there's enthusiasm
| for it.
|
| We should not be put in control of anything, ever. If that
| weren't already common sense, you'd just need to put half a
| dozen policy threads from Hacker News in front of a
| congressional committee to have them warning of the dire
| effects of engineer influence. Stuff we create should be
| heavily regulated when it attempts to "disrupt" society,
| like Uber or a lot of Silicon Valley startups.
|
| Uncharitably, you might say HN has a ton of Dunning-Kruger
| about anything not directly technology related. I wouldn't
| put it that way: it's everyone's right to speculate about
| politics, the future, and values, but most people here
| don't actually think they should be put in charge of
| anything.
| petschge wrote:
| > Uncharitably, you might say HN has a ton of Dunning-
| Kruger about anything not directly technology related.
|
| It's even worse. It is people thinking that because they
| are brilliant in some technical field (JS frameworks, or
| compilers, or machine learning or whatever) they are also
| brilliant in every other technical field (be it
| astronomy, high performance computing or medicine).
| caconym_ wrote:
| The path to fixing ground-based broadband in America doesn't
| seem obvious given how deeply entrenched the big ISPs are.
| It's probably actually much, much cheaper to build, launch,
| and operate a thousands-strong satellite constellation than
| it would be to dig out Comcast and its ilk, and quicker too.
| That's an extremely depressing fact (assuming it's correct,
| being a semi-educated guess), but it is what it is.
|
| But there's another dimension, which is that Starlink is
| supposed to be funding the only company that's materially
| doing anything new in the domain of spaceflight technology.
| For a bunch of nerds who grew up drenched in science fiction
| and promises of humanity's bright future in space, who've
| instead seen decades of regression in capabilities, and who
| live in the same world where my first paragraph is true ...
| that's very meaningful, far beyond the "fanboy" slur.
|
| Not saying I come down on either side of the Starlink
| should/should not exist fence, but I think the motives and
| attitudes of its proponents are often misrepresented and
| that's no way to have a productive conversation about it.
| kian wrote:
| Firefly. And ouch
| FeepingCreature wrote:
| I don't think that opinion has significantly changed.
| wiredfool wrote:
| I see a cube sat and I want it painted black
|
| No sparkles any more I want them to turn black.
| tinco wrote:
| Is there a specific reason we're still doing ground based
| astronomy? With satellites becoming ever cheaper, sure we at some
| point should be able to get a significant telescope up there
| right? Are we waiting for the bigger rockets to accomplish that?
| redisman wrote:
| Is there a specific reason we're still doing ground based
| datacenters? With satellites becoming ever cheaper, sure we at
| some point should be able to get a significant datacenter up
| there right? Are we waiting for the bigger rockets to
| accomplish that?
|
| That thought exercise should give you 90% of the answers to
| your question. The atmosphere and light pollution from cities
| are pretty easy to counteract with location and bigger optics.
| ubertakter wrote:
| Yeah. Depending on the spectrum, the telescope might need to be
| really big. Not to mention at the moment a telescope in orbit
| would hard, if not impossible, to service.
|
| Perhaps a review of telescope design is in order:
| https://en.wikipedia.org/wiki/Telescope
| https://en.wikipedia.org/wiki/Optical_telescope
|
| Building large telescopes is hard enough. Putting them in orbit
| just adds to all the costs. Look at the James Webb Telescope
| (which still hasn't been launched).
| https://en.wikipedia.org/wiki/James_Webb_Space_Telescope
|
| It seems possible to launch multiple small telescopes and
| operate them as one large scope using aperture synthesis. I
| don't know if there are any existing designs or plans for this.
|
| Also: somewhat ninja'd, see other replies as well.
| petschge wrote:
| > It seems possible to launch multiple small telescopes and
| operate them as one large scope using aperture synthesis. I
| don't know if there are any existing designs or plans for
| this.
|
| We know how to do that in radio (VLBI), have some experience
| in IR (ALMA), are doing research on how to do that in
| optical. But in practice that is much harder than you think.
| The relative distances of the telescopes have to be known and
| constant to within a few fractions of the wavelength you are
| using. Hard when you are using centimeter radiowaves,
| insanely hard with optical light that has 600 nanometers
| wavelength.
| clmul wrote:
| It's very expensive to build (especially large) space
| telescopes (JWST is already costing more than 8 billion at this
| point), and astronomy is not very well funded.
| tinco wrote:
| Aren't they mainly large so they have less hindrance of
| earth's atmosphere? Couldn't telescopes that are in space be
| smaller and have similar performance?
| petschge wrote:
| The are mainly large to increase resolution and
| sensitivity. Atmosphere limits how large you can make the
| mirror before hitting diminishing returns, but that is
| mitigated by good site selection, adaptive optics and lucky
| imaging (taking many exposures and keeping the least blurry
| ones).
| clmul wrote:
| Telescopes in space could have better performance, because
| you are not limited by atmospheric conditions for your
| angular resolution. But you still need a larger aperture to
| increase your theoretical angular resolution (see the
| Rayleigh criterion), and increase light gathering power.
| outworlder wrote:
| Can't you have a fleet (something like StarLink, but
| telescopes) and have a bigger effective aperture?
| HorstG wrote:
| Theoretically yes, through interferometry. But that is
| really difficult when there is relative motion within the
| constellation such as with starlink.
| petschge wrote:
| For radio we might be able to make it work. But we
| currently don't have the ability to position satellites
| to within 10 nanometers, which would be required to make
| this work in the optical range that you have just killed
| off on the ground.
| AWildC182 wrote:
| Large aperture means more light makes it into the
| telescope. JWST has a mirror assembly bigger than most
| ground based systems. It comes down to cost vs performance.
| For the cost of putting a small-mid sized satellite in
| orbit you can build one hell of an observatory that will
| function longer and have a much bigger tube. At a certain
| point it makes more sense to use orbital systems but only
| for certain types of experiments.
| LeifCarrotson wrote:
| It's fascinating to me that the telescope costs so much more
| than the launch.
|
| A high-quality 24" or 1-meter university-grade observatory
| telescope can be had for well under $1 million. If you
| multiply that by a factor of 100 to mount it on a satellite,
| you're still at 'just' $0.1 billion and can buy a whole
| Ariane-5 launch just like the JWST to put it at your desired
| orbit for $0.15B, for a total of $0.25B (a Falcon Heavy runs
| about half the cost for a launch). You could launch 30 of
| those (hopefully improving your factor-of-100 cost increase
| to something more manageable) for less than what the JWST
| will cost.
|
| I get that JWST is a 6.5 meter telescope, not a piddly
| backyard 24" device, but why do we have to launch the best
| single scope possible?
|
| There are only 7 visible-light space telescopes listed at htt
| ps://en.wikipedia.org/wiki/List_of_space_telescopes#Visib....
| I wish there were 70 or 700, with live Internet feeds.
| ISL wrote:
| JWST is being built to do things that are truly impossible
| on Earth. It is an infrared telescope that will image
| things that cannot be seen through Earth's atmosphere.
|
| JWST is not the first IR telescope (Spitzer Space
| telescope, retiring this month comes to mind, 0.85 m
| diameter primary), but its size will allow both improved
| resolution (diffraction limit falls like 1/diameter) and
| improved collection efficiency (grows like diameter^2).
| Without constellation-flying and interferometric telescopes
| (see Keck Observatory), one cannot get either one from an
| array of small telescopes.
|
| There are a lot of scientists grumpy about JWST because of
| its huge budget, but as long as JWST works, the view it
| gives of our universe will be spectacular. At this point, I
| think everyone _really_ wants JWST to work, as so much has
| been sacrificed to make it possible.
| Rebelgecko wrote:
| Your $1 million university telescope probably wouldn't work
| long in space without maintenance, the ability to regulate
| temps, and rad-hard electronics.
| trenning wrote:
| The university grade telescope, not sure what the entails,
| but I'm guessing it isn't hardened for radiation exposure
| and heat cycles seen in space. You can't use some off the
| shelf product unfortunately.
|
| Making things survive in space is hard. Working
| functionally for the lifespan of the telescope is really
| hard. There's not a lot you can do once it's up there.
| petschge wrote:
| See https://doi.org/10.1117/1.2031216 for the scaling of
| cost with size. It is very much not linear. Rather if you
| double the diameter the cost goes up by about a factor of
| 3.5 (closer to the area that went up by 4).
| boznz wrote:
| $500m for the telescope. $7500m for the pork.
| [deleted]
| superkuh wrote:
| Innumberable reasons. Data transfer, stability, power, heat
| dissipation, ability to use large area parts, accessibility for
| fixing and upgrades, and on and on.
| msla wrote:
| If SpaceX doesn't roll out a constellation like what SpaceX is
| proposing, someone else will, and that other entity (China,
| Russia, India, some up-and-coming African nation) will likely not
| be as receptive to the complaints of astronomers when they think
| their economic future rests on a quick, cheap Internet roll-out.
| fma wrote:
| What's stopping other entities from doing it...especially being
| able to say "Well SpaceX did it...".
| m4rtink wrote:
| Mainly electromagnetic spectrum allocations.
| Traster wrote:
| Can we stop with the whole "You've got to let an American
| company completely screw things up, because if you don't then a
| Chinese company might! And if a Chinese company does we won't
| be able to stop them even though when the American company
| screws things up we don't stop them anyway!" Routine. It's old
| and unconvincing and I don't think the people making this
| argument even really believe it. It was played out when Zuck
| said it to congress, let alone now.
| ZhuanXia wrote:
| Astronomers will have to get used to this. If we ban these for
| such nonsense reasons, it will be Chinese satellites blocking
| their view.
| going_to_800 wrote:
| Well put.
| bscphil wrote:
| Isn't this exactly the same view as "if we regulate the use of
| fossil fuels, China will use way more than us and outcompete us
| economically" and "if we limit the number of nuclear weapons we
| create, there's going to be a gap between our nuclear firepower
| and Russia's"?
|
| Creating a livable planet is not easy, but nationalistic
| thinking makes it a hundred times harder.
| Mangalor wrote:
| "nonsense reasons"
|
| You mean..."Science"?
| fastball wrote:
| What _useful_ science has been achieved in the last 100 years
| thanks to astronomy?
|
| Meanwhile, what kind of useful science do you think can be
| facilitated by globally accessible high-speed internet? The
| value generated by such a network is clearly orders of
| magnitude more useful than observing the cosmos, at this
| juncture of human endeavor. Not too mention that Starlink
| will allow SpaceX to re-invest more and more money into space
| launches / space travel. I'd much prefer humans actually
| visit other celestial bodies rather than just staring at
| them.
| SiempreViernes wrote:
| We pretty much _have_ globally accessible high speed
| internet though, and poverty is the main factor blocking
| significant further access, not mountains.
| petschge wrote:
| What useful thing has been produced by the internet? I'd
| much rather have humans enjoy nature than writing about it
| on the internet.
| fastball wrote:
| Surely you can't be serious.
| [deleted]
| modeless wrote:
| The satellites can be seen with the naked eye. There's a visible
| pass over San Francisco tonight around 6:15 PM:
| https://james.darpinian.com/satellites/?special=starlink-lat...
|
| The viewing window is actually pretty small. For most of the
| night the satellites are not visible because they are in Earth's
| shadow. There is an impact on astronomy but it is being
| overstated by journalists hungry for yet another "Big Tech bad"
| story.
| scrumbledober wrote:
| hopefully the clouds clear up before then!
| growlist wrote:
| > The impact on astronomy is being overstated by journalists
| hungry for yet another "big tech bad" story.
|
| Indeed, and let's not forget that Elon has upset a lot of
| applecarts with SpaceX and Tesla.
| petschge wrote:
| Depending on source class and telescope location it ruins
| between 1/3 and 1/2 of the available observing time. Are you
| willing to pay $1 more in taxes to to fund the extra telescopes
| we need to make up the short fall? Please write to your
| representatives and senators if you do.
| modeless wrote:
| Yes, I am for building more telescopes, and especially space
| based ones which should become much cheaper to launch when
| SpaceX's Starship is ready.
| petschge wrote:
| Space based works for optical, but not all other wave
| length. For example it will also reduce the sensitivity of
| air cherenkov telescopes that detect gamma rays and that
| can not be moved to space.
| dnautics wrote:
| is cherenkov radiation even observable during dawn/dusk
| +/- 2 hours? I imagine that the atmospheric refraction of
| the sun would seriously hamper those observations during
| that time period.
| petschge wrote:
| On traditional telescope using photomultipliers such as
| Magic, Hess or Veritas: no. But systems with solid state
| detectors such as FACT are moving in that direction.
| xur17 wrote:
| Why can't those be moved to space?
| rtkwe wrote:
| They are imaging the flashes as the relativistic
| particles slam into our atmosphere. No atmosphere, no
| flash.
|
| https://en.wikipedia.org/wiki/IACT
| HorstG wrote:
| Because cherenkov radiation is only observable in a
| transparent medium like air or water. Space doesn't work
| because the speed of light in space equals the speed of
| light in vacuum, therefore no cherenkov radiation.
| Taniwha wrote:
| Couldn't they look down?
| petschge wrote:
| The Cherenkov emission is boosted in the direction of
| travel, i.e. downward. And there are too many lights on
| the surface of the Earth.
| HorstG wrote:
| Cherenkov telescopes for neutrinos do look down for
| reasons of schielding. Neutrinos can pass the earth,
| other particles not so much.
|
| But those are a special case, air cherenkov telescopes
| are looking for "less weird" particles like photons or
| protons. Those can only be seen looking up, since the
| primary particles moving down focuses the cherenkov light
| down in a narrow cone.
| m4rtink wrote:
| While this certainly requires non trivial large scale
| space engineering, you should be able to build in in
| principle.
|
| Basically a big bubble filled with the most useful gas
| for this + bunch of photodetectors inside at the
| appropriate places. You could also make the whole
| detection chamber much larger, than the ~30 km (?) of
| reasonably thick atmosphere you get on Earth.
| [deleted]
| Ajedi32 wrote:
| Would air cherenkov telescopes be significantly affected
| by additional satellites in orbit? It sounds like they're
| designed to detect high energy gamma rays striking the
| atmosphere, so probably not?
| gizmo385 wrote:
| Satellites and space-based telescopes are still
| monumentally expensive even if you ignore launch cost. The
| James Web Space Telescope has cost almost 10 billion
| dollars in development and won't even launch until (unless
| the schedule slips again) next year.
| [deleted]
| modeless wrote:
| One of the reasons JWST is expensive is its complex
| folding mechanism. Starship could launch a mirror bigger
| than JWST's in one piece.
|
| Another reason is that they're only launching one and it
| has to work perfectly the first and only time it's
| launched. That level of reliability in a one-off product
| is incredibly expensive to achieve. With dramatically
| cheaper launches it would make sense to launch a much
| larger number of less reliable but much less expensive
| telescopes.
|
| Another reason is politics, but SpaceX can't solve that
| one.
| pawelk wrote:
| > it would make sense to launch a much larger number of
| less reliable but much less expensive telescopes
|
| What if... SpaceX made up for the pollution they
| introduce by making the Starlink satellites look up the
| other way and push the captured data back to earth? The
| lens and CCD would be small, but with the massive volume
| (and clear sky) it could add up. Like the amateur set ups
| using an array of consumer grade cameras.
| FeepingCreature wrote:
| Space-based telescopes are expensive in part because
| launches are expensive, making it more effective to spend
| a lot of money on single telescopes.
| pfdietz wrote:
| Which telescopes are observing at 6:15 pm local time?
|
| The satellites are not in sunlight unless the sun is not that
| far below the horizon.
| reaperducer wrote:
| _The viewing window is actually pretty small._
|
| Tonight. And what about when SpaceX gets all 11,000 satellites
| up there? And then Amazon's constellation. and then all the
| other American companies planning to do the same thing. And the
| European companies. And the Chinese companies and the Indian
| companies, and on and on and on.
|
| Dropping a piece of plastic in a lake isn't a big deal. Until
| it's 11,000 pieces of plastic. And then hundreds of other
| people do it, too.
| modeless wrote:
| The viewing window is the same length no matter how many
| satellites there are at the same altitude, because Earth's
| shadow is the same for all of them.
| esaym wrote:
| That's an amazing site, thanks!
| prpl wrote:
| No, it's not. This hurts survey telescopes and it's an orders
| of magnitude issue.
|
| A rule of astronomy is that if you can see it with your eyes
| near a city than it's really really fucking bright, if you can
| see it with your eyes in the wilderness after your eyes have
| adjusted for 10 minutes, than it's still extremely bright.
|
| Bright, fast-moving things are pretty terrible.
|
| Even if Starlink doesn't kill astronomy, the next 4 companies
| with similar deployment will definitely exclude types of
| sciences and ruin billions of dollars of investments in new
| observatories.
| shadowgovt wrote:
| > Bright, fast-moving things are pretty terrible.
|
| Why is that? Almost everything astronomy studies isn't fast-
| moving. Shouldn't it be easy to filter out that noise?
| tspike wrote:
| Bright = overexposure or unmanageable dynamic range
|
| Fast-moving = more likely for it to traverse your field of
| view while the shutter is open
| hackinthebochs wrote:
| This is what I'm wondering. It seems pretty trivial to
| filter out with some basic image processing.
| Klathmon wrote:
| I think there are 2 issues here, and it's making the
| conversation around it difficult.
|
| First is the impact to "professional astronomers", and
| from what I've seen this group won't be impacted nearly
| as much as the other. This group has the ability to use
| satellite based telescopes, or has the tech already to be
| able to filter/post-process the images to remove
| satellites, planes, meteor showers, and any other stuff
| that might get in the way.
|
| Then you have "amateur astronomers", this groups is
| likely to be impacted by starlink. This group doesn't
| have access to the digital filtering stuff that the "big
| guys" do, from what i've seen, most of the people in this
| group just use normal long-exposure setups and adding in
| a processing step would mean a pretty significant change
| to their process, and probably a lot of additional costs.
|
| Even still, the impact to amateur astronomers seems
| limited to when the sats are in sunlight, which
| traditionally isn't a super popular time for stargazing
| (although I may be wildly wrong on this, as I've read
| that these sats are removing up to 1/3 of the normal
| viewing time for some astronomers, so don't take this as
| gospel), and I still think the impacts will be a lot less
| doom and gloom than some are saying, but I still hope
| that SpaceX can work with the astronomy community to see
| if there are solutions or mitigations that can help
| everyone out.
| zAy0LfpBZLC8mAC wrote:
| So, you clear your CCD, collect photons for 30 minutes,
| then some satellite sprays you with a multiple of the
| number of photons collected thus far, and then ... what?
| reaperducer wrote:
| Everything is "trivial" when it's someone else's problem.
| Ididntdothis wrote:
| That's 100% true!
| [deleted]
| BurningFrog wrote:
| I think you're missing OP's point:
|
| Once the sun is set in their orbit, they should be invisible
| both to the eye and telescopes.
| reaperducer wrote:
| "Invisible" isn't quite correct. They won't be visible as
| white spots, they'll be black spots blocking out the things
| behind them. Not a big deal for human eyes. Quite a big
| deal for astronomers.
| lutorm wrote:
| This is totally false, the solid angle subtended by the
| satellites is tiny so the effect of their obscuration is
| totally negligible.
| reaperducer wrote:
| If it's flying in front of the sun, you are correct. If
| it's flying in front of an object 100 light years away,
| you are incorrect.
| natch wrote:
| The relative (apparent) motion differences and the fact
| that the locations of the satellites are known should
| take care of that, no? It's unlikely that the motions are
| going to track each other exactly in most cases.
|
| In fact if, as you believe, these satellites would
| actually occlude things beyond them, they sound very
| useful for calibration and education.
| modeless wrote:
| The satellites are not only small, they are also fast. A
| fast moving satellite can only occlude a 100 light years
| away object for a couple of microseconds before it
| passes. This is absolutely negligible for an astronomical
| observation lasting seconds to minutes. And even if you
| launched billions of opaque satellites they couldn't come
| close to blocking a big enough percentage of the sky for
| this to matter at all.
| DuskStar wrote:
| It'll block a star for ~1/2500th of a second (assuming a
| three meter blocking radius, and 7500m/s) - I wouldn't be
| surprised if that went undetected 99% of the time. At
| most it would read as a minor brightness fluctuation,
| right?
| endorphone wrote:
| It'd be in front of an object 100 light years away for an
| absurdly tiny amount of time. The percentage of the sky
| occluded by these satellites is absolutely minuscule.
| This is not a rational notion.
|
| These are not geosynchronous satellites, but instead are
| 200-500 miles above the Earth, moving many, many
| thousands of mph. No, it isn't blocking anything 100
| light years away unless your shutter speed is in the
| single-digit nanoseconds.
| ogre_codes wrote:
| Saying it will "Kill astronomy" is pretty hyperbolic.
|
| It will likely affect some earthbound astronomy
| significantly, but much (most?) of the most important work in
| modern astronomy is satellite based.
|
| I'm on the fence on this whole issue. It's not exactly clear
| what impact it will have on astronomy. Nor what impact it
| will have on making the internet pricing and availability.
| Where I used to live, the only options for internet access
| were expensive and really bad, the positive impact this might
| have is potentially quite big.
|
| It's hard with a story like this to suss out what the long
| term effects will be so it's a big grey area.
| HorstG wrote:
| It will kill astronomy pretty good.
|
| The key point is usable observation time. Our current
| handful of satellite telescopes provide 24h of time a day.
| Each terrestrial telescope provides maybe 8h. However,
| there are a magnitude more telescopes on Hawaii alone than
| in space. You would need to get a hundred satellite
| telescopes to begin to replace earthbased observation time.
|
| And that doesn't even begin to talk about the possible
| instruments, mirror sizes, astronomical costs of buulding
| and running satellites, etc.
| rtkwe wrote:
| Most astronomy is long exposure which the eventual mega
| constellation is particularly harmful too because there's
| no way currently to deal with the light reflecting off
| them.
| [deleted]
| CamperBob2 wrote:
| You know they don't use film plates for those exposures
| anymore, right? They stack images digitally. Removing
| satellite trails is the _easiest_ part of the post
| processing flow, or it damned well should be.
| rtkwe wrote:
| Digit and film single long exposures are functionally
| identical and for very dim objects you still need long
| exposures because the amount of light reaching the sensor
| is very low. You can't image stack if the object is too
| dim to appear in the shorter exposure's you're stacking.
| CamperBob2 wrote:
| _Digit and film single long exposures are functionally
| identical_
|
| Wow, OK. We're done here.
| petschge wrote:
| Astronomical sensors typically are 12 bit. So anything
| 4000 times brighter will overflow the sensor and can not
| be subtracted. And of course you have perfect solutions
| to Poisson noise, bleeding pixels, and increased dead
| time caused by shorter read out intervals as well, right?
| We are done here. But not for the reasons you think. You
| did not win this discussion.
| clmul wrote:
| The amount of important work in modern astronomy that is
| satellite based is limited, as pointed out elsewhere on
| this thread.
| CamperBob2 wrote:
| Because access to space is insanely expensive.
|
| Don't fight the people who are trying to fix this.
| SiempreViernes wrote:
| Also dangerous and inflexible.
| stcredzero wrote:
| For now. Do the Elon Musk analysis from first principles.
| The future of astronomy is clearly outside of Earth's
| gravity well and atmosphere.
| 317070 wrote:
| Yes, but the current budgets clearly are not.
| eecc wrote:
| He's working on that ;)
|
| /s (jeez, your sense of humor folks...)
| CamperBob2 wrote:
| Well, he is. For the Luddites in these threads, it's
| enough to cite the JWST as a reason to keep doing things
| the same old way, over and over, in space _and_ on Earth.
|
| Of course, the reason why people who enjoy lecturing
| others about why something can't be done differently or
| shouldn't be done differently seem to gravitate to a site
| called "Hacker News" is one of those universal mysteries
| that can't be answered with a computer or a telescope.
| Ididntdothis wrote:
| "It will likely affect some earthbound astronomy
| significantly, but much (most?) of the most important work
| in modern astronomy is satellite based."
|
| Not true at all. Ground based is much cheaper and easier to
| maintain and reconfigure with new and different equipment.
| Just look at the cost of the upcoming >30m telescopes vs
| the James Webb or Hubble.
| maccam94 wrote:
| On the plus side, SpaceX is making launches much bigger
| and cheaper, which will make space-based telescopes much
| more affordable. Cheaper launches = more, cheaper
| satellites.
| Ididntdothis wrote:
| That's good but I am not sure if the launch cost is where
| the money goes for telescopes.
| SiempreViernes wrote:
| > but much (most?) of the most important work in modern
| astronomy is satellite based.
|
| You're going to have to point out which source you pulled
| that out of! As a simple example, more than half of the
| Nobel prizes awarded for astronomy since 2000 are for
| discoveries made with ground based detectors. And of those
| awarded to satellite experiments, _none_ was actually
| competing with a ground based experiment, so satellites
| mainly bring different, _not better_ , capabilities.
| jessaustin wrote:
| _...ground based detectors..._
|
| When I encounter this phrase I think of things like the
| neutrino detector in Antarctica, which of course isn't
| affected by satellites at all. How much contemporary
| astronomy relies on visible-light telescopy?
| petschge wrote:
| A very large fraction. Optical is still the most
| important band, probably followed by radio, x-ray, IR and
| gamma ray in that order. And less then 10% of optical is
| done using satellites.
| Rebelgecko wrote:
| >It will likely affect some earthbound astronomy
| significantly, but much (most?) of the most important work
| in modern astronomy is satellite based.
|
| I'm not an astronomer but I'm not convinced that that's the
| case. The number of space telescopes pales in comparison to
| the number of terrestrial observatories. Moreover, advances
| like adaptive optics have done a lot to close the gap
| between ground and space capabilities (for optical
| telescopes). Even once you've invested in expensive tech
| like adaptove optics, a telescope in space still costs an
| order of magnitude more than one on the ground (thats being
| really conservative. JWST has already cost ~10x more than
| the most expensive ground telescope ever, and the thing
| hasn't even launched yet)
|
| There were a few space based radio telescopes in the past,
| but I don't think there are any now. Imagine building
| something like the Arecibo Observatory[1] or VLA[2] in
| space. And speaking of the VLA, some of the techniques for
| getting high quality results (e.g. interferometry without
| physically conjoining the receivers) are difficult if not
| impossible to do in space.
|
| [1]: https://en.wikipedia.org/wiki/Arecibo_Observatory
|
| [2]: 27 of these guys, which are able to move around
| precisely on rails to generate constructive interference
| with the different waves they're receiving:
| https://public.nrao.edu/wp-
| content/uploads/2016/04/vla_panor...
| shadowgovt wrote:
| Can adaptive optics be applied to filter out objects like
| Starlink satellites?
| toomuchtodo wrote:
| You can filter them out computationally without adaptive
| optics with enough frames captured.
| SiempreViernes wrote:
| No, they are too bright and will saturate the detector
| with even very short exposures. Best you can do is just
| discard the affected area, at worst you have to discard
| several exposures because the saturation effected the
| readout electronics.
| HorstG wrote:
| Modern astronomy works at the edges of whats possible, a
| single frame might take hours. Needing multiple frames
| would mean multiple days per observation. It would mean
| no longer seeing faint and distant objects, limiting us
| to younger, closer and frankly far more boring objects.
| It would make observing variability impossible for
| certain timescales.
|
| You need old distant objects for cosmology, observing the
| structure if the universe, big bang and stuff. You need
| variability for finding exoplanets, measuring distance
| and observing transitions such as supernovae.
|
| Oh, and then a huge part is taking spectra, which means
| bouncing the light directly off a grating. Filtering
| transients is hard to impossible there. You need spectra
| for relative motion, magnetic fields, composition of
| matter and radiation and of course temperature.
|
| Needing such filters would set astronomy back a few
| decades
| toomuchtodo wrote:
| Astronomy will need to catch up or pay for a resource
| they've been getting for free (unobstructed sky). Or
| start lifting more advanced platforms to orbits (whether
| that's Earth or Lagrange points).
| HorstG wrote:
| Well then, we should also have Elon pay rent for use of
| space...
| toomuchtodo wrote:
| I think it's hard to argue it belongs to you if you can't
| get there. If you can't defend it or control it, you
| can't stake a claim to it.
|
| https://en.wikipedia.org/wiki/Extraterrestrial_real_estat
| e
| HorstG wrote:
| Defense would actually be quite easy. Just undesirable.
| There are working antisat weapons in the major powers'
| arsenals. However, they would produce nasty debris
| clouds.
|
| And then there is also the vulnerability of the lauch
| site and control center...
| [deleted]
| gpderetta wrote:
| And it is probably significantly cheaper to take down a
| sat than putting it up. So it would be a losing battle.
| shadowgovt wrote:
| Not in general. A kinetic striker would require as much
| energy to reach the satellite as the satellite used to
| get there. Something fancier, like a targeted laser, to
| my knowledge doesn't exist with anything like the wattage
| needed to punch through atmo and still have effective
| kill on anything that far out (assuming you could solve
| the targeting problem to resolve the beam that tightly in
| the first place).
| gpderetta wrote:
| The satellite is in orbit. It requires significantly more
| energy to put something in orbit than merely reachin that
| altitude. Satellite killers are relatively small rockets
| that can use a small supersonic fighter jet as first
| stage, while it requires a much bigger rocket to put a
| satellite in space (it would depend on the orbit of
| course).
|
| It is true that spacex can put a significant amount of
| satllites in orbit witha single launch though, so it
| probably evens it out.
| shadowgovt wrote:
| This is actually one of the more interesting questions in
| space exploration in general. It has been ever since
| someone tried charging NASA for parking on the section of
| the moon they claim ownership of.
| SiempreViernes wrote:
| And why does SpaceX get the privilege to rule the sky and
| the radio waves simply because they could stream Seinfeld
| somewhat cheaply?
| shadowgovt wrote:
| It's a complicated question, but there are echoes of it
| in "Why does the US get the privilege of having their
| flag on the moon, just because they could get it there
| and nobody can take it back down?" or "Why do people have
| any right to the land they occupy, merely because they
| got there before other people did?"
|
| First-mover advantage is real.
| toomuchtodo wrote:
| It's not complicated. The answers to your questions are,
| "Because they can." Possession, control, and force carry
| much more weight than some would like. It just makes
| those without power, authority, or any other stakeholder
| equity uncomfortable.
|
| The US is not a super power because it asked politely and
| a committee granted it permission. Similarly, SpaceX will
| move forward because anyone with the authority to
| challenge them allows them to proceed.
| [deleted]
| shadowgovt wrote:
| That makes the relationship sound adversarial, when
| really there's mutual benefit to SpaceX and the
| international astronomy community. Astronomy can use
| cheap lifting capabilities.
| toomuchtodo wrote:
| Yes, entirely agree, and SpaceX should shoulder some of
| the cost of lifting more advanced platforms if that's
| what's needed to obviate pollution caused by StarLink
| sats.
|
| My concern are those who might delay satellite
| constellations that can deliver enormous value to the
| ground, not considering that we have a lot of space out
| there to replace ground observation. The only constant is
| change.
| Rebelgecko wrote:
| Don't think so. Adaptive optics works by changing the
| physical shape of the mirror. If you measure the
| atmosphere continuously and bend the mirror the right
| way, you can remove atmospheric distortion from the
| image. If anything, AO just gets you sharper images of
| the starlink satellites (or significantly worse ones if a
| satellite flies in front of the guidestar that you're
| using as a reference point to measure atmospheric
| distortions).
| ogre_codes wrote:
| > I'm not an astronomer but I'm not convinced that that's
| the case.
|
| I'm not entirely certain what the balance is here. I
| don't think my post made it clear that I'm not certain
| how big the effect would be, only that there is a
| tradeoff here which is hard to quantify.
|
| I do know there is a _lot_ of significant astronomy done
| by space telescope and that the importance of space
| astronomy is only growing.
|
| Seems to me the answer is that those who benefit from the
| new satellite constellations (SpaceX, etc) should finance
| additional investment in astronomy to mitigate the
| effects.
| cptskippy wrote:
| What about amateur astronomy? Are we now saying that only
| those with the means to afford space telescopes or
| expensive software can participate?
| ogre_codes wrote:
| Are you an amateur astronomer or just trying to be the
| devil's advocate?
|
| I'd be curious to know what the impact is on impactful
| amateur astronomy (as opposed to backyard hobbyists who
| are just engaged for personal pleasure). I know some
| amateurs use images created by public telescopes, I'm
| _not sure_ how much meaningful work is done by amateurs
| using backyard equipment anymore.
|
| Not being dismissive, genuinely curious.
| Rebelgecko wrote:
| In recent news, the only confirmed interstellar comet in
| our solar system was found by a dude who worked at an
| observatory (not as an astronomer) and decided to build
| own telescope for fun in his spare time. It's one of only
| two known interstellar visitors we've had, and because he
| found it early enough the pros were able to make very
| detailed observations.
|
| A decent number of asteroids and comets are still found
| by backyard astronomers.
| cbanek wrote:
| Variable star observing is actually a place where
| amateurs really help, since it's about observation time,
| and not necessarily some hugely powerful telescope. And
| the more powerful a telescope is, the more people want to
| use it to point at all sorts of things, which makes it
| kind of expensive to use those telescopes for variable
| star observations which take a lot of time.
|
| "Since professional astronomers do not have the time or
| the resources to monitor every variable star, astronomy
| is one of the few sciences where amateurs can make
| genuine contributions to scientific research." [0]
|
| [0] https://en.wikipedia.org/wiki/American_Association_of
| _Variab...
| FeepingCreature wrote:
| If SpaceX works out, we'll probably see a lot more
| telescopes in space. Wouldn't be that expensive at that
| point for, say, a school class to launch a telescope
| cubesat.
|
| I'd trade amateur ground astronomy for that.
| SiempreViernes wrote:
| I'm not entirely sure how you think looking at an image
| on a computer screen compensates for the experience of
| doing observations with your own eyes.
|
| There are plenty of good pictures on wikipedia already,
| do looking at those compare to going out on a clear night
| and looking at the stars yourself?
| fastball wrote:
| A LEO satellite constellation will absolutely _not_
| prevent you from looking into the night sky with a
| telescope and seeing stars.
| petschge wrote:
| The dead of night will be fine. But during (astronomical)
| twilight, the time when you are most likely awake and
| looking up, it will have ugly extra dots.
| fastball wrote:
| What makes a dot ugly?
| nwallin wrote:
| Arecibo and VLA aren't affected by starlink at all. Those
| are radio telescopes. They don't even need to wait until
| nighttime to observe. It's only an optical/ir problem.
| manicdee wrote:
| Starlink uses radio to communicate with the ground. A
| common complaint from radio astronomers is new radio
| satellite operators promising to not interfere with radio
| astronomy and then making no effort to follow through in
| that promise.
| optimiz3 wrote:
| Is there any way, perhaps with software, that we could remove
| a moving object, from an otherwise mostly static set of
| images?
| wnkrshm wrote:
| Also, asteroid detection may be hampered - there is still a
| significant contribution of 'amateur' observations to
| detecting them.
| CamperBob2 wrote:
| A shortsighted attitude, IMO. Terrestrial observatories are
| in a good position to clean up satellite artifacts digitally.
| They already have to do more image processing than the staff
| at Playboy. Meanwhile, cheaper access to orbit can only be a
| good thing for astronomy, given that we've picked most of the
| low-hanging fruit in terrestrial-bound optical observations.
| TrainedMonkey wrote:
| Staring at a night sky in a designated dark sky area is
| amazing. Given the pace of SpaceX launches amount of time you
| can do that without sky crawling with LEO constellations is
| pretty limited. So days of humans experiencing night sky raw
| are pretty limited (some would argue it is already
| impossible). However, I think astronomers will find a way to
| operate even in a noisy environment of mega-constellations.
| Given that the objects are bright they can be tracked
| extremely well. Filtering out them out of the datasets does
| not seem intractable. Am I missing anything here?
|
| Moreover, I think mega-constellations will actually be a boon
| for astronomy. Think of it as a platform, while initial
| iterations will be focused on communication systems, what is
| stopping them from adding sensor packages looking both
| inwards and outwards? They already have the bandwidth to
| downlink all of that. Once on the ground those streams could
| be combined to produce datasets of unprecedented coverage and
| fidelity.
| bryanlarsen wrote:
| It's bright because it's in a low orbit and a lot closer to
| us. Because it's in a low orbit it's in the earth's shadow
| for most of the night. It's not bright while in shadow.
| chrisco255 wrote:
| Personally, I don't want to be limited to observing the stars
| from planet Earth for too much longer. The development of
| commercially viable space technology will fund and fuel
| investment in interplanetary expeditions and help us move to
| the next stage of human progress.
| lutorm wrote:
| First, satellites are only visible in the optical when they
| are illuminated by the Sun, which is only for a fairly short
| window after sunset and before sunrise. The exact size of the
| window depends on how high they are, but most of the good
| "dark" time should be unaffected.
|
| Second, astronomers already use image stacking to reject any
| number of transient artifacts, like satellites, airplanes,
| cosmic rays, etc.
|
| Third, while these constellations are going to greatly
| increase the number of satellites in orbit, it's only by
| about an order of magnitude. Yes, that's worse, but it's not
| like it's a problem that hasn't existed before.
|
| The type of observations that are likely to be most affected
| are surveys that actually search for moving near-Earth
| objects, especially near the Sun (and radio astronomy which
| apparently can detect terrestrial emissions scattering off of
| satellites) but I fail to see how this will mean anything
| like "the end of astronomy" (and I have a Ph.D. in
| astronomy.)
| martythemaniak wrote:
| Could you explain how something that orbits 500km up could be
| seen at night?
| [deleted]
| TeMPOraL wrote:
| Like most other satellites, it can be seen when it reflects
| the Sun. Satellites tend to be shiny. For an extreme case,
| check out "Iridium flares" - a brief but bright flares on
| the sky caused by old Iridium satellites, whose antennas
| were essentially large, rectangular mirrors.
| HorstG wrote:
| Depending on the type of measureme t taken, a dark
| transient is also harmful. However, by far not as bad as
| a bright transient.
| martythemaniak wrote:
| To reflect sunlight you need the sun. If a satellite is
| 500km up (and 300km for later revisions), there is no way
| for sunlight to reach it.
|
| There is no way to see Starlink at night. You can
| potentially see them for a short period around twilight.
| outworlder wrote:
| > There is no way to see Starlink at night. You can
| potentially see them for a short period around twilight.
|
| The time window is limited, yes. So it is not the end of
| the world. It is still a problem.
| reaperducer wrote:
| You've really never looked into a night sky and seen a
| satellite? Unless you live underground or never leave a
| big city, it's quite easy and there are dozens of apps
| that will help you understand what you're looking at.
| outworlder wrote:
| I guess the point they are trying to make is that 500km
| (or 300km) is essentially hugging the planet. Which means
| that, if it is night, they will be in the shadow for the
| majority of the time.
|
| The satellites you can easily see at any time are much
| higher up.
| downrightmike wrote:
| Why can't they just use modern AI tech to remove the satellites
| like we do with people?
| https://www.theverge.com/2019/6/25/18715676/camera-app-bye-a...
| dodobirdlord wrote:
| Astronomy telescopes are pretty different from the sorts of
| optical sensors used to take pictures of people. Through
| amplification they can detect very small numbers of photons.
| The error margin of trying to exclude something like a bright
| satellite in the field of view is going to be significantly
| larger than the detection threshold.
| malandrew wrote:
| I imagine that the bright objects also make it difficult to see
| less bright objects so it's not just a matter of removing the
| brighter objects.
| justinclift wrote:
| Wonder if they're using VantaBlack, Black 3.0, or some other
| variant of "super black" for this experiment?
|
| https://en.wikipedia.org/wiki/Vantablack
|
| https://culturehustle.com/collections/black/products/black-3...
| knodi123 wrote:
| That's a juicy detail, you'd have heard about that if they
| were.
|
| But odds are they're only going as far as is required, which
| would be "no brighter than typical satellites" - right?
| petschge wrote:
| There will be many more than typical satellites, so it is
| only fair to require "much dimmer than usual".
| cbanek wrote:
| It's possible, although it's kind of tricky to use in practice.
|
| From the Vantablack wikipedia article:
|
| When light strikes Vantablack, instead of bouncing off, it
| becomes trapped and is continually deflected amongst the tubes,
| eventually becoming absorbed and dissipating into heat.[7]
|
| Dealing with heat in space isn't easy, since you have no air to
| dissipate heat into.
| galangalalgol wrote:
| Black radiates heat faster than white as well as absorbin it
| faster, so ostensibly the side in shadow should dump heat
| quickly if you have something like heatpipes to move it
| there.
| ben_bai wrote:
| Black satellites are nothing new. Just ask any Surveillance
| Agency how they handle the heating problem due to black
| paint.
|
| Oops that's classified. But probably such satellites need a
| dedicated cooling system.
|
| It's never as easy as, just paint it black and hope for the
| best.
| cbanek wrote:
| Right, but that means that stealth costs mass (weight) and
| means less satellites per launch. So that means making them
| less visible costs more money.
|
| For non spy satellites where stealth isn't one of the top
| goals, that might mean people don't do it.
|
| Also, typically one does not simply ask a surveillance
| agency how they do things. They would probably respond with
| something like, "NO SUCH PERSON AT THIS ADDRESS, RETURN TO
| SENDER."
| m4rtink wrote:
| It depends - coating on a low orbiting satellite needs to
| conform to various requirements:
|
| - needs to survive vacuum
|
| - needs to survive atomic oxygen, that does show up at low
| Earth orbital altitudes
|
| - needs to handle the thermal cycling as the satellite goes in
| and out of Earths shadow
|
| - needs to survive unfiltered sunlight without any atmospheric
| convection to normalize temperature
|
| - needs to avoid overheating the part of the satellite it is
| covering
|
| - should not emit particles, that could collide with other
| satellites
|
| - needs to keeps doing this for about 5 years (design lifetime
| of individual Starlink satellites)
|
| - should harmlessly burn up on satellite reantry
|
| If the given material can do all the above, while still keeping
| it's desirable properties, then it can be used on a Starlink
| satellite. :)
| dr_orpheus wrote:
| One of the targeted markets of VantaBlack was the aerospace
| industry to paint the inside of baffles on telescopes and
| optical sensors. It is currently being used in some star
| trackers on satellites [1].
|
| Overheating is definitely a big concern for painting your
| satellite back. There is a lot of work that goes in to
| thermal design of satellites and that surfaces have the
| proper optical properties for absorption, reflection and
| emission.
|
| [1] http://www.eurekamagazine.co.uk/design-engineering-
| news/worl...
| moftz wrote:
| They are probably using something like Aeroglaze Z307, it's a
| black thermally and electrically conductive paint used on many
| aerospace applications.
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