top | item 30022304

Starlink satellites hindering detection of near-Earth asteroids, study finds

280 points| nixass | 4 years ago |caltech.edu

373 comments

order
[+] DennisP|4 years ago|reply
For anyone who would like a better source than the Daily Star, here's an article at Caltech:

https://www.caltech.edu/about/news/palomar-survey-instrument...

It includes this perspective:

> Study co-author Tom Prince, the Ira S. Bowen Professor of Physics, Emeritus, at Caltech, says the paper shows a single streak affects less than one-tenth of a percent of the pixels in a ZTF image.

> "There is a small chance that we would miss an asteroid or another event hidden behind a satellite streak, but compared to the impact of weather, such as a cloudy sky, these are rather small effects for ZTF."

[+] BurningFrog|4 years ago|reply
IOW, since the satellites are visible, they can occasionally obscure something behind them.

Reminds me of the SF housing madness where you can build housing, as long as it doesn't cast a shadow.

[+] wwilson|4 years ago|reply
Funny given that Starlink itself has potential to be one giant synthetic aperture radar installation.

From Casey Handmer’s excellent post (https://caseyhandmer.wordpress.com/2021/11/17/science-upside...):

“Starlink SAR is great for Earth observation, but the same principle can be applied looking outwards. Starlink is a network of thousands of software defined radios with highly precise PNT information and high speed data connections. It is practically begging to be integrated into a world-sized radio telescope. With 13000 km of baseline (trivially extendable with a handful of GTO Starlink launches) and the ability to point in any desired direction simultaneously, Starlink could capture practically holographic levels of detail about the local radio environment. Literally orders of magnitude better resolution than ground-based antennas like the Very Large Array. Cheaper than repairing Arecibo and independent of Earth’s rotation. Potentially capable of resolving exoplanets.”

[+] ajnin|4 years ago|reply
> Potentially capable of resolving exoplanets

I was curious about that claim, so I did a bit of research and made a "back of the envelope" calculation. According to Wikipedia [1], the angular resolution of a telescope is proportional to <wavelength of light>/<diameter>. Starlink seems to operate from 10 to 40GHz, so assume the hardware has a 50% design margin so is capable of reaching 60GHz. Visible light has a frequency of 400 to 800THz, so take the middle of 600THz. Using those figures, it come out that the Starlink satellites, used as a telescope, would have the same angular resolution as a 1.3m visible light telescope. Is it enough to resolve exoplanets ? I'm not sure but I think not. Hubble is 6m and can apparently resolve some exoplanets so it's not too far off. Some launches to GEO would boost the resolution to the equivalent of 8.4m in visible. (IANAA)

1: https://en.wikipedia.org/wiki/Angular_resolution

[+] welterde|4 years ago|reply
Even the full planned constellation has a smaller collecting area than Arecibo had (~60 000 m^2 vs ~73 000 m^2 for Arecibo) - and that's not even considering that for half the constellation the earth will be in the way, not the full dimensions of the satellite are usable as antenna, they are pointing the wrong way, etc. etc. Nevermind that one looses quite a lot of sensitivity when using these arrays..
[+] suifbwish|4 years ago|reply
Their claim is the equivalent of complaining that the weight of a large vehicle engine is bad because it makes the vehicle more difficult to carry up a hill. Get in, start the engine and drive up the hill lol. I’m curious what you mean by “holographic levels of detail”

If starlink were used as an outward sensor array, with the correct software and enough compute you could generate a live 3D model of the entire sky and almost anything in it down to quite a small resolution.

[+] idealmedtech|4 years ago|reply
If their primary mission was observation, they would be an incredible astronomical resource. However, I think that given the fuel constraints and SLA they aim to provide, I would be shocked if they used any fuel to orient for extraterrestrial observation.
[+] hinkley|4 years ago|reply
I think it's likely there will be a dope deal at some point where low-earth satellite clusters have to offer sky observation services that offset the loss of fidelity from ground-based systems.

If the satellites can swing between sky and ground scanning several times in a single orbital period, they could use off-peak hours in the early morning to scan the skies.

I don't know if that practically will work out, as Starlink has lower speed of light delays than undersea cables. Accessing content on the other side of the world will become more attractive with lower latency. For instance a lot more people using VPNs to watch BBC.co.uk at 4 am GMT.

[+] lokimedes|4 years ago|reply
Does the StarLink constellation have sufficiently accurate time synchronization and phase stability to allow it to act as a long baseline multi-static radar? I have been contemplating using it as a passive radar source, but here the limitation is its phased array nature. It is not really optimal for non-cooperative receivers.
[+] cronix|4 years ago|reply
You could also install cameras pointing back towards Earth and basically have 24/7 coverage of everyone's movements similar to what Darpa's ARGUS-IS[1](2013) does except using a global network of satellites instead of drones and build the greatest video surveillance platform on the planet. Instead of covering a city for a limited time with a drone stuffed with an array of off the shelf cell phone cameras, you could have "persistent stare" for the entire planet. I wonder if the NSA has thought about that.

[1]https://www.youtube.com/watch?v=QGxNyaXfJsA

[+] ngcc_hk|4 years ago|reply
You just do a sensor and lens manipulated opposite to where the unwanted light source are (earth, moon and sun) and sent the info back. I am not sure the radio channel the thing operate affect this approach. Just no one seem to think of this as complement to the earth one.

Synergy not fight then.

[+] ianai|4 years ago|reply
Yes. If Elon was as concerned about the survival of humanity as he claims with his mars initiatives then he’d outfit these with some equipment for this. There’s got to be a way to do both internet and radio astronomy.
[+] thro1|4 years ago|reply
I made that question once on HN (2020, relating to Arecibo) and it was downvoted: Couldn't it be receivers on Starlink satellites plus some computing power instead? - but I've got great feasibility study by teraflop as the answer for that: https://news.ycombinator.com/item?id=25051151 .
[+] seventytwo|4 years ago|reply
Or…

We just stop letting the broadband companies regulate themselves and nationalize the system.

Then we don’t have multiple layers of bandaids.

[+] kitsune_|4 years ago|reply
Stupid question, but what international treaties currently regulate private citizens and corporations when it comes to space? Like, who can claim which orbits? Is this just first come, first serve? What would happen if someone crashes Starlink satellites, for instance by putting projectiles on a collision course?

Edit, found an interesting link: https://www.spacelegalissues.com/orbital-slots-and-space-con...

> The geostationary orbit is part of outer space and, as such, the customary principle of non-appropriation and the 1967 Space Treaty apply to it. The equatorial countries have claimed sovereignty, then preferential rights over this space. These claims are contrary to the 1967 Treaty and customary law. However, they testify to the concern of the equatorial countries, shared by developing countries, in the face of saturation and seizure of geostationary positions by developed countries. The regime of res communis of outer space in Space Law (free access and non-appropriation) does not meet the demand of the developing countries that their possibilities of future access to the geostationary orbit and associated radio frequencies are guaranteed. New rules appear necessary and have been envisaged to ensure the access of all States to these positions and frequencies.

[+] finnx|4 years ago|reply
> approximately 4 × 10−4 of all pixels would be lost over the course of a year. However, simply counting pixels affected by satellite streaks does not capture the entirety of the problem, for example resources that are required to identify satellite streaks and mask them out or the chance of missing a first detection of an object

It looks like the main problem is not the amount of data lost but amount of extra manual work this situation causes. I assume Starlink tracks and knows where their satellites are, so why don't they just provide data feed to trusted third parties who might be affected by their satellites? That way researchers could automatically classify these trails.

[+] Frost1x|4 years ago|reply
I'd be surprised if the positions weren't already public data. Surely the US government requires or pressures knowledge of the positions since its a US based company and the satellites could certainly interfere with things NASA and other agencies want and need to do.
[+] mlindner|4 years ago|reply
> It looks like the main problem is not the amount of data lost but amount of extra manual work this situation causes. I assume Starlink tracks and knows where their satellites are, so why don't they just provide data feed to trusted third parties who might be affected by their satellites? That way researchers could automatically classify these trails.

The information on where Starlink is is already publicly available through the US government. Anyone who wants to know where the satellites are can view the live positions at any time.

[+] SiempreViernes|4 years ago|reply
Starlink satellites are supposed to perform movements on their own, mainly to avid other satellites. But this means you might not know where they are all the time, just for the most part.
[+] capableweb|4 years ago|reply
> I assume Starlink tracks and knows where their satellites are, so why don't they just provide data feed to trusted third parties who might be affected by their satellites?

I'm not sure if this is in any way official and/or the right way of doing it, this area is all outside of my normal competence. But, stumbled upon a python library (https://github.com/python-astrodynamics/spacetrack) that supposedly connects to space-track (space-track.org) and you should be able to get the position there. How the data comes into space-track I'm not sure.

But there are bunch of small services for seeing the live location, so I'm sure someone is tracking the location somewhere, like this one: https://findstarlink.com/

[+] simondotau|4 years ago|reply
It seems to me that if you know where the satellites will be, it’s not so much a problem of removing streaks but rather factoring it into automated scheduling so that you never have any streaks to remove.
[+] travisporter|4 years ago|reply
The title doesn't reflect the contents of the article; was the link changed but the sensationalist title remains?

"the paper shows a single streak affects less than one-tenth of a percent of the pixels in a ZTF image."

[+] shantara|4 years ago|reply
Any explanation how it affects the asteroid detection? It is not a manual sky search it was decades ago, but a completely automated process with a computer controlled telescope, orbit calculation software, check against a database of known objects and a submission of the new findings.
[+] mkj|4 years ago|reply
"So far, ZTF science operations have not yet been severely affected by satellite streaks, despite the increase in their number observed during the analyzed period"

So it requires processing for mitigation, but isn't as dire as the title suggests.

[+] andrewclunn|4 years ago|reply
Wait, we're using terrestrial telescopes for this? I would have assumed that satellite based ones would be favored for this kind of thing.
[+] iso1631|4 years ago|reply
You can build far more and far larger telescopes on the ground than you can in space, for the same money.
[+] JoeAltmaier|4 years ago|reply
Satellites are relatively cheap. Certainly cheaper than the right-of-way to run cables through every expensive heavily populated city in America for instance.

In fact, it would seem obvious that a LEO power station would make a lot of sense for the same reason. Earth-bound stations have the disadvantage of ~50% duty cycle due to a periodic eclipse phenomenon known as 'night'.

[+] WithinReason|4 years ago|reply
Starlink gets a lot of bad press from astronomers, so I want to leave this here to balance it out. It's written by Casey Handmer, an (ex) NASA astrophysicist. Source: https://caseyhandmer.wordpress.com/2021/11/17/science-upside...

Sorry for the wall of text, but I think it's worth reading:

Starlink will ultimately be a network of tens of thousands of satellites connecting to hundreds of millions of user terminals located all over the Earth. Its radio encoding scheme adapts the signal rate to measured atmospheric opacity along the signal line of sight across 10 different frequency bands in real time. Collectively, the system measures trillions of baselines of Earth’s entire atmosphere every day. This data, fed into standard tomography algorithms such as those used by medical CT imagers, can resolve essentially all weather structure in the atmosphere. No more careful scrutiny of remote weather station pressure gauge measurements. No more reliance on single mission oxygen emission line broadening. Instead, complete real time resolution of the present state of the entire atmosphere, a gift for weather prediction and climate study.

Starlink satellites are equipped with perhaps the most versatile software defined radios ever put into mass production. Each antenna allows the formation of multiple beams at multiple frequencies in both send and receive. With sufficiently accurate position, navigation and timing (PNT) data from GPS satellites, Starlink satellites could perform fully 3D synthetic aperture radar (SAR) of the Earth’s surface, with enough bandwidth to downlink this treasure trove of data. Precise ocean height measurements. Precise land height measurements. Surface reflectivity. Crop health and hydration. Seismology and accumulation of strain across faults. City surveying. Traffic measurements in real time. Aircraft tracking for air traffic control. Wildlife study. Ocean surface wind measurements. Search and rescue. Capella has produced extraordinary radar images with a single satellite. Now imagine the resolving power with birds from horizon to horizon.

Starlink SAR is great for Earth observation, but the same principle can be applied looking outwards. Starlink is a network of thousands of software defined radios with highly precise PNT information and high speed data connections. It is practically begging to be integrated into a world-sized radio telescope. With 13000 km of baseline (trivially extendable with a handful of GTO Starlink launches) and the ability to point in any desired direction simultaneously, Starlink could capture practically holographic levels of detail about the local radio environment. Literally orders of magnitude better resolution than ground-based antennas like the Very Large Array. Cheaper than repairing Arecibo and independent of Earth’s rotation. Potentially capable of resolving exoplanets.

There’s no reason to do only passive radio astronomy. Starlink can exploit its exceptional resolving power and onboard amplifiers to perform active planetary radar, for examination of close-flying asteroids and transmission of radio signals to distant missions in support of the Deep Space Network. As of November 2021, all Starlink satellites are flying with lasercoms so in principle the DSN application could also support laser, as well as radio, communication with distant probes. No need to build even larger dishes than the 70 m monsters. The potential to greatly increase our data rates from distant probes.

And while Starlink can derive PNT from the GPS constellation, it need not depend on it forever. High capacity radio encoding schemes such as QAM4092 and the 5G standard contain zero-epoch synchronization data, meaning that any radio capable of receiving Starlink handshake signals is able to obtain approximate pseudorange information. What Starlink’s onboard clocks may lack in atomic clock-enabled nanosecond stability, they make up in sheer quantity of connections and publicly available information about their orbital ephemerides. Already a group from OSU has demonstrated <10 m accuracy, while a group based at UT Austin is developing a related method for robust PNT estimation using Starlink hardware. It seems likely to me that Starlink could support global navigation with few to no software changes and no hardware changes, improving the resilience of satellite navigation especially in a case where the relatively small GPS constellation is disabled. I won’t go into vast detail, but GNSS signals are not only used for pizza delivery, but also support a vast array of Earth science objectives, including the monitoring of tectonic drift.

Starlink has received its fair share of criticism, drawn perhaps by its overwhelming scale and potential impacts to ground-based astronomy. But Starlink can also be the single greatest scientific instrument ever built, a hyperspectral radio eye the size of the Earth, capable of decoding information about the Earth and the universe that is right up against the limits of physics.

[+] thro1|4 years ago|reply
Great idea! ;) Feasibility study - regarding outwards, by teraflop (Nov 2020) https://news.ycombinator.com/item?id=25051151 , shortly:

.. dishes on every one of the 12,000 satellites for the same total area [as Arecibo] each have to be over 9 feet. That's about the same size as the chassis of the satellite itself..

.. the receivers need to have very precisely synchronized clocks, and their relative positions need to be known to within a small fraction of the wavelengths you're interested .. you might need to add atomic clocks to every satellite as well..

.. you have to think about how to aim the antennas..

.. fairly sensitive, low-noise, specialized signal processing equipment .. power .. weight..

.. satellites have a roughly 5-year design lifetime..

then, can it be done ?

[+] __m|4 years ago|reply
i doubt that it can handle that many users. I even doubt it can handle enough users to cover the cost of replacing its satellites every 5 years
[+] kaba0|4 years ago|reply
Why should that be owned by a private entity though? What right do they have for that? I wouldn’t mind it being run by a public (international) organization, for public good, but that’s very different.
[+] GuB-42|4 years ago|reply
I think that's the thing we should strive for. It has been shows time and time again that Elon Musk takes PR very seriously. We should make the company aware of astronomers so that they incorporate scientific objectives into Starlink. And pointing both the the nuisances and potential is one way to do it.
[+] secondcoming|4 years ago|reply
That's great but sometimes it's nice to be able to see the stars unobstructed on a cloudless night.
[+] spacexsucks|4 years ago|reply
And who controls access to using starlink satellites for research and the cost? The space research is now a monopoly in control of spacex. Whereas it used to be that any one could get started in their backyard.

Fuck spacex and its apologists

[+] keewee7|4 years ago|reply
Starlink is only a benefit for a small dwindling population of rural people in high income countries.

Their claim about bringing Internet to poor countries is bullshit. Countries like Kenya, Nigeria and India have already shown that terrestrial long-distance networking (4G and soon 5G) is the way to reach mass connectivity in developing countries.

Why should we let one American ISP pollute our global nigh skies with 42,000 planned satellites? What happens when an European or Chinese competitor launches another 42,000 satellites? We need to stop this madness.

[+] spacexsucks|4 years ago|reply
If you are that cocnerned for a small group of people to get decent internet, then vote for breaking the monopoly of xfinity instead of creating a new one comtrolled by a lunatic narcisstic megalomaniac billionaire with no empathy

Everyday a billionaire wakes up and does nothing with those billions but make more of those and hold on to them. They are nothing like anybody else but other billionaires

[+] mlindner|4 years ago|reply
Title is editorialized. Should be “ Palomar Survey Instrument Analyzes Impact of Starlink Satellites”
[+] ThinkBeat|4 years ago|reply
Does Starlink represent a precedence?

Since they were "allowed" to launch (potentially) thousands of satellites. Does that mean that every other company and/or country can do the same?

[+] markdown|4 years ago|reply
OT but related... Starlink would really be useful in Tonga right about now, with their fibre-optic connection severed and expected to be out of commission for at least a month.
[+] ricardobeat|4 years ago|reply
Where is the link to the study?

> Musk, the world's richest man, has been sending an increasing amount of satellites into orbit since 2019 through his company SpaceX.

The personal tone in news about Tesla/SpaceX is funny. Sounds like SpaceX is the post office where Elon Musk goes to send his packages.

[+] jagger27|4 years ago|reply
Would it be totally insane for SpaceX to offer free/very cheap launches every now and then to pure science missions to make up for these types inconveniences?

For context: plain old Falcon 9 could launch a Hubble-sized telescope to LEO (with a bit of room to spare) and return for reuse.

It feels like the right thing to do and could gain them a bit of goodwill.

[+] LinuxBender|4 years ago|reply
Semi off-topic question. Would it be possible or reasonable to mount small energy efficient high resolution cameras on the opposing side of the satellite and make a real time grid picture of space, then open source the data to any scientists or astronomers that want it? Could that be a feature request for the next model of their satellite?
[+] sklargh|4 years ago|reply
Momentarily setting aside the human tragedy of losing the night sky for...broadband internet. We can manage externalities through taxation. Large constellations should be funding space-based sensors across all spectrums for regular astronomy and planetary defense. I feel like we could get here via a launch license fee.