
SATCON1 Report on Impact of Satellite Constellations on Astronomy - spenczar5
https://noirlab.edu/public/products/techdocs/techdoc003/
======
tectonic
We've been covering this issue frequently in Orbital Index
([https://orbitalindex.com](https://orbitalindex.com)). With around 10,000
stars visible with the naked eye, there will be significantly more satellites
than stars, even from a single constellation like Starlink or Project Kuiper.
Granted, most of those satellites won't be visible at any given time, but I do
worry about the ability of LSST and other wide-field observatories to do their
(very expensive & important) jobs—one of those jobs is spotting near Earth
asteroids with a collision potential.

Here's a recording of the recent 'Impacts of Satellite Constellations on
Optical Astronomy' webinar that discussed this and had someone from SpaceX:
[https://www.youtube.com/watch?v=LaR6v0p6pB4](https://www.youtube.com/watch?v=LaR6v0p6pB4)

~~~
jessriedel
As a side note, let me say that Orbital Index is a fantastic service. It's the
only newsletter that I read every week without fail.

~~~
tectonic
I'm so glad you're enjoying it!

------
ideals
What are going to be the cultural effects of having a constant stream of
satellites wizzing around the night sky?

I've sat here for a few minutes thinking selfishly about never being able to
experience Alaska wilderness on a clear night. Or late night stroll on a beach
looking up, etc, etc forever about all kinds of personal moments that will
never be the same.

However there's billions of people who have no idea what Starlink or Kuiper
are that are going to find out the hard way when they no longer have that same
night sky either.

I hadn't really thought about it much before because it was always framed as
an astronomy problem, but it's really a whole Earth's peoples problem.

~~~
ideals
Follow on comment, what are indigenous tribes who aren't part of our connected
world going to interpret this change as? I'm thinking about groups of people
like the Sentinelese.

~~~
mlindner
People appear to be downvoting my other comment so much that I can't even edit
it so reposting again. Indigenous tribes won't have an issue with it as they
don't have superhuman eyes to see 7th magnitude objects in the night sky. The
satellites are not generally visible to the naked eye after changes SpaceX has
made to the operations of the satellites and physical modifications to the
satellites themselves.

[https://www.spacex.com/updates/starlink-
update-04-28-2020/](https://www.spacex.com/updates/starlink-
update-04-28-2020/)

------
avmich
Dense satellite groups are a real game-changer in how we observe the sky from
the surface of Earth.

We're at the choosing point right now, what's better for us - a good uniform
global communications or the pristine sky. The sky was always the norm; but it
ceases to be so.

In order to have some compensation to astronomical society - that is, the
whole population of Earth, as even looking to bight sky is getting be
different - it would be good for SpaceX to create a program of high-orbit
astronomical observatories. Working together with Earth astronomers, the
company can participate in changes to observation possibilities in a way which
has some upside as well, in addition to anticipated degradation. Hubble space
telescope was launched some 30 years ago; an observatory of similar class or
better can be significantly more affordable today, there can be several - or
many - of them and that could be a worthy trade-off to the degradation of
Earth-visible sky. I'm sure astronomical society would be very interested in
participating and helping with building such a group of space observatories.

~~~
avmich
Two more ideas here. First, it would help if each satellite can have an
astronomical payload; this is likely hard to achieve due to quite conflicting
requirements between these two different goals.

Here is the second one. Earth observatories demonstrate streaks of satellites
across astronomical images taken over comparatively long time. We know that at
each moment satellite is in just one place in the sky; more, those
constellations tend to have rather predictable orbits. Image sensing devices
can use knowledge of satellite orbits to suppress reading a particular pixel
at particular time if a satellite is expected to shine towards that pixel.

It's quite delicate task, I understand, but I also know that practical
astronomy is known for inventing solutions to very diverse problems. This
approach won't completely restore the abilities to observe the sky, but can
significantly diminish the impact, discussed in the article. Especially if
Earth-based devices would be constructed with such "shielding" (remember star
shielding invention when working on exoplanetary discoveries?) in mind.

~~~
spenczar5
Satellites are not new, so many techniques have been used and tested.
[https://aas.org/sites/default/files/2020-07/MitigationWG_Pre...](https://aas.org/sites/default/files/2020-07/MitigationWG_Present5_bySaunders.pdf)
is a relatively nontechnical survey of some of the techniques that Rubin plans
to employ.

Suppressing pixel readings is not plausible with the current CCD designs, as
far as I'm aware. These devices are so sensitive that any wiring needs to be
done _extremely_ carefully to minimize crosstalk and keep temperatures
extremely low (think under -100C).

Masking in data processing is the more likely technique.

~~~
avmich
> Suppressing pixel readings is not plausible with the current CCD designs

Better than suppressing pixel reading would be suppressing pixel changes. The
first process lets pixel to change as a result of incoming photons, the second
one maintains the "unread" state.

Yes, current CCD devices can't do that. Advantage of this change is also in
reducing crosstalk - if we need, say, to remove accumulated charge and for
that we need to draw the current, the current may influence our reading of
neighboring pixels. I'm tempted to look towards "smart mirrors" \- MEMS
systems, even for mirrors of 1 sq. micron - but purely electrical solutions
might be possible.

------
tekstar
I'm generally a technologist however I am completely appalled at a private
company getting the right to significantly impact humanity's view of the night
sky, the original source of wonder.

~~~
avmich
Yes, this is a kind of Wild West situation. We should figure out the best way
out, ideally with all interested parties getting something good.

~~~
leeoniya
except you as an individual could opt out of the original Wild West; this one,
not so much.

perhaps it's exactly like the Wild West from the viewpoint of Native
Americans: we're taking your skys.

~~~
avmich
Yes, that's very unfortunate.

I hesitate, however, concluding that we should ban satellite constellations on
these grounds. Do you think that would be a good approach?

~~~
tekstar
Yes, unless they are invisible in the sky. Put a barrier in place to force
innovation.

~~~
avmich
Anything in the sky is something which at least obstructs the view. If we have
too many even black body satellites - which have zero reflection or emission
in interesting spectral parts - we're still can't see through them. If we have
too many of them, we still have a problem. So - theoretically - it's a choice
between space flights and astronomy.

Maybe there can be a more optimal solution than what we have today.

------
ISL
The document has an executive summary and clear images denoting the impact of
these satellites on humanity's view of the stars.

It does a great job of highlighting the collision between high-sensitivity
wide-field imaging of both deep fields and transients with the nascent
satellite constellations.

Direct link to the PDF:
[https://noirlab.edu/public/media/archives/techdocs/pdf/techd...](https://noirlab.edu/public/media/archives/techdocs/pdf/techdoc003.pdf)

Astronomers have been working for decades toward the Vera Rudin Observatory
(nee LSST). It has been the big thing on the horizon for my entire career as a
professional scientist. It sees first light in 2021. Images like that seen on
page 7 of the PDF will be what they see.

[https://en.wikipedia.org/wiki/Vera_C._Rubin_Observatory](https://en.wikipedia.org/wiki/Vera_C._Rubin_Observatory)

~~~
nsilvestri
LSST/Vera is probably the project most impacted by these satellites. Per my
contacts, smaller scopes like LBT/Keck/MMT aren't as drastically affected yet.
But if we start approaching 100k+ satellites, even they will be having some
major issues to deal with.

~~~
ISL
The real tragedy, from a scientific standpoint in the optical, is that we're
entering a new world of wide-field and sensitive time-domain astronomy due to
huge improvements in computing power and sensors at the same time that
humanity is about to generate thousands of bright transients.

The only practical approach I can think of for combating the constellations is
distributed arrays of wide-field transient-hunters. As long as the transient
is common-mode across telescopes, then it is real. If there are three LSSTs,
and not too many constellation-satellites, that might work.

I just noted, in passing, that the term for the satellite arrays appears to be
"constellation"; that is a bummer in this context.

------
mchusma
This NIMOP ("Not In My Orbital Plane") movement is very concerning and I feel
the need to speak out against the dangers of this "luddite movement" type
thinking.

First, of course its good for companies to reduce the negative externalities
of things in space (paint, shades, etc). I think there is near universal
agreement here, including from SpaceX.

However, there is no way to become a space faring civilization without putting
lots of things in space, period. I want to see 1,000,000x more objects in
space, including much larger ones.

If we truly become space faring, we have the matter and resources to have a
quadrillion humans living in comfort (likely in large rotating space habitats
like"O Neil Cylinders"). This is the kind of dream we could have, imagine over
100,000x the humans, artists, friendship, science, and love. We can
simultaneously make earth an ecological paradise, with most of the planet
reserved for nature.

This "anti-satellite" movement seems to generally have 4 kinds of attacks
against the satellites: 1) The satellites "impede my rights to view the sky".
The implication is that anyone who attempts to build in their "view to
infinity" violates their rights. This seems like an extremely presumptuous
statement, like they own trillions of miles. This also doesn't match the
current legal framework of any country (nobody needs your permission to fly
over your house in aircraft or space). 2) The usecase of these satellites is
bad because they are "like cell towers". Getting low cost internet access for
the planet is IMO an extremely good thing, one of the best things for the
poor. 3) The satellites will kill astronomy. This is absurd, we will have much
better astronomy if we are a space fairing species with cheap space access and
many things/expertise in space and giant telescopes outside our atmosphere. It
may kill amateur astronomy from earth eventually, but I just don't think that
as society a relatively fringe hobby should stop the progress of humanity.
Many hobbies have been killed over time. I personally think this will inspire
more people to look to space, and have the opposite effect. 4) We should not
put things into space, and we should look to reduce our impact on the
universe. This also manifests itself in those that want to see population
reduction on Earth. I believe consciousness is better than lifeless rock. I
say this as a human and a parent who has brought consciousness into the world.

Lets upgrade our dreams, take to the stars, and make the universe a more
interesting place.

~~~
jacquesm
Right. The problem is not that it is 'in my orbital plane', the problem is
that it is in _everybody 's_ orbital plane whether or not they - or their
government - has a say in the matter. You can't escape it. There is no
backyard where this isn't an issue.

This is now presented as a fact we will have to live with and if you are
against 10's of thousands of orbital satellites you are now - according to you
- immediately against progress. This obviously isn't the case.

So, let's stop the clock for a bit until we have a much better idea of what
the impact of all this littering will be and whether or not there is something
that can be done about it before we end up with a situation that is out of
control. SpaceX is _not_ the world, LEO is not US property and whether or not
low cost satellite access is such a good thing that we should give up easy
access to visible light astronomy is not a given.

This has nothing to do with 'taking to the stars', 'making the universe a more
interesting place' or 'upgrading our dreams'. It is a simple commercial
proposition.

~~~
DennisP
> This has nothing to do with 'taking to the stars'

Actually it does, because Starlink is intended to fund Starship development
and Mars colonization.

~~~
jacquesm
Sorry, but Mars colonization is nonsense. It isn't going to happen in the
foreseeable future and the people that believe this stuff are no less stupid
than the ones following the next messiah. I wrote about it here:

[https://news.ycombinator.com/item?id=24058911](https://news.ycombinator.com/item?id=24058911)

Just to put this into perspective a bit: every little bit of civilization in
_Iceland_ , every nail, every staple, every fruit, every tool has to be flown
in or brought in by boat. Everything. And Iceland is a place that compared to
Mars is paradise. The only things they have plenty of are energy, fish and
sheep. And on Mars you wouldn't even have that.

It's just too silly to take serious.

Musk and Hughes have a lot in common. They are both genius, wealthy, capable
and at times a bit batty. I'm fine with Elon being a bit batty, if that give
us electric cars, reusable rockets and more. But I'm not buying into the cult.
Starlink is borderline for me. I can see the utility. But the idea that space
can be commercialized with such total disregard for what effectively is our
largest commons is simply wrong to me.

------
dvaun
The technical report is quite large (105MB). Here is a compressed version
(6MB):
[https://www.dvaun.com/files/satcon1-compressed.pdf](https://www.dvaun.com/files/satcon1-compressed.pdf)

I'm a bit confused by why they included such high-res images in the PDF in the
first place.

Edit: After taking a look at the original I see that they embedded some of the
files they created with Photoshop and After Effects directly into the
document. They forgot to resize the images, hence the huge object streams in
the file.

~~~
ISL
Agreed that they could have downsampled it for expedience, though the point is
that systems spanning the gamut from the human eyeball to cryogenically-cooled
3.2 gigapixel imaging sensors are impacted by these constellations.

Those sensors are 3.2 gigapixels at 16-bit depth, so each image alone is 6.4
gigabytes. 108 MB seems small by comparison; that is only one telescope out of
all the sky-imaging (optical and radio) systems on the planet.

~~~
dvaun
I appreciate the sense of scale that your explanation brings. I understand
that.

The size of the PDF is not a symbol for the work being done here, though.
Reducing it makes it cheaper to distribute and easier for viewers to read
their findings. That is my reasoning for putting up another version.

------
4gotunameagain
Whether you agree or disagree with huge sat constrellations, I think that a
matter that clearly impacts the entire world should not be decided by a
handful of people from a single country.

~~~
sschueller
Nor a single billionaire.

If China or Russia was the one building starlink the reception in the US would
be a lot different.

------
jacquesm
It's littering on the largest scale imaginable.

~~~
mlindner
So solar panels and cell phone towers are littering too?

~~~
mhh__
Unless you live in a country with 20000ft tall people where do you see solar
panels? Cell towers can also be hidden fairly easily when needed.

------
kome
People, let's get real for a minute.

Why are we allowing a private company to ruin the night sky for everybody, and
by everybody, I mean literally everybody on this planet?

This should be discussed in a democratic and international way. It’s nor going
to be easy, but it is necessary.

I can't believe future generations won't see a pristine night sky anymore...

~~~
mlindner
> Why are we allowing a private company to ruin the night sky for everybody,
> and by everybody, I mean literally everybody on this planet?

They're not being ruined for everybody. There's so many misinformed comments
in this thread. These satellites aren't visible to the human eye generally.

~~~
kome
"generally" is the key: not long ago in northern Italy everybody was freaking
out because of this:

[https://cdn.dmove.it/images/18547/StarMain.jpg](https://cdn.dmove.it/images/18547/StarMain.jpg)

Those are the ones by Starlinks. That's not acceptable.

They are so invisible to the naked eye, that the weather website gives you the
exact time and date of their passage in the sky:
[http://www.meteoweb.eu/2020/05/passaggio-satelliti-
starlink-...](http://www.meteoweb.eu/2020/05/passaggio-satelliti-
starlink-14/1433303/) (in Italian)

~~~
mlindner
1\. That is only in the roughly week following launch, which doesn't harm
anyone.

2\. They changed operations immediately after launch and so you generally
can't see this anymore.

They are indeed invisible after launch. Your article is from March, before
changes were made. Try to find anyone taking pictures of them in that chain of
pearls form in the last few months.

------
jankotek
Cheap rockets will make space telescopes way more accessible. Ground survey
telescopes have serious limitations. So for science this could be a positive
thing.

I am more worried about monopolies and accessibility of this new internet. If
it ruins sky for everyone, but only a few can afford it, that would be a
terrible deal.

~~~
Rebelgecko
>Cheap rockets will make space telescopes way more accessible.

I'm not convinced that's true. If you look at past space telescopes, launch
costs are not a large part of the budget. Even if SpaceX gave everyone _free_
launches as a goodwill measure, you'd only make space telescopes maybe 2-5%
cheaper. There's very real challenges that space based telescopes have that
Earth based ones don't (how do you make a cryocooler that doesn't vibrate your
optics? How do you make a machine that can run for years without maintenance?
How do you get precise enough positioning to interferometry?). My
understanding is that due to adaptive optics, being ground based isn't much of
a problem for visual telescopes. And for large radio telescope arrays, I don't
see how it's possible at all to move to space

~~~
mlindner
> If you look at past space telescopes, launch costs are not a large part of
> the budget.

Satellites are built to narrow margin to reduce weight because of the weight
restrictions on satellites. Right now we have reusable rockets but the rockets
aren't any bigger so while the cost of launch has come down the volume/mass
that can be launched in one go has not gone up. If laser interferometry gets
better then large telescopes can be launched as constellations. Larger
reusable rockets are also being worked on. When that happens they can care
less about mass margin and make cheaper lower margin telescopes.

Telescopes are also generally built as a one-off which also increases cost. I
hope the technology for telescope constellations will improve.

~~~
Rebelgecko
Even if there's room for additional weight, that doesn't help with the other
aspects of SWAP.

Size: There's still a finite fairing size. Even the biggest upcoming rockets
can't fit a 30m mirror in one piece.

Weight: say you want to put something like ALMA in space, which weighs over
ten million pounds. Even with platforms like starship,you're not going to be
able to do that in one go. _Maybe_ one launch for each of the 66 antennas,but
even that is iffy.

Power: Hubble's power consumption is around 2Kw. Using ALMA as an example
again, each individual antenna uses about 10x more electricity than that on
average. More electricity means you need RTGs or nuclear reactors (not
politically popular, complicates thermal regulation, potential for spreading
radioactive waste across orbit and earth a la RORSAT), or massive arrays of
solar panels. Massive solar panels means even more weight and space required

For interferometry, knowing your location to the nanometer is just the first
of many challenges. You have to station keep across the constellation (tricky
to do continuously while you're in orbit!), it becomes even more important to
minimize vibrations, etc

~~~
mlindner
Is ALMA even affected by satellites? I would imagine parallax would make
satellites disappear and satellites would just slightly increase the noise
floor. So I'm not sure why you're using that as an example.

> For interferometry, knowing your location to the nanometer is just the first
> of many challenges. You have to station keep across the constellation
> (tricky to do continuously while you're in orbit!), it becomes even more
> important to minimize vibrations, etc

I didn't say it wasn't an engineering problem, but the major reason it hasn't
been used yet is there was no real benefit to doing that over launching a
single large telescope in terms of launch cost. I hope to see these problems
solved soon in the future.

~~~
Rebelgecko
At least from what other radio telescopes, the issue isn't actually the
physical satellites. It's the spectrum they're using

>no real benefit to doing that over launching a single large telescope in
terms of launch cost

It would be hugely beneficial to do it in space. When you do interferometry on
the ground, your maximum aperture size is the diameter of the Earth (if you
had two observatories at opposite points on the Earth). When you do it in
space, the size of your synthetic aperture is practically limitless.

------
hinkley
I thought this was going to be about collisions between satellites from two
constellations.

As someone loudly lamented a long time ago: please stop using the word
“impact” as a substitute for figuring out effect/affect.

~~~
reaperducer
_As someone loudly lamented a long time ago: please stop using the word
“impact” as a substitute for figuring out effect /affect._

"A long time ago" might be the 1700's, because it's been in use that way for
several hundred years. So don't hold your breath.

~~~
hinkley
I’m this case it was within this century, which is quickly becoming a time
before some participants here had learned to read. The older you get, the more
the line between “long enough” and “a long time ago” begins to blur.

