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SpaceX working on fix for Starlink satellites so they don’t disrupt astronomy

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Re: SpaceX working on fix for Starlink satellites so they don’t disrupt astronomy

#261

Post by Rebelgecko »

wongarsu wrote: post #20
vasili111 wrote: post #12

Also do not forget that SpaceX is not the only company that wants to launch low orbit satelites. I do not think it is possible to find any other real solution other then to move telescopes to space.

With James Web having an decently sized mirror on a space telescope that's not as ridiculous as it once was. Still we should search for cheaper solutions first. https://www.eso.org/public/usa/images/eso1617z/?lang

For some added context, JWST costs about 10x more than the most expensive terrestrial telescope ever built.

Re: SpaceX working on fix for Starlink satellites so they don’t disrupt astronomy

#262

Post by Rebelgecko »

jsjohnst wrote: post #254

Since there are folks here in the field, does anyone know what the feasibility of building something similar to the VLA, but with thousands of smaller satellites? If doable, seems potentially possible to cover a lot more sky at once with less terrestrial interference. No idea if this is practical or not.

There's a number of problems w/ doing interferometry in space, which vary a bit depending on the frequencies you're working with—

Thermal: Parts of the detectors need to be very cold. Depending on what you're doing you may have to cool parts of the satellite down to 5 kelvin (-450°F) or even lower. You need to use a cryocooler than won't vibrate too much and impact your measurements.

Power: Each VLA antenna uses about 18kW just for cooling. That's a lot of juice— back of the envelope math says you need a lot of solar panels for that. An area smaller than a football field but bigger than a tennis court. It's manageable if you're only building a few of these, but less practical if you want to build 64 or even thousands.

Positioning: Most proposals for space based interferometry didn't actually consist of individual satellites. They're typically one big satellite with telescopes sticking out on different arms. If they're free-flying, it gets a lot harder to know the precise relative positions of the different receivers.

Re: SpaceX working on fix for Starlink satellites so they don’t disrupt astronomy

#263

Post by nordsieck »

calabin wrote: post #248
nordsieck wrote: post #112

Earlier quoted context omitted.

> Still doesn't matter for the typical home user. One very important market they're going after is global arbitrageurs.

Do you have any evidence of this? I work in algorithmic trading/finance and I'm relatively certain that this isn't true.

> Do you have any evidence of this?

My only evidence is a very basic evaluation of their publicly stated capabilities.

> I work in algorithmic trading/finance and I'm relatively certain that this isn't true.

It sounds like you have a much better informed opinion than I do.

With my limited knowledge, I see no reason why SpaceX wouldn't aggressively go after that market, but like I said, my knowledge is limited.

Re: SpaceX working on fix for Starlink satellites so they don’t disrupt astronomy

#264

Post by jsjohnst »

Rebelgecko wrote: post #262
jsjohnst wrote: post #254

Since there are folks here in the field, does anyone know what the feasibility of building something similar to the VLA, but with thousands of smaller satellites? If doable, seems potentially possible to cover a lot more sky at once with less terrestrial interference. No idea if this is practical or not.

There's a number of problems w/ doing interferometry in space, which vary a bit depending on the frequencies you're working with— Thermal: Parts of the detectors need to be very cold. Depending on what you're doing you may have to cool parts of the satellite down to 5 kelvin (-450°F) or even lower. You need to use a cryocooler than won't vibrate too much and impact your measurements. Power: Each VLA antenna uses abou…

> Each VLA antenna uses about 18kW just for cooling.

That’s likely at minimum partially proportional to the size of each VLA antenna, no? Each VLA antenna is larger than any antenna ever put in space I believe.

> If they're free-flying, it gets a lot harder to know the precise relative positions of the different receivers.

That’s exactly what I thought would be one of the biggest challenges, but wasn’t sure if we’d solved that problem or not yet.

Re: SpaceX working on fix for Starlink satellites so they don’t disrupt astronomy

#265

Post by avmich »

wpietri wrote: post #156
mstipetic wrote: post #151

Earlier quoted context omitted.

Well let's figure out a way to assemble them in space. Hubble is thirty years old, and is being used now as a reference. I don't understand all this negativity. Had we had this mindset, Hubble would not have been there

Part of the negativity is who benefits from the problem versus who has to pay to fix it. If SpaceX were causing a problem for astronomers while also for free launching radically better space-based tools, it wouldn't be nearly as big a deal. But instead SpaceX hopes to pocket a lot of money, while the harms are falling on other people.

> SpaceX hopes to pocket a lot of money

and SpaceX customers hope to pocket a lot of use for that money. So taking that point literally - tiny astronomer's society is against the whole Earth load of Spacelink customers, and of course those customers' needs on average trump astronomers' ones.

I'm exaggerating, of course.

Re: SpaceX working on fix for Starlink satellites so they don’t disrupt astronomy

#266

Post by avmich »

Rebelgecko wrote: post #260
mstipetic wrote: post #187

Earlier quoted context omitted.

We shouldn't have been able to land on the moon using whiteboard engineering and calculator level computers, but we did

Why shouldn't we have been able to land on the moon?

Because, as you've said, we can't manufacture complex objects in space.

Re: SpaceX working on fix for Starlink satellites so they don’t disrupt astronomy

#267

Post by avmich »

hgoel wrote: post #257
mstipetic wrote: post #187

Earlier quoted context omitted.

We shouldn't have been able to land on the moon using whiteboard engineering and calculator level computers, but we did

That won't magically make it feasible to manufacture such precise objects in space anytime soon.

In fact, in space we can make something which we can't do on Earth - weightlessness being the critical enabling factor.

With capabilities to launch as cheap as Spaceship promises, we can develop space manufacturing rather soon.

Re: SpaceX working on fix for Starlink satellites so they don’t disrupt astronomy

#268

Post by avmich »

ixf wrote: post #162
mstipetic wrote: post #147

Earlier quoted context omitted.

JWST is a great project and a type of project we should strive for. I'm personally just annoyed why the conversation is so defensive and negative. I don't know much about astronomy, but from what I understand the Earth's atmosphere is hard to deal with, why aren't we talking more about what can be done with this new tech, and not how it makes current things more difficult

Earth's atmosphere is annoying, yes, but for huge swathes of observational science it's not a deal-breaker. Not having massive telescopes on the ground where you can fiddle with your instrumentation and take advantage of apertures and construction techniques simply not possible in space _is_ a deal-breaker. The required precision for construction of telescopes is incredible, and doesn't translate to space well, espec…

> Not having massive telescopes on the ground where you can fiddle with your instrumentation and take advantage of apertures and construction techniques simply not possible in space _is_ a deal-breaker.

Why do you think telescopes in space - where they don't need to fight gravity just to stand - can't soon, with reasonable development, surpass land-based ones in capabilities?

Re: SpaceX working on fix for Starlink satellites so they don’t disrupt astronomy

#269

Post by wpietri »

avmich wrote: post #265
wpietri wrote: post #156

Earlier quoted context omitted.

Part of the negativity is who benefits from the problem versus who has to pay to fix it. If SpaceX were causing a problem for astronomers while also for free launching radically better space-based tools, it wouldn't be nearly as big a deal. But instead SpaceX hopes to pocket a lot of money, while the harms are falling on other people.

> SpaceX hopes to pocket a lot of money and SpaceX customers hope to pocket a lot of use for that money. So taking that point literally - tiny astronomer's society is against the whole Earth load of Spacelink customers, and of course those customers' needs on average trump astronomers' ones. I'm exaggerating, of course.

You're also confusing money with value. If we only go by market price, air pollution should be fine, since lots more people buy electrical power than die from coal plant particulates. But market price only captures a relatively narrow slice of value, and it's heavily biased in favor of people with money.

Re: SpaceX working on fix for Starlink satellites so they don’t disrupt astronomy

#270

Post by Rebelgecko »

jsjohnst wrote: post #264
Rebelgecko wrote: post #262

Earlier quoted context omitted.

There's a number of problems w/ doing interferometry in space, which vary a bit depending on the frequencies you're working with— Thermal: Parts of the detectors need to be very cold. Depending on what you're doing you may have to cool parts of the satellite down to 5 kelvin (-450°F) or even lower. You need to use a cryocooler than won't vibrate too much and impact your measurements. Power: Each VLA antenna uses abou…

> Each VLA antenna uses about 18kW just for cooling. That’s likely at minimum partially proportional to the size of each VLA antenna, no? Each VLA antenna is larger than any antenna ever put in space I believe. > If they're free-flying, it gets a lot harder to know the precise relative positions of the different receivers. That’s exactly what I thought would be one of the biggest challenges, but wasn’t sure if we’d s…

True that 18kW isn't a totally fair comparison. On one hand it's easier to cool because you don't have to worry about the air warming you up. OTOH it's harder because sunlight is way stronger once you get out of the atmosphere.
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