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Tiny satellites ushering in a new space revolution

bloomberg.com

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Re: Tiny satellites ushering in a new space revolution

#31

Post by kerkeslager »

emagdnim2100 wrote: post #29
kerkeslager wrote: post #28

Earlier quoted context omitted.

It sounds like you're relying on the satellites de-orbiting and burning up in the atmosphere. Are there any steps taken to ensure the satellites de-orbit in a timely manner? Are there any estimates on how many of the satellites will de-orbit and when, absent such an intervention?

Anything in LEO will de-orbit unless you actively keep it there, due to atmospheric drag. This is like watching someone drop a ball and asking if they are taking any steps to ensure it will fall.

Obviously, but how long does that take, and is that long enough that collisions are negligibly probable?

It's possible that the problem will take care of itself, but the information provided is not adequate to model the problem and prove that the problem will take care of itself.

Re: Tiny satellites ushering in a new space revolution

#32

Post by panzagl »

kerkeslager wrote: post #31
emagdnim2100 wrote: post #29

Earlier quoted context omitted.

Anything in LEO will de-orbit unless you actively keep it there, due to atmospheric drag. This is like watching someone drop a ball and asking if they are taking any steps to ensure it will fall.

Obviously, but how long does that take, and is that long enough that collisions are negligibly probable? It's possible that the problem will take care of itself, but the information provided is not adequate to model the problem and prove that the problem will take care of itself.

It's a Bloomberg article, not an intro to astrodynamics. If you know the orbit you can figure out when it will decay relatively accurately.

Re: Tiny satellites ushering in a new space revolution

#33

Post by Retric »

kobeya wrote: post #24
InclinedPlane wrote: post #9

Earlier quoted context omitted.

This is simply ignorant of the plans. Firstly, there are levels of functionality, being able to provide service being the highest one. Out of service satellites are still most likely to be able to execute a controlled re-entry. Secondly, these satellites will be in low Earth orbit. If they become completely inoperable they have an orbital lifetime of only a few years before they re-enter. Only with routine station ke…

> Out of service satellites are still most likely to be able to execute a controlled re-entry How? By a burn? That's a lot of fuel reserve to use up.

It takes minimal energy to deorbit from LEO. By changing the shape of the orbit you spend some time in denser atmosphere which increases drag which quickly deorbits you. Controlled just means they start the processes at a specific time.

Re: Tiny satellites ushering in a new space revolution

#34

Post by lorenzhs »

shawn-butler wrote: post #25
kumarvvr wrote: post #3

That is a pretty cool engineering feet. Never knew a shoe box sized telescope can give such detailed pictures. They have sent about 200 satellites, cost "six figures" each, so an estimate of 200,000 a piece, they have spent about 40 million dollars, excluding the price of launches. The data collected is definitely worth the price IMO. Imagine the ability to monitor storms and hurricanes, analyze their data and update…

I'm not sure if this includes the Skylabs-TerraBella launches? Skylabs had seven high-res SkySat satellites that Planet got via acquiring Skylabs/TerraBella complementing its existing fleet of medium res satellites. Planet’s existing network could only get three to five meter resolution, while Skybox’s satellites could manage “sub-meter" accuracy. 80 million in funding seems low. The price of the Skybox/TerraBella ac…

There was substantial uncertainty about the cost of TerraBella's acquisition, see https://techcrunch.com/2017/01/25/google-satellite-planet/ which says "We’ve not heard a firm price. Aside from the $300 million figure we heard, another described Terra Bella as essentially being “donated” to Planet."

As of April 2015, Planet had raised $183M according to https://techcrunch.com/2015/04/13/planet-labs-rockets-to-118...

Re: Tiny satellites ushering in a new space revolution

#35

Post by vanderZwan »

kobeya wrote: post #23
snaily wrote: post #20

Earlier quoted context omitted.

From first principles, I'm not seeing how a LEO collision pushes a significant amount of debris notably higher, but I'm certainly missing something: Post collision, all debris orbits will still be passing through the point of collision. Any deflection with a vertical component (up or down towards the earth) will have a part of their orbit go through thicker atmosphere, which will make them deorbit faster. That leaves…

When collisions are more frequent than once per orbit you get effects where more than one collision cause a bit of debris to have itself lifted. MOST debris is deorbited, but a small fraction is lifted into a higher orbit overall. As these collide with other objects the total mass of the system might go down (from reentry), but the number of objects and the frequency of collision goes up, continuing the process of so…

> more frequent than once per orbit

My gut feeling says that statistically, even just going from one impact to two impacts being likely would require an immense density of satellites, let alone having more collisions than that.

Then there's also the fact that every impact would have a loss of kinetic energy (because it gets converted to heat as the objects deform), which would also make a reduction in orbit likely.

If the debris keeps fragmenting, which maybe could increase odds of impact, the remaining kinetic energy would be divided over each object. The smaller the debris gets, the more drag it should feel too, because of the square-cube law[0]. So that too would only make it more likely to deorbit.

[0] https://en.wikipedia.org/wiki/Square%E2%80%93cube_law

Re: Tiny satellites ushering in a new space revolution

#36

Post by snrplfth »

kobeya wrote: post #23
snaily wrote: post #20

Earlier quoted context omitted.

From first principles, I'm not seeing how a LEO collision pushes a significant amount of debris notably higher, but I'm certainly missing something: Post collision, all debris orbits will still be passing through the point of collision. Any deflection with a vertical component (up or down towards the earth) will have a part of their orbit go through thicker atmosphere, which will make them deorbit faster. That leaves…

When collisions are more frequent than once per orbit you get effects where more than one collision cause a bit of debris to have itself lifted. MOST debris is deorbited, but a small fraction is lifted into a higher orbit overall. As these collide with other objects the total mass of the system might go down (from reentry), but the number of objects and the frequency of collision goes up, continuing the process of so…

Not how orbits work. A collision can't cause, for example, an object with a circular orbit at 400km (passive reentry regime) to become fragments with a circular orbit at, say, 2000km (non-passive reentry regime.) Like snaily said, all fragments originating from a collision will still pass through the point of collision, which, if it is still in the upper atmosphere, will lead to reentry. Orbital debris is actually very dissimilar to gas escape.

Re: Tiny satellites ushering in a new space revolution

#37

Post by llccbb »

a_d wrote: post #17
currydove wrote: post #14

Earlier quoted context omitted.

The other comments that are replying to you have it fairly accurate. It's not widely known but it isn't a secret either: the point of the doves is to be deployed en masse and with more capability with every subsequent build. A quick refresh in the constellation means there is fresh hardware in space every so often. This means the intention is indeed for re-entry into the atmosphere after the operational lifespan of t…

Unrelated and probably a stupid question -- but I am curious. What would these satellites see if they looked the other way - i.e. Outwards towards space. Would they see just darkness? Some stars? Lots of stars? Would you know?

I don't work for Planet but I know the doves have a space-looking camera that is used to help understand the satellite's orientation based on the location of stars in the image.

Re: Tiny satellites ushering in a new space revolution

#38

Post by 659087 »

westmeal wrote: post #6
kumarvvr wrote: post #3

That is a pretty cool engineering feet. Never knew a shoe box sized telescope can give such detailed pictures. They have sent about 200 satellites, cost "six figures" each, so an estimate of 200,000 a piece, they have spent about 40 million dollars, excluding the price of launches. The data collected is definitely worth the price IMO. Imagine the ability to monitor storms and hurricanes, analyze their data and update…

Global surveillance networks.

"Google/Facebook: Please step outside and look up for 10 seconds to verify your identity"

Re: Tiny satellites ushering in a new space revolution

#39

Post by teh_klev »

a_d wrote: post #17
currydove wrote: post #14

Earlier quoted context omitted.

The other comments that are replying to you have it fairly accurate. It's not widely known but it isn't a secret either: the point of the doves is to be deployed en masse and with more capability with every subsequent build. A quick refresh in the constellation means there is fresh hardware in space every so often. This means the intention is indeed for re-entry into the atmosphere after the operational lifespan of t…

Unrelated and probably a stupid question -- but I am curious. What would these satellites see if they looked the other way - i.e. Outwards towards space. Would they see just darkness? Some stars? Lots of stars? Would you know?

I'd hazard a guess at probably not a lot. The onboard telescopes and cameras are likely calibrated to look at and focus on specific sized patches (say 15km by 15km) of the earth between certain altitudes (say LEO distance + -450m to 9000m).

Turning them to look outwards might just capture something if it happened to be inside the size of patch and whatever the telescope/camera combo can focus on (which would be the LEO distance plus or minute a bit). But space is big, even at 500km above the earth, so the likelihood of finding something in your field of view such as another satellite is probably quite low. Stars and other astronomical objects might be too dim/out of focus.

[Disclaimer: not a rocket scientist]

Re: Tiny satellites ushering in a new space revolution

#40

Post by teddyh »

hi41 wrote: post #26

Kindly can someone tell me how these snall satellites are able to remain in orbit. Don't we need jet propulsion to have them stay in orbit and not fall into earth? I don't much about satellites.

The moon doesn’t need any propulsion to stay in orbit around the Earth. A satellite is just a very small and very close moon. The fact that it’s closer than the moon just means that it will orbit faster than the moon does.
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