Author Topic: Planetary Resources  (Read 198963 times)

Online douglas100

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Re: Planetary Resources
« Reply #40 on: 05/05/2012 09:49 AM »

I'm not sure what excites me more about the potential of Planetary Resources:
Having a catalogue of potentially civilization saving information (orbits of NEO's)
Discovering zillions of exoplanets through optical interferometry
The new data we can collect about our solar system, including through visual observations.
A map of noteable Kuiper and Oort objects along with high-res photos of many of them.
The improved resolution of various interstellar phenomenon
Having very regular high-res updates (and historical database) to google earth (or perhaps it will be called PR-Earth)
The potential for abundant volatiles and metals that could be processed in space and used for in-space habitation and transportation by all comers
The impact it will have on STEM outreach

You would think from that list that PR are about to supplant large areas of astronomy. They are not. I do not believe they will attempt optical interferometry with multiple spacecraft any time soon. It has never been done before. The precision required controlling and measuring the baseline between the individual spacecraft is a formidable technical problem.

The zillions of exoplanets, the high resolution pictures of Kuiper and Oort objects (have you any idea how far the Oort cloud is?), all that is unrealistic.

Likewise, why should their spacecraft be any better than the dozens of Earth observing satellites currently operating? They are not going to make billions in Earth observation.

Without interferometry their telescopes have modest resolution. I can see them being used as they advertise, as NEO survey instruments. Whether they would do a better job than large ground instruments remains to be seen.

What I like about their proposal is the use of their spacecraft as amateur space telescopes.
Douglas Clark

Offline Robotbeat

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Re: Planetary Resources
« Reply #41 on: 05/05/2012 05:18 PM »
Their telescopes are just a cheap platform to do astronomy and Earth observation. Optical interferometry is hard, though, and I think it'd be wise not to jump to conclusions about their ability to do that.
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Offline Blackjax

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Re: Planetary Resources
« Reply #42 on: 05/05/2012 06:46 PM »
Their telescopes are just a cheap platform to do astronomy and Earth observation. Optical interferometry is hard, though, and I think it'd be wise not to jump to conclusions about their ability to do that.

I agree, it is premature to jump to conclusions about their ability to do optical interferometry, however I think there are a lot of small scattered indications that support the conclusion that they intend to try. 

Every indication is that their business plans focus on mass production and operation of hardware.  Telescopes of this size, even in space, don't have particularly impressive capabilities when used singly.  There is every reason to think they intend to try to use them in a swarm.

Given that this is relatively low cost hardware that can be test flown as design iterations very frequently if they choose, I don't see any reason except their own motivation to not keep iterating until they work the kinks out of how to make it work.

I'd be dubious if the hardware were much more expensive, or if they didn't have such deep pockets backing them, but they are talking about something that should be pretty amenable to testing and tweaking and seem to have the financial wherewithal to do so. 

So the real question is whether they are interested enough to keep messing with it until they figure out how to make it work.

Online douglas100

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Re: Planetary Resources
« Reply #43 on: 05/05/2012 08:43 PM »

I agree, it is premature to jump to conclusions about their ability to do optical interferometry, however I think there are a lot of small scattered indications that support the conclusion that they intend to try. 

Given that this is relatively low cost hardware that can be test flown as design iterations very frequently if they choose, I don't see any reason except their own motivation to not keep iterating until they work the kinks out of how to make it work.

I'd be dubious if the hardware were much more expensive, or if they didn't have such deep pockets backing them, but they are talking about something that should be pretty amenable to testing and tweaking and seem to have the financial wherewithal to do so. 

That was partially my point: that if they wish to do interferometry the hardware will be much more expensive. However, as you say, they have considerable financial wherewithal.

Like a number of people on the forum I am not much convinced by the asteroid mining goal, but I am intrigued by the astronomical implications of their spacecraft. It will be interesting to watch this develop.
Douglas Clark

Offline Blackjax

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Re: Planetary Resources
« Reply #44 on: 05/05/2012 10:48 PM »
That was partially my point: that if they wish to do interferometry the hardware will be much more expensive. However, as you say, they have considerable financial wherewithal.

What makes you so confident that there is no (relatively) low cost way they might come up with to solve this problem?

(please take this as a genuine question, and not disagreement disguised as a question, I know absolutely nothing about the technical challenges involved and I am curious)

Offline BrightLight

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Re: Planetary Resources
« Reply #45 on: 05/05/2012 11:38 PM »
An interferometer is a device that folds waves onto itself and the contructive or destructive components are used to construct enhanced contrast data, such as with RF signals or images. To do this with disparit sensors requires good knowledge of there orientation, time of acquisition, and spatial coordinates. These measurements require a IMU, high precision clocks, and the ability to maintain orientation and position. Without knowing what components are in the telescopes and how they are integrated, I dont see how statements can be made about how they will be used.

Offline Robotbeat

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Re: Planetary Resources
« Reply #46 on: 05/06/2012 05:08 AM »
I will say that the Intensity Correlation Imaging is a VERY clever idea that I had not heard of before (though not one that Planetary Resources came up with or even mentioned... it's something someone else said that perhaps they could use). That has requirements that are a lot easier than trying to do direct beam combining and interferometry. Of course, that idea is not limited to just Planetary Resources. But having a cheap bunch of telescopes in LEO may be pretty useful for that sort of idea.
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Offline as58

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Re: Planetary Resources
« Reply #47 on: 05/06/2012 06:28 AM »
Lots of small space telescopes would be a strange choice for intensity interferometry.

Online douglas100

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Re: Planetary Resources
« Reply #48 on: 05/06/2012 09:47 AM »
That was partially my point: that if they wish to do interferometry the hardware will be much more expensive. However, as you say, they have considerable financial wherewithal.

What makes you so confident that there is no (relatively) low cost way they might come up with to solve this problem?

(please take this as a genuine question, and not disagreement disguised as a question, I know absolutely nothing about the technical challenges involved and I am curious)

No, that's a reasonable question. See

http://proceedings.aip.org/resource/2/apcpcs/387/1/245_1?isAuthorized=no

For an optical interferometer to work, the distance between the elements (the telescopes in this case) has to be controlled to something of the order of the size of the wavelength of light. This has been done for ground astronomical instruments like Keck or VLT.

As far as I know, this level of accuracy has never been achieved by free flying spacecraft. I believe it will be very expensive to develop. I don't think telescopes in LEO can station keep to this accuracy because there are to many perturbing forces, like drag and gravity gradient. I think a multiple telescope interferometer would have to be located in interplanetary space. PR have not mentioned doing such a thing.

Remember, PR are talking about launching their telescopes as secondary payloads. This is not the way you build a constellation of formation flying satellites doing interferometry.

I don't think PR's prime goal is to do cutting edge astronomy. Their mission is first to find suitable asteroids. They need to know orbits and spectral characteristics. The small space telescopes they propose seem adequate for that. Later on they can send their follow up spacecraft to the most promising candidates and examine them directly.

So what do they need interferometry for?
Douglas Clark

Offline ChefPat

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Re: Planetary Resources
« Reply #49 on: 05/06/2012 02:44 PM »
So what do they need interferometry for?
$$$
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Online douglas100

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Re: Planetary Resources
« Reply #50 on: 05/06/2012 04:23 PM »
How is interferometry going to make them a lot of money?
Douglas Clark

Offline Robotbeat

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Re: Planetary Resources
« Reply #51 on: 05/06/2012 04:31 PM »
How is interferometry going to make them a lot of money?
It could make them some money. (But I don't think they'll do traditional interferometry if they do it at all.)
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Offline BrightLight

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Re: Planetary Resources
« Reply #52 on: 05/06/2012 05:51 PM »
The number one issue for an imaging interferometer is the time of acquisition, all the imagers must have good synchronized clocks - at least at nanosecond time scales, these exist and are not terribly hard to operate in space (invar mounts, rad hardened, insulated, thermal stabilized), but without this minimum capability all else is moot.

Offline Robotbeat

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Re: Planetary Resources
« Reply #53 on: 05/06/2012 06:17 PM »
The number one issue for an imaging interferometer is the time of acquisition, all the imagers must have good synchronized clocks - at least at nanosecond time scales, these exist and are not terribly hard to operate in space (invar mounts, rad hardened, insulated, thermal stabilized), but without this minimum capability all else is moot.
GPS can be used to assist time synchronization. Though obviously that's a little more tricky in orbit.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline BrightLight

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Re: Planetary Resources
« Reply #54 on: 05/06/2012 06:23 PM »
The number one issue for an imaging interferometer is the time of acquisition, all the imagers must have good synchronized clocks - at least at nanosecond time scales, these exist and are not terribly hard to operate in space (invar mounts, rad hardened, insulated, thermal stabilized), but without this minimum capability all else is moot.
GPS can be used to assist time synchronization. Though obviously that's a little more tricky in orbit.
Absolutely, but GPS NEMA strings are around 2 Hz, and even with WAAS, you have millisecond timing, one needs atomic clock scale timing on each platform.

Online A_M_Swallow

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Re: Planetary Resources
« Reply #55 on: 05/06/2012 06:39 PM »
The number one issue for an imaging interferometer is the time of acquisition, all the imagers must have good synchronized clocks - at least at nanosecond time scales, these exist and are not terribly hard to operate in space (invar mounts, rad hardened, insulated, thermal stabilized), but without this minimum capability all else is moot.
GPS can be used to assist time synchronization. Though obviously that's a little more tricky in orbit.
Absolutely, but GPS NEMA strings are around 2 Hz, and even with WAAS, you have millisecond timing, one needs atomic clock scale timing on each platform.

Can you have the master clock on one satellite and derive the time from a control signal at the other satellites?

If you bounce the control signal back distance and time delay can be measured.

Offline BrightLight

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Re: Planetary Resources
« Reply #56 on: 05/06/2012 06:44 PM »
The number one issue for an imaging interferometer is the time of acquisition, all the imagers must have good synchronized clocks - at least at nanosecond time scales, these exist and are not terribly hard to operate in space (invar mounts, rad hardened, insulated, thermal stabilized), but without this minimum capability all else is moot.
GPS can be used to assist time synchronization. Though obviously that's a little more tricky in orbit.
Absolutely, but GPS NEMA strings are around 2 Hz, and even with WAAS, you have millisecond timing, one needs atomic clock scale timing on each platform.

Can you have the master clock on one satellite and derive the time from a control signal at the other satellites?

If you bounce the control signal back distance and time delay can be measured.
That technique is used on some coordinated assets but has not been used for interferometers as far as I know.  Master clocks - one on the master platform and one on the ground receive side would have to trigger the sensors - how do you get thenm to trigger at the same time?

Offline Robotbeat

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Re: Planetary Resources
« Reply #57 on: 05/06/2012 06:45 PM »
The number one issue for an imaging interferometer is the time of acquisition, all the imagers must have good synchronized clocks - at least at nanosecond time scales, these exist and are not terribly hard to operate in space (invar mounts, rad hardened, insulated, thermal stabilized), but without this minimum capability all else is moot.
GPS can be used to assist time synchronization. Though obviously that's a little more tricky in orbit.
Absolutely, but GPS NEMA strings are around 2 Hz, and even with WAAS, you have millisecond timing, one needs atomic clock scale timing on each platform.
It's still pretty close to being in the range of some good temp-controlled crystal oscillators. And even Rubidium standards are pretty small and cheap these days (a couple kg, a few thousand bucks).

But with fancy GPS signal processing, even a Rubidium standard isn't necessarily required.
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Offline Jason1701

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Re: Planetary Resources
« Reply #58 on: 05/06/2012 07:15 PM »
Would interferometry work for getting higher resolution of Earth from orbit?
« Last Edit: 05/06/2012 07:15 PM by Jason1701 »

Offline Robotbeat

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Re: Planetary Resources
« Reply #59 on: 05/06/2012 07:17 PM »
Would interferometry work for getting higher resolution of Earth from orbit?
Not terribly. With targets in space, you have a nice black background, for the most part.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

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