Author Topic: PlanetLabs Constellation as Space Telescope?  (Read 2714 times)

Offline Danderman

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PlanetLabs Constellation as Space Telescope?
« on: 12/09/2016 02:52 pm »
A kind of wild and crazy idea that needs some grounding in reality:

The PlanetLabs Dove satellites contain a low rez telescope used for visible light imagery. Presumably these satellites are not functional during night, ie on the "back side" of the planet away from the Sun. So, my question is whether any sort of useful astronomy could be performed by an aggregate of the satellites, with dozens focused on the same patch of night sky at the same time, thousands or hundreds of miles apart.

Here, I am ignoring power and thermal issues, but rather the optical usefulness of large numbers of small apertures separated by great distance.

Offline RonM

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Re: PlanetLabs Constellation as Space Telescope?
« Reply #1 on: 12/09/2016 03:41 pm »
Radio interferometry observations can be recorded and combined later, but optical interferometry requires the images to be combined live because of the short wavelength, so that's not an option.

Observing stellar occultations would be very useful. Can be used to determine asteroid sizes and might even spot asteroid moons.

Offline as58

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Re: PlanetLabs Constellation as Space Telescope?
« Reply #2 on: 12/09/2016 04:44 pm »
Potentially also exoplanet transits and other transient phenomena. Individual telescopes on TESS and Plato for example are not much bigger than what each PlanetLabs satellite has. Of course, the devil is in the details.

Offline Danderman

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Re: PlanetLabs Constellation as Space Telescope?
« Reply #3 on: 12/09/2016 04:53 pm »
Radio interferometry observations can be recorded and combined later, but optical interferometry requires the images to be combined live because of the short wavelength, so that's not an option.


Since PlanetLabs does have the capability of downloading of images in near real time, does this allow for interferometry using the constellation?

Offline as58

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Re: PlanetLabs Constellation as Space Telescope?
« Reply #4 on: 12/09/2016 04:55 pm »
Radio interferometry observations can be recorded and combined later, but optical interferometry requires the images to be combined live because of the short wavelength, so that's not an option.


Since PlanetLabs does have the capability of downloading of images in near real time, does this allow for interferometry using the constellation?

No, nothing even close.

Online gongora

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Re: PlanetLabs Constellation as Space Telescope?
« Reply #5 on: 12/09/2016 04:56 pm »
Can the Doves even be pointed away from Earth?

Offline hop

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Re: PlanetLabs Constellation as Space Telescope?
« Reply #6 on: 12/09/2016 05:41 pm »
The closest operating analog is probably the BRITE constellation https://en.wikipedia.org/wiki/BRITE

You can find some good papers describing the concept, challenges and results on arxiv.

As as58 says, interferometry is totally out of the question. At optical wavelengths, you need to physically combine the light from the telescopes, and also maintain the separation with extreme precision. However, simultaneous observations can be valuable for other reasons, and a constellation can provide continuous coverage that might not otherwise be achievable.

I strongly suspect that cubsats optimized for earth observation would not be very useful. In most cases, getting useful scientific observations requires a lot more than just pointing a camera in the general direction of interest.

Offline Danderman

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Re: PlanetLabs Constellation as Space Telescope?
« Reply #7 on: 12/09/2016 11:24 pm »
Hmmm ... if only there were a company that was deploying multiple generations of optical satellites using rapid prototyping.

Offline eeergo

Re: PlanetLabs Constellation as Space Telescope?
« Reply #8 on: 05/08/2018 12:33 am »
Look at that :)



Did you have something to do with this, Danderman?

Seen thanks to a tweet from Dr McDowell: https://twitter.com/planet4589/status/993639129798889476


Technical Note: Asteroid Detection Demonstration from SkySat-3 B612 Data using Synthetic Tracking


https://arxiv.org/abs/1805.01102
-DaviD-

Offline Asteroza

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Re: PlanetLabs Constellation as Space Telescope?
« Reply #9 on: 05/08/2018 03:41 am »
Radio interferometry observations can be recorded and combined later, but optical interferometry requires the images to be combined live because of the short wavelength, so that's not an option.

Observing stellar occultations would be very useful. Can be used to determine asteroid sizes and might even spot asteroid moons.
Since PlanetLabs does have the capability of downloading of images in near real time, does this allow for interferometry using the constellation?

No, nothing even close.
The closest operating analog is probably the BRITE constellation https://en.wikipedia.org/wiki/BRITE

You can find some good papers describing the concept, challenges and results on arxiv.

As as58 says, interferometry is totally out of the question. At optical wavelengths, you need to physically combine the light from the telescopes, and also maintain the separation with extreme precision.

A hey, interferometry without combining beams, using software instead...

https://www.nasa.gov/directorates/spacetech/niac/2018_Phase_I_Phase_II/Spectrally-Resolved_Synthetic_Imaging_Interferometer

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