A lot of cheap space telescopes will enable disruption of satellite imaging and satellite data markets.
It would be great if someone here could compare and contrast the Arkyd telescopes with those used on ISS by the crew to image the Earth.
Quote from: advancednano on 04/26/2012 11:28 pmA lot of cheap space telescopes will enable disruption of satellite imaging and satellite data markets.Please explain how a cheap space telescope provides LandSat class multi-spectral imagery.
Quote from: Danderman on 04/27/2012 02:36 pmIt would be great if someone here could compare and contrast the Arkyd telescopes with those used on ISS by the crew to image the Earth.I think PR's competition is more with SkyBox imaging than with ISS or the bigger earth observation satellites.~Jon
I am working on the TerraSAR-X / TanDEM-X SAR earth observation project, and I can tell you that downlink bandwith is a major limiting factor for the amount of datatakes you can do.
Quote from: rklaehn on 04/27/2012 02:46 pmI am working on the TerraSAR-X / TanDEM-X SAR earth observation project, and I can tell you that downlink bandwith is a major limiting factor for the amount of datatakes you can do. That's an interest point that most people miss; is this due to Tandem not being able to access a sufficient number of ground stations - is that a programatic or technical problem?
Laser groundstations would be a good way to get sufficient downstream bandwidth, but you do need many of them spread over a large area because obviously they are useless if you have cloud cover.
Quote from: Danderman on 04/27/2012 02:55 pmQuote from: rklaehn on 04/27/2012 02:46 pmI am working on the TerraSAR-X / TanDEM-X SAR earth observation project, and I can tell you that downlink bandwith is a major limiting factor for the amount of datatakes you can do. That's an interest point that most people miss; is this due to Tandem not being able to access a sufficient number of ground stations - is that a programatic or technical problem?It's an economic problem. Of course you could get sufficient bandwidth by booking lots of ground stations. But that costs a lot of money.
High bandwidth + quick return = lots of ground stations.On the other hand, returning images of NEOs is not time sensitive and probably not that data intensive.
Quote from: rklaehn on 04/27/2012 03:10 pmLaser groundstations would be a good way to get sufficient downstream bandwidth, but you do need many of them spread over a large area because obviously they are useless if you have cloud cover.Maybe it would be laser communication between these things. Whichever ones happen to be near a cloudless ground receiver are the ones that communicate down for the ones that can't.
Quote from: jongoff on 04/27/2012 02:39 pmQuote from: Danderman on 04/27/2012 02:36 pmIt would be great if someone here could compare and contrast the Arkyd telescopes with those used on ISS by the crew to image the Earth.I think PR's competition is more with SkyBox imaging than with ISS or the bigger earth observation satellites.~JonMy point is that the focal lengths of the Arkyd telescopes seem to be similar to the ISS photography lenses. I could be wrong on that, but my recollection is that the ISS telescopes used by the crew are close to a meter in length.One could argue that the PR telescopes will be operating in a very low orbit, and thus have greater resolution than the ISS telescopes, but this begs the question of how the PR telescopes get piggyback rides to very low orbits.For that matter, exactly which current systems offer piggybag rides to LEO? Which launch vehicles offer rides that would put the telescopes into "constellations" as described by others here?
Quote from: go4mars on 04/27/2012 03:16 pmQuote from: rklaehn on 04/27/2012 03:10 pmLaser groundstations would be a good way to get sufficient downstream bandwidth, but you do need many of them spread over a large area because obviously they are useless if you have cloud cover.Maybe it would be laser communication between these things. Whichever ones happen to be near a cloudless ground receiver are the ones that communicate down for the ones that can't. If you invoking intersatellite links for these "affordable" small satellites, you might as well suggest that each one will carry its own pony, too.The ability to transmit laser signals is not the same as being able to receive laser signals. Sending down a laser signal to a ground station a few hundred miles away is different than sending a laser signal to another satellite that might be thousands of miles away.
Quote from: Danderman on 04/27/2012 02:52 pmQuote from: jongoff on 04/27/2012 02:39 pmQuote from: Danderman on 04/27/2012 02:36 pmIt would be great if someone here could compare and contrast the Arkyd telescopes with those used on ISS by the crew to image the Earth.I think PR's competition is more with SkyBox imaging than with ISS or the bigger earth observation satellites.~JonMy point is that the focal lengths of the Arkyd telescopes seem to be similar to the ISS photography lenses. I could be wrong on that, but my recollection is that the ISS telescopes used by the crew are close to a meter in length.One could argue that the PR telescopes will be operating in a very low orbit, and thus have greater resolution than the ISS telescopes, but this begs the question of how the PR telescopes get piggyback rides to very low orbits.For that matter, exactly which current systems offer piggybag rides to LEO? Which launch vehicles offer rides that would put the telescopes into "constellations" as described by others here?Aperture, not focal length, is the limiting factor for resolution.I don't believe the ISS scopes have as large of aperture. Or rather, they're comparable. Besides, it's likely these will be cheaper.
If you invoking intersatellite links for these "affordable" small satellites, you might as well suggest that each one will carry its own pony, too.
The ability to transmit laser signals is not the same as being able to receive laser signals. Sending down a laser signal to a ground station a few hundred miles away is different than sending a laser signal to another satellite that might be thousands of miles away.
Quote from: Danderman on 04/27/2012 03:23 pmIf you invoking intersatellite links for these "affordable" small satellites, you might as well suggest that each one will carry its own pony, too.I have a disproportionate reaction when pony and unicorn types of comparisons get made on here. I prefer statements like, "that's currently unlikely because X" or "that is against the laws of physics". Comparison to a little kids desires for a pony or a unicorn is at best rude and discourages further conversation or education. Quote from: Danderman on 04/27/2012 03:23 pmThe ability to transmit laser signals is not the same as being able to receive laser signals. Sending down a laser signal to a ground station a few hundred miles away is different than sending a laser signal to another satellite that might be thousands of miles away.Perhaps the earlier systems would always have another satellite within an appropriate communication range. What are the limitations on intersatellite links? How would more distant "interceptor" versions that go to NEO's be assumed to communicate their findings and photos? I need to do some reading on laser communication receivers. Any recommended sources? Or should I just google?
Quote from: go4mars on 04/27/2012 03:16 pmQuote from: rklaehn on 04/27/2012 03:10 pmLaser groundstations would be a good way to get sufficient downstream bandwidth, but you do need many of them spread over a large area because obviously they are useless if you have cloud cover.Maybe it would be laser communication between these things. Whichever ones happen to be near a cloudless ground receiver are the ones that communicate down for the ones that can't. You still need many laser communications groundstations to handle the raw amount of data. So you might as well have more on-board storage and downlink directly.Earth has a land area of 148,940,000,000,000 m^2. Even if you image it in a relatively low resolution of 1m with 24 Bit/Pixel, and you want monthly updates, that is a constant data rate of ~1 GBit/s. But you don't get constant contact with low-flying satellites.I am not saying that this is impossible. Far from it. But it requires a major infrastructure investment.