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Spacecraft-on-a-chip
algorimancer
post Apr 29 2011, 01:17 PM
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http://www.spacedaily.com/reports/Chip_sat...launch_999.html


"A group of Cornell-developed, fingernail-sized satellites may travel to Saturn within the next decade, and as they flutter down through its atmosphere, they will collect data about chemistry, radiation and particle impacts. Three prototypes of these chip satellites, named "Sprite," will be mounted on the International Space Station after the space shuttle Endeavour delivers them on its final flight, which is scheduled to launch at 3:47 p.m. EDT on Friday, April 29.
...
The thin, 1-inch-square chips, in development for three years in the lab of Mason Peck, associate professor of mechanical and aerospace engineering, will be mounted to the Materials International Space Station Experiment (MISSE-8) pallet, which will be attached to the space station, exposing them to the harsh conditions of space to see how they hold up and transmit data.

Although grapefruit-size satellites have been launched before, they have functioned much like larger satellites. The flight dynamics of a chip satellite are fundamentally different from these larger "CubeSats."

"Their small size allows them to travel like space dust," said Peck. "Blown by solar winds, they can 'sail' to distant locations without fuel. ... We're actually trying to create a new capability and build it from the ground up. ... We want to learn what's the bare minimum we can design for communication from space," Peck said.
...
"we had been working on the satellite-on-a-chip program for a long time, and over the next week we put together these prototypes," Peck said.
...
The current prototypes are mostly made of commercial parts, but Peck's group has partnered with Draper Lab in Boston to work on making a more space-ready prototype.

"We're seeing such an explosion in personal electronics ... all these components are super high performance, and they have far outstripped what the aerospace industry has at its disposal," said Peck, noting that these technologies were used on the small satellites.
...
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nprev
post Apr 29 2011, 02:34 PM
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Interesting, but I don't know precisely how they expect to get comm from something that small at interplanetary distances. Seems at the very least that you'd need a relay spacecraft in place at the target world.


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Greg Hullender
post Apr 29 2011, 02:52 PM
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A UV Laser might be something you could generate from a chip in a tight enough beam. Thing is, I'm thinking that's what you'd need just to make the chip communicate with the relay satellite. A chip that could send a signal a few million km seems hard enough.

--Greg
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machi
post Apr 29 2011, 03:12 PM
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"and as they flutter down through its atmosphere, they will collect data about chemistry, radiation and particle impacts"
Communication from atmosphere is even harder. Maybe via some kind of communication net (chip->chip->chip->relay satellite->Earth).
But it's not only problem with communication system, you need either enough energy for it.


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nprev
post Apr 29 2011, 03:25 PM
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Yeah, I was thinking of power constraints as well.

Maybe they're betting on VAST (and quite possibly unrealistic) improvements in receiver/signal processing capabilities.


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helvick
post Apr 29 2011, 06:55 PM
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I'd be interested to see what the proposed comms concepts are for near earth uses but for deep space scenarios the problems become immense. Laser comms doesn't strike me as a runner at all given how hard it has been to implement in large (stable) spacecraft - how are you going to deliver the stability needed to aim the transmitter for a start, but perhaps I've missed something recently.

For more traditional RF comms Huygens' 10W 8kbps (to Cassini) LGA should serve as a good baseline example for the difficulty of the challenge. The signal was detectable at earth range by the 100m Green Bank Telescope but not well enough to be able to get anything other than the carrier. For a 2cm "chipsat" you'd be talking about three or four orders of magnitude less transmit power. Even assuming you could just shrink things down (which you can't) you would need to increase the gain on the ground by 30-40dB above that achieved by the Green Bank Telescope just to be able to detect the signal. This paper about using the Square Kilometer Array for DTE comms puts an upper limit of about 10bps with a 5W transmitter at 10AU which sort of puts this in perspective. We don't have the SKA yet either and with a cost of between 1.5 and 2bn it isn't ever going to be a cheap receiver to use.

Edited to add: Having read some of the presentations and other content on the programme's homepage they answer quite a few questions I had. The key message that I take from it is that they are quite clear that micro\nano\femto scale "spacecraft" are more smart sensors with some orientation\signalling capability than anything remotely like even the smallest systems in use today. Right now they are primarily interested in proving some basic concepts around propulsion\stabilisation dynamics (from solar pressure and lorentz force propulsion amongst others) and basic comms.

The initial comms plan appears to be sending a single bit or at most a very small burst of data (e.g. a sensor saying "I found it!") using a burst from a 10mW transmitter. The Atchinson,Manchester & Zhou presentation about the Sprite demo gives some info on the expected S/N ratio for their demo which is challenging but doable for a ChipSat at LEO using what appears to be a fairly standard UHF receiver. By my very rough calculations (assuming the current DSN can manage about 50dB better S/N than a room temperature UHF YAGI) you just might be able to detect these at lunar distances. Even with a working SKA I can't see this working at planetary ranges without a revolutionary improvement in some other part of the comms architecture but it's clearly plausible for near earth uses, or as a fleet of sensors talking back to a relay around another solar system body.

It is some very interesting work.
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algorimancer
post Apr 29 2011, 11:24 PM
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Given a network of these things which has good mutual position awareness, it strikes me as conceivable that they might act together to transmit a signal as a phased array. Someone who understands the physics better please feel free to address feasibility or lack of it.
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brellis
post Apr 30 2011, 02:40 AM
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A ship with dozens or hundreds of micro devices could approach a complex system like the outer planets and have options available as information is gathered from the mission. Wouldn't it be great if Cassini had some tiny stowaways onboard? smile.gif
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KickSat
post Oct 11 2011, 12:04 PM
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Hello, you might be interested in a follow up to this story.

Zac Manchester is hoping to launch a CubeSat filled with at least one hundred Sprite ChipSats to sub-ISS LEO as a technology demonstrator. He is doing this as a spare time project and is looking for people who would like to sponsor a Sprite they could call their own to help make it happen.

If you would like to take part, have a look at:

http://KickSat.org

More than forty people have already pledged support - here's your chance to help kick start the personal space age!
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