During an encounter with an exoplanet, the nanocraft’s camera would need to rotate in order to image the target. If the planet were imaged with a focal plane area, it would be necessary to hold the planet still within the image plane during the integration time for exposure.
If an object-to-nanocraft distance of 1 AU and a velocity of 0.2c are assumed, an angular rate of (6x107m/s) / (1.5x1011 m) ~ 80 arc sec/s is needed. The nanocraft would traverse a distance of 1 AU in about 2500 seconds. To stabilize the image, the camera would need to “slew” at this rate.
The slewing would be accomplished either by using the photon thrusters or via motion in the focal plane. For example, using a 4-meter-scale camera array at a distance of 1 AU would provide image resolution of order 40km, assuming visible spectrum imaging. The resolution scale could be improved by closer approaches of less than 1 AU. Extremely efficient image compression and smart feature detection algorithms would be crucial.
Another challenge is locating the planet inside the Alpha Centauri system. This would be achieved through the use of ‘star trackers’ based on the star’s ephemeris (orbital position at specific times) and the planet’s position relative to the star. The star would be very bright and the planet reasonably bright. Dead reckoning navigation is being considered that would be updated by measurements of the location of the star and planet. Image recognition software would be required to decide which target had the highest value, and it currently seems the most promising form of rudimentary artificial intelligence for this mission.
Research:
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Pilinski, E. B., and Lee, A. Y. "Pointing-Stability Performance of the Cassini Spacecraft," Journal of Spacecraft and Rockets, Vol. 46, No. 5, pp. 1007-1015 (2009)
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Legge, R. S., and Paulo, L. C. "Electrospray Propulsion Based on Emitters Microfabricated in Porous Metals," Journal of Propulsion and Power, Vol. 27, No. 2, pp. 485-495 (2011)
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Weis, L. and Peck, M. "Attitude Control for Chip Satellites using Multiple Electrodynamic Tethers," AIAA Guidance, Navigation, and Control Conference (2012)
Apr 13, 2016 13:34
Štěpán Pilař
Posted on: Breakthrough Initiatives
Hi, first of I want to apologize for my English, because I'm from Czech Republic.
I was taught, that atmosphere kind of 'depletes' from a planet. So why not to put there some pressure measuring system to see, when the craft flies by the planet. And if there were more segments of the system, it could detect the exact 'position' of the planet.
The idea of this is that when the craft passes by a planet, the 'pressure' of molecules, the craft hits, pushes to the barometer.
It would require a precise 'shooting' of the craft near enough of the targetted planet tho. So it may be more of a setback than a step forward :-)
Apr 17, 2016 06:12
john.hayden1@gmail.com
Posted on: Breakthrough Initiatives
It may not be necessary to slew the physical camera. What matters is that the _image_ accumulating in the detector array stays aligned with the incoming light.
If the detector array is built so that it can shift accumulated CCD charges on a precomputed pixel track, the final image may be captured without blur, by motion compensation.
Not exactly the same as SteadiCam, but similar (we might not need to move the lens elements)
May 02, 2016 23:34
Edward Friday
Posted on: Breakthrough Initiatives
We should plan for, perhaps, hundreds of Nanoc raft encountering an exoplanet over a period of weeks. During cruise, each craft would communicate with its nearest neighbor and the group would self-organize into a network.
Upon encounter and flyby, tracking information of increasing precision could be relayed to the next craft. The final craft would relay imagery and other data to earth.
May 26, 2016 16:05
michael.million@sky.com
Posted on: Breakthrough Initiatives
The best way to slew the camera would be using electrical signals so there are no moving mechanical parts to go wrong, perhaps a capacitive effect between the lens and the main craft with a springy material whisker as the tensioner.
Jul 23, 2016 21:22
Breakthrough Initiatives
Posted on: Breakthrough Initiatives
Excellent questions. Thank you.
We discuss this at some length in the “roadmap” below but there are a variety of options here. The “roadmap” discusses the bulk body motion of the wafer as well as electronic pixel shifting. Modern cell phone cameras and DSLR use a similar approach known as “image stabilization”. This can also be does with piezo or magnetic controlled optical sub elements.
For technical details see section 10.1,2,3,4 in the paper “A Roadmap to Interstellar Flight”:
http://arxiv.org/abs/1604.01356
It will often be referred to as the “roadmap” paper.
– Prof. Philip Lubin, Breakthrough Starshot
Aug 29, 2016 22:06
Joshua West
Posted on: Breakthrough Initiatives
I did not see in the calculation where moving at .2c's effect on the observer was taken into effect. The camera onboard is going to move "slower" relative the slow moving planet, like the age of the twin orbiting the earth. This is good for battery life but bad for camera rotation. There is simply less time to do it.
If we have to take relativity into effect when using satellites then this seems necessary.
Sep 25, 2016 20:16
Stan Evans
Posted on: Breakthrough Initiatives
You could use a network of the crafts at differing distances to use the pressure caused by the atmosphere to mao the direction of the planet.
Nov 05, 2016 04:34
Breakthrough Initiatives
Posted on: Breakthrough Initiatives
RE:
"Aug 29, 2016 22:06Joshua WestPosted on: Breakthrough Initiatives
I did not see in the calculation where moving at .2c's effect on the observer was taken into effect. The camera onboard is going to move "slower" relative the slow moving planet, like the age of the twin orbiting the earth. This is good for battery life but bad for camera rotation. There is simply less time to do it. If we have to take relativity into effect when using satellites then this seems necessary."
Answer:
For a discussion on relativistic effects, see the recent study https://arxiv.org/pdf/1608.08230.pdf
- Avi Loeb, Breakthrough Starshot
