Communication | Sending images with laser using sail as antenna

Images of the target planet could be transmitted by a 1Watt laser onboard the nanocraft, in a ‘burst mode’ which uses the energy storage unit to rapidly draw power for the power-intensive laser communications mode. Upon approach to the target, the sail would be used to focus the laser communication signal.

For a 4m sail, for example, the diffraction limit spot size on Earth would be on order of 1000m. A kilometer-scale receiving array would intercept 10-14 of the transmitted signal. The main challenge is to use the sail as diffraction limited optics for the laser communication system. This would be achieved by shaping the sail into a ‘Fresnel lens’ upon approach to the target. The sail structure could be different at the launch and communication phases. In order to maintain a high transmission through the Earth’s atmosphere, the communication would need to operate at a wavelength shorter than that used by the launch laser system, due to the Doppler shift of the nanocraft relative to the Earth.

Comments (33)

  1. Breakthrough Initiatives:

    Aug 27, 2016 19:08benedictrodgers@hotmail.comPosted on: Breakthrough Initiatives
    "This is an excellent project and I hope that it inspires Earthlings to look up and get a sense of perspective. However I think that the "policy" challenge, the most utterly mundane and tedious of all the challenges ("obtain permission from the government"), may well turn out to be the one with the longest timescale.

    The truth is that, as the world order is presently constituted, it is and will remain impossible to obtain a worldwide consensus on the construction of a laser with the power of a hundred nuclear power stations. Whose laser, they will ask, will it be? Will it be a Chilean laser? An American laser? Chinese? Russian? Until we have established a worldwide legal framework which makes these cretinous questions otiose, the project is not going to happen. I mean not to rain on this parade! I mean merely to say that those of us who are not blessed with maths, may have a role to play in realising this project."

    Thank you for your interest. The issue of policy and legality are indeed grand challenges. Striving for mutual understanding on the topic of space exploration requires a global discourse as does the guarantee of safe operating procedures. There is ongoing research into how one would tackle the concerns you have addressed and such research will likely become a key component of this program.

    - Breakthrough Initiatives

  2. Allen Hall:

    seems totally improbable the shape constraints are difficult to the extreme on earth ... to precision align that many space craft with ultra-precise narrow beam lasers that will not diffuse over trillions of kilometers seems like wishful thinking. The sails were heated, stretched by >300kg load during acceleration and pummeled by high-speed interstellar hydrogen impacts at a rate of 1.8 million impacts per cubic meter per meter at 20% the speed of light (drag?) and an unknown amount of dust. Considering the construction of sail materials, I cant see the final shape of the sails being consistent or predictable after their 4 light year journey.

  3. Breakthrough Initiatives:

    "Nov 30, 2016 20:13 Allen Hall Posted on: Breakthrough Initiatives"

    Thank you for your question. We consider the sail shape and composition a profound challenge. One possible approach is to fly the sail edge on to the velocity vector, thereby minimizing exposure to dust and gas along the trip. Another approach is to role the material into a very tight cylinder during the voyage. This might prove possible by creating a sail constructed out of a material that is either UV sensitive or IR sensitive. In this way when it is in the system it assumes the required shape and then when it is in deep space it assumes the lowest frontal area shape. These materials are available today but with a significant mass penalty.

    - Pete Klupar, Breakthrough Starshot

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