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.

Nov 05, 2016 04:55 Breakthrough Initiatives Posted on: 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

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

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.

Jan 05, 2017 03:23 Breakthrough Initiatives Posted on: 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

Mar 12, 2017 10:35 Posted on: Centauri Dreams

Rolling the sail into lose cigar shape may allow us to use the ions in the ISM as energy, these charged particles could potentially give energy as they whistle through between the layers.

Mar 21, 2017 19:02 Breakthrough Initiatives Posted on: Breakthrough Initiatives

Mar 12, 2017 10:35 Posted on: Centauri Dreams

Thanks for your input. This is indeed a good idea. It has been shown that a Bussard Ramjet is actually a losing proposition. But it may be possible to scavenge energy from the ions in deep space.

- Pete Klupar, Breakthrough Starshot

Nov 15, 2020 01:07 John Weiss Posted on: Breakthrough Initiatives

Very low transmitter frequency will transmit further, with better obstacle avoidance, than high-frequency. Transmit at lowest possible frequency. Hz range?

Mar 30, 2021 21:56 Breakthrough Initiatives Posted on: Breakthrough Initiatives

Thanks for the comment! There are a number of disadvantages to very low frequency transmission - here are a few:

i) the diffraction from the transmitting aperture means that the beam area at a given distance (in the far field) from the spacecraft is proportional to the wavelength squared. This means that the power received on the Earth in a fixed aperture is reduced by this factor. This can be overcome by having a larger receiving aperture. For a few Hz, the wavelength is much larger than the diameter of the Earth (and the diameter of the spacecraft) so there is an additional loss of efficiency in transmit and receive.
ii) the Earth's ionosphere is not transparent to electromagnetic waves with frequencies lower than about 50 MHz so you would have to build a receiver in space
iii) the astrophysical background radiation increases at low frequencies (from radio galaxies) so there is more noise

Also, there are not really any problems with obstacle avoidance between us and nearby stars - if there were, we wouldn't be able to see the stars with our eyes.

Prof. Phil Mauskopf, ASU
Starshot Communications Lead

Jun 04, 2021 23:23 Roberto Navacchia Posted on: Breakthrough Initiatives

If we only think about a ship, we would certainly need to create an apparatus (which does not yet exist according to the literature suggested by the project) . However, if we imagine hundreds or thousands of ships (nanocrafts) acting as a swarm of bees surrounding the object or objects and each one returning its small 'narrow field of observation' through chain communication (of information data) we would have certainty an image and analyze the object in its entirety, much more comprehensive and certainly with enough energy.

Jun 30, 2021 21:29 Breakthrough Initiatives Posted on: Breakthrough Initiatives

Roberto, thank you for your comment. The Starshot spacecraft, like the New Horizons probe, will be traveling too fast to be able to slow down enough to orbit any of the bodies at the target star system. Therefore, each probe will obtain its data during a relatively short flyby. It could be possible to coordinate these flyby observations in order to maximize the information from the system. One example would be for different probes to obtain images in different wavelength bands and therefore build up spectral information. This would have to be balanced with the desire for redundancy. Additional coordination between probes either for obtaining data or communication could be achieved by tuning the travel speeds of multiple probes so that they arrive and fly through the star system at approximately the same times.

Phil Mauskopf
Lead, Starshot Interstellar Communications Research

Comments: 39


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