Communication | Receiving images with light beamer array

Recent advances by groups at MIL Lincoln Labs and the Jet Propulsion Laboratory have demonstrated that it is possible to detect single photons emitted by lasers from very large distances. The current record holder is the LADEE Laser Communication system, which was able to operate from lunar distances. The technique uses cryo-cooled nanotubes. The current performance is of order 2 bits per photon. That system uses a 10cm optics on the spacecraft, and a 1-meter telescope on the ground. As the StarChip cruised out, it would rely on communications from earth to update its clock and its estimation of the stars’ ephemeris (orbital position at specific times).

The ground system and the StarChip transmitter will implement forward error correction, matched filtering, and other contemporary approaches to increasing the gain of this transmission through signal processing, beyond the direct detection of single photons that has already been demonstrated in existing systems. The Starshot light beamer would be used in reverse, as a receiving array to receive the laser communications from the nanocraft. Using it as a phased array telescope would offer a sufficient collecting area to receive the signal.

Research:

Dec 31, 2019 04:21 Randy Sookoo Posted on: Breakthrough Initiatives

Attached is a VERY high level idea (brainstorm) along the same lines as Prof. Sasha Buchman. I think we should explore all options without putting money as a constraint at this point. Some ideas although expensive at the initial thought could be customized to be made economical. Just my two cents.,

So, since the distance is HUGE (~4 light years), therefore it's a bit impractical to use only ground stations for receiving data. There needs to be a communication nanosat network built in parallel with the nanocraft deployment to Alpha Centauri. Time is not on our side with this project since it will take a generation to get any data back should this concept of light sails work.

So, a nanosat communication network could be deployed in clusters in increments, thereby eliminating single points of failures. The nanocrafts could use the nansat network similar to how airplanes use cell towers/LEO satellites for providing wi-fi to passengers. The nanosat network could potentially use TCP/IP routing protocols to get the data back to the geo-sat network orbiting earth and, then back to ground SATCOM facilities. There would need to be custom tuning of the TCP/IP to limit re-transmissions due to propagation delays. Custom routing protocols may need to be developed.

There are challenges with this design since communications based nano crafts will have to be positioned along the path to Alpha Centauri. My diagram has them at every 5 years but, that's just for illustration. I don't know what is the max distance for laser transmission using optoelectronics is but, that would be the limiting factor as to the distance between the nanosat clusters. Ofcourse, this will all need to be tested in a small scale to determine if it will work.

Again, this is all VERY high level and, wanted to share my thoughts. Any and all comments welcomed!

-Randy Sookoo, Computer Network Engineer

Dec 31, 2019 04:22 Randy Sookoo Posted on: Breakthrough Initiatives

Attached is a VERY high level idea (brainstorm) along the same lines as Prof. Sasha Buchman. I think we should explore all options without putting money as a constraint at this point. Some ideas although expensive at the initial thought could be customized to be made economical. Just my two cents.,

So, since the distance is HUGE (~4 light years), therefore it's a bit impractical to use only ground stations for receiving data. There needs to be a communication nanosat network built in parallel with the nanocraft deployment to Alpha Centauri. Time is not on our side with this project since it will take a generation to get any data back should this concept of light sails work.

So, a nanosat communication network could be deployed in clusters in increments, thereby eliminating single points of failures. The nanocrafts could use the nansat network similar to how airplanes use cell towers/LEO satellites for providing wi-fi to passengers. The nanosat network could potentially use TCP/IP routing protocols to get the data back to the geo-sat network orbiting earth and, then back to ground SATCOM facilities. There would need to be custom tuning of the TCP/IP to limit re-transmissions due to propagation delays. Custom routing protocols may need to be developed.

There are challenges with this design since communications based nano crafts will have to be positioned along the path to Alpha Centauri. My diagram has them at every 5 years but, that's just for illustration. I don't know what is the max distance for laser transmission using optoelectronics is but, that would be the limiting factor as to the distance between the nanosat clusters. Ofcourse, this will all need to be tested in a small scale to determine if it will work.

Again, this is all VERY high level and, wanted to share my thoughts. Any and all comments welcomed!

Just a note, the website isn't allowing me to upload my .jpg drawing.,

-Randy Sookoo, Computer Network Engineer

Apr 08, 2020 12:34 Kamil Kartal Posted on: Breakthrough Initiatives

Language of Mars and Proxima B (and of vessel)

https://www.facebook.com/notes/kamil-kartal/language-of-mars-and-proxima-b-and-of-vessel/2704783146248258/

May 21, 2020 15:27 Breakthrough Initiatives Posted on: Breakthrough Initiatives

All “outside the box” thinking along these lines is strongly encouraged! There may be innovative system concepts that should be further pursued. In considering your idea, however, there are a few issues you need to take into account. Probes have no means of stopping or slowing, so they are always moving away from earth at 10-20% of c. At 20% of c the propagation distance between probes is 1.5 AU per hour inter-launch interval, with a one-way signal propagation delay of 12 minutes. Due to energy limitations, only one probe can be launched at a time, and as a practical matter the inter-launch interval is probably more on the order of a day or week. So not only are inter-probe propagation delays large, but the propagation distances are on the order of the outer planets to earth. If you want a nanosat network in the vicinity of the target star at all times, it will have to be regularly re-launched (at an estimated energy cost for each individual node launch on the order of $5M USD). When a node is near the target star it may be able to derive photovoltaic energy, but only for a few hours at most. Due to the large signal propagation delays, any sort of retransmission protocol is likely to be impractical, especially at the target star to earth distances (where the one-way signal propagation delay is 4 years). Thus it is likely we will have to rely on forward error-correction coding (with a low but non-zero level of residual errors) exclusively. The transmission links among your nodes will accumulate the data from multiple probes, and require correspondingly higher data rate as a result.

Direct-to-ground transmission involves a long signal propagation distance, true, but this can be compensated by using a large collector on earth, something that could never be reproduced on a low-mass probe. Our calculations tend to suggest that direct-to-ground transmission can obtain considerably higher data rates as a result, but of course this comes at the expense of a large and expensive terrestrial collection array (fortunately a one-off). We are putting together a draft paper with this calculation right now.

David G Messerschmitt
Member, Starshot Advisory Committee
Roger Strauch Emeritus Professor, Dept. of EECS, University of California at Berkeley

Apr 08, 2021 04:56 Randy Sookoo Posted on: Breakthrough Initiatives

Mr. Messerschmitt,

Is it possible to share your draft paper with me? My email address is sookoor@gmail.com. Thank you for your response to my post.

Although the nano crafts are constantly in motion, if a group at a time is launched in intervals, a communication link could be established between each groups of crafts. Each group could be considered a node in the communication network. Once all the nodes are established in motion, it will be like a long pipe with each cluster acting like a repeater along the path. The only issue is nodes will continually have to be launched since all the others are constantly in motion., If we can figure out a way for them to be placed and stay in a specific point along the path, that may work and, be more cost effective.,

Randy Sookoo, Computer Engineer

Apr 08, 2021 20:49 Randy Sookoo Posted on: Breakthrough Initiatives

Mr. Messerschmitt,

Have you considered doing any kind of modeling and simulation for this communications solution? I don't know if NASA has any proprietary systems that can model this based on the distance from earth to Alpha Cantauri. However, there is a product called OPNET with an SDK capability that can be customized depending on what is being modeled.

Here is a link for the product that is free and not associated and used for research projects.,

https://opnetprojects.com/opnet-network-simulator/

Apr 22, 2021 16:12 Breakthrough Initiatives Posted on: Breakthrough Initiatives

Randy,

I appreciate your interest in the interstellar communication issues. Here is the paper in which we have analyzed a relay through a chain of repeaters solution.

https://arxiv.org/abs/2007.11554

It concludes tentatively that a relay solution is less attractive than a direct to earth solution, depending on the criterion used about for or five orders of magnitude less attractive. A major point that is easy to miss is that at relativistic speeds the distance between relays is still quite large, and requires impractically large apertures for a space probe, especially a low-mass probe. Fortunately with a direct-to-earth solution it is feasible build a very large receive collector. In that paper you will find references to previous papers in which we analyzed a direct-to-earth solution in some depth.

You ask about simulation. I do not believe that the large effort necessary to do a simulation is warranted at this point. What we do is model the comm link using known fundamental limits on communication. It is true that actual performance will fall short of the fundamental limits, but with today’s knowledge and technology that gap will likely be not-to-great. But one thing that is certain is that if fundamental limits point to unfeasibility, then there is no practical way to get around around that. Practical solutions and the need for simulation only becomes compelling when the fundamental limits are marginally satisfactory.

—Dave Messerschmitt
Member, Starshot Advisory Committee
Roger Strauch Emeritus Professor, Dept. of EECS, University of California at Berkeley

Feb 02, 2022 21:19 Nathan Bemis Posted on: Breakthrough Initiatives

Been a while since last post,
Idea: For more streamlined communication you may have stationary multipurpose relay transmitters to transfer information back and forth along the designated paths of various project destinations. Hopefully, this can help with addressing a few different challenges or inspire some improved ideas that works for the needs of the project.

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