Gravitational lensing via neighboring stars for enhanced SETI

The possibility has been discussed of using the space-distorting properties of the Sun as a gravitational lens to focus SETI signals. The size of the Sun would make for huge gains in signal strength.
Unfortunately, it would be necessary to travel out to at least 550 astronomical units (a bit over 5 billion miles) from the Sun to reach the closest focal point. A major undertaking, given our rudimentary space travel capabilities.
Frank Drake, in his book: 'Is Anyone Out There', mentions that beyond the 550 A.U. distance, there an an infinite number of these focal points, extending further out into space.
It occurred to me that we might be able to make use of this fact by aiming radio telescope dishes at a neighboring star and using it as our gravitational lens. There may, of course, be some technical reason that this could not work. If anyone is aware of one, I would like to hear it.

Hi, Ross.

There may, of course, be some technical reason that this could not work.

One I see is: movements !!

In the "drawings" under here, it seems simple !!
______o_________O__________0
____earth_______sun________aimed sun system.

or
______x_________O__________0
____focal_______sun________aimed sun system.

BUT, I guess we have to consider that:
we turn around the earth's surface,
earth turns around the sun,
sun turns around the galaxy. . .

Soooooooo, ALL is moving relatively to each other.
It is surely impossible to use our sun to aim another sun,
with all those movements. . .? Right ?

Even if we go to the distance of the focal point also,
the 2 suns WILL be moving relatively to the focal point !
Sooooooooo, impossible to make a long & stable signal. . .?

Blue skies.

i whole heartedly approve of the OP! not just for the astronomy either. this is one thing we need for an interstellar robotic probe mission or even a manned Interstellar exploration mission. you would need a communications receiver and relay station at one of these lensing points to enable an telemetry or voice link or otherwise the power and mass requirements on board a vessel or probe just for communications would be enormous. This has already been discussed in articles and blogs about our first interstellar and interstellar precursor missions. things like the tau mission not to mention actual honest to goodness "let's go to alpha (Rigil) Kentaurus" missions. something like this would bring it down to 3 MW to 5 MW. And with this already in place for non related astronomy reasons cuts an enormous slice of the price for an interstellar mission down.

mis-post please disreguard.

C-JEAN
Hi, Ross.

There may, of course, be some technical reason that this could not work.

One I see is: movements !!


BUT, I guess we have to consider that:
we turn around the earth's surface,
earth turns around the sun,
sun turns around the galaxy. . .

Soooooooo, ALL is moving relatively to each other.
It is surely impossible to use our sun to aim another sun,
with all those movements. . .? Right ?

Even if we go to the distance of the focal point also,
the 2 suns WILL be moving relatively to the focal point !
Sooooooooo, impossible to make a long & stable signal. . .?

Blue skies.

If i recall correctly there are suitable meta stable Solar lagrange points near some of the the lensing focus sites. from there it could be relayed to an earth satellite and bounced down to the surface stations.

I hadn't thought of the problem caused by motion. Thanks for mentioning it. Assuming that the radio telescope was kept pointed at the star, the rotation of the Earth and its revolving around the Sun would apparently have the effect of shifting the view afforded by the star's gravitational lens. The latter effect would be much slower, of course, but would cause a much larger shift, eventually.
If we were fortunate, we might receive at least a brief recognizable signal before the Earth's rotation changed the view to some other point in space. The effect might be similar to rapidly tuning a radio across the band, first one signal heard, followed by another, and so on. By the way, I dropped a zero somewhere in my calculations. 550 astronomical units is about 51 billion miles, not 5 billion.

citeseerx.ist.psu.edu...

and according to this article the power of the transmitter is many orders of magnitude lower than i had read too:

www.space.com...

the error rate would be comparable to the deep space network's fidelity inside the solar system with a relay at the distant site as well as one around the sun.

With these relays in place, the error rate between the two points would drop from 1-in-2 to 1-in-2 million – on par with the accuracy achieved by the DSN in our local solar environment.

Shockingly little transmitting power is needed, too: just one-tenth of a milliwatt, or several orders of magnitude less than the DSN's antennas, Maccone found.

Maccone also gauged the focal points and transmission strengths for two other nearby stars: Barnard's star, a small red dwarf, and Sirius, a blue giant, which are located 5.6 and 8.6 light-years from Earth, respectively.

my goodness. a cell phone would be able to phone home from distant stars using lensing.

It was my hope that this idea could be tried out from Earth's surface. This would, of course, simplify certain matters a great deal. Perhaps using a series of radio telescopes could offset the problem of Earth's rotation causing the viewpoint to shift, as mentioned above. I suspect there is some other technical problem with applying this idea, and that it has been considered and discarded as unworkable by far wiser heads than mine.

Ross 54
It was my hope that this idea could be tried out from Earth's surface. This would, of course, simplify certain matters a great deal. Perhaps using a series of radio telescopes could offset the problem of Earth's rotation causing the viewpoint to shift, as mentioned above. I suspect there is some other technical problem with applying this idea, and that it has been considered and discarded as unworkable by far wiser heads than mine.

i have not found it yet but i will continue to look: i read a article on an interstellar mission that used gravity lensing to bring down the size and power requirements of the probe's transmitter and size of its transmitter dish. that article said that there is a semi stable lagrange like point near the natural lens position so a relay satthere would need far less propellant for station keeping which could be achieved with ion propulsion, solar sails, or an M2P2 engine. when i find it i'll try to post it.