Some proposals for a flyby of the Alpha Proxima system (system due to the discovery of a planet), have the space probe achieving 0.2 c - such as Starshot (Breakthrough Initiatives) , which is great and all, but assuming we could transmit back and all, what could we find out at these speeds, especially regarding the planet in the goldielocks zone?
Not much I don’t think. How much camera can you put on a postage stamp-sized cube that weighs a gram? Could it aim and focus? It would have to get pretty close to something worth photographing and at those speeds it might only have a couple minutes to do it.
I find the idea that these ‘nano’ spacecraft could produce a signal that could even be discerned at this distance to be somewhere near ‘preposterous’.
At that speed, you’d have about two days to take photographs from within the solar system. More if you count approach shots, the Oort cloud and other objects. Some of our very best images are long exposures, so you’ll be a little bit limited in what you can see well. Some planets rotate slowly enough that you won’t even be able to image the entire planet surface.
You’ll have to do the flyby on essentially a straight line, which means that you won’t be able to get very close to very many planets. Maybe not any at all if you don’t have good information about where they’ll be, since the proposed probe has no maneuvering capability. So a lot of your pictures won’t even be as good as what Earth-based systems can see of our own solar system’s planets.
On any planet with weather, there’s a question of what is covered by clouds as you pass by. It’s not likely you’ll get a chance to use instruments that can image the ground through the clouds like we’ve done with Venus.
And levdrakon’s point is a good one: who knows what kind of instruments it can carry at all? The whole thing is impossible with current technology. Even the project’s own page says it is hoping for proof-of-concept more than anything else.
Looking at the page, I don’t think the idea is that you’d spend a lot of money constructing one of these and wait 20 years for what it can beam back as a payoff. It sounds to me like they expect the main cost to be building the laser, testing the system, and getting the probes into space by the ‘thousands’, where each gets a few hours of laser time to reach interstellar speeds. If the individual probes are cheap, you don’t need to get a whole lot of information back from each one, you can have multiple shots. That can’t be done now, but I don’t think the idea of cheap probes is completely out of the question.
This makes a lot more sense than a one off probe.
I don’t see how you will get any information back at all. You need a very large amount of power to send information over interstellar distances. The current deep space probes have about 300W of power on board. If we assume 1/10 is for transmitting that is 30W transmitter for about 7.5 billion kilometers (distance to pulto). The nearest start is more than 5000 times that. So with the invers square law you need 25 million times the power. So we are talking about 10 of megawatts. You can play games with data rates etc to get the power down a few orders of magnitude but the current deep space probes are not nano anything.
How much power you need depends on the size of your receiver, too. Presumably, by the time we’d be able to build the launch infrastructure, we’d also be able to build similarly-large radio telescopes.