As usual, stolen from a book I just read ("Chindi" by McDevitt)
Title: Chindi
Era: Any
Setting: Starship
You are forewarned that this is outright theft of ideas from Jack McDevitt's "Chindi" novel, and as such, if you plan to read the book, stop now.
While exploring a planet, from orbit, where a nuclear holocaust destroyed the civilization, a small Nova-class vessel up and exploded. The crew's ship is sent in to figure things out, including picking up the twenty or so survivors who are floating around in escape pods who made it in time: but nearly no one has a clue what happened... One engineer says that the chief told him to get a good night's sleep, because they were bringing something into the cargo bay from orbit of the planet.
There aren't enough ruins, however, of the ship in orbit. After looking, they spot cloaked sattelites - very barely visible to sensors, and only if you're really looking. They also realize that one of htem is brand-spanking new, and the theory is this: if you turn one of them off, they release nanotech to try and replicate themselves, in the process likely destroying whatever ship took them aboard, if that's the case. If they just ran down normally, likely the nanotech would seek out a piece of an asteroid or something.
Then they find a signal, on a subspace frequency designed to be very difficult to locate.
The satellites work in a trio to send their signal outbound to another system, and they appear to be of a technology different than the obliterated planet. Warping there doesn't take too long, and sure enough, three more satellites are in orbit of a gas giant that will, in about a hundred years or so, smash into a planet that must have been yanked out of its orbit by the giant. No life here, just those sattelites - and the incoming signal is also outgoing to yet another system...
The signals sometimes point to life, sometimes to an interesting stellar event, and then finally to something really rather frightening: A pair of Gas giants locked in a gravity dance with each other, with rings around each of them and rings around the entire duet of them, and a moon that must have been artificially set into a polar orbit of the lot - which offers a spectacular view of the gorgeous display - from an abandoned observatory/small village-sized outpost.
With three sattelites around it, recording. Here we find, however, graves that have been freshly dug up and then returned to their natural state: but th ebodies were originally buried about four thousand years ago. No obvious reason as to why the outpost died - or had time to bury its dead.
The sattelites are aiming off in another direction, but as the ship is ready to go, a ship arrives in the system from the opposite side of the gas giants. And starts scooping into the atmosphere of them, refuelling. It's huge: an asteroid with engines, pretty much, and communications fail. No way to beam rigt in, but a shuttle could land on it and in suits, people could enter through the hatches.
Once they do so, they'll find themselves in a huge museum in motion: Full of mostly empty rooms, now and then a room has a very lifelike diorama, or a holographic representation, of a scene that the ship must have visited. Robotic minions wander about taking care of things. No people seem to live here.
Then, without much warning, the thing hits warp with your people on board. They have whatever supplies they took with them, and it might be necessary to come up with a seriously interesting "rescue" mission - their shuttle is blown off the hull by the accelleration, and in the meantimg, the people inside lose communication witht he ship and can go exploring.
They even find early pictures of Earth in one holosuite, and Andor. And Vulcan. And so on. These people have been watching for a long time. Inside the ship is environmentally null: vaccuum. If there used to be an atmosphere, it's gone, but it doesn't look like it ever had one.
On the ship, the flight path of the extremely slow vessel (which uses a kind of gravity drive warp system (about warp 2.3 or something like that) can plot ahead to find that in about eighteen years, the ship will arrive in its next destination, a system way out there. But a fly-by rescue at warp is necessary, with all manner of technical and scientific snafoos required to cope with the gravometic/warp disturbance and the speeds involved and no use of transporters, etc.
Once the people are off, the ship can warp to the next destination, where again, sattelites are orbiting a dwarf star that doesn't seem interesting in the slightest - why are they here? Until they find a remnant that might have once been a very termporary wormhole, and then find something really shocking: a pre-federation earth ship floating, now lifeless, with an automated radio distress call playing. This is where the ship is going next... it seems to jump around wherever its huge sattelite network finds things of interest.
End the ep with no real conclusion about the ship or its people, except that Starfleet Science is working on the signals in the satellites (tapping into them, however, tends to make the satellites turn themselves off - it's almost like a prime directive thing: they're switching off if they're noticed by anyone nearby). A husk of a sattelite that failed to self destruct is found in orbit of Andor, and seems to have been nonfunctional by its own design since just about the time ANdorians developed significant astronomical survey technology. It seems to have a faulty detonator. It also weighs in at about ten thousand years old.
Who these people are, and what they are doing is an unknown. The vessel itself is a scientific smorgasboard, though the Federation is going to wait 18 years to place people on it when it arrives at the site of the old earth ship. They're even tempted to find a way to put an atmosphere inside the ship itself, and so on and so forth.
IT's up to you to figure out if you want these aliens to ever arrive, or if this museum/ark/time capsule was their way to learn and share - is there a "recall" switch somewhere inside it? Or does it travel until it's full?
The Doc
So you think, 'Might as well,
Dance a Tango to Hell,
at least I'll have Tangoed at all.'
-- "Rent," Jonathan Larson