It's hard to come up with "original" ideas, of course. This story is totally a trope, and I know it. It's still the story that came to my brain last night, so it's the story you're getting!
"Captain, there's...something weird here."
Captain Baldursdottir looked up from her pad to stare at the back of the reporting lieutenant. They had, only an hour ago, completed a successful skip into the heliopause of TRAPPIST-1, a system that had been known to be rich in planets since the early 21st Century. The mission of her ship, overburdened with the name Lewis and Clark, was simple: take a survey of what was actually here, so that folks back home could decide if it was worth doing something with.
Nothing weird really should be happening. Certainly not this early.
When the lieutenant was not forthcoming from the prompt of the unseen stare alone, Baldursdottir's exec, Commander Li, replied, "I don't suppose, Lieutenant, that you have a particular definition of 'weird' you'd like to share with us?"
Baldursdottir fought very hard not to snort out loud.
"Sorry, sir. It's just...well..." and then, rather than give a proper report, without asking, the lieutenant put what he was seeing up on the big board, as if that explained everything.
It really didn't, but Baldursdottir by now could see the boy was clearly rattled, so she simply asked, "What am I seeing, Lieutenant?"
The young officer reluctantly turned away from his screen to address his captain. "Sorry, sir. It's just...unexpected. This is a modulated signal, captain. Deliberately modulated. Artificially, deliberately modulated, on wavelengths we use for our own communication. It's a digital encoding of some sort on top of an AM signal."
The captain straightened in her chair, having immediately recognized the import of the statement. A moment later she heard Li let out a breath and knew the penny had dropped for him as well. Other heads around the bridge came around to face the screen, or the lieutenant, as what they'd heard sunk in.
"So," Baldursdottir said, deliberately even in her tone, "somebody else is here."
"Yes, sir. And I'm seeing similar modulation along a host of other bands as well. I'd say more than just a few somebodies else are here."
From across the bridge came a new voice, from one of the other sensor crews. "Captain, I think I can now corroborate that. As soon as I saw the signals up there, I pulled the data he was seeing to try to get loci from the sensor drones. I figured we'll still want to scan the whole system as planned, but if we've got signals, that's the priority, right?"
If pressed at that moment, Baldursdottir would have had to admit that the younger woman--Lieutenant MacPhail--was thinking much more clearly than she herself was. Baldursdottir was spending a lot of her energy trying to appear calm and collected and commanding. Inside, she was kind of screaming a lot.
"Excellent thinking, Lieutenant. What do you have?"
"Stations, skipper. At least, that's what I think they are. We're pretty far out for even our best scopes to get much on 'em, other than that they're comparatively regular shapes in the middle of a bunch of rocks, but the inner asteroid belt appears to be peppered with stations of varying sizes. If we drew an arbitrary line from our current position toward the star, and called its intersection point "zero" and sweep the numbers clockwise, then early indications are that there's a denser arc of them centered at minus-thirty degrees, and then progressively sparser around the curve. Of course we don't have any kind of read on what might be on the far side of the star at the moment."
The officer who had begun all this, Lieutenant Carstairs, had put his headphones back on and had been frantically working his board, with eyes that showed he was playing a hunch. At this point in MacPhail's recital, he let out a sudden yelp of surprise and exclaimed, "Is that Hebrew?!"
Everyone shut up.
After a beat, Li once again rescued the moment. "Did you have something, Lieutenant?"
"Yes, sir. It seemed absurd that it would be as easy as just trying to run the signal through our codecs as if it were another of our own ships--I mean, if it were an alien race, even if they're using recognizable radio modulation, their data encoding, everything...I mean...forget about language. Decoding an actual alien signal would take months, maybe years, right?
"But I ran it through, and the computer immediately found a match. It's an unencrypted audio signal. It's not a voice codec we currently use, but it was pretty common from pre-Collapse times. And I swear on my bubbe's latkes that it's not only human, but Hebrew. Accent is a little weird, but I'm recognizing about three words in ten--which is not bad when I haven't been to synagogue in a decade..."
He trailed off at that point, perhaps realizing he was babbling, perhaps because he was back to focusing on what he was hearing. He'd gone back to his controls and then let out another yelp. "Dammit. That was English."
Baldursdottir managed a response this time. "What was?"
"I changed channels. Same audio encoding, and again, the accent isn't one I recognize, but...definitely English. Six words in ten, now, and if I listened to it a bit longer to get the hang of the accent I'd probably be able to catch most of it. If they've been here long enough for the accent to have shifted at all, there's probably new vocabulary I wouldn't get, but other than that..."
That kind of thing went on for a few hours. Carstairs was able to catalogue several channels of audio traffic--mostly routine stuff between the stations, some that seemed like they might be from craft transiting between the stations, just based on what context they could parse. At one point, they found what was clearly an entertainment broadcast, and Li opined, "I am so glad I am not the only person in the galaxy that remembers The Rolling Stones." The entire bridge was immersed in listening to the transmissions, engrossed in their eavesdropping, and so everyone practically climbed out of their skins when an alarm sounded.
MacPhail silenced it, then reported, "Captain...we've been painted. Whoever the heck they are, they know we're here. They've got someone who knows their math, too. They just pinged a laser off the hull, which they would have had to have triggered 43 minutes ago."
"Was there any signal, or just the ping?"
"Just the ping, Captain. And really quick. I don't think they're planning anything hostile, but I would be surprised if we don't hear something more from them in a couple of hours..."
In the event, it was just shy of two hours later that a radio signal, much more directional than the leakage they'd been listening in on, hit their receptors. This one was not digitally encoded at all, but a simple analogue amplitude modulation. Carstairs opined, "They're probably hedging their own bets that we're aliens. Analog AM audio quality isn't great, but it is easy to decode compared to anything digital. Then all an alien would have to do is actually figure out language. Not that that's easy, but..."
The message itself was simple. Fortunately, the speaker had chosen English, and not Hebrew, although Carstairs later insisted he could have translated if he'd had to.
The English was, as Carstairs had said, oddly accented, but it was clear the speaker was making an effort to be as precise as she could. There was not much nuance to it. "Shalom. Peace. Newer York welcomes you. We know it may take you time to understand this message. We do not know how to make it any easier. You are our first contact with anyone outside our system since we arrived here. If you respond, we will do our best to understand. We hope you will do the same. We are trying to to determine how best to help you understand us, should establishing communication prove difficult. We look forward to getting to know you. Newer York, clear."
Silence, again, reigned on the bridge, before Li spoke up. "They're going to be terribly disappointed when we just say, 'Hi there! Where can we get a good bagel around here?' Aren't they?"
Carstairs was feeling bold, or perhaps punchy. "We could fake it. Draw it out, pretend it took us a while to figure out they were even trying to talk to us, that kind of thing. Maybe babble randomly back at them, run it through a voice mod..."
The quelling look the captain was giving him made him finally wind down.
"We are not going to punk them just because they weren't what we expected either, Lieutenant."
"Due respect to the captain, but you're no fun any more...sir." Definitely punchy. But it was hard to blame him.
"I'll remember you said that next time we're matched for handball. Meanwhile...let's get this over with. Same encoding for reply. Once they figure out we can talk, we can probably agree on a video encoding, too, but for now, let's keep it simple."
Carstairs mocked a pout, turned to his board, and set up the recording, giving her the high-sign when he was ready.
Baldursdottir drew a breath and then began. "Shalom aleichem. This is Captain Athalros Baldursdottir, speaking for the exploration vessel Lewis and Clark, 183 days out of Sol. Which I'm sure is going to come as a surprise to you, but then, we weren't expecting to find anyone here, either, so I think we've got a lot to talk about. Lewis and Clark, clear."
Roughly forty-three minutes later, in her office onboard Dream of Spring, the Mayor listened to the response relayed to her by the communications tower. She played it back three more times. Then, she leaned back in her chair, closed her eyes, pinched the bridge of her nose, and quietly exhaled, "Oy, gevalt!".
Set in the same timeline with "Carry water. Chop wood. Kvetch." and "Why is this shift cycle different from other shift-cycles?", perhaps 250 Earth-years after the Dream of Spring made Starfall.