You can talk to the International Space Station right now. Here’s how to do it.

By Rob Boffard

Of all the things that shouldn’t be possible but are, talking to the International Space Station ranks right up there with Steph Curry’s basketball skills and the existence of Donald Trump.

Think about it. How weird is it that NASA can put a $150bn space station into orbit, which can then be contacted by anybody on Earth? Even you? It’s one of those things that gives you pause — the kind of thing you’re vaguely certain is against the law, somewhere.

It’s not something you’re going to be doing tonight — not unless you have the relevant equipment already to hand. It takes a little bit of work. But it’s entirely possible, even for those of us who aren’t geeks.

You need: a radio

Obviously. And not just any radio. Your basic walkie-talkie set isn’t going to cut it.

It’s really, really easy to get technical here. Radio communication is a complex, difficult science, and there’s an enormous amount written about it online that is only understandable by 3.2% of people who read it. We’ll try to keep this simple.

Essentially, what you need is a VHF transceiver radio that puts out over ten watts of power. Then you need to hook it up to something known as a quarter-wave vertical antenna. The power rating is important. Imagine the ISS coming over the horizon to your left, passing above you, then vanishing under the horizon to your right, like a sun. Obviously, at the start of this arc, the station will be a lot further away from you than it is at the top of the arc, so you’ll need more power to contact it. You might reasonably ask why you’re just try to get hold of the astronauts on board when the station is closest to you, and save on power. We’ll get into that. For now, just trust us: get as much power as possible.

You can, if you’re so inclined, go a lot deeper into this, but if you manage to get those two things, you’ll be well on your way.

You need: some maths

Sorry.

The ISS is moving about five miles a second. No matter where you are near, it’s probably going spend no more than a minute and a half above you, twice a day. That assumes, of course, that you’re somewhere underneath its orbit. Hawaii is generally considered to be among the best spots for contacting the astronauts, but in 2015, a man named Adrian Lane from Gloucestershire managed to get hold of them.

So you need to be in the right place, at the right time. Then — and again, we’re really sorry about this — you have to do some maths. In order to know exactly where to point your antenna, you need to do some calculations to figure out the elevation and range of the space station. This is also why you need a high-power radio: you’ve got a minute and a half to locate something moving across a vast sky very, very quickly, and you can’t guarantee you’ll be able to find it at the optimal point.

There are plenty of online resources that will help you figure this out, including some helpful PDF frequency tables put together by space enthusiast Ron Hashiro.

You need: luck

The annoying part is, you could do absolutely everything right, and still get bupkis.

The astronauts could be asleep, or busy, or otherwise disinclined to talk to some nosy so-and-so on the radio. There could be others in your neighbourhood on the same frequency, muddling up the airwaves. Your communications could be disrupted by a million things, from the curvature of the Earth to a plane passing overhead.

It’s a little frustrating that so much of this is out of your control, but that doesn’t mean it’s impossible. Far from it. Of course, you’ll actually need to figure out what to say to the astronauts if you do make contact, and we’re afraid we can’t help you there.

Or, the easy way

Of course, you could just do this the easy way, and drop them a message on Twitter. It’s less personally satisfying, but they regularly respond to those of us on the ground. They are Tim Peake (@astro_timpeake) and Tim Kopra (@astro_tim). Third astronaut Yuri Malenchenko doesn’t appear to be on Twitter.

Rob Boffard is a South African author who splits his time between London, Vancouver and Johannesburg. He has worked as a journalist for over a decade, and has written articles for publications in more than a dozen countries, including the Guardian and Wired in the UK. Tracer is his first novel.

His voice has already been heard in space, when Rob did the first author reading in space.