JS Variable outside function / global var [duplicate]

probably a stupid/very simple question but I can’t figure it out. I get the sat_id from an API, which I want to append to a new API URL. So I need the sat_id outside the function. How do I do that?
Here is the script:

const sat_url = 'https://api.wheretheiss.at/v1/satellites';
let sat_id = 0; 

async function getISS() {
           const response  = await fetch(sat_url);
           const data = await response.json();
           sat_id = data[0].id;
           console.log(sat_id); //here is the correct sat_id
}

getISS();

console.log(sat_id); //here ist the "0" from above but not the sat_id from the function

const data_url ='https://api.wheretheiss.at/v1/satellites/' + sat_id;

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