Ten years ago this week I was in Chile for complicated reasons and decided on a whim (!) to go to the Atacama desert, as you do. If you've never been it really is the most amazing place
It was totally safe, kinda! Just one British guy and his bike and no one else around for about ten miles, with occasional stops for mild altitude sickness
Yup dead easy, prob even easier now. Two-hour flight IIRC and then a bus ride past amazing lithium mines. But I am guessing it might be pretty hot in January?