As I checked out of my hostel, they asked me if I was on my way to Bolivia. I wished I was. Sadly my direction now was south, and I caught the bus to Calama instead of heading up into the Altiplano.

San Pedro is among some of the most incredible scenery in the Atacama. On my first journey here from Calama six years ago, I was blown away by the outrageous desert, and since then I had travelled this road another five times. Today it was my seventh trip along the road, and it seemed even wilder and even more incredible than before. I had the seat at the front of the bus, and I spent the whole hour and a half just staring out and enjoying the expansive views of the driest place on Earth.

We headed back down from Chajnantor, exhausted by the altitude but impressed by the place. We stopped at the base camp and were shown around the antenna constructions, but I was not really concentrating very much – I had a slight headache that might have been altitude-related, or might have been because I hadn’t had any coffee for almost seven hours. So I followed the group around the facilities but didn’t really take any of it in.

The next day a group of us went on a trip to see some of the salt lakes in the desert near San Pedro. We headed to Laguna Chaxa, where flamingoes paddled in the shallow waters. The scenery was breathtaking, with the salt plains, lakes, volcanoes and deep blue sky all looking otherworldly. I’d crossed the Salar de Uyuni six years ago, and it was flat, white and it tasted of salt. The Salar de Atacama was different – rumpled and dirty grey and apparently containing all sorts of things like arsenic and lithium. I didn’t try tasting it.

Near to ALMA is APEX, a single dish radio telescope built as a precursor to the main array, to establish that the site was excellent and to test the technology to be used. We drove over to APEX, and I felt a little more clear-headed. Here, we were slightly higher than ALMA and had amazing views over the plateau.

Near to APEX, the last of the winter snows were melting away. In places like this, snow melts in strange ways, turning into strange formations called penitentes, serrated peaks and valleys waving across the red desert landscape. We walked among the penitentes, which were about half as high as we were. The vandalistic among us tried pushing them over; some fell very easily, others were on more solid foundations.

ALMA is the cutting edge of astronomy. Currently being built on the breathless heights of the Llano de Chajnantor, 5100m above sea level in the Atacama, it will consist of 66 12-metre radio telescopes all operating together to perceive detail smaller and fainter than has ever been possible before.

I was hoping that at some point during my time in Chile, I’d get a chance to visit the observatory. The chance came much sooner than expected – a trip was arranged as part of a meeting in Chile of all the fellows from ESO’s headquarters in both Germany and here. We all travelled up to the north, spending a night in San Pedro de Atacama before heading up to Chajnantor the next day.

It was my third visit to San Pedro. It was strange to be back again, six years after I first arrived there half way through my epic journey around South America. The small dusty town has changed quite a lot since then, with power 24 hours, and cash machines that work. In 2005 I’d had to borrow money to get a bus to Calama to get money out.

On the day of the visit, we drove from San Pedro to the ALMA base camp, near the village of Toconao at 2900m above sea level. We had medical tests here, to check blood pressure and oxygenation, before heading on up to the heights. I knew from previous trips to high altitude that I was probably going to feel spaced out and confused, and it turned out as I expected; I felt a little bit out of body by the time we got up to 5100m, hardly able to understand what people said to me and only capable of shuffling slowly across the plateau from the main building to the antennae.

My oxygen-deprived memories are very hazy but I think it was awesome. The array is not complete and only about a third of the eventual number of antennae have been installed so far, but it looked incredibly futuristic with all of the dishes strung out across the barren desert plateau. I staggered around and took lots of photos, and occasionally took shots of oxygen from the canisters we’d all been given.

One thing that I really notice here is how dry it is. The humidity is always low, my clothes dry in minutes when I take them out of the washing machine, and in the two months since I arrived, it’s only rained once in Santiago – a slightly drizzly evening in early October. London in comparison is damp and dank and I wonder how I didn’t have permanent prune skin when I lived there.

Today it rained for the second time. I was in the centre of town, going up Cerro San Cristóbal and then walking around Bellavista and Recoleta, and enjoying another hot sunny day. But in the eastern suburbs there was some kind of shower. I got back to Las Condes to find that the sun was shining but the streets were wet, and clouds were roiling over the mountains. I headed back up to my apartment and watched the retreating rainclouds being lit up by the evening sun.

Apparently when the first site tests were being carried out at Paranal, almost thirty years ago, the dryness was so extreme that it was sometimes thought that the instrument measuring the humidity was stuck on zero. As soon as you arrive there you feel like the moisture is being sucked out of you and into the endless desert. The desert is almost completely barren; red rocky terrain as far as you can see with no hint of green anywhere.

It’s not a place where human being should live. But it’s amazing for astronomy. The sky is almost always clear, the atmosphere is very stable, and it’s a better place to observe the night sky than almost anywhere else on Earth.

Part of my job here in Chile is to assist in the running of the world’s premier visible light observatory, the Very Large Telescope. A couple of days ago I made my first journey here from Santiago, flying up to Antofagasta and getting a bus from there up into the savagely dry Atacama desert, to the observatory at Cerro Paranal.

What a place Paranal is. I’ve been to several observatories but none have been anything like this. The residencia is an awesome piece of architecture, the scale of the operation is immense, the level of activity is impressive, and the unbelievably harsh desert is terrifyingly beautiful. I will be coming here about once a month for the next three years so perhaps I will get bored of it. But on this first visit, I’m feeling impressed.

All of my stuff arrived from the UK today. It had made the journey much more quickly than I’d expected it to, arriving in Chile before I’d even got around to trying to work out where on the high seas it was.

On a cool autumn day in London, I’d seen it all disappear into the bowels of a huge lorry, and as I watched it drive away from my flat I couldn’t help wondering if I’d ever see any of it again. Then there was a story on the news about a container ship sinking off New Zealand. So when it actually arrived I was extremely happy. It seemed quite strange to see all my familiar old possessions again, on this hot summer day in Santiago.

The two things that I most wanted to arrive intact were my coffee machine, and a kilogram of Marmite that I’d packed in. I was a bit worried that the Marmite could get confiscated, as Chile has very strict rules about food import. But it made it, and with great joy I cracked it open.

I ate so much that I got stomach ache. I don’t think I’ll eat any more for a few days.

My previous attempt to see the Cajon del Maipo had been a bit half-arsed, relying on public transport and ending up in the nondescript hamlet of San Gabriel, instead of actually out in the mountains hiking.

So I tried again this weekend, with a couple of other ESO people. We hired a car, and left reasonably early. Having your own wheels definitely makes a big difference, and instead of spending hours on the bus chugging through all the distant Santiago suburbs, we were in the valley in less than an hour.

But we didn’t get everything right. We stopped in Baños Morales for a lengthy and tasty lunch, planning to hike to a glacier afterwards. But by the time we rolled up to the national park entrance, sated and sleepy but none the less keen to hike, we were told the trail had closed 20 minutes earlier.

So we had to find something else to do. We randomly ended up spotting a large red rocky outcrop, high up in the hills above Lo Valdes, and decided to go there. It was a good hike, scrambling up some steep and precarious scree slopes. The skies threatened but only delivered a few spots of rain. We made it to the outcrop without getting wet, and from it we got awesome views over the valley.

After we headed back down, the heavens finally did open, but we were safe in our car by then, and we drove down the valley as the sun broke through the rain clouds again.

I moved into a new flat yesterday. I was perhaps a bit rash, as it was only the second place I looked at, but it was more or less the kind of thing I was looking for and I didn’t want to spend any longer than necessary in my temporary accommodation.

What really persuaded me was the views from the balcony. London is not a high-rise city, and I’d almost always lived in houses while I was there. The one time I lived in a block of flats I was on the first floor. So this flat, up high on the 15th floor, was something new. And it faces east towards the mountains, so the height is worth having.