APEX: The Atacama Pathfinder Experiment

Desert Eco-Lodge Alto Atacama 

The day starts early: too early for me. The reason? No, sadly not because of astronomy - rather, it is Adam
Donneky, the Director from In House Films who has a tendency to snore... quite loudly. Not helped by the plentiful and incredible Chilean red consumed the night previously - we enjoyed some superb hospitality at the desert lodge Hotel Alto Atacama. Wonderful fresh local ingredients like quinoa, chanar syrup, charquicán, purple potatoes, algarrobo... Amazing, and all with a backdrop of the desert and cliffs! However, after the snoring I am edging toward thoughts of torture - thankfully I resist the urge to dispense with Adam and turn my thoughts to
meeting researchers at APEX and discussing sub-millimetre
astronomy in depth.

The theory: all things emit radiation, even clouds of cold gas. APEX has superb resolution and can scan large areas of the sky quickly, looking for this radiation being emitted: cold regions of gas radiating energy. The intensity of the signal reveals how dense the emitting object is. These celestial objects could be a hydrogen-dense star-forming region or a proto-planetary disk, gravitationally attracting material as it forms a new planet.

Sub-millimetre astronomy is special! We look beyond the optical part of the light spectrum through which we "see" the Universe, investigating amongst other things, astrochemistry. The wavelengths are much longer and are often referred to as microwave radiation. One of the properties of microwave radiation is that it is readily absorbed by water. Microwave radiation excites water molecules and cause them to vibrate by transfer of energy, hmmm interesting, this is precisely why our microwave ovens are so successful at heating up food! Problem is: there is a lot of water in Earths' atmosphere, which absorbs the radiation before it can reach our telescopes.

The Chajnantor plateau in the shadow of APEX

Luckily, the higher you go up the less water there is... so this observatory is high: 5100 metres! It's spectacular, high on the Chajnantor plateau in Chile’s Atacama region. Set so high up, the telescopes here 'catch' the radiation from the Universe before it can be absorbed by moisture in the Earth's atmosphere, giving APEX a clear view into space. You can see some of what we experience in this video trailer from ESO!

Michael Dumke, Lead Astronomer at APEX

We arrive at the APEX control room and meet our host Michael Dumke, the lead astronomer at this incredible laboratory. APEX is the pre-cursor to ALMA with a 12m antenna concentrating in the sub-millimetre wavebands of light. The control facility is down in the valley floor, an ancient sea bed from prehistoric Earth. APEX sits in the bushes and shrubs and to me it feels like an eco holiday village in Atacama... quite different to some of the other ESO sites we've visited. I foolishly say this to Michael: oh dear! I'm forgiven though, and the tour continues to show me the seriousness of the research done here. Lots of interviews (you'll see these when the documentary is
released) and I also see a superb image of the
Horsehead Nebula stuck on the wall, in the sub
millimetre range... cooool (for a geek like me)!

The Horsehead Nebula in visible, infra red and microwave images (the final two)!

Now we head off to the antennae itself - to see first hand the APEX telescope! I am looking forward to

The APEX facility - spot the Moon!

getting up there - this is our second attempt as the first trip up to the 'high side' was foiled by a blizzard. Today however, the skies are beautifully clear! The 1 hour drive is spectaular, but very difficult because of the very low oxygen levels. We feel all sorts of strange physical effects: tiredness, sickness...

But on arrival we are met by Michael's staff and led into the control room which is oxygenated, ahh relief! After our briefing we head outside -  seeing the colour gradient in the blue of the sky was uniquely special. Smothered in UV 50 sunscreen we wander out to take pictures and conduct interviews.

Yes - it's a telescope!

Despite the sickness, the filming schedule and the pressure - I am in heaven. As we leave the facility, night starts to draw in and we stop to take pictures and film.The telescope, as you can see, is beautiful and we feel SO excited to be so close up!

As our conversations with Michael deepen it becomes apparent that just like a protoplanetary disk, we have 'accreted' another friend and plans are made for dinner that night in San Pedro de Atacama. Our group of 3 turns into 18...

ALMA and San Pedro de Atacama

The astrowagon in the Atacama...

ALMA and San Pedro de Atacama!


As you know, we have left the VLT at Paranal ... and next on our itinerary are the Atacama Pathfinder Experiment Telescope (APEX) and the Atacama Large Millimeter/submillimeter Array (ALMA) near to the desert town of San Pedro de Atacama. So we set off once more in our astro-wagon for the foothills of the Andes...

ALMA finds early galaxies in the very young Universe!

So, to introduce these two incredible facilities... APEX operates only in the submillimeter range of the electromagnetic spectrum - the smaller wavelengths of light. It has a massive field of view, scanning the skies to find objects of interest in the Universe. One job of ALMA is to zoom in on objects found so that we can investigate them in more detail - it is the most ambitious and technologically advanced instrument on earth involving astronomical observations.

In case you're wondering what "millimeter/submillimeter range" means: it describes the size of the wavelengths of light. Using these instruments, we can see the cold matter in the Universe... the stuff which doesn't emit light and so it's not much of a stretch to say that APEX and ALMA help us to see things in our Universe which are invisible to the human eye! Boy was I going to remember this place…

The Observatory at the Tierra Atacama, our
heavenly basecamp for 6 nights at
San Pedro de Atacama!

Anyway a bit about San Pedro first: a bohemian town full of charm and backpackers! With muddy roads, dried under the hot desert sun and shops selling Alpaca jumpers and scarfs with a multitude of colours, tourists throng around planning desert adventures. As I arrive, it is dark and pouring with rain. I turn up one way dirt roads, get lost, am met by the local police who in no uncertain terms turn this gringo around… 2 hours later we find our hotel. After 7 days sharing a campervan with the film crew, I am about to have a bed to sleep in, a shower to wash in... could this be true?! We stay at the Tierra Atacama, a beautiful and eco-friendly hotel with a minimum-impact policy. Interested in our message of astronomy outreach and in our documentary, they offer us a deal which suits our charity budget, we can hardly believe it as we stroll through the gardens. We discover plants which they have grown in the deset soil... a small orchard, a vegetable garden and a medicinal herb garden as well as several fields of alfalfa and other crops. We swim in the infinity pool, gazing out at FIVE volcanoes. And I spot a little Observatory!

Next morning, we are well rested and off to ALMA however we were not expecting what happened next… the Atacama desert is the driest place on Earth and it very rarely rains: last time was 2 years ago, hmm and also the day I arrived! Not just the unlikely rain however - when we ascend to the summit 5,100m above sea level, we had a a blizzard, a total white out! I couldn't see a thing at all, there was a blanket of white, so we have a quick look around and see the 50 spectacular 12m diameter antennas and additional compact array of 7m and 12m diameter antennas. This is a little bit like seeing a 16km field of view into the Universe!

She said YES!!!

As the snow builds, we have to leave. But before we go, our executive producer Dr David Murphy chooses this spectacular and romantic location to propose to his girlfriend, and she says yes! We all celebrate before we head off... I was gasping for breath: at this altitude it is not easy to breathe and boy do you feel it. I especially at this stage am starting to feel quite low, exhausted from our filming schedule and the altitude. I have to admit I am even starting to crave coming home - so strange because I know this is the professional outreach project of a lifetime. I'm sure it's the altitude effects, but it's really hard...

Dr Andreas Lundgren

We hit base camp and meet some great scientists. I wake up enough to film interviews with some of them. Dr Andreas Lundgren is the Deputy Lead of the Programme Manager Group at ALMA and his PhD was in theoretical astrophysics. I feel slightly intimidated but Andreas was fantastic - approachable and fascinating. He tells me about the future of ALMA... the antennae will eventually spread out across the Chajnantor plateau, providing a large aperture instrument capable of seeing through the vast regions of cold dark gas: the gas which normally obscures visible light from objects like galaxies and star forming regions.

Base Camp at ALMA...with snow-topped
mountains in the background.

After a tour of the facility, we pause to get our breath back and some lunch we are met by Valerie who is a bubbly happy lady (a common theme happy people I mean…) who tells us that we are allowed to come back the following day to try again and visit the site, this time hopefully in better weather conditions!