Though it seems like I’ve been here just taking pretty pictures of the snow, I’ve come here with a purpose – to use my talents as an engineer.
Since the days of Cambridge that I’ve been working in all the projects that are going to be under my responsibility for the next year or so. So far it has been mostly virtual work and only now I have the opportunity to mess around with the real equipment.
Lifetime of Halley is a simple project on paper: around the station there are several specific points that are being followed daily using an high precision GPS. These points are then used to create flow charts, that is, with the daily position of these points we can tell the speed and direction in which this piece of ice we call home is moving around.
Now the technical part. In each of these points, called sites, is a nice piece of Antarctic engineering.
For starters, the GPS receiver is not the kind of GPS that we have in our mobile phones or car nor one of those fancy ones that you can buy in sport stores so that you don’t get lost in the woods while jogging. These are high precision instruments that are built to survive extreme environments. Actually, the GPS part is the smaller one of the whole thing. The receiver is the size of a dictionary and the antenna is slightly larger than a tea saucer.
But the yearly maintenance of these stations takes a whole day worth of work. That’s because, in order for it to work a whole year, Winter and antarctic storms included, a protection structure is needed and, mainly, a power supply.
Each one of these GPS sets is powered through batteries, the same ones that are used in cars, but slightly better. Each site has four of these inside two wooden boxes. Why the boxes you ask? For them to survive Winter where the blows are going to bury them under a meter of snow at least.
Four big batteries last a long time but not a whole year, specially if you bury them in snow after a few months. As such its necessary to charge them and here we use Antarctica for it. Each site has also a photo-voltaic panel and a wind generator both connected, through a charging circuit, to the battery boxes.
Between the several sunny months and the magnificent blows that we get around here, these sites can work all year long with a minimum of issues.
Each site is between 5 to 20 km away from the station. Then how do we get their daily position? There’s one last element missing: a radio frequency antenna, much like the ones that we used to have in our roofs to get television before cable and fiber optics. In homes these antennas were used for reception only, but they can also be used to transmit. And that’s what we do here. The final piece in this arrangement is a 6 meter long pole with a Yagi antenna on top that is used once per day to send the position back to station.
In practice each one of these sites only works for 2 hours each day. We don’t need more than that since we aren’t moving towards the ocean that fast. The system is fully automatic: every day, around lunch time, the GPS receiver “wakes up” (it has built in functions for that), spends a few good minutes sampling the current position, establishes a connection to the base, sends its position and then turns off for another 22 hours.
Since it is not always possible to establish a connection to the station, specially the sites further away in the field (the range of these antennas is not that great), the daily position is also stored in a memory card inside the GPS receiver. Data redundancy is always a good policy.
So where do I fit in this equation? Well, in a day to day basis, I’m just monitoring the system’s behavior and making a couple of nudges in the software when necessary. But once per year I need to physically travel to each one of these stations and dig them up… literally.
One year of Antarctica means a meter of snow, at least, on top of everything: antennas, battery boxes, solar panel, etc…
Most of these elements are assembled on metal poles and are easy to dig out. The worst ones are the battery boxes really. These, not only weight around 50 kg each, need to be almost totally uncovered from snow before we can move them, since most of the time the snow beneath them has frozen around the base and they are stuck.
In its essence, every year we invert the site’s arrangement around the GPS antenna. This one is not moved so that the carefully plotted position map doesn’t get messed up, but the rest of the junk is placed on its opposite side once its dug up. Besides, we need to create new snow anchors to hold the poles or these will fly off in the first serious blow. Then I need to replace the memory card in the GPS receiver for a blank one, while the old one is brought back to base and its data backed up. Finally, with the site all nice and shinny, I make a last communications test with the base to make sure that everything is working OK.
Its a whole day of work, between the trip, digging up boxes, dig in new snow anchors and secure everything back into place. In these trips I always need to take a field guide, since its not a good idea to go alone, and normally I tend to take one or two little helpers to help with all the digging around.
Funny thing is, I never had a shortage of volunteers for this task, not even after I told them that we are going to dig copious amounts of snow and carry boxes full of heavy batteries around. Actually it happens exactly the opposite: I have to choose one or two in the middle of lots of hands in the air and biscuit briberies. Folks around here love a chance to go out and do a long trip in a field Ski-Doo and I don’t blame them. Its awesome!
This project boosted my popularity around the station!