Something to watch over you
WHAT ARE YOU doing right now? The US department of defence could probably tell you using the global positioning systems (GPS) satellite technology it has been selling globally for decades. The Americans might have a monopoly on GPS for now, but the rest of the world is catching up.
There are thousands of satellites orbiting the Earth and the dawn of nano-satellites (miniature satellite devices no bigger than a shoe box) means it no longer costs millions to launch one.
Two PhD students from DIT are preparing to launch their own nano satellite over the summer. “We won a European Space Agency [ESA] competition tender to send a rocket from northern Sweden,” says co-designer, Dinesh Vather.
“Our satellite is a priming system for atmospheric probes which are put outside the rocket to take readings. It looks like an umbrella, which opens out when it is deployed. Upon entering the stratosphere it will be travelling at around 1.4km per second. So the satellite will basically test how well the system functions in harsh conditions.”
These days satellites are used for everything from telecommunications to weather forecasting, land interpretation, space exploration, surveillance for military applications and even monitoring people’s movements.
You can breath a sigh of relief though. Given the cost of operating this type of technology, surveillance of individuals by the US military is probably limited to nuclear physicists in Iran or North Korea.
Here in Ireland, surveillance activity is used to measure changes over time in Ireland’s lands and seas. University College Cork leads the way in monitoring everything from storm surges to soil moisture.
“We have just begun a new ESA-funded climate-change initiative,” says Dr Ned Dwyer of the UCC Coastal and Marine Research Centre. “We have global soil-moisture measurements going back to the 1980s. All this imagery from satellites has been archived and systematically catalogued, so we can compare the situation in the 1980s to now and see which areas are more or less dry.”
Dwyer is also involved in measuring activity at sea. “In 2005 Hurricane Katrina caused a major storm surge as did Cyclone Nargis in Burma in 2008,” he says. “We can look at these historical events through satellite imagery and assess how we could better prepare for similar weather in the future. In Europe, storm surges are on a smaller scale. The best-known surge was in 1956 when parts of eastern England and Holland were badly damaged. Ireland is susceptible, too, though. Cork city is low lying.”
Dwyer’s colleague, Dr Fiona Cawkwell, is involved in the development of an Irish land-mapping observatory. Currently, national coverage of Ireland is monitored through the EU-wide Corine land inventory programme but it maps the whole of Europe in a very generalised way.
“It maps the land cover of Europe at a common spatial scale,” says Cawkwell. But there are hundreds of different land cover types, from the Mediterranean olive groves up to the tundra in Scandinavia.
“So the EPA here are interested in alternative approaches to land mapping, taking into account the vagaries of the Irish landscape, with a focus on agriculture. Rather than looking at one point, we take a time series of images throughout the year and see how the land cover changes,” he says.
The big problem in this country for satellite-based land mapping is cloud cover. While radar monitoring is unaffected, satellites relying on optical measurements are constantly hampered by that blanket of grey that rarely leaves the Irish sky.
“We are looking into using unmanned aerial vehicles in the future,” says Cawkwell. “They are the equivalent to drones on the ground but they can fly at 100m altitudes and always be below the cloud cover. The technology is really starting to develop in earnest right now. But it’s hampered by legal regulations in terms of what can and cannot be done so we may be waiting quite a while.”
Irish scientists are also involved in ESA space-exploration projects. Irish technology company Captec is assisting in the Bepi Colombo mission to Mercury. “Our specific area is the software that goes aboard the satellite,” says Jon Kennedy of Captec.
“This is a very ambitious project. The satellite will be exposed to a lot of heat from the sun so a lot of different technology is being used on board the mission and we’re involved in various specifications for the requirements for the satellite.”
Likewise, scientists at Trinity are involved in an even bolder ESA project. “We’re helping to design a satellite that will fly past Venus and Mercury and around the sun,” explains Dr Peter Gallagher of TCD. “This will be as close as humanity has ever gotten to the sun and Irish researchers are involved in the project. It will take approximately €500 million to build and another half a billion to launch.”
That satellite will be the size of a small bungalow. But nano technology has revolutionised the industry making it more manageable in scale and affordability.
“Nano satellite technology has really advanced in Ireland in the last number of years,” says Dr Marek Rebow of DIT. “You can now build a device for around €100,000. Soon we’ll all have our own satellites flying above us.”
Space debris: Garbage in outer space
Space junk or debris creates a cloud of waste around our planet. Everything from spent rockets, defunct satellites, erosion, explosion and fragments from collisions, are all orbiting the Earth with nowhere to go. Most of the millions upon millions of particles are no bigger than a centimetre in length. Some, however, are as big as houses.
All satellites have a shelf life. Some of the more expensive ones could last for decades while smaller, nano satellite, devices may only be usable for a few months before they give up the ghost. Given the fact there are thousands of them up there, that makes for quite a lot of space junk that needs to be taken care of.
The vacuum in space means you cannot drag the satellites in any direction once they’re in orbit and incommunicado. So figuring out ways to bring defunct ones down from the vacuum – instead of simply waiting for gravity to eventually pull them back into the Earth’s atmosphere – has puzzled scientists for years.
“Removing satellites that have been orbiting for many years is a major concern as they can cause problems for other satellites and the International Space Station,” says Dr Marek Rebow of DIT. “Satellites at one altitude could hit ones at lower altitudes if they descend.”
One novel approach takes advantage of the Sun’s energy. “We can create an artificial drag through solar wind,” says Rebow. “If we deploy a really big parachute with a signal that can be directed from Earth, it could harness the solar wind, which would create a small drag and gradually change the trajectory of the satellites. It could still take up to one year to bring them down but many take years to finally make it back down to Earth.” – John Holden