Jan Erik Rasmussen/Datagraf

Satellites in new orbits aid Arctic monitoring

Tuesday 04 Mar 14
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Michael Linden-Vørnle
Astrophysicist and Chief Adviser
DTU Space
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DTU and the Danish military are developing technological solutions to improve communications and Arctic monitoring. One option is to employ so-called molniya satellites.

By Sabine Askholm Larsen

The Danish military is tasked with maintaining coastline security throughout the Danish realm. From the mild temperate climate of Denmark’s approximately 7,000 km long coastline to Greenland’s 44,000 km long coastline in the unpredictable and inhospitable Arctic regions.

Thanks to a framework grant from the Danish Agency for Science, Technology and Innovation— DTU Space and Polar DTU are working closely with the Danish military to develop Arctic solutions with both military and civil applications.

One of Greenland’s biggest challenges is creating a better communications infrastructure. The geostationary satellites that provide broadband coverage at lower latitudes simply cannot cover the Arctic due to their orbit.

One possible solution therefore is to send up satellites in an elliptical orbit so they pass more slowly over the Arctic, thus providing better broadband coverage. This type of satellite is known as a molniya satellite, and in contrast to the geostationary satellites, it will enable the expansion of Greenland’s communications infrastructure. An improvement that will significantly boost the Danish military’s monitoring capability and at the same time support small settlements in Greenland.

“In today’s modern world, we are highly dependent on the internet. A better communications infrastructure will also give the small settlements access to high-speed internet. Greater internet access can also help to promote telemedicine and distance learning, once again improving our ability to support small settlements in Greenland. Achieving this, however, will require sufficient bandwidth and a stable internet connection,” explains Michael Linden-Vørnle, astrophysicist and Senior Executive Officer at DTU Space—and the anchorman responsible for collaboration with the military.

Jan Erik Rasmussen/Datagraf

Better Arctic monitoring
Another technology which together with molniya satellites can boost military monitoring capability is unmanned craft—something that can also prove useful to scientists. The combination of satellites with high monitoring capability and low-flying unmanned craft that can see in greater detail works well.

Among other things, this will benefit Greenland’s maritime security. The greater the number of sources of information, the safer locals and transitory traffic will be able to navigate in Greenland’s waters. The combination of different types of technology will also prove extremely useful to scientists.
“One thing is that data can be used here and now to generate a situational overview. As the data become historical, they can provide the basis for analytical analyses and statistical material in scientific studies benefiting scientists, authorities and private businesses,” assesses Michael Linden-Vørnle.

Far out in space

Ordinary geostationary satellites orbit above the equator and therefore cannot cover the Arctic. What is known as ‘Molniya’ satellites follow an elliptical path and orbit slowly when they are far from the Earth. As a result, they can remain above the Arctic for a protracted period and provide better communication at latitudes higher than 81 degrees north, where standard geostationary satellites cannot reach.

‘Molniya’ means lightning in Russian. Scientists from the Soviet Union originally came up with the idea of launching satellites on elliptical paths. The concept has been tried previously, but there are no Molniya satellites orbiting the Earth at present.

 

 Jan Erik Rasmussen/Datagraf

Satellite at hour 6:

  • Molniya satellites for use over the Arctic follow an elliptical path, which takes them to distances of between 600 and 40,000 km from the Earth, while geostationary satellites maintain a constant distance of 36,000 km from the planet. To compensate for the longer distance, Molniya satellites are equipped with more powerful transmitters.

The path—for example with a line to hour 2 or 10:

  • Between hours 2 and 10, Molniya satellites provide full coverage of the northern hemisphere.

Satellite at hour 0:

  • Permanent coverage therefore requires two Molniya satellites to take over from one another.

Rings on the Earth:

  • The satellites send signals towards the Earth as a series of rays (illustrated by the rings) which, together, constitute the satellite’s area of coverage on the Earth.

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25 JULY 2017