Keeping satellites in the sky

Satellite in space with Earth below

29 August 2018 by Ingrid Cnossen

As part of a series of interviews with new NERC Independent Research Fellows, Ingrid Cnossen talks about the beauty of flexible working and how understanding the weather can help to keep satellites in orbit.

I applied for a NERC Independent Research Fellowship (IRF) because, since having a daughter in 2016, I have been looking for an opportunity that would allow me the flexibility to work remotely from anywhere in the UK, while allowing me to spend extra time with my family. The IRF allows me to do this and affords me the luxury of being able to set my own research agenda.

I obtained my PhD in 2009 from the University of Leicester, then I did postdocs at the British Antarctic Survey in Cambridge and then at the National Center for Atmospheric Research in Boulder, Colorado, USA. In 2013, I began a two-year NERC postdoctoral fellowship at the British Antarctic Survey, and I was a visiting scientist at the GFZ German Research Centre for Geosciences in Potsdam, for six months in 2016, just prior to having a baby.

After I had my daughter in August 2016, I ended up having a career break until March this year, when I started working part-time as an external science consultant for the University of Michigan. They allow me to work remotely from the UK and have been very flexible with my working hours, so that I have been able to gradually get back into work, initially starting with two days a week, now three days a week, and soon to be four days a week. Towards the end of the year I will finish my contract with the University of Michigan and take up the NERC Independent Research Fellowship at the British Antarctic Survey, also on a part-time basis, four days a week, so I can continue to spend an extra day a week with my daughter. I think this will give me a good balance between my work and personal life.

Ingrid Cnossen

Ingrid Cnossen

In my fellowship I will investigate how the effects of climate change in the lower and middle atmosphere influence the upper atmosphere and what impact these changes will have on satellites operating in low-Earth orbits which, among many other things, we rely upon for global communications and navigation systems.

The lower and middle atmosphere are thought to affect the upper atmosphere through the spread of atmospheric waves. Atmospheric waves are caused by disturbances that change the pressure, or density, of the air in a region and that, like waves in the ocean, then spread outwards and, unlike ocean waves, upwards. Most of these wave sources are found in the lower atmosphere, but if the conditions are right, the waves can travel upwards into the middle and upper atmosphere and interfere with a satellite.

When these waves travel upwards, there is less atmosphere weighing down on them (the atmospheric pressure decreases) and this allows the waves' height (amplitude) to massively increase. Eventually however, the waves become so large that they become unstable and break (similar to waves breaking on a beach) and their energy and momentum transfer to the surrounding atmosphere. Very large waves therefore can have a significant impact on the motion of the upper atmosphere.

For my fellowship work, I plan to use computer simulations of the whole atmosphere and test how changes in the lower atmosphere (that happen where there are increased greenhouse gas concentrations) affect the climate in the upper atmosphere, and predict any long-term changes in its density.

Given our increasing reliance upon satellite-based technologies that operate within the outer regions of the Earth's atmosphere, being able to make these predictions will be essential. This is because all objects that operate in a low-Earth orbit interact with the upper atmosphere and experience drag that can destabilise their orbits and cause them to fall back to Earth - the greater the atmospheric density, the greater the drag. For operational satellites, this can be a problem because the drag slows them down and they eventually fall out of orbit.

The greatest danger to satellites comes from space junk - the graveyard of defunct satellites and fragments of spent spacecraft that share their orbit. Even a collision with a tiny piece of space debris can damage or de-orbit a satellite.

By understanding how changes in the lower atmosphere will affect the upper atmosphere in the future, we will be able to make long term 'weather' predictions for the upper atmosphere. These predictions will allow us to keep operational satellites in orbit for longer by placing them in orbits where they will experience minimal drag. It will also allow us to predict how long pieces of space junk will remain in orbit and how their orbits might change - knowledge that we could use to ensure that operational satellites avoid collisions.

The NERC Independent Research Fellowship  scheme is designed to develop scientific leadership among the most promising early-career environmental scientists, by giving all fellows five years' support, which will allow them sufficient time to develop their research programmes and to gain international recognition.

Applications for the current Independent Research Fellowship call closes on 2 October 2018. Further information can be found on the Independent Research Fellowship webpage.