Discoveries have shown that ionization from the sun is responsible for physics in the ionosphere. But the new NASA mission ICON wants to show how planet Earth and its weather seem to play a substantial part as well.
Over the next few months and years, NASA is planning to launch many exciting missions. One of them is ICON, short for Ionosphere Connection, an investigation on space weather, fitted into a busy schedule of planned launches. The mission will start this summer, as part of NASA’s long-standing Explorer program. Since 1958 there have been over 50 successful Explorer missions, with just four ending in failure. Over the years, they have studied wide-ranging topics from cosmic rays to micrometeorites, atmospheric heating and ultra-violet space sources. By definition, each Explorer mission must not exceed $200 million in total costs (excluding the launch vehicle). Indeed, the fact that the program has lasted over fifty years and is still going strong, demonstrates how successful the Explorer missions are deemed by NASA leadership.
As for the imminent mission ICON, its aim is to explore how the mixture of neutral and charged particles in the ionosphere (a layer of the atmosphere close to Earth), affect the path of radio communications and GPS signals in that region. Molecules in the atmosphere consist of a nucleus of positive and neutral charge, surrounded by orbiting electrons, which are negatively charged. Some of these molecules have their electrons ripped off by the powerful ultra-violet radiation originating from the Sun in a process known as ionization. This leaves the remainder of the molecule (the nucleus), which is positively charged. These charged particles are known as ions and many of them together are known as plasma, which move in constantly shifting streams and sheets around the ionosphere. Most of the behaviour happens at the equator where the intensity of the Sun’s rays is greatest. Until recently it was thought that the physics occurring in the ionosphere was mainly affected by solar activity. However, it has recently been shown that weather on Earth (both on a seasonal and a daily basis) is also responsible for what happens in the ionosphere. Winds in the Earth’s atmosphere affect winds in the ionosphere, which can affect radio and GPS signals here on Earth, and this is exactly, what ICON wants to explore further.
A shuttle full of instruments
In order to explore the physics happening in the ionosphere, ICON is carrying four instruments to find out what is going on. The science that needs to happen includes measuring the temperature and speed of neutral particles in the atmosphere, measuring the speed of charged particles and taking photographs of glowing oxygen in the upper atmosphere, in order to measure the height and density of the daytime ionosphere. One example of an instrument on board is the FUV (the Far Ultra-Violet instrument), which will take photographs of the upper atmosphere in the far ultra-violet wavelength range. The instruments will sit on board the host spacecraft and orbit the Earth at an altitude of 360 miles.
Justifying the mission
We all are familiar with radio communication here on Earth and how frustrating it can be when you get a noisy channel. Anyone who has ever used a car satellite navigation system knows how difficult it can be sometimes to get a signal. It is that kind of problem which ICON wants to address. But the economic impact of being able to potentially avoid this everyday issue should not be underestimated. The data found by the ICON mission will be combined with those from a sister NASA mission, named Global-scale Observations of the Limb and Disk, ‘GOLD’ for short. GOLD has a single instrument on board, an ultra-violet camera which will measure the density and temperature of the ionosphere. The mission payload will be hosted by a commercial communications satellite, and will travel around the Earth in a geostationary orbit for at least two years after its launch in 2017. Meanwhile ICON is carrying on from a previous NASA mission, named CINDI, that explored the weather in the ionosphere. The Coupled Ion Neutral Dynamic Investigation was launched in April 2008 and the satellite’s orbit eventually decayed back in 2015. Scientists at NASA are still working through the masses of data obtained through this mission, with aims not too different from ICON. Since scientists working on this wanted to better understand space weather as well, CINDI also had an Ion Velocity Meter (IVM) instrument on board.
More and more space weather missions
But it’s not only NASA that has made space weather a priority for investigation. In 2015, ESA (the European Space Agency) and the Chinese Academy of Sciences announced a joint mission called Smile (the Solar Wind Magnetosphere Ionosphere Link Explorer), which will probe how the solar wind interacts with the magnetosphere. The magnetosphere acts as a barrier around the Earth to solar winds and this is where the process of ionization mainly takes place. The proposed collaborative Smile mission will launch in 2021. Meanwhile ESA’s Cluster mission is currently in the process of modeling the magnetosphere, improving our knowledge of space plasma physics and space weather more generally.
Overall, a great deal of activity in ionosphere physics is done, giving ICON its fitting place as one part amongst this great exploration of the frontier of space. With more similar missions either imminent or planned further down the road, it certainly is an exciting time to be a space scientist.
Peter Fox is studying for a PhD in Physics
Banner image: Artist’s conception of ICON, NASA Goddard’s Conceptual Image Lab/B Monroe