Hitch-hikers help to monitor space weather
A number of small sensors, 'hitch-hiking' on ESA Science missions, are helping in ESA’s effort in space science and applications and could pave the way for a wider network of future space weather monitors.
Although 150 million kilometres away, the Sun is capable of causing great disturbance to our life on Earth. Just as it can give us breathtaking aurorae, our star’s intense activity can affect the technology we depend on in our everyday lives.
The effects of the Sun’s unpredictable moods on the space environment are called ‘space weather’. Most space weather data are provided by a flotilla of spacecraft which have specially designed instruments for continuously monitoring the Sun and the processes affecting our planet.
ESA missions such as Ulysses and Cluster, and the joint ESA/NASA SOHO, are already providing unprecedented amounts of data, which are helping us to understand the Sun, its atmosphere and the Earth’s magnetosphere.
Several years from now, ESA’s Solar Orbiter will travel closer to our star than any solar mission has gone before, just one-fifth of the Earth's distance from the Sun, where sunlight will be 25 times more intense than we feel it.
These are dedicated scientific spacecraft, designed with advanced sensors and communications systems. However, useful space weather data are also provided by small, low-cost ‘hitch-hiker’ instruments now being flown on ESA’s science missions.
One of these instruments is the Standard Radiation Environment Monitor (SREM). This instrument provides data on the space weather radiation in the vicinity of the spacecraft and has already been flown on several ESA missions, including Integral. Integral is in a highly eccentric orbit, and goes through the Earths' inner and outer radiation belts and is therefore exposed to high-energy solar particle storms.
SREMs measure space radiation fluxes and the ‘radiation dose’ (the amount of energy from radiation absorbed by materials), counting energetic electrons, protons and heavy ions encountered during each mission.
They are usually flown on science missions like Integral or Planck because these missions have instruments, such as CCD imagers, which are very sensitive to high-energy radiation that creates a lot of background signal (‘noise’) and maybe even permanent damage to the instrument. SREMs help to monitor the quality of the data gathered and also the health of the spacecraft.
Although they are not specifically designed to provide a global and continuous watch of space weather activity, they are very useful in helping us to understand certain physical processes that influence space weather.
The next science missions waiting in line to fly SREMs are Rosetta, Herschel, Planck and Gaia. Rosetta is ESA’s comet-chaser mission, and its SREM will monitor the radiation environment along its interplanetary path.
Herschel, Planck and Gaia are all observatory missions that will be positioned at the Lagrangian point L2, 1.5 million kilometres behind Earth as seen from the Sun. SREMs will also fly on other ESA missions, for example, the Galileo System Test Bed V2, a demonstration mission for the future Galileo navigation system.