DSCOVR has reached the halfway mark to L1 – Norwegian Centre for Space Weather (NOSWE)

Probably one of the most important means in forecasting short-term space weather effects is the NASA’s Advanced Composition Explorer (ACE) satellite. It is positioned at about 1.5 million km from Earth, where the gravity between the Earth and sun is perfectly balanced. At this neutral spot, called Lagrange 1 (L1), a satellite affected only by gravity can maintain a stable orbit relative to the two larger celestial bodies.

Diagram of the five Lagrange points associated with the sun-Earth system, showing DSCOVR orbiting the L-1 point. Image is not to scale. Credits: NASA/WMAP Science Team — Diagram of the five Lagrange points associated with the sun-Earth system, showing DSCOVR orbiting the L-1 point. Image is not to scale.
Credits: NASA/WMAP Science Team

In the supersonic flow of plasma originated on the sun, called solar wind, the L1 spot is also an ideal position to measure this constant flow as it passes by. The speed of solar wind varies roughly in the range of 400-900 km/s. This means that we can get from about 15 to 60 minutes advance information on approaching solar wind structures at L1, before it actually reaches Earth, where it may affect sensitive technology (satellite based positioning systems and communications, power grids) and human beings (enhanced radiation on polar flights, manned space missions). Hence ACE’s importance in forecasting space weather up to hours-long time scale.

After 18 yrs of service ACE is being replaced by the Deep Space Climate Observatory, or DSCOVR. The DSCOVR was successfully launched from Cape Canaveral, Florida on February 11, 2015, and is now reached the halfway mark to the L1 position.

Workers conduct a light test on the solar arrays. Credits: NASA — Workers conduct a light test on the solar arrays.
Credits: NASA

The DSCOVR carries three key science instruments on board to measure solar wind properties*. The raw input from these instruments into readily available models will allow us to provide continous observation and forecast of near-Earth space weather.

Three instruments will help measure the solar wind on the DSCOVR mission: (shown from left to right), the Faraday cup to monitor the speed and direction of positively-charged solar wind particles, the electron spectrometer to monitor electrons, and a magnetometer to measure magnetic fields. Credits: NASA/DSCOVR — Three instruments will help measure the solar wind on the DSCOVR mission: (shown from left to right), the Faraday cup to monitor the speed and direction of positively-charged solar wind particles, the electron spectrometer to monitor electrons, and a magnetometer to measure magnetic fields.
Credits: NASA/DSCOVR

You can find more information on ACE here,

More information on DSCOVR are attainable here.

*Note that the DSCOVR will also be used for Earth observation not discussed here.