Sen—Although observing the Sun from the Earth gives us a great view, we’re hampered by two things. First is our atmosphere, which absorbs many of the wavelengths of the light that the Sun emits, such as X-rays and much of the ultraviolet light. Without being able to view the Sun across the whole of the electromagnetic spectrum we become blind to the hottest gases in the Sun’s atmosphere and much of its powerful activity. But we can literally rise above this challenge by putting our telescopes onto satellites orbiting hundreds of kilometers above the surface of the Earth and far above the atmosphere.
The next thing that inhibits what we can measure is the Earth’s magnetic field that stretches for tens of thousands of kilometers above us as we look toward the Sun. But we can get past that too, and a new American spacecraft funded by the National Oceanic and Atmospheric Administation (NOAA) has recently done just that.
First though, let’s look at why we want to get beyond the Earth’s magnetic field to study the Sun. It’s not so much about what you can see from the outside (although there are benefits from being that far away from the Earth) but about what a spacecraft can feel. Once outside our magnetic field, a spacecraft finds itself immersed in a flow of an electrically charged gas and magnetic field that comes from the Sun. This is the solar wind and its detection was one of the first major discoveries of the space era. The wind is all the time flowing out from the Sun’s million degree atmosphere, and it gets diverted around our magnetic field like a stream flows around any rocks in its way. This month a new spacecraft reached its intended position in the solar wind flow after a four-month journey.
The spacecraft is called DSCOVR—the Deep Space Climate Observatory—which launched in February this year. On June 7 DSCOVR reached a point in the Solar System known as the 1st Lagrange (L1) point. DSCOVR will now remain at the L1 point, 1.5 million km away from the Earth in the direction of the Sun.
DSCOVR orbits the Sun at a location called the Lagrange point 1, or L1. Image credit: NOAA
As it looks back at us, it will take images of the entire sun-lit side of the Earth so that we can study the ozone, volcanic dust and aerosols in the atmosphere and monitor changes in vegetation on the ground.
But also onboard are instruments that will measure the charged particles and magnetic field in the solar wind in advance of this flow reaching the Earth. And this is an important job. Once the solar wind reaches the Earth and encounters our magnetic field, it pushes against it, and sometimes it’s even able to penetrate our magnetic shield. Strong gusts in the wind come in the form of solar eruptions known as coronal mass ejections. This gusty environment around us has become known as space weather and during stormy times the changes can create problems with technology such as communication satellites, radio communications and electricity distribution.
DSCOVR joins two missions that are already at the L1 point—NASA’s ACE spacecraft and the joint ESA-NASA mission known as SOHO. Together they act as sentinels in space that allow us to monitor the best and the worst that the Sun can throw at us.
But the SOHO and ACE spacecraft were launched in 1995 and 1997 respectively and have now lasted far beyond their nominal lifetimes. Indeed, not all the instruments on these spacecraft are still being used.
DSCOVR is the new kid on the block, working along side the older generation and ready to ensure that we don’t lose our ability to protect ourselves from the new natural hazard of space weather when they retire.
Workers conduct a light test on the solar arrays on the DSCOVR spacecraft, in the Building 1 high bay at the Astrotech payload processing facility in Titusville, Florida, near the Kennedy Space Center. Image credit: NASA/Ben Smegelsky