STEREO

The STEREO (Solar TErrestrial RElations Observatory) was a special project by NASA to watch the Sun very closely. It used two almost identical spacecraft called STEREO-A and STEREO-B. These spacecraft were sent into space in 2006 to move around the Sun in ways that let them see the Sun from different places. This helped scientists make special 3D pictures of the Sun and its big bursts of energy, called coronal mass ejections.

Because of this special way of moving, the two spacecraft could watch solar storms and other Sun activities from different angles, like how we use both eyes to see things in 3D. This helped us learn much more about how the Sun behaves and how it can affect Earth.

Sadly, in 2014, we lost touch with STEREO-B when it started spinning in a way that stopped its solar panels from getting enough energy from the Sun. We tried to fix the problem in 2016, but we were not able to get it working again, and finally had to accept that we could no longer use STEREO-B.

Mission profile

The two STEREO spacecraft were launched on October 26, 2006, from Cape Canaveral Air Force Station in Florida. They used the Moon's gravity to move into orbits around the Sun. One spacecraft, called STEREO-A, moved ahead of Earth, while the other, STEREO-B, fell behind.

Over time, the two spacecraft moved farther apart from each other. They were exactly on opposite sides of the Sun in February 2011, which allowed scientists to see the entire Sun at once for the first time. In 2014, contact was lost with STEREO-B, but NASA was able to reconnect in 2016. However, efforts to fully recover the spacecraft were stopped in 2018.

Mission benefits

The main benefit of the STEREO mission was getting special 3D images of the Sun. Because the two spacecraft were at different places around the Sun, they could see parts of the Sun that we cannot see from Earth. This helped scientists watch the far side of the Sun directly, instead of guessing what is happening there.

These spacecraft helped us learn more about big bursts of solar material, which can affect our communications, power grids, and satellites on Earth. Before STEREO, it was hard to see these bursts when they happened on the far side of the Sun. With STEREO, scientists can now watch the whole Sun all the time, which helps them give better warnings about possible problems.

STEREO also helped scientists study stars and discover new ones that change in brightness.

Science instrumentation

Each spacecraft carries special cameras and tools to study the Sun. One set of tools, called SECCHI, has five cameras that take pictures of the Sun and its outer atmosphere. These cameras help scientists watch big bursts of solar material moving toward Earth.

Other tools measure tiny particles and radio waves from the Sun, giving us more information about space weather and how it affects our planet.

Spacecraft subsystems

Each STEREO spacecraft weighed 547 kilograms when empty and 619 kilograms at launch. When folded up for launch, they were small, about 2 meters long, 1.2 meters wide, and 1.1 meters high. After unfolding, they grew larger, especially the solar panels, which stretched out to about 6.5 meters wide. Fully deployed, including all instruments, they measured roughly 7.5 meters long, 8.7 meters wide, and 5.9 meters high. The solar panels provided enough power for the spacecraft's needs.

The spacecraft were kept steady using special tools that tracked their position in space. They had tiny sensors to notice any changes in direction and a star tracker to know where they were pointing. Inside each spacecraft was a special computer that helped control and send data back to Earth. These computers were built to work well even in the tough conditions of space travel. They also had memory to store pictures and information from their instruments until they could be sent back home.