The sun is the star of our solar system. It provides us with light, heat, and energy. It also influences our weather, climate, and technology. But how much do we really know about the sun and its activity? How can we study the sun from space and learn more about its secrets?
NASA has launched several missions to answer these questions and explore the sun from different perspectives. One of these missions is STEREO-A (Solar TErrestrial RElations Observatory-Ahead), which is a spacecraft that orbits the sun and studies its activity. On August 12, 2023, STEREO-A will make its first Earth flyby after 17 years of operation. This will be a rare and exciting opportunity for STEREO-A to collaborate with other NASA missions near Earth and provide a stereoscopic, or 3D, view of the sun by combining its data with that of other spacecraft.
In this article, we will explain what the STEREO-A mission is, what it has achieved in its 17 years of operation, and what it will do during its first Earth flyby. We will also discuss the significance and implications of the STEREO-A mission for advancing our knowledge and understanding of the sun and its impact on Earth and the solar system.
What is the STEREO-A mission?
The STEREO-A mission is part of a larger project called STEREO (Solar TErrestrial RElations Observatory), which consists of two identical spacecraft: STEREO-A (Ahead) and STEREO-B (Behind). These spacecraft were launched together in 2006, but they separated shortly after launch and followed different orbits around the sun. The idea was to have two spacecraft observe the sun from different angles and distances, creating a stereoscopic, or 3D, view of the sun and its activity.
The main objectives of the STEREO mission are to study the structure and evolution of solar storms, such as coronal mass ejections (CMEs) and solar flares, which are eruptions of plasma and radiation from the sun’s surface. These storms can travel through space and reach Earth, affecting our satellites, communications, power grids, and astronauts. By understanding how these storms form and propagate, we can better predict their effects and protect ourselves from them.
To achieve these objectives, STEREO-A and -B are equipped with several instruments and technologies that allow them to observe the sun and its activity in different wavelengths of light, such as visible, ultraviolet, X-ray, and radio. They also measure the magnetic fields, particles, and plasma in the solar wind, which is a stream of charged particles that flows from the sun. Additionally, they use a technology called heliospheric imaging, which enables them to see the space between the sun and Earth by capturing images of sunlight scattered by dust particles.
What has STEREO-A achieved in its 17 years of operation?
STEREO-A has made many scientific achievements and discoveries in its 17 years of operation. Some of them are:
- STEREO-A and -B were the first spacecraft to see the entire sun as a sphere, when they reached a 180-degree separation in their orbits in 2011. This gave scientists a new perspective on the sun’s features and phenomena, such as coronal mass ejections, solar flares, and sunspots.
- STEREO-A was able to track CMEs from their origin on the sun to their arrival at Earth or other planets. This helped scientists understand how CMEs change shape and speed as they travel through space, and how they interact with other CMEs or solar wind structures.
- STEREO-A detected several CMEs that were not visible from Earth or other spacecraft near Earth. These CMEs were either too faint or too far away from Earth’s line of sight. By observing these CMEs, STEREO-A provided valuable information about their frequency, size, direction, and impact on the solar system.
- STEREO-A observed some of the most powerful solar flares ever recorded, such as the X28 flare in 2017 and the X9 flare in 2020. These flares produced intense bursts of radiation that could damage satellites or harm astronauts. By measuring the radiation levels and spectra of these flares, STEREO-A helped scientists assess their potential hazards.
- STEREO-A discovered some new features and phenomena on the sun or in space, such as coronal waves (ripples on the sun’s surface caused by CMEs), coronal jets (spikes of plasma ejected from small regions on the sun), stealth CMEs (CMEs that have no obvious source on the sun), interplanetary dust rings (rings of dust particles around the sun), and interplanetary shocks (shock waves in the solar wind caused by CMEs or solar flares).
STEREO-A also faced some challenges and difficulties in its 17 years of operation, such as:
- STEREO-A lost contact with its twin spacecraft, STEREO-B, in 2014, after a planned reset. STEREO-B went into a spin and could not point its antenna or solar panels toward Earth or the sun. NASA tried to reestablish contact with STEREO-B for several years, but without success.
- STEREO-A experienced communication delays and data loss due to its distance from Earth and the interference from the sun. As STEREO-A moved farther away from Earth, it took longer for its signals to reach Earth or vice versa. Also, when STEREO-A was behind the sun from Earth’s perspective, it could not communicate with Earth at all, because the sun’s radiation blocked its signals. This meant that STEREO-A had to store its data on board and wait for a better opportunity to transmit them to Earth.
- STEREO-A endured solar storms and extreme temperatures that could damage its instruments or systems. As STEREO-A orbited the sun, it was exposed to high levels of radiation and heat from the sun, as well as cold from the space. These conditions could affect the performance or functionality of STEREO-A’s instruments or systems, such as its cameras, sensors, batteries, or memory.
What will STEREO-A do during its first Earth flyby?
On August 12, 2023, STEREO-A will make its first Earth flyby after 17 years of operation. This will be a rare and exciting opportunity for STEREO-A to collaborate with other NASA missions near Earth and provide a stereoscopic, or 3D, view of the sun by combining its data with that of other spacecraft.
During its flyby, STEREO-A will pass by Earth at a distance of about 7.4 million kilometers (4.6 million miles), which is about 19 times the distance between Earth and the moon. It will use Earth’s gravity to adjust its orbit and speed around the sun. It will also use this opportunity to calibrate its instruments and systems by comparing them with those of other spacecraft near Earth.
One of the main goals of STEREO-A’s flyby is to collaborate with other NASA missions that study the sun and its influence on space weather, such as Parker Solar Probe, Solar Dynamics Observatory, Solar Orbiter, and Solar Terrestrial Relations Observatory (STEREO). By combining their data and observations, these missions will be able to create a stereoscopic, or 3D, view of the sun and its activity. This will allow scientists to see the sun from different angles and distances, and to study its features and phenomena in more detail and accuracy.
Another goal of STEREO-A’s flyby is to test a new technology that could enable faster and better communication from deep space. This technology is called DSOC (Deep Space Optical Communications), which is a project that will use lasers instead of radio waves to transmit data from space to Earth. DSOC will be carried by another NASA mission called Psyche, which will launch in October 2023 and explore a metal-rich asteroid named Psyche. DSOC will demonstrate how lasers can speed up data transmission from deep space by up to 10 times compared to radio waves. This could enable broadband communications for future human missions to Mars.
Why is the STEREO-A mission important?
The STEREO-A mission is important for advancing our knowledge and understanding of the sun and its impact on Earth and the solar system. By studying the sun from different perspectives and distances, STEREO-A has provided us with valuable information about the sun’s features and phenomena, such as coronal mass ejections, solar flares, and sunspots. These information can help us better predict and protect ourselves from space weather events that can affect our satellites, communications, power grids, and astronauts.
The STEREO-A mission is also important for testing new technologies and collaborating with other missions that study the sun and its influence on space weather. By making its first Earth flyby after 17 years of operation, STEREO-A will be able to calibrate its instruments and systems, collaborate with other NASA missions near Earth, provide a stereoscopic view of the sun by combining its data with that of other spacecraft, and test a new technology that could enable faster and better communication from deep space.
The STEREO-A mission is one of the many ways that NASA is exploring the sun and beyond. If you are interested in learning more about the STEREO-A mission or following its progress online or on social media, you can visit [NASA’s website] or [Twitter account]. Thank you for reading this article and we hope you enjoyed it.
