Stereo Spacecraft


STEREO is a solar observation mission and stands for Solar TErrestrial RElations Observatory. It was the third mission in NASA’s Solar Terrestrial Probes program and the first mission using the moon’s gravity to redirect multiple spacecraft launched aboard a single rocket to their respective orbits. STEREO was launched from Cape Canaveral Air Force Station on October 25 2006 aboard a Delta II rocket.

STEREO Spaceraft Picture - Solar Terrestrial Relations Observatory

One of the Solar Terrestrial Relations Observatory (STEREO) spacecraft….an artist’s conception.

STEREO is a two year mission that uses two nearly identical space-based observatories – one ahead of Earth in its orbit, the other trailing behind – to provide the first-ever stereoscopic measurements to study the Sun and the nature of its coronal mass ejections, or CMEs.

The aim of the Stereo Mission is to:

1. Understand the causes and mechanisms of coronal mass ejection (CME) initiation.
2. Characterize the propagation of CMEs through the heliosphere.
3. Discover the mechanisms and sites of energetic particle acceleration in the low corona and the interplanetary medium.
4. Improve the determination of the structure of the ambient solar wind.


The two STEREO observatories are nearly identical. The building of the spacecraft bus and the integration of the instruments were done by the Johns Hopkins University Applied Physics Laboratory (APL). The United States, the United Kingdom and several European countries provided the various STEREO instruments.

The two solar-powered observatories with 3-axis-stabilization, each had a mass at launch of approximately 1,364 pounds (620 kilograms, including propellant). The spacecraft communicate with the APL-based Mission Operations Center via NASA’s Deep Space Network.

The spacecraft bus consists of six operational subsystems supporting two instruments and two instrument suites. This combination provides a total of 16 instruments per observatory. The subsystems include: command and data handling; radio frequency communications; guidance and control; propulsion; power; and thermal.

The following four instrument packages are mounted on each of the two STEREO spacecraft:

1. Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) has four instruments: an extreme ultraviolet imager, two white-light coronagraphs and a heliospheric imager. These instruments will study the 3-D evolution of CME’s from birth at the Sun’s surface through the corona and interplanetary medium to its eventual impact at Earth. Principal Investigator: Dr. Russell Howard, Naval Research Laboratory, Washington, D.C.

2. STEREO/WAVES (SWAVES) is an interplanetary radio burst tracker that will trace the generation and evolution of travelling radio disturbances from the Sun to the orbit of Earth. Principal Investigator Dr. Jean Louis H. Bougeret, Centre National de la Recherche Scientifique, Observatory of Paris, and Co-Investigator Mr. Michael Kaiser of Goddard, lead the investigation.

3. In-situ Measurements of Particles and CME Transients (IMPACT) will sample the 3-D distribution and provide plasma characteristics of solar energetic particles and the local vector magnetic field. Principal Investigator: Dr. Janet G. Luhmann, University of California, Berkeley.

4. PLAsma and SupraThermal Ion Composition (PLASTIC) will provide plasma characteristics of protons, alpha particles and heavy ions. This experiment will provide key diagnostic measurements of the form of mass and charge state composition of heavy ions and characterize the CME plasma from ambient coronal plasma. Principal Investigator: Dr. Antoinette Galvin, University of New Hampshire.


 – On November 9, 2005 both spacecraft were shipped from Johns Hopkins University Applied Physics Laboratory to Goddard Space Flight Center, in preparation for launch.

– STEREO was launched from Cape Canaveral Air Force Station on October 25 2006 at 8:52 pm EDT aboard a Delta II rocket.

 – NASA’s twin Solar Terrestrial Relations Observatories (STEREO) sent back their first images of the sun in mid December 2006.

 –  The SECCHI/HI-1A instrument on the NASA STEREO-A (Ahead) spacecraft captured an unprecedented view of the brightest comet of the last 40 year: Comet McNaught during the period of January 11- 18, 2007.

 – On February 25, 2007 there was a transit of the Moon across the face of the Sun, but it could not be seen from Earth. This sight was visible only from the STEREO-B spacecraft in its orbit about the sun, trailing behind the Earth.

Solar Terrestrial Relations Observatory Picture

Since 2009 NASA’s twin STEREO probes has studied a mysterious region of space to look for remains of an ancient planet which once orbited the Sun not far from Earth. If they find anything, it could solve a major puzzle, the origin of the Moon. The name of the planet is Theia. As of 30 Sept 2012 it has not been found.

The new view from STEREO will greatly improve our ability to forecast the arrival time of severe space weather. Until now, imaging capability did not show the front of a solar disturbance as it travelled all the way from the sun to Earth, so scientists had to make estimates of when the storm would arrive. These estimates were uncertain by a half day or so. With STEREO, scientists can track the storm front from the sun all the way to Earth and forecast its arrival within a couple hours.

Did you know?

* Coronal Mass Ejections are powerful eruptions that can blow up to 10 billion tons of the Sun’s atmosphere into interplanetary space. Travelling away from the Sun at speeds of approximately one million mph (1.6 million kph), CMEs can create major disturbances in the interplanetary medium and trigger severe magnetic storms when they collide with Earth’s magnetosphere.

* Large geomagnetic storms directed towards Earth can damage and even destroy satellites and are extremely hazardous to Astronauts when outside of the protection of the Space Shuttle performing Space Walks (Extra Vehicular Activities) and they have been known to cause electrical power outages.


Space Weather by Volker Bothmer and Ioannis A. Daglis

Sentinels of the Sun: Forecasting Space Weather by Barbara B. Poppe (Author), Kristen P. Jorden 

Coronal Mass Ejections by H. Kunow, N.U. Crooker, J.A. Linker, R. Schwenn, R. Von Steiger 

Solar Eruptions and Energetic Particles by Natchimuthukonar Gopalswamy 

Stereo Spacecraft Links

Stereo Spacecraft: by NASA GSFC
Stereo: John Hopkins University
NASA Stereo in the UK:
Where is STEREO:
NASA’s STEREO Hunts for Remains of an Ancient Planet near Earth.
NASA – STEREO Beauty Pass: Image Credit

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