i - A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory 

OUR EYE ON THE SUN

Solar Dynamics Observatory

SDO

www.nasa.gov

A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory
 ii - A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory 

SDO Science

SDO Instruments

SDO Story Lines

SDO Feature Stories

Solar Dynamics Observatory: A Solar Variability Mission

Avalanche! The Incredible Data Stream of SDO

SDO Mission Q&A

SDO Launch and Operations Quick Facts

Background Science:

NASA’s Living With a Star Program 

A Timeline of Solar Cycles

Acronyms and Abbreviations

Abbreviations for Units of Measure

Solar Science Glossary

SDO Mission Management 

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Table of Contents

Mission Description

SDO will study how solar activity is created and how space weather results from that activity. 

Measurements of the Sun’s interior, magnetic field, the hot plasma of the solar corona, and the 

irradiance will help meet the objectives of the SDO mission. 

SDO will improve our understanding of the physics behind the activity displayed by the Sun’s 

atmosphere, which drives space weather in the heliosphere, the region of the Sun’s influence, and in 

planetary environments. SDO will determine how the Sun’s magnetic field is generated, structured, 

and converted into violent solar events that cause space weather. SDO observations start in the 

interior of the Sun where the magnetic field that is the driver for space weather is created. Next, SDO 

will observe the solar surface to directly measure the magnetic field and the solar atmosphere to 

understand how magnetic energy is linked to the interior and converted to space weather causing 

events. Finally, SDO will measure the extreme ultraviolet irradiance of the Sun that is a key driver to 

the structure and composition of the Earth’s upper atmosphere.
A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory - 1

SDO Science

The Solar Dynamics Observatory (SDO) is designed 

to probe solar variability in a way that no other 

mission can match. High-speed cameras on SDO 

will take rapid-fire snapshots of solar flares and 

other magnetic activity. This will have the same 

transformative effect on solar physics that the 

invention of high-speed photography had on many 

sciences in the 19th century.

SDO doesn’t stop at the stellar surface. A sensor on 

the observatory can actually look inside the Sun at the 

very source of solar activity—the solar dynamo itself. 

There SDO will find vital clues to the mystery of the 

solar cycle and help scientists predict the future of 

solar activity.

Solar activity and variability are key concerns of our modern, increasingly technological society. 

Solar flares and coronal mass ejections can disable satellites, cause power grids failure, and disrupt 

communications. Furthermore, because the Sun is so powerful, even small changes in its irradiance 

could have effects on climate.

Solar storm shooting into space.

Solar storm impacting Earth and its magnetic shield.
 2 - A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory 

The Solar Dynamics Observatory has three main instruments.

The Atmospheric Imaging Assembly (AIA) is 

a battery of four telescopes designed to photograph the Sun’s surface and atmosphere. AIA 

filters cover 10 different wavelength bands, or 

colors, selected to reveal key aspects of solar 

activity. AIA was built by the Lockheed Martin 

Solar and Astrophysics Laboratory (LMSAL), 

Palo Alto, California. AIA’s Principal Investigator 

is Dr. Alan Title of LMSAL.

The Extreme Ultraviolet Variability Experiment (EVE) will measure fluctuations in the 

Sun’s ultraviolet output. The solar extreme 

ultraviolet (EUV) radiation has a direct and 

powerful effect on Earth’s upper atmosphere, 

heating it, puffing it up, and breaking apart 

atoms and molecules. Researchers don’t know 

how fast the Sun can vary at many of these

wavelengths, so they expect to make many 

new discoveries about flare events. EVE was 

built by the University of Colorado, with Dr. 

Tom Woods of University of Colorado as the 

Principal Investigator.

The Helioseismic and Magnetic Imager (HMI) will map 

solar magnetic fields and peer 

beneath the Sun’s opaque surface using a technique called 

helioseismology. A key goal of 

this experiment is to decipher 

the physics of the Sun’s magnetic dynamo. HMI was built by 

the Lockheed Martin Solar and 

Astrophysics Laboratory of the 

Lockheed Martin (LMSAL), Palo 

Alto, California. The Principal 

Investigator for HMI is Dr. Phil 

Scherrer of Stanford.

SDO Instruments

Magnetic activity on the surface of the Sun.

Identifying some features of the SDO spacecraft.
A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory - 3

Atmospheric Imaging Assembly (AIA)

What will AIA study?

The AIA will image the corona, or 

outer layer of the Sun’s atmosphere, 

in multiple wavelengths nearly simultaneously. 

How does it work?

AIA is an array of four telescopes that 

will observe the surface and atmosphere of our star with big-screen 

clarity and unprecedented time resolution. It’s like an IMAX® camera for 

the Sun.

AIA will produce a high-definition 

image of the Sun in eight selected 

wavelengths out of the ten available 

every 10 seconds. The ten wavelength bands include nine ultraviolet 

and extreme ultraviolet bands and one visible light band to reveal key aspects of solar activity. To 

accomplish this, AIA uses four telescopes, each of which can see details on the Sun as small as 725 

km (450 mi) across—equivalent to looking at a human hair held 10 m (33 ft) away.

Because such fast cadences 

with multiple telescopes have 

never been attempted before by 

an orbiting solar observatory, the 

potential for discovery is significant. In particular, researchers 

hope to learn how storms get 

started near the Sun’s surface 

and how they propagate upward 

through the Sun’s atmosphere 

toward Earth and elsewhere 

in the solar system. Scientists 

will also use AIA data to help 

them understand how the Sun’s 

changing magnetic fields release 

the energy that heats the corona 

and creates solar flares.

SDO Instruments

The Sun, as observed by STEREO, in four wavelengths of extreme 

UV light and taken at nearly the same time. SDO will take images 

in 10 wavelengths every 10 seconds.

The AIA instrument as it is being assembled. It is like an 

IMAX® camera for the Sun.
 4 - A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory 

Extreme Ultraviolet Variability Experiment (EVE)

What will EVE study?

Solar scientists will use the Extreme ultraviolet Variability Experiment (EVE) to measure the Sun’s 

brightness in the most variable and unpredictable part of the solar spectrum. The extreme ultraviolet, 

or EUV, ranges in wavelength from 0.1 to 105 nm.

EUV photons are much 

more energetic and dangerous than the ordinary 

UV rays that cause sunburns. If enough EUV rays 

were able to reach the 

ground, a day at the beach 

could be fatal. Fortunately, 

Earth’s upper atmosphere 

intercepts the Sun’s EUV 

emissions.

In fact, solar EUV photons 

are the dominant source of 

heating for Earth’s upper 

atmosphere. When the 

Sun is active, EUV emissions can rise and fall by 

factors of hundreds to 

thousands in just a matter 

of seconds. These surges 

heat the upper atmosphere, puffing it up and increasing the drag on man-made satellites. EUV 

photons also can break the bonds of atmospheric atoms and molecules, creating a layer of ions that 

alters and sometimes severely disturbs radio communications and GPS navigation.

How does it work?

EVE will allow solar scientists to monitor EUV emissions between 0.1 and 105 nm with the highest 

time resolution (10 seconds) and the highest spectral resolution (better than 0.1 nm) ever achieved 

by a space-based observatory. EVE also measures the very important Lyman a line at 121.6 nm, 

the single brightest line in the EUV. EVE will collect data 24 hours a day, 7 days a week, offering 

the first complete picture of solar EUV fluctuations that vary by factors of 2-100 over time scales 

of minutes.

SDO Instruments

This is the completed EVE instrument. It will have the highest time 

resolution (10 seconds) and the highest spectral resolution (better 

than 0.1 nm) ever achieved by a space-based solar observatory.
A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory - 5

Helioseismic and Magnetic Imager (HMI)

What will HMI study?

HMI will use the waves and magnetic field measured at the surface of the Sun to study the motions 

of material inside the Sun and the origins of the solar magnetic field.

How does it work?

Solar physicists will use HMI to measure the waves rippling across the surface of the Sun and the 

magnetic field that erupts through the surface of the Sun. HMI measures the Doppler shift of a spectral line (the change in a 

wave’s frequency when 

the source moves 

toward or away from 

an observer) to give the 

velocity over the Sun’s 

entire visible disk. The 

Zeeman effect is used 

to interpret the polarization of the same line 

to give the magnetic 

field over the visible 

face of the Sun. 

We use the wave data to study the inside of the Sun. 

As the waves travel through the Sun they are influenced by conditions inside the Sun. The speed of 

sound increases where solar material is hotter, so 

the speed and angle at which the wave is generated 

determine how far it will penetrate into the solar interior. The shallower the angle, the shallower the penetration; the steeper the angle, the deeper the wave 

will travel. It takes about 2 hours for a sound wave to 

propagate through the Sun’s interior. The frequency 

and spatial pattern the waves make on the surface indicate where the waves have traveled. Scientists learn 

about the temperature, chemical makeup, pressure, 

density, and motions of material throughout the Sun 

by analyzing the detailed properties of these waves.

HMI will provide the first rapid cadence measurements of the strength and direction of the solar magnetic field over the visible disk of the Sun. Scientists 

use this information to understand how the magnetic 

field is produced and, when combined with measurements from AIA, how that field produces flares 

and CMEs, the storms of space weather.

SDO Instruments

Magnetogram (magnetic image) of the Sun 

showing magnetically intense areas (active 

regions) in black and white.

The HMI instrument gets a close look as it is being assembled.
 6 - A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory 

The Sun is a Variable Star

“The Sun is a variable star,” says Judith Lean of the Naval 

Research Lab in Washington DC. “It could have many surprises in store for us.” 

“The Solar Dynamics Observatory is designed to study 

solar variability like no other spacecraft in NASA history,” 

says Lika Guhathakurta of NASA headquarters in Washington DC. “SDO may be considered the Solar Variability 

Mission.”

Danger: Solar Storm Warning! 

Human society depends on a network of interconnected 

high-tech systems for the basics of daily life. Power grids, 

GPS navigation, air travel, financial services, radio communications—they can all be knocked out by intense solar activity. According to the 2008 Severe Space 

Weather Events—Understanding Societal and Economic Impacts: A Workshop Report by the National Academy of Sciences, a century-class solar storm could cause twenty times more economic 

damage than Hurricane Katrina.

“Understanding solar variability is 

crucial,” says Lika Guhathakurta of 

Washington DC. “Our modern way 

of life depends upon it.”

The 11-year solar cycle is largely 

unpredictable. It’s not even 11 years 

long! No one knows when the next 

big solar storm will come.

“The solar minimum of 2008-2009 

has taken us by surprise,” says David Hathaway of the Marshall Space 

Flight Center. “It highlights how far 

we still have to go to successfully 

forecast the solar cycle.”

SDO will observe the Sun faster, 

deeper, and in greater detail than 

previous observatories, breaking 

barriers of time-scale and clarity 

that have long blocked progress in 

forecasting dangerous solar storms. 

175

150

125

100

75

50

25

0

Sunspot Number

ISES Solar Cycle Sunspot Number Progression

Data Through September 2009

01 02

Updated 2009 Oct 6 NOAA/SWPC Boulder, CO USA

Smoothed Monthly Values

Monthly Values

Predicted Values (Smoothed)

00 03 04 05 06 07 08 09 10 11 12 13 14 15

Jan

16

Jan

SDO Story Lines

Chart showing the progression and estimated

track of the next solar cycle from 2000 to 2016.

Looping arcs of particles spiraling along 

magnetic field lines rising up from beneath 

the surface and back into the Sun.
A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory - 7

SDO Can See Inside the Sun

A sensor on SDO called the “Helioseismic Magnetic Imager” (HMI) can see through the Sun’s surface to study what 

lies beneath. 

“It is like taking an ultrasound picture of a baby still inside 

her mother,” says Dean Pesnell of the Goddard Space 

Flight Center, “the details are fuzzy but we can see many 

important things.”

“There’s a lot going on inside the Sun that we don’t understand,” says Todd Hoeksema, a solar physicist at Stanford 

University, where the HMI was built. “The Solar Dynamics 

Observatory is bound to deliver some big discoveries.”

A key target of HMI is the Sun’s inner magnetic dynamo, 

the source of all solar activity. It lies about 140,000 miles below the Sun’s surface.

“Understanding how the dynamo works is a holy grail for stellar physics,” says Pesnell.

High-Definition Movies of the Raging Sun... 24/7!

Imagine watching a high-definition movie that never 

stops. The enormous screen is filled with the raging 

Sun, unleashing huge solar flares and billion-ton clouds 

of hot plasma. The amount of data and images SDO will 

beam back per day is equivalent to downloading half-amillion songs each day.

“By some estimates, SDO will transmit as much as 

50 times more science data than any mission in NASA 

history,” says Dean Pesnell of the Goddard Space 

Flight Center. 

Images with 10 times greater resolution than highdefinition television recorded every 0.75 seconds will 

reveal every nuance of solar activity.

“Because such fast cadences have never been attempted before by an orbiting observatory,” Pesnell adds, 

“the potential for discovery is great.”

Researchers believe SDO’s high-speed photography of the Sun could have the same transformative 

effect on solar physics that the invention of high-speed photography had on many sciences in the 

19th century.

SDO’s images are super HD

SDO will study the solar interior.
 8 - A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory 

Scientists, educators, and members of the general public will be able to browse this huge volume 

of data using a new software program called HelioViewer (www.Helioviewer.org). Files from different 

instruments can be combined, panned, and zoomed, giving researchers and others a powerful new 

way to view the Sun. 

Deadly Sunburns

SDO will observe the Sun at scorching “extreme ultraviolet” wavelengths. This is where 

the Sun is most variable.

“If human eyes could see extreme ultraviolet 

(EUV), no one would doubt that the Sun is a 

variable star,” says Tom Woods of the University of Colorado. 

EUV photons are high-energy cousins of regular UV rays that cause sunburns. Fortunately, 

our atmosphere blocks solar EUV; otherwise a 

day at the beach could be fatal. 

During a solar flare, the Sun’s extreme ultraviolet output can vary by factors of 2-100 over 

time scales of minutes. Surges of EUV photons 

heat Earth’s upper atmosphere, causing the 

atmosphere to “puff up” and slowly drag down 

low-orbiting satellites. EUV rays also break 

apart atoms and molecules, creating a layer of 

ions in the upper atmosphere that can severely 

disturb radio signals.

“EUV is where the action is,” says Woods, the lead scientist for SDO’s Extreme-ultraviolet Variability 

Experiment (EVE). “EVE will reveal the Sun as a variable star!”

SDO is the First Mission of NASA’s Living With a Star Program

What if you woke up one morning and found your planet had been swallowed by the atmosphere 

of a star?

Get out of bed, look out the window. Auroras are dancing along the horizon. Dark sunspots crackle 

overhead—each little ‘pop’ is more powerful than a nuclear bomb. On TV, a weather forecaster 

warns astronauts, “a solar flare is sure to erupt,” although he can’t say exactly when. Moments later, 

the satellite signal begins to flicker.

Where is this place? Welcome to planet Earth.

A powerful solar flare erupts as observed

in extreme UV light.
A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory - 9

“It’s true. Earth orbits inside the atmosphere of the 

Sun,” says Lika Guhathakurta, program manager of 

NASA’s Living with a Star (LWS) program. “Truly, we 

are living with a star.”

The Solar Dynamics Observatory is the first mission of NASA’s Living With a Star Program. It will 

reveal how solar activity affects our planet and 

help us anticipate what lies ahead.

The SDO spacecraft getting a final checkout 

before heading to Cape Canaveral for launch.

WITH A STAR

LIVING
 10 - A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory 

Solar Dynamics Observatory: A Solar Variability Mission

For some years now, an unorthodox idea has been gaining favor among astronomers. It contradicts 

old teachings and unsettles thoughtful observers, especially climatologists.

“The Sun,” explains Lika Guhathakurta of NASA headquarters in Washington DC, “is a variable star.”

But it looks so constant!

That’s only a limitation of the human eye. Modern telescopes and spacecraft have penetrated the 

Sun’s blinding glare and found a maelstrom of unpredictable turmoil. Solar flares explode with the 

power of a billion atomic bombs. Clouds of magnetized gas (CMEs) big enough to swallow planets 

break away from the stellar surface. Holes in the Sun’s atmosphere spew million mile-per-hour gusts 

of solar wind.

And those are the things that can happen in just one day.

Over longer periods of decades 

to centuries, solar activity waxes and wanes with a complex 

rhythm that researchers are still 

sorting out. The most famous 

“beat” is the 11-year sunspot 

cycle, described in many texts 

as a regular, clockwork process. In fact, it is frustratingly 

unpredictable.

“It’s not even 11 years,” says 

Guhathakurta. “The cycle ranges in length from 9 to 12 years. 

Some cycles are intense, with 

many sunspots and solar flares; others are mild, with relatively little solar activity. In the 17th century, 

the cycle appeared to stop altogether for about 70 years, and no one knows why.”

There is no need, however, to go so far back in time to find an example of the cycle’s capriciousness. Right now the Sun is in the pits of a century-class solar minimum that almost no one seems to 

have predicted, and no one knows when it will end.

“The solar minimum of 2008-2009 has taken us by surprise,” says David Hathaway of the Marshall 

Space Flight Center. “It highlights how far we still have to go to successfully forecast solar activity.”

That’s a problem, because human society is increasingly vulnerable to solar flare ups. Our modern 

world depends on a network of interconnected high-tech systems for the basics of daily life. Smart 

power grids, GPS navigation, air travel, financial services, emergency radio communications—they 

can all be knocked out by intense solar activity.

SDO Feature Stories

A very dynamic Sun (left) compared to a Sun deep in solar 

minimum (right) helps to illustrate the extremes of a solar cycle.
A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory - 11

According to a 2008 study by the National Academy of Sciences, a century-class solar storm could 

cause twenty times more economic damage than Hurricane Katrina.

“Understanding solar variability is crucial,” says space scientist Judith Lean of the Naval Research 

Lab in Washington DC. “Our modern way of life depends upon it.”

Enter the Solar Dynamics Observatory—“SDO” for short—slated to launch in 2010 from the Kennedy 

Space Center in Florida.

SDO is designed to probe solar variability unlike any other mission in NASA history. It will observe 

the Sun faster, deeper, and in greater detail than previous observatories, breaking barriers of timescale and clarity that have long blocked progress in solar physics.

“SDO is the Solar Variability Mission,” says Guhathakurta, “and it is going to revolutionize our view 

of the Sun.”

The revolution begins with high-speed photography. A bank of multi-wavelength telescopes and 

cameras called the “Atmospheric Imaging Assembly” (AIA) will record IMAX®-quality images of the 

Sun every 10 seconds. For comparison, previous observatories have taken pictures at best every 

few minutes with resolutions akin to what you see on the web, not at a movie theatre. Researchers 

believe that SDO’s rapid-fire cadence could have the same transformative effect on solar physics 

that the invention of high-speed photography had on many sciences in the 19th century.

SDO doesn’t stop at the stellar surface. A sensor onboard SDO, the Helioseismic Magnetic Imager 

(HMI), can actually look inside the Sun at the solar dynamo itself.

The solar dynamo is a network of deep plasma currents that generates the Sun’s tangled and sometimes explosive magnetic field. It regulates all forms of solar activity from the lightning-fast eruptions 

of solar flares to the slow decadal undulations of the sunspot cycle.

“Understanding the inner workings of the solar

dynamo has long been a ‘holy grail’ of stellar physics,” says Dean Pesnell of the Goddard Space 

Flight Center. “HMI could finally deliver this to us.”

The dynamo is hidden from view by about 

140,000 miles of overlying hot gas. SDO penetrates the veil using a technique familiar to 

geologists—seismology. Just as geologists probe 

Earth’s interior using waves generated by earthquakes, solar physicists can probe the Sun’s 

interior using acoustic waves generated by the 

Sun’s own boiling turbulence. An instrument 

onboard SDO called the “Helioseismic Magnetic 

Imager” (HMI) detects the waves, which researchers on Earth can transform into clear pictures of 

the structures below the solar surface.

Illustration of convoluted magnetic field lines 

extending out all over the Sun.
 12 - A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory 

Solar Dynamics Observatory: The 

Solar Variability-Mission (Continued)

Just as geologists probe Earth’s interior using 

waves generated by earthquakes, solar physicists can probe the Sun’s interior using acoustic 

waves generated by the Sun’s own boiling turbulence. An instrument onboard SDO called the 

“Helioseismic Magnetic Imager” (HMI) detects 

the waves, which researchers on Earth can 

transform into fairly clear pictures.

Finally—and of most immediate relevance for 

Earth—SDO will observe the Sun at wavelengths where the Sun is most variable—the 

extreme ultraviolet (EUV). EUV photons are 

high-energy cousins of regular UV rays that 

cause sunburns. Fortunately, our atmosphere 

blocks solar EUV; otherwise a day at the beach could be fatal. In space, solar EUV emission is easy 

to detect and arguably the most sensitive indicator of solar activity.

“If human eyes could see EUV wavelengths, no one would doubt that the Sun is a variable star,” 

says Tom Woods of the University of Colorado.

During a solar flare, the Sun’s extreme ultraviolet output can vary by factors of hundreds to thousands in a matter of seconds. Surges of EUV photons heat Earth’s upper atmosphere, causing the 

atmosphere to “puff up” and slowly drag down low-orbiting satellites. EUV rays also break apart 

atoms and molecules, creating a layer of ions in the upper atmosphere that can severely disturb radio signals. According to Judith Lean, “EUV controls Earth’s environment thoughout the entire atmosphere above about 100 km.”

“EUV is where the action is,” agrees Woods.

That’s why Woods and colleagues built an extreme ultraviolet sensor for SDO called the EUV Variability Experiment (“EVE”). “EVE gives us the highest time resolution (10 sec) and the highest spectral resolution (<0.1 nm) that we’ve ever had for measuring the Sun, and we’ll have it 24/7,” he says. 

“This is a huge improvement over past missions.”

Woods expects EVE to reveal how fast the Sun can change—“we really don’t know,” he points out—

and to surprise astronomers with the size of the outbursts.

AIA. EVE. HMI. For the next five years, the Solar Dynamics Observatory will use these instruments 

to redefine our star and its potential for variability. What unorthodox ideas will they beam back? Old 

teachings beware!

Measurements from the SORCE mission indicate that 

the variability of total solar irradiance has decreased 

over the past six years.
A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory - 13

Solar Constant is an Oxymoron

For years, astronomers were so convinced of the 

Sun’s constancy, they called the irradiance of the 

Sun “the solar constant,” and they set out to measure it as they would any constant of Nature.

By definition, the solar constant is the amount of 

solar energy deposited at the top of Earth’s atmosphere in units of watts per meter-squared. All wavelengths of radiation are included—radio, infrared, 

visible light, ultraviolet, x-rays, and so on. The approximate value of the solar constant is 1361 W/m2

.

Measuring the solar constant from Earth’s surface is 

difficult because of clouds, atmospheric absorption, 

and other complicating factors. So NASA has spent 

decades carefully measuring the solar constant from 

space. Today, the VIRGO, ACRIM, and SORCE instruments are measuring the Sun’s irradiance vs. 

time with precisions approaching 10 parts per million per year. Future instruments scheduled for 

flight on NASA’s Glory and NOAA’s NPOESS spacecraft aim for even higher precisions.

To the amazement of many researchers, the solar constant has turned out to be not constant.

“Solar constant is an oxymoron,” says Judith Lean of the Naval Research Lab. “Satellite data 

show that the Sun’s total irradiance rises and falls with the sunspot cycle by a significant amount.”

“It is like taking an ultrasound picture of a baby still inside her mother,” says Dean Pesnell of the 

Goddard Space Flight Center, “the details are fuzzy but we can see many important things.”

At solar maximum, the Sun is about 0.1% brighter than it is at solar minimum. That may not sound 

like much, but consider the following: A 0.1% change in 1361 W/m2

 equals 1.4 Watts/m2. Averaging this number over the spherical Earth (divide by 4) and correcting for Earth’s reflectivity (multiply 

by 0.7) yields 0.24 Watts for every square meter of our planet.

“Add it all up and you get a lot of energy,” says Lean. “How this might affect weather and climate 

is a matter of—at times passionate—debate.”

While the Solar Dynamics Observatory revolutionizes observations of the solar dynamo and 

extreme-ultraviolet variability, other NASA spacecraft will measure changes in the Sun’s total 

irradiance and spectral irradiance at longer wavelengths. Working together, SDO and the others 

could shed new light on this important topic—perhaps revealing some other oxymorons as well.

SDO will be able to detect helioseismic

waves inside the Sun.
 14 - A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory 

Avalanche! The Incredible Data Stream of SDO

When NASA’s Solar Dynamics Observatory (SDO) leaves Earth 

aboard an Atlas V rocket, the thunderous launch will trigger an 

avalanche.

Mission planners are bracing themselves—not for rocks or snow, 

but an avalanche of data.

“SDO will beam back 150 million bits of data per second, 24 hours 

a day, 7 days a week,” says Dean Pesnell of the Goddard Space 

Flight Center in Greenbelt, Md. That’s almost 50 times more science data than any other mission in NASA history. “It’s like downloading 500,000 iTunes® songs a day.”

SDO is on a mission to study the Sun in unprecedented detail. 

Onboard telescopes will scrutinize sunspots and solar flares using 

more pixels and colors than any other observatory in the history 

of solar physics. And SDO will reveal the Sun’s hidden secrets in a 

prodigious rush of pictures.

“SDO is going to send us images ten times better than high definition television,” says Pesnell, the project scientist for the new 

mission. A typical HDTV screen has 1280 x 720 pixels; SDO’s 

images will have almost four times that number in the horizontal 

direction and five times in the vertical. “The pixel count is comparable to an IMAX® movie—an IMAX® filled with the raging Sun, 24 

hours a day.”

Spatial resolution is only half the story, though. Previous missions have photographed the Sun no 

faster than once every few minutes. SDO will shatter that record.

“We’ll be getting IMAX®-quality

images every 10 seconds,” says 

Pesnell. “We’ll see every nuance 

of solar activity.” Because these 

fast cadences have never been 

attempted before by an orbiting 

observatory, the potential for 

discovery is great.

To illustrate the effect this 

might have on solar physics, 

Pesnell recalls the 18th century 

photographer Eadweard Muybridge, who won a famous bet for racehorse owner Leland Stanford. In 

those days, horses were widely thought to keep at least one hoof on the ground even in full gallop. 

That’s how it appeared to the human eye. 

In early photography, high-cadence images revealed details of 

motion more than the human eye could see

SDO will beam back 150 million 

bits of data every second
A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory - 15

“But when Muybridge photographed horses using a new high-speed camera system, he discovered 

something surprising,” says Pesnell. “Galloping horses spend part of the race completely airborne—

all four feet are off the ground.”

Pesnell anticipates similar 

surprises from high-speed 

photography of the Sun. The 

images could upend mainstream ideas about sunspot 

genesis, what triggers solar 

flares, and how explosions 

ripple through the Sun’s atmosphere en route to Earth. 

The Solar Dynamics Observatory has three main instruments. The Atmospheric 

Imaging Assembly (AIA) is 

a battery of four telescopes 

designed to photograph the 

Sun’s surface and atmosphere. AIA filters cover 10 

different wavelength bands, 

or colors, selected to reveal 

key aspects of solar activity. The bulk of SDO’s data 

stream will come from these 

telescopes.

The Extreme Ultraviolet Variability Experiment (EVE) will measure fluctuations in the Sun’s ultraviolet 

output. EUV radiation Sun has a direct and powerful effect on Earth’s upper atmosphere, heating it, 

puffing it up, and breaking apart atoms and molecules. “We really don’t know how fast the Sun varies at these wavelengths,” notes Pesnell. “We’re guaranteed to learn something new.”

The Helioseismic and Magnetic Imager (HMI) will map solar magnetic fields and peer beneath the 

Sun’s opaque surface using a technique called helioseismology. A key goal of this experiment is to 

decipher the physics of the Sun’s magnetic dynamo.

To gather data from all three instruments, NASA has set up a pair of dedicated radio antennas near 

Las Cruces, New Mexico. SDO’s geosynchronous orbit will keep the observatory in constant view of 

the two 18-meter dishes around the clock for the duration of the observatory’s five-year mission. Not 

a single bit should be lost.

“We’re ready,” says Pesnell. “Let the avalanche begin!”

One of two large radio antennas that serve as SDO’s dedicated 

ground station near Las Cruces, NM.
 16 - A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory 

WHAT IS SDO?

SDO stands for the Solar Dynamics Observatory.

WHAT IS SDO’S PURPOSE AND MISSION?

SDO will study how solar activity is created and how space weather results from that activity. Measurements of the Sun’s interior, magnetic field, the hot plasma of the solar corona, and the irradiance 

will help meet the objectives of the SDO mission.

WHAT IS UNIQUE OR DIFFERENT ABOUT SDO?

SDO is a mission that utilizes, for the first time, a unique orbit to provide high-resolution solar magnetic field images, EUV images, and measurements of the solar UV flux falling on the Earth. It will 

provide new views of the solar interior and the subsurface structures. By some estimates, SDO will 

transmit as much as 50 times more science data than any mission in NASA history. Images with 10 

times greater resolution than high-definition television recorded every 0.75 seconds will reveal every 

nuance of solar activity. SDO data rate is equivalent to downloading a half million songs a day. For 

context, the Solar and Heliospheric Observatory (SOHO) provides a picture of the Sun once every 

12 minutes, and the Solar Terrestrial Relations Observatory (STEREO) once every 90 seconds.

WHEN WILL SDO LAUNCH?

SDO is scheduled to launch no earlier than February 3, 2010.

HOW LONG WILL THE SDO MISSION LAST?

SDO’s primary science mission is anticipated to last 5 years. However, the satellite has enough fuel 

to last 10 years.

WHERE WILL SDO ORBIT?

SDO will use a geosynchronous orbit at the longitude of New Mexico and inclined 28° from the 

equator. This allows continuous contact with the ground station near Las Cruces, New Mexico. The 

actual path in the sky will be a figure eight.

WHAT IS THE EXPECTED COST OF THE SDO MISSION?

Mission managers anticipate the SDO mission will cost approximately $850 million, which includes 

the cost of the satellite, its launch, and 5 years of operations and data analysis.

HOW WILL THE SDO MISSION BENEFIT THE AVERAGE PERSON?

The SDO mission will allow scientists to gain far better understanding of the causes of space weather 

that can disable satellites, cause power grid failure, and disrupt GPS communications. Also, insights 

gained from SDO observations will lead to an increased understanding of the role solar variability 

plays in changes in atmospheric chemistry and dynamics.

ARE SOLAR STORMS A DANGER TO ASTRONAUTS?

Yes. The protons and plasma from large solar storms can expose astronauts, who aren’t within 

Earth’s protective atmosphere, to harmful or lethal amounts of radiation. By improving our ability to 

predict and understand these storms with instruments like those aboard SDO. The SDO mission will 

also help engineers design safer spacecraft for future astronauts.

WHO WILL LOOK AT THE DATA PRODUCED BY SDO?

The solar science community of 2,000 researchers, the space-weather community, educators, and 

SDO Mission Q&A
A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory - 17

the public will look at SDO data. It is expected that SDO data will supplement the nation’s operational space weather missions.

WHAT SCIENCE INSTRUMENTS WILL SDO CARRY?

SDO will carry three science instruments: Atmospheric Imaging Assembly (AIA), Extreme Ultraviolet 

Variability Experiment (EVE), and Helioseismic and Magnetic Imager (HMI).

WHERE WILL THE DATA BE STORED AND ARCHIVED?

Stanford University in Palo Alto, California, will analyze, archive, and manage the data from SDO’s 

HMI and AIA instruments; Lockheed Martin’s Solar and Astrophysics Laboratory (LMSAL) in Palo 

Alto, California, will create and serve data products from AIA; the University of Colorado Laboratory 

for Atmospheric and Space Physics in Boulder, Colorado, will analyze, archive, and manage the data 

from the EVE instrument.

WHAT IS THE SOLAR CYCLE?

The Solar Cycle is an 11-year pattern in the number of sunspots, coronal mass ejections (CMEs), solar 

flares, and other solar activity. About every 11 years the Sun’s magnetic field changes polarity from north 

to south. Eleven years later it flips back. People may have heard of this as the 22-year magnetic cycle 

because after two 11-year sunspot cycles the Sun’s magnetic field will be back the way it was at the start 

of the 22 years. During solar minimum, the Sun may churn out strong CMEs every two days; that’s approximately 180 CMEs per year, although only about 10 to 15 CMEs are directed at Earth. During solar 

maximum, the Sun averages five CMEs daily and sends about 100 to 150 CMEs toward Earth each year.

WHAT IS SPACE WEATHER?

Space weather originates with the variable magnetic activity of the Sun. Activity on the Sun’s surface, such as CMEs and solar flares, can cause high levels of radiation in space. This radiation 

comes to Earth as plasma (electrically charged particles) or electromagnetic radiation (light), including X-rays and ultraviolet wavelengths.

WHAT IS THE DIFFERENCE BETWEEN SOLAR ACTIVITY AND SPACE WEATHER?

Solar activity describes events that take place on the Sun, while space weather describes the effect 

solar activity has on our planet, technology, and the magnetic organization of the solar system.

HOW WILL SDO IMPROVE OUR KNOWLEDGE AND UNDERSTANDING OF 

SPACE WEATHER?

SDO will improve our understanding of the physics behind the activity displayed by the Sun’s atmosphere, which drives space weather in the heliosphere and in planetary environments. SDO will determine how the Sun’s magnetic field is generated, structured, and converted into violent solar events 

that cause space weather. SDO observations start in the interior of the Sun where the magnetic field 

that is the driver for space weather is created. Next, SDO will observe the solar surface to directly measure the magnetic field and the solar atmosphere to understand how magnetic energy is linked to the 

interior and converted to space weather causing events. Finally, SDO will measure the extreme ultraviolet irradiance of the Sun that is a key driver to the structure and composition of the Earth’s upper 

atmosphere.

WHAT IS HELIOPHYSICS?

Heliophysics is the exploration of the magnetic variable Sun, its effects on the planets of the solar 

system including Earth, and space environmental conditions and their evolution.
 18 - A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory 

• SDO is anticipated to launch no earlier than February 3, 2010.

• SDO is planned to launch aboard an Atlas V rocket from Cape Canaveral, Fla.

• Total mass of the spacecraft at launch is 3,100 kg (6,800 lb) that includes 290 kg (640 lb) for the 

instrument payload and 1,450 kg (3,086 lb) for the fuel.

• Overall length of the spacecraft along the Sun-pointing axis is 4.5 m (14.8 ft), and each side is 

2.22 m (7.3 ft).

• Span of the spacecraft with extended solar panels is 6.5 m (21.3 ft).

• Mission operations center will be located at NASA’s Goddard Space Flight Center in Greenbelt, 

Maryland.

• SDO will be a major component of the Heliophysics System Observatory, a fleet of science missions developed by the NASA Heliophysics Division. Each mission concentrates on understanding 

a different aspect of the Sun and its heliosphere—the region of the Sun’s influence in the galaxy.

• SDO is the first mission in NASA’s Living With a Star program. The spacecraft’s long-term measurements will give solar scientists in-depth information about changes in the Sun’s magnetic field.

Launch and Operations Quick Facts

Illustration of the SDO spacecraft keeping a watchful eye on the Sun, all day, every day.
A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory - 19

NASA’s Living With a Star Program

The goal of NASA’s Living With a Star (LWS) Program is to provide the scientific understanding 

needed for the United States to effectively address those aspects of Heliophysics science that may 

affect life and society. The ultimate goal is to develop an understanding that will allow for predictive 

capability of the space weather conditions at Earth and in the interplanetary medium.

LWS missions have been formulated to answer specific science questions needed to understand the 

linkages among the interconnected systems that impact us. These missions will give us a far better 

understanding of the causes of space weather that can disable satellites, cause power grid failure, and 

disrupt GPS communications. Also, insights gained from SDO observations will lead to an increased 

understanding of the role solar variability plays in changes in atmospheric chemistry and climate. The 

coordinated LWS program includes strategic missions, targeted research and technology development, 

a space environment testbed flight opportunity, and partnerships with other agencies and nations.

LWS is a crosscutting program whose goals and objectives have the following links:

Space Science:

LWS quantifies the physics, dynamics, and behavior of the 

Sun-Earth system over the 11-year solar cycle.

Earth Science:

LWS improves understanding of the effects of solar variability 

and disturbances on terrestrial climate change.

Human Exploration and Development:

LWS provides data and scientific understanding required for 

advanced warning of energetic particle events that affect the 

safety of humans.

Aeronautics and Space Transportation: 

LWS provides detailed characterization of radiation environments 

useful in the design of more reliable electronic components for air and space transportation systems.

Biological and Physical Research:

LWS defines the radiation environment beyond the Earth’s magnetosphere to enable exploration of 

interplanetary space by humans.

LWS Web Sites:

Missions:

SDO http://sdo.gsfc.nasa.gov/

RBSP http://nasascience.nasa.gov/missions/rbsp

BARREL http://nasascience.nasa.gov/missions/barrel-1

Solar Orbiter http://nasascience.nasa.gov/missions/solar-orbiter

Solar Probe Plus http://nasascience.nasa.gov/missions/solar-probe

Other Program Elements:

LWS Targeted Research and Technology Program http://lwstrt.gsfc.nasa.gov/

Space Environment Testbed Flight Opportunity http://lws-set.gsfc.nasa.gov/

International Living With a Star Program http://ilws.gsfc.nasa.gov/
 20 - A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory 

Some Major Solar Storms

9/2/1859 Strongest solar storm recorded, with aurora worldwide 

 and telegraph disruptions

5/13/1921 Storm shuts down NY City transit system with induced 

 ground currents 

3/25/1940 Easter Sunday storm halts U.S. long distance phone 

 service for hours; radio and wire services disrupted

2/10/1958 Radio blackout caused by one of the 10 strongest storms

3/13/1989 Quebec power grid collapses for nine hours

10/29/2003 “Halloween” storms cause numerous satellite problems and 

 produce the brightest X-ray flare ever recorded

The Monthly Sunspot Number since 1750

A Timeline of Solar Cycles
A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory - 21

AIA Atmospheric Imaging Assembly

CME Coronal Mass Ejection

EUV Extreme Ultraviolet

EVE Extreme Ultraviolet Variability Experiment

GSFC Goddard Space Flight Center

H Hydrogen

He Helium

HF High Frequency

HMI Helioseismic and Magnetic Imager

ISM Interstellar Medium

LASP Laboratory for Atmospheric and Space Physics

NASA National Aeronautics & Space Administration

NSSDC National Space Science Data Center

RHESSI Reuven Ramaty High Energy Solar Spectroscopic Imager

SDO Solar Dynamics Observatory

SOHO Solar & Heliospheric Observatory

STEREO Solar Terrestrial Relations Observatory

TRACE Transition Region and Coronal Explorer

TSI Total Solar Irradiance

UV Ultraviolet

Acronyms and Abbreviations

A solar storm blasts particles and 

magnetic field out into space from 

an active region on the Sun.

Hz Hertz—cycles per second

K kelvin

kg kilogram

m meter

MHz megahertz

mm millimeter

m/s meters per second

nm nanometer

W watt

W/m2 watts per meter squared

Abbreviations for Units of Measure
 22 - A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory 

ACE — Advanced Composition Explorer satellite (monitors the solar wind)

Aurora — A display of colored light in the atmosphere, 

caused by collisions between charged particles from a 

planet’s magnetosphere and atmospheric gases near 

the planet’s magnetic poles. Auroras are visible on Earth 

as the aurora borealis, or northern lights, and the aurora 

australis, or southern lights.

Chromosphere — 2,500 km thick (1,600 mi) layer of 

plasma above the Sun’s photosphere. Temperatures 

range from ~4500 K to 60,000 K (110,000 to 8,000°F). 

The word chromosphere means, literally, “color sphere” 

and refers to its reddish color when seen with the naked 

eye during a total solar eclipse.

Convection — The movement of matter due to changes 

in temperature and density. Warm material rises because it is less dense (lighter) and cool material sinks 

because it is more dense (heavier).

Convective Zone — The Sun is made up of different layers. From its center outward, the Sun’s layers include the core, the convective zone, the radiative zone, the photosphere, the chromosphere, 

and the corona. The convective zone extends from just below the photosphere to the radiative zone. 

In this region convection currents transport the Sun’s energy to the surface. 

Core — The innermost layer of the Sun, where energy is released by the fusing together of nuclei to 

form heavier nuclei (nuclear fusion).

Corona — The outermost layer of the Sun’s outer atmosphere. This halo of ions extends millions of 

miles into space and consists of a gas that is much thinner than Earth’s atmosphere. The temperature is greater than one million kelvin. The corona is visible to the 

naked eye only during a solar eclipse.

Coronagraph — An instrument designed to study the Sun’s corona 

by covering the bright disk of the Sun. This instrument creates an artificial eclipse that allows us to see the Sun’s faint outer atmosphere. 

Each STEREO observatory has two coronagraphs.

Coronal Hole — An area of the corona that appears dark when 

viewed in ultraviolet light. They are usually located around the poles 

of the Sun, but can occur at other latitudes as well. The magnetic 

field lines in a coronal hole extend out into the solar wind rather than 

coming back down to the Sun’s surface. Because the magnetic field 

lines extend into space, they carry hot material with them and leave 

patches of the solar surface cooler.

Coronal Mass Ejection (CME) — A catastrophic expansion of a part 

of the coronal magnetic field that causes a huge bubble of plasma 

and magnetic field to erupt from the Sun. A CME can last for several 

hours and travels though space at a million miles per hour. CMEs 

are usually accompanied by a solar flare. The charged particles and 

A coronal hole in extreme

UV light.

In this coronagraph, the white circle 

represents the size of the Sun.

Solar Science Glossary
A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory - 23

magnetic fields associated with CMEs can cause power 

and communications outages, damage to satellites, and 

health problems for astronauts. They usually take about 

three days to reach Earth, but very fast ones can arrive 

in under a day.

Electromagnetic Radiation — Energy that travels 

through space at the speed of light and moves by the 

interaction of electric and magnetic fields.

Electromagnetic Spectrum — The entire range of 

wavelengths of electromagnetic energy, including (from 

short to long wavelengths) gamma rays, X rays, ultraviolet light, visible light, infrared, and radio waves.

Energetic Particles — The atoms and molecules of a 

gas are in constant motion, colliding rapidly and filling all 

available space. The hotter the gas, the faster the atoms 

move, and the more energy each holds. In a plasma, the 

free ions and electrons behave the same way, though 

they are often much more energetic and move at a large fraction of the speed of light (300,000 km/

sec or 186,000 mi/sec). Researchers believe high-energy particles in the solar wind are not merely 

heated, but actually accelerated by shock waves in front of CMEs and by electric and magnetic effects in flares.

Faculae — Bright blotches on the surface of the Sun that emit more radiation than surrounding areas and increase solar irradiance.

Filament — A prominence viewed against the solar disk. See prominence.

Flare — A rapid release of vast magnetic energy in a sunspot region, causing temperatures to rise 

tens of millions of degrees in a small area above the solar surface. The resulting radiation surge can 

cause blackouts of communication signals and damage to satellites. Flares can produce dangerous 

EUV radiation, X-rays, gamma rays, and high-energy protons.

Gamma Rays — Created from nuclear reactions, these are the 

most energetic wavelengths of electromagnetic radiation emitted 

by the Sun.

Geomagnetic Storm — A worldwide disturbance of Earth’s magnetic field, caused by solar activity. These storms can cause power outages, communications blackouts, health risks for astronauts 

in space, damage to satellites, and auroras.

Granules — Short-lived cells of plasma that carry heat to the 

Sun’s surface via convection (rising and falling).

Infrared — The range of invisible radiation wavelengths from 

about 700 nm, just longer than red in the visible spectrum, to 1 

mm, on the border of the microwave region.

Ion — An atom or molecule that has lost or gained one or more 

electrons and has become electrically charged as a result.

Ionization — A process that produces ions, typically collisions Granules on the Sun’s surface, with 

each about the size of Texas.

A coronal mass ejection.
 24 - A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory 

between atoms or electrons, or by interaction with electromagnetic radiation.

Irradiance — The amount of radiant energy from a selected source that falls on a surface in a given 

amount of time.

Magnetic Loops — Field lines illuminated by hot plasma flowing along the magnetic field lines.

Magnetism — A force generated by electrical currents and changing 

electric fields. Magnetism is responsible for almost every feature in the 

solar atmosphere, from sunspots to CMEs to flares.

Magnetosphere — An area around a planet in which the planet’s magnetic field is stronger than the magnetic field carried by the solar wind.

Maunder Minimum — From 1645 to 1715, scientists believe there 

was a decrease in the total energy output from the Sun, as indicated 

by little or no sunspot activity. This period coincided with a climate 

event on Earth known as the Little Ice Age.

Photosphere — The Sun’s surface, from which the light we actually 

see (with the human eye) is emitted. Temperatures average 5,800 K 

(9,900°F).

Plasma — Plasmas are materials whose atoms have lost electrons 

and become a mixture of ions and electrons. The Sun is made up of 

plasma created by hot temperatures. Lightning and fluorescent lights 

are earthly forms of this “thermal” plasma. Wires contain plasma created by the interactions of metal atoms. Because plasmas are dominated by charged particles, they 

interact strongly with electric and magnetic fields. Plasma is often considered the fourth state of 

matter (along with solid, liquid, and gas) as most of the matter in the universe is in a plasma.

Prominence — A structure in the corona consisting of cool plasma supported by magnetic fields. 

In visible light, prominences appear as bright structures over the solar limb, but dark when viewed 

against the bright solar disk. Prominences seen on the disk are also known as filaments. Prominences may become parts of CMEs.

Radiative Zone — A layer of the Sun lying between the core and convection zone where energy travels outward through the slow radiation, absorption, and re-radiation of energy by tightly 

packed atoms.

Radio Waves — Electromagnetic radiation with a wavelength 

greater than 1 mm (beyond infrared). 

Solar Cycle — An approximately 11-year pattern in the number 

of sunspots, coronal mass ejections (CMEs), solar flares, and 

other solar activity. About every 11 years the Sun’s magnetic 

field changes from north to south, and then back again in another 11 years.

Solar Spectral Irradiance (SSI) – The amount of radiant energy of a particular wavelength that falls on a surface in a given 

amount of time.

Solar Ultraviolet Irradiance — The amount of energy released 

from the Sun in the ultraviolet portion of the spectrumat wavelengths shorter than 400 nm. A large solar prominence

Magnetic loops
A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory - 25

Solar Wind — A stream of plasma coming out of the Sun in all directions at very high speeds—an 

average of about 400 km/sec, or a million mph. Solar wind is responsible for the tails of comets 

pointing away from the Sun and for the shape of the magnetosphere around the planets. Solar wind 

can also have a measurable effect on the flight paths of spacecraft.

Space Weather — Refers to conditions on the Sun, 

in the solar wind, and in Earth’s space (magnetic field, 

ionosphere, and thermosphere) that can influence 

space- and ground-based technological systems and 

endanger humans working in space. Adverse conditions 

in the space environment can disrupt satellite operations, communications, navigation, and electric power 

distribution grids.

Spectrograph — A device that separates light by 

wavelength (color) in order to produce a spectrum that 

allows for the identification of elements within the light 

source.

Sunspots — Dark areas on the Sun created by strong 

magnetic fields beneath the Sun’s surface. Sunspots 

appear dark because they are cooler than the surrounding areas of the photosphere. They range in size 

from 2,400 km (1,500 mi) to several times Earth’s size. 

Sunspots usually occur in pairs or groups of opposite 

magnetic polarity that rotate with the surface of the 

Sun. They are the footprints of magnetic loops pushing 

through the surface and holding plasma below.

Total Solar Irradiance — The total amount of radiant 

energy from the Sun that falls on a surface in a given 

amount of time.

Transition Region — Area of the Sun’s atmosphere 

with temperatures between those of the chromosphere 

and the corona, 20,000 and 1,000,000 K (35,000 and 

1,800,000°F), respectively.

Ultraviolet — Electromagnetic radiation at wavelengths 

shorter than 400 nm.

Visible Light — Electromagnetic radiation from about 

400 to 700 nm, which is detectable by the human eye.

Wavelength — The distance between one peak or crest of a wave (of light, heat, or other energy) 

and the next corresponding peak or crest. Wavelengths of light from the Sun range from radio waves 

to gamma rays.

Zeeman effect — A splitting of a spectral line into several components due to the presence of a 

static magnetic field. The Zeeman effect is measured using polarized filters. When astronomers measure the effect in absorption lines, it is called the Inverse Zeeman effect.

Close-up of a sunspot group

Caption?
 26 - A Guide to the Mission and Purpose of NASA’s Solar Dynamics Observatory 

NASA’s Solar Dynamics Observatory (SDO) is a five-year mission to study the Sun. As the first mission of NASA’s Living With a Star Program, SDO will investigate the causes of solar variability. The 

spacecraft will study the solar atmosphere in many wavelengths simultaneously to determine how the 

Sun’s magnetic field is generated and structured, and how this stored magnetic energy is converted 

and released in the form of the solar wind, energetic particles, and changes in solar irradiance. SDO 

will be managed by NASA’s Goddard Space Flight Center for the Agency’s Science Mission Directorate at NASA Headquarters in Washington DC.

SDO Mission Management

SDO Program Scientist

Madulika Guhathakurta

NASA Headquarters

Madhulika.Guhathakurta@nasa.gov 

SDO Project Scientist

William Dean Pesnell

NASA Goddard Space Flight Center

William.D.Pesnell@nasa.gov

SDO Deputy Project Scientist

Barbara Thompson

NASA Goddard Space Flight Center

Barbara.J.Thompson@nasa.gov

 

SDO Deputy Project Scientist

Phillip C. Chamberlin

NASA Goddard Space Flight Center

Phillip.C.Chamberlin@nasa.gov

SDO Education & Public Outreach

Emilie Drobnes

NASA Goddard Space Flight Center

Emilie.Drobnes-1@nasa.gov

Public Affairs Contacts:

Dwayne Brown • NASA Headquarters

Dwayne.C.Brown@nasa.gov

 

Don Savage • NASA Goddard Space Flight Center

Donald.Savage@nasa.gov

SDO Instrument Web Sites:

http://hmi.stanford.edu

http://aia.lmsal.com

http://lasp.colorado.edu/eve

SDO Web Sites for More 

Information:

http://www.nasa.gov/sdo

http://sdo.gsfc.nasa.gov

SDO Program Executive

Dana Brewer

NASA Headquarters

Dana.A.Brewer@nasa.gov 

 

SDO Project Manager

Elizabeth Citrin

NASA Goddard Space Flight Center

Elizabeth.A.Citrin@nasa.gov

SDO Deputy Project Manager

Robert Lilly

NASA Goddard Space Flight Center

Robert.B.Lilly@nasa.gov

NP-2009-10-101-GSFC