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Quick Facts: Solar Dynamics Observatory/EUV Variability Experiment (SDO/EVE)

Mission Introduction

SDO spacecraft

SDO carries three instruments that will observe the Sun simultaneously, performing the entire range of measurements necessary to understand the variations on the Sun. (Courtesy NASA/GSFC)

The Solar Dynamics Observatory (SDO) is the first mission to be launched for NASA’s Living With a Star (LWS) Program, a program designed to understand the causes of solar variability and its impacts on Earth. SDO is designed to help us understand the Sun’s influence on Earth and near-Earth space by studying the solar atmosphere on small scales of space and time and in many wavelengths simultaneously.

With the exception of the slow evolutionary changes in solar structure over the last 4.5 billion years, almost all solar variability is magnetic in origin. The solar cycle is a magnetic cycle in which the Sun’s magnetic poles reverse with a periodicity of approximately 11 years and intense magnetic fields erupt through the surface in sunspots whose numbers wax and wane with the cycle. Solar flares and coronal mass ejections occur when magnetic fields are stressed beyond their limits. The very structure of the corona and the solar wind is determined by the structure of the magnetic field. The heating of the Sun’s corona and the acceleration of the solar wind are thought to be due to interaction between small-scale magnetic elements.

SDO will help us to understand the mechanisms of solar variability by observing how the magnetic field is generated and structured and how this stored magnetic energy is released into the heliosphere and geospace. The goals of SDO are to:

  • Understand how magnetic fields appear, distribute, and disappear from their origin in the solar interior
  • Understand the magnetic topologies that give rise to rapid high-energy release processes
  • Study and gauge the dynamic processes which influence space weather phenomena
  • Study the variations in irradiance and solar structure which occur on short timescales, as well as over the solar cycle

LASP Roles

EVE instrument with labels

A key requirement for EVE is to measure the EUV radiation with an accuracy of 25% or better, thus on-board calibration channels are included to go with underflight calibration experiments to be conducted during the SDO mission. (Courtesy LASP)

LASP provides:

  • The Extreme Ultraviolet Variability Experiment (EVE)
  • Mission operations for the EVE instrument
  • Annual underflight rocket calibrations
  • EVE Principal Investigator, Tom Woods

LASP Instrument

The EVE instrument is designed to measure the solar extreme ultraviolet (EUV) irradiance. The EUV radiation includes the 0.1-105 nm range, which provides the majority of the energy for heating Earth’s thermosphere and creating Earth’s ionosphere (charged plasma). This wide spectral range requires the use of multiple channels. Some key requirements for EVE are to measure the solar EUV irradiance spectrum with 0.1 nm spectral resolution and with 20 sec cadence. These drive the EVE design to include grating spectrographs with array detectors so that all EUV wavelengths can be measured simultaneously. Another key requirement for EVE is to measure the EUV radiation with an accuracy of 25% or better, thus on-board calibration channels are included to go with underflight calibration experiments to be conducted during the SDO mission.

The primary objectives of the EVE instrument are to:

  • Specify the solar EUV spectral irradiance and its variability on multiple time scales
  • Advance current understanding of how and why the solar EUV spectral irradiance varies
  • Improve the capability to predict the EUV spectral irradiance variability
  • Understand the response of the geospace environment to variations in the solar EUV spectral irradiance and the impact on human endeavors

For more information about the SDO/EVE mission, see:

For more information about the LASP/CU Calibration Rocket Experiment for EVE, see:

Quick Facts

Launch date: February 11, 2010
Launch location: Kennedy Space Center, Cape Canaveral, Florida
Launch vehicle: Atlas V
Mission target: Continuous solar observations from Earth geosynchronous orbit
Mission duration: 5 years
Other organizations involved:

  • NASA’s Goddard Space Flight Center (GSFC)
  • University of Southern California
  • Naval Research Laboratory
  • MIT Lincoln Laboratory
  • Virginia Tech
  • NOAA/Space Weather Prediction Center
  • Space Environment Technologies
  • Utah State University

AIMClick on the image to view a PDF (524 KB) of SDO-EVE FAQs.