Solar Dynamics Observatory

The Solar Dynamics Observatory (SDO) is a NASA mission which has been observing the Sun since 2010.[4] Launched on February 11, 2010, the observatory is part of the Living With a Star (LWS) program.[5]

Solar Dynamics Observatory
Mission typeSolar research[1]
OperatorNASA GSFC[2]
COSPAR ID2010-005A
SATCAT no.36395
Websitehttp://sdo.gsfc.nasa.gov
Mission durationPlanned: 5–10 years
Elapsed: 10 years, 4 months, 15 days
Spacecraft properties
Launch mass3,100 kilograms (6,800 lb)
Dry mass1,700 kilograms (3,700 lb)
Payload mass290 kilograms (640 lb)
Start of mission
Launch dateFebruary 11, 2010, 15:23:00 (February 11, 2010, 15:23:00) UTC
RocketAtlas V 401
Launch siteCape Canaveral SLC-41
ContractorULA
Orbital parameters
Reference systemGeocentric
RegimeGeosynchronous
Longitude102° west
Semi-major axis42,164.71 kilometers (26,199.94 mi)[3]
Eccentricity0.0002484[3]
Perigee altitude35,783 kilometers (22,235 mi)[3]
Apogee altitude35,804 kilometers (22,248 mi)[3]
Inclination28.05 degrees[3]
Period1436.14 minutes[3]
EpochJanuary 24, 2015, 10:48:18 UTC[3]
 

The goal of the LWS program is to develop the scientific understanding necessary to effectively address those aspects of the connected Sun–Earth system directly affecting life and society. The goal of the SDO is to understand the influence of the Sun on the Earth and near-Earth space by studying the solar atmosphere on small scales of space and time and in many wavelengths simultaneously. SDO has been investigating how the Sun's magnetic field is generated and structured, how this stored magnetic energy is converted and released into the heliosphere and geospace in the form of solar wind, energetic particles, and variations in the solar irradiance.[6]

General

The SDO spacecraft was developed at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and launched on February 11, 2010, from Cape Canaveral Air Force Station. The primary mission lasted five years and three months, with expendables expected to last at least ten years.[7] Some consider SDO to be a follow-on mission to the Solar and Heliospheric Observatory (SOHO).[8]

SDO is a 3-axis stabilized spacecraft, with two solar arrays, and two high-gain antennas, in an inclined geosynchronous orbit around Earth.

The spacecraft includes three instruments:

  • the Extreme Ultraviolet Variability Experiment (EVE) built in partnership with the University of Colorado at Boulder's Laboratory for Atmospheric and Space Physics (LASP),
  • the Helioseismic and Magnetic Imager (HMI) built in partnership with Stanford University, and
  • the Atmospheric Imaging Assembly (AIA) built in partnership with the Lockheed Martin Solar & Astrophysics Laboratory.

Data which is collected by the craft is made available as soon as possible, after it is received.[9]

As of February 2020, SDO is expected to remain operational until 2030.[10]

Instruments

Helioseismic and Magnetic Imager (HMI)

The Helioseismic and Magnetic Imager (HMI), led from Stanford University in Stanford, California, studies solar variability and characterizes the Sun's interior and the various components of magnetic activity. HMI will take high-resolution measurements of the longitudinal and vector magnetic field over the entire visible solar disk thus extending the capabilities of SOHO's MDI instrument.[11]

HMI produces data to determine the interior sources and mechanisms of solar variability and how the physical processes inside the Sun are related to surface magnetic field and activity. It also produces data to enable estimates of the coronal magnetic field for studies of variability in the extended solar atmosphere. HMI observations will enable establishing the relationships between the internal dynamics and magnetic activity in order to understand solar variability and its effects.[12]

Extreme Ultraviolet Variability Experiment (EVE)

The Extreme Ultraviolet Variability Experiment (EVE) measures the Sun's extreme ultraviolet irradiance with improved spectral resolution, "temporal cadence", accuracy, and precision over preceding measurements made by TIMED SEE, SOHO, and SORCE XPS. The instrument incorporates physics-based models in order to further scientific understanding of the relationship between solar EUV variations and magnetic variation changes in the Sun.[13]

The Sun's output of energetic extreme ultraviolet photons is primarily what heats the Earth's upper atmosphere and creates the ionosphere. Solar EUV radiation output undergoes constant changes, both moment to moment and over the Sun's 11-year solar cycle, and these changes are important to understand because they have a significant impact on atmospheric heating, satellite drag, and communications system degradation, including disruption of the Global Positioning System.[14]

The EVE instrument package was built by the University of Colorado at Boulder's Laboratory for Atmospheric and Space Physics, with Dr. Tom Woods as Principal Investigator,[7] and was delivered to Goddard Space Flight Center on September 7, 2007.[15] The instrument provides improvements of up to 70 percent in spectral resolution measurements in the wavelengths below 30 nm, and a 30 percent improvement in "time cadence" by taking measurements every 10 seconds over a 100 percent duty cycle.[14]

Atmospheric Imaging Assembly (AIA)

The Atmospheric Imaging Assembly (AIA), led from the Lockheed Martin Solar and Astrophysics Laboratory (LMSAL), provides continuous full-disk observations of the solar chromosphere and corona in seven extreme ultraviolet (EUV) channels, spanning a temperature range from approximately 20,000 Kelvin to in excess of 20 million Kelvin. The 12-second cadence of the image stream with 4096 by 4096 pixel images at 0.6 arcsec/pixel provides unprecedented views of the various phenomena that occur within the evolving solar outer atmosphere.

The AIA science investigation is led by LMSAL, which also operates the instrument and – jointly with Stanford University – runs the Joint Science Operations Center from which all of the data are served to the worldwide scientific community, as well as the general public. LMSAL designed the overall instrumentation and led its development and integration. The four telescopes providing the individual light feeds for the instrument were designed and built at the Smithsonian Astrophysical Observatory (SAO).[16] Since beginning its operational phase on May 1, 2010, AIA has operated successfully with unprecedented EUV image quality.

AIA wavelength channelSource[17]Region of solar atmosphereCharacteristic
temperature
White light (450 nm)continuumPhotosphere5000 K
170 nmcontinuumTemperature minimum, photosphere5000 K
160 nmC IV + continuumTransition region & upper photosphere105 & 5000 K
33.5 nmFe XVIActive region corona2.5×106 K
30.4 nmHe IIChromosphere & transition region50,000 K
21.1 nmFe XIVActive region corona2×106 K
19.3 nmFe XII, XXIVCorona & hot flare plasma1.2×106 & 2x107 K
17.1 nmFe IXQuiet corona, upper transition region6.3×105 K
13.1 nmFe VIII, XX, XXIIIFlaring regions4×105, 107 & 1.6×107 K
 9.4 nmFe XVIIIFlaring regions6.3×106 K

Photographs of the Sun in these various regions of the spectrum can be seen at NASA's SDO Data website.[18] Images and movies of the Sun seen on any day of the mission, including within the last half-hour, can be found at The Sun Today.

Comparison of HMI Continuum images immediately after an eclipse, and then after the sensor has re-warmed.

Communications

SDO down-links science data (K band) from its two onboard high-gain antennas, and telemetry (S-band) from its two onboard omnidirectional antennas. The ground station consists of two dedicated (redundant) 18-meter radio antennas in White Sands Missile Range, New Mexico, constructed specifically for SDO. Mission controllers operate the spacecraft remotely from the Mission Operations Center at NASA's Goddard Space Flight Center. The combined data rate is about 130 Mbit/s (150 Mbit/s with overhead, or 300 Msymbols/s with rate 1/2 convolutional encoding), and the craft generates approximately 1.5 terabytes of data per day (equivalent to downloading around 500,000 songs).[7]

Launch
AttemptPlannedResultTurnaroundReasonDecision pointWeather go (%)Notes
110 Feb 2010, 3:26:00 pmScrubbed—Weather (high winds) [19]10 Feb 2010, 4:26 pm ​(T-3:59, immediately after T-4:00 hold)40%[20]window 10:26 to 11:26a EST, attempts made at 10:26, 10:56 and 11:26
211 Feb 2010, 3:23:00 pmSuccess0 days, 23 hours, 57 minutes60%[20]Window: 10:23 to 11:23a EST
The launch Thursday, 11 February 2010 15:23:00 UTC (10:23 a.m. EST)
See also: Launch window

NASA's Launch Services Program at Kennedy Space Center managed the payload integration and launch.[21] The SDO launched from Cape Canaveral Air Force Station Space Launch Complex 41, utilizing an Atlas V-401 rocket with a RD-180 powered Common Core Booster, which has been developed to meet the Evolved Expendable Launch Vehicle (EELV) program requirements.[22]

Orbit
Animation of Solar Dynamics Observatory's trajectory from February 11, 2010 to April 11, 2010
  Solar Dynamics Observatory ·   Earth

After launch, the spacecraft was placed into an orbit around the Earth with an initial perigee of about 2,500 kilometres (1,600 mi). SDO then underwent a series of orbit-raising maneuvers which adjusted its orbit until the spacecraft reached its planned circular, geosynchronous orbit at an altitude of 35,789 kilometres (22,238 mi), at 102° W longitude, inclined at 28.5°.[23] This orbit was chosen to allow 24/7 communications to/from the fixed ground station, and to minimise solar eclipses to about an hour a day for only a few weeks a year.

Sun dog phenomenon

Moments after launch, SDO's Atlas V rocket flew past a sun dog hanging suspended in the blue Florida sky and when the rocket penetrated the cirrus cloud, shock waves rippled through the cloud and destroyed the alignment of the crystals of the sun dog making a visible rippling effect in the sky.[24]

Mission mascot - Camilla

Camilla Corona is a rubber chicken (similar to a children's toy), and is the mission mascot for SDO. It is part of the Education and public outreach team and assists with various functions to help educate the public, mainly children, about the SDO mission, facts about the Sun and space weather.[25] Camilla also assists in cross-informing the public about other NASA missions and space related projects. Camilla Corona SDO uses social media to interact with fans.

  • Camilla Corona SDO.
  • SDO 3-D schematic.
  • SDO Instruments.
  • SDO ready to be placed on Atlas rocket for launch.
  • First light image from the SDO showing a prominence eruption.
  • An image of the 2012 Transit of Venus taken by SDO.

See also

References
  1. "SDO Our Eye on the Sun" (.PDF). NASA. Retrieved February 13, 2010.
  2. Dean Pesnell; Kevin Addison (February 5, 2010). "SDO – Solar Dynamics Observatory: SDO Specifications". NASA. Archived from the original on January 30, 2010. Retrieved February 13, 2010.
  3. "SDO Satellite details 2010-005A NORAD 36395". N2YO. January 24, 2015. Retrieved January 25, 2015.
  4. Bourkland, Kristin L.; Liu, Kuo-Chia. "Verification of the Solar Dynamics Observatory High Gain Antenna Pointing Algorithm Using Flight Data". American Institute of Aeronautics and Astronautics. hdl:2060/20110015278. Cite journal requires |journal= (help)
  5. Justin Ray. "Mission Status Center: Atlas 5 SDO". Spaceflight Now. Retrieved February 13, 2010.
  6. Dean Pesnell; Kevin Addison (February 5, 2010). "SDO – Solar Dynamics Observatory: About The SDO Mission". NASA. Retrieved February 13, 2010.
  7. "Solar Dynamics Observatory — Our Eye on the Sky" (PDF). NASA. February 1, 2010. Retrieved February 13, 2010.
  8. "Solar and Heliospheric Observatory Homepage". ESA / NASA. February 9, 2010. Retrieved February 13, 2010.
  9. "Solar Dynamics Observatory — Exploring the Sun in High Definition" (PDF). NASA. Retrieved February 13, 2010.
  10. Johnson-Groh, Mara (February 11, 2020). "Ten Things We've Learned About the Sun From NASA's SDO This Decade". NASA. Retrieved March 13, 2020.
  11. Dean Pesnell; Kevin Addison (February 5, 2010). "SDO – Solar Dynamics Observatory: SDO Instruments". NASA. Retrieved February 13, 2010.
  12. Solar Physics Research Group. "Helioseismic and Magnetic Imager Investigation". Stanford University. Retrieved February 13, 2010.
  13. "SDO – EVE-Extreme ultraviolet Variability Experiment". LASP. May 27, 2010. Archived from the original on July 16, 2011. Retrieved March 12, 2020.
  14. Woods, Tom (September 12, 2007). "Extreme Ultraviolet Variability Experiment (EVE) on the Solar Dynamics Observatory (SDO) | Analogy on How the SDO EVE Measurements of the Solar Extreme Ultraviolet Irradiance will be Greatly Improved" (PDF). LASP. Archived from the original (PDF) on July 16, 2011. Retrieved September 22, 2011.
  15. Rani Gran (September 7, 2009). "First Solar Dynamic Observatory (SDO) Instrument Arrives at NASA Goddard Space Flight Center". Goddard Space Flight Center. Retrieved February 17, 2010.
  16. "AIA – Atmospheric Imaging Assembly". Lockheed Martin. February 3, 2010. Retrieved February 14, 2010.
  17. "Atmospheric Imaging Assembly – Descriptions and Manuals of Instruments, Data, and Software Packages". Lockheed Martin. Retrieved June 27, 2012.
  18. "SDO – Solar Dynamics Observatory". Goddard Space Flight Center. NASA. Retrieved March 13, 2020.
  19. Dunn, Marcia. "Stiff wind delays NASA launch of solar observatory". The Associated Press. Retrieved February 10, 2010.
  20. "AFD-070716-027" (PDF). United States Airforce, 45th Weather Squadron. Archived from the original (PDF) on June 13, 2011. Retrieved February 7, 2010.
  21. "A New Eye on the Sun" (Press release). NASA. Archived from the original on June 19, 2010. Retrieved February 13, 2010.
  22. "SDO Launch Services Program" (PDF). Retrieved February 13, 2010.
  23. Wilson, Jim (February 11, 2010). "NASA — Solar Dynamics Observatory". Retrieved February 13, 2010.
  24. Phillips, Tony (February 11, 2011). "SDO Sundog Mystery". NASA. Retrieved March 13, 2020.
  25. "SDO - Solar Dynamics Observatory". sdo.gsfc.nasa.gov. Retrieved May 3, 2018.

Instruments
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