 Solar Dynamics Observatory satellite | |
| Names | SDO |
|---|---|
| Mission type | Solar research[1] |
| Operator | NASA GSFC[2] |
| COSPAR ID | 2010-005A |
| SATCATno. | 36395 |
| Website | http://sdo.gsfc.nasa.gov |
| Mission duration | 5 years (planned) 15 years, 3 months, 6 days (elapsed) |
| Spacecraft properties | |
| Spacecraft type | Solar Dynamics Observatory |
| Manufacturer | Goddard Space Flight Center |
| Launch mass | 3,100 kg (6,800 lb) |
| Dry mass | 1,700 kg (3,700 lb) |
| Payload mass | 290 kg (640 lb) |
| Start of mission | |
| Launch date | 11 February 2010, 15:23:00UTC |
| Rocket | Atlas V 401 |
| Launch site | Cape Canaveral,SLC-41 |
| Contractor | United Launch Alliance |
| Orbital parameters | |
| Reference system | Geocentric orbit[3] |
| Regime | Geosynchronous orbit |
| Longitude | 102° West |
 Solar Dynamics Observatory patch Large Strategic Science Missions Heliophysics Division Living With a Star program | |
TheSolar Dynamics Observatory (SDO) is aNASA mission which has been observing theSun since 2010.[4] Launched on 11 February 2010, the observatory is part of theLiving With a Star (LWS) program.[5]
The goal of the LWS program is to develop the scientific understanding necessary to effectively address those aspects of the connectedSun–Earth system directly affecting life on Earth and its 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 theSun's magnetic field is generated and structured, how this stored magnetic energy is converted and released into theheliosphere andgeospace in the form ofsolar wind, energetic particles, and variations in thesolar irradiance.[6]
The SDO spacecraft was developed at NASA'sGoddard Space Flight Center inGreenbelt, Maryland, and launched on 11 February 2010, from Cape Canaveral Air Force Station (CCAFS). 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 theSolar and Heliospheric Observatory (SOHO).[8]
SDO is athree-axis stabilized spacecraft, with twosolar arrays, and two high-gain antennas, in an inclinedgeosynchronous orbit aroundEarth.
The spacecraft includes three instruments:
Data which are collected by the craft are made available as soon as possible after reception.[9]
As of February 2020, SDO is expected to remain operational until 2030.[10]
TheHelioseismic and Magnetic Imager (HMI), led fromStanford University inStanford, California, studies solar variability and characterizes the Sun's interior and the various components of magnetic activity. HMI takes high-resolution measurements of the longitudinal and vector magnetic field by viewing the entirety of the Sun's disk, with emphasis on various concentrations of metals in the Sun; specifically it passes the light (the variety of usable frequencies of which are centered on the solar spectrum's 617.3-nmFraunhofer line) through five filter instruments including aLyot filter and twoMichelson interferometers to rapidly and frequently createDoppler images andmagnetograms. The full-disk focus and advanced magnetometers improve on the capabilities ofSOHO's MDI instrument which could only focus within the line of sight with limited magnetic data.[11][12]
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.[13]
The Extreme Ultraviolet Variability Experiment (EVE) measures theSun'sextreme ultraviolet irradiance with improvedspectral resolution, "temporal cadence", accuracy, and precision over preceding measurements made byTIMED SEE,SOHO, andSORCEXPS. 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. The instrument incorporates physics-based models in order to further scientific understanding of the relationship between solarEUV variations and magnetic variation changes in the Sun.[14]
The Sun's output of energetic extreme ultravioletphotons is primarily what heats theEarth'supper atmosphere and creates theionosphere. Solar EUVradiation output undergoes constant changes, both moment to moment and over the Sun's 11-yearsolar cycle, and these changes are important to understand because they have a significant impact onatmospheric heating,satellite drag, andcommunications system degradation, including disruption of theGlobal Positioning System.[15]
The EVE instrument package was built by theUniversity of Colorado Boulder'sLaboratory for Atmospheric and Space Physics (LASP), with Dr. Tom Woods asprincipal investigator,[7] and was delivered to NASAGoddard Space Flight Center on 7 September 2007.[16] The instrument provides improvements of up to 70% in spectral resolution measurements in the wavelengths below 30 nm, and a 30% improvement in "time cadence" by taking measurements every 10 seconds over a 100%duty cycle.[15]
The Atmospheric Imaging Assembly (AIA), led from theLockheed Martin Solar and Astrophysics Laboratory (LMSAL), provides continuous full-disk observations of the solarchromosphere andcorona in sevenextreme 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 theSmithsonian Astrophysical Observatory (SAO).[17] Since beginning its operational phase on 1 May 2010, AIA has operated successfully with unprecedented EUV image quality.
| AIA wavelength channel | Source[18] | Region of solar atmosphere | Characteristic temperature |
|---|---|---|---|
| White light (450nm) | continuum | Photosphere | 5000K |
| 170nm | continuum | Temperature minimum,photosphere | 5000K |
| 160nm | C IV + continuum | Transition region and upperphotosphere | 105 and 5000K |
| 33.5nm | Fe XVI | Active regioncorona | 2.5×106K |
| 30.4nm | He II | Chromosphere andtransition region | 50,000K |
| 21.1nm | Fe XIV | Active regioncorona | 2×106K |
| 19.3nm | Fe XII, XXIV | Corona and hotflareplasma | 1.2×106 and 2x107K |
| 17.1nm | Fe IX | Quietcorona, uppertransition region | 6.3×105K |
| 13.1nm | Fe VIII, XX, XXIII | Flaring regions | 4×105, 107 and 1.6×107K |
| 9.4nm | Fe XVIII | Flaring regions | 6.3×106K |
Photographs of the Sun in these various regions of the spectrum can be seen at NASA's SDO Data website.[19] Images and movies of the Sun seen on any day of the mission, including within the last half-hour, can be found atThe Sun Today.
SDO down-links science data (K-band) from its two onboardhigh-gain antennas, andtelemetry (S-band) from its two onboardomnidirectional antennas. The ground station consists of two dedicated (redundant) 18-meter radio antennas inWhite Sands Missile Range,New Mexico, constructed specifically for SDO. Mission controllers operate the spacecraft remotely from theMission Operations Center atNASAGoddard Space Flight Center. The combined data rate is about 130 Mbit/s (150 Mbit/s with overhead, or 300 Msymbols/s with rate 1/2convolutional encoding), and the craft generates approximately 1.5Terabytes of data per day (equivalent to downloading around 500,000 songs).[7]
| Attempt | Planned | Result | Turnaround | Reason | Decision point | Weather go (%) | Notes |
|---|---|---|---|---|---|---|---|
| 1 | 10 Feb 2010, 3:26:00 pm | Scrubbed | — | Weather (high winds)[20] | 10 Feb 2010, 4:22 pm (T-3:59, immediately after T-4:00 hold) | 40%[21] | window 10:26 to 11:26 EST, attempts made at 10:26, 10:56 and 11:26 EST |
| 2 | 11 Feb 2010, 3:23:00 pm | Success | 0 days 23 hours 57 minutes | 60%[21] | Window: 10:23 to 11:23 EST |
NASA'sLaunch Services Program atKennedy Space Center managed the payload integration and launch.[22] The SDO launched fromCape Canaveral Space Launch Complex 41 (SLC-41), utilizing anAtlas V-401 rocket with aRD-180 poweredCommon Core Booster, which has been developed to meet theEvolved Expendable Launch Vehicle (EELV) program requirements.[23]
Sun dog phenomenon: Moments after launch, SDO's Atlas V rocket penetrated acirrus cloud which created visibleshock waves in the sky and destroyed the alignment of ice crystals that were forming asun dog visible to onlookers.[24]
After launch, the spacecraft was deployed from the Atlas V into anorbit around theEarth with an initialperigee of about 2,500 km (1,600 mi).[25]
SDO then underwent a series of orbit-raising maneuvers over a few weeks which adjusted its orbit until the spacecraft reached its plannedcircular,geosynchronous orbit at an altitude of 35,789 km (22,238 mi), at 102° Westlongitude, inclined at 28.5°.[25] This orbit was chosen to allow 24/7 communications to/from thefixed ground station, and to minimisesolar eclipses to about an hour a day for only a few weeks a year.
Camilla Corona is arubber chicken and is the missionmascot for SDO. It is part of theEducation and public outreach team and assists with various functions to help educate the public, mainly children, about the SDO mission, facts about the Sun andSpace weather.[26] Camilla also assists in cross-informing the public about otherNASA missions and space related projects. Camilla Corona SDO usessocial media to interact with fans.
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In 2021, the United States Postal Service released a series of foreverstamps using images of the Sun taken by the Solar Dynamics Observatory.[27]
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