SOHO Mission Extension

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SOHO Mission Extension

• 2 ¾ years April 2007 December 2009

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Outline

• Recent Science Highlights
• Why keep SOHO going?
• Instruments Status
• Spacecraft Status
• Some Statistics

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Science Highlights

• Over 2400 papers in refereed literature
• Representing the work of more than 2300
  scientists

• TSI continuity over two solar cycles
• Limit on solar forcing of historical
  terrestrial climate
• Improved precision of solar interior models
• Rotation of the deep interior
• Rotation rate variations at the tachocline
• Equatorward migration of zonal flows
• Helioseismic imaging of the far side of the Sun
• Helioseismic response to surface events
• Solar Subsurface Weather
• Solar cycle variations in the size of the Sun
• The magnetic carpet
• Nanoflares
• Blinkers and explosive events
• Coronal dimming
• Flows as a function of temperature
• Source of solar wind in coronal holes
• Lower wind speed in low-latitude coronal holes
• Origin of solar wind in coronal hole funnels
• Long-period oscillations in polar plumes

• 3-D pB imaging of CMEs
• Coronal waves
• Coronal inflows
• Coronal He abundance
• Tracing a CME/ICME from Sun to Saturn
• Catalog summarizing properties of over 10,000
  CMEs
• Multi-stage SEP acceleration and CME connection
• Evidence for reconnection-driven heating in
  post-CME structures
• Discovery of heavy ion depletion events
• Discovery of interplanetary highway for
  energetic particles
• Deceleration of H flow at heliopause
• Interstellar compass from different directions
  of H and He flow
• Discovery of a comet, undetected in the visible
  from UV signature of ice sublimation
• Discovery of comets shadow
• Over 1100 comets discovered, over 75 by amateurs
  using freely available LASCO data

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Data Availability

• Completely open data policy
• The Sun is shining for everybody
• All data and software available through SOHO
  archives and PI sites
• IDL Solarsoft routines
• Calibration
• Analysis

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Solar Interior Structure, Flows, Far
Side Imaging, Magnetic Fields

• Sound speed variations relative to a standard
  solar model.
• Solar cycle variations in the sub-photospheric
  rotation rate.
• Solar meridional circulation and differential
  rotation.
• Sunspots and plage contribute to solar irradiance
  variation.
• MHD model of the magnetic structure of the
  corona.
• Synoptic map of the subsurface flows at a depth
  of 7 Mm.
• EIT image and magnetic field lines computed from
  the photospheric field.
• Active regions on the far side of the sun
  detected with helioseismology.
• Magnetic connectivity in sunspots.
• Sound speed variations and flows in an emerging
  active region.

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Improved Far-side Imaging

• New, improved analysis technique of helioseismic
  holography allows to see the entire far side of
  the Sun, including the poles.
• Combines 2-2 skip and 1-3 skip methods

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On-line CME Cataloghttp//cdaw.gsfc.nasa.gov/CME_
list/

• Properties of gt 10,000 CMEs observed by LASCO
  since launch
• Central position angle
• Angular width
• Heliocentric distance with time
• Average speed
• Acceleration
• Movies

Yashiro et al. 2004, GRL, Vol. 109, A7
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Solar Activity and Space Weather
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Why Keep SOHO Going?

• To complete cycle 23 and observe the rise of the
  next solar cycle
• New science opportunities by combining SOHO
  observations and complementary observations from
  STEREO and Solar-B.
• Cross-calibration of EIT and MDI with AIA and HMI
  on SDO in 2009
• Space Weather SOHOs space weather capabilities
  will remain unique (even after the launch of
  STEREO in 2006)
• LASCO will remain the only coronagraph on the
  Sun-Earth line to detect halo CMEs

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Joint Science with Solar-B

• Solar-B highly complementary instruments
• 50 cm optical telescope with vector magnetic
  field capabilities
• Combination with EIT, CDS, LASCO ? origin of CMEs
• Soft X-ray telescope (SXI) to image the hot
  corona (3-6 MK plasma)
• Complementing the cooler EUV channels of EIT
  (60K, 1, 1.5, 2 MK)
• EUV imaging spectrometer (EIS) operating in the
  170-210Å and 250-290Å range
• Higher temperature coronal lines
• Connection to chromosphere and transition region
  SUMER and CDS
• Plasma diagnostics
• Thermal structure of loops where are loops
  heated?
• Only CDS and SUMER cover lower temperature lines
  for Differential Emission Measure (DEM) studies
• Transition region dynamics Interface between
  lower atmosphere and corona
• No other UV or EUV spectrometer covering this
  important temperature regime in development or
  even in planning, until the Solar Orbiter epoch,
  some 10 years hence

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3rd Eye of STEREO

• Addition of third viewpoint (LASCO) can eliminate
  critical ambiguities in reconstructing CME
  morphology and CME mass
• STEREO spacecraft separate at a rate of 22.5 per
  year
• Area of overlap decreases and ambiguities
  increase as multiple features begin to fall along
  the same line of sight for one spacecraft or the
  other
• Adding EIT will double the length of time over
  which reconstructions of EUV loop morphology will
  be possible
• Multipoint SEP sampling
• Measuring the composition and energy spectra of
  energetic particle events from multiple locations
  will narrow the range of acceleration geometries

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Coronal Tomography 3 vs. 2

• Assume a flux-rope CME model
• How does it look to 3 coronagraphs?
• Just 2 coronagraphs

Original
Reconstruction
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Coronal Tomography 3 vs. 2

• Assume a flux-rope CME model
• How does it look to 3 coronagraphs?
• 3 in ecliptic

Original
Reconstruction
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Coronal Tomography 3 vs. 2

• Assume a flux-rope CME model
• How does it look to 3 coronagraphs?
• 2 in ecliptic, 1 over pole

Original
Reconstruction
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Instrument Status 1/2

• GOLF nominal
• VIRGO nominal
• MDI nominal
• 100,000,000 exposures
• Mean annual degradation in throughput 4
• SUMER
• Detector A can only be operated with reduced
  spatial resolution (row averaging)
• Detector B fully operational and will remain
  radiometrically calibrated for another 2-3 years,
  based on extrapolation from past performance
  (campaign mode operations)
• Azimuthal pointing mechanism has to be operated
  in high-current mode (since 1997)
• CDS nominal
• EIT nominal
• Instrument throughput decrease stopped and even
  reversed since 2003

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Instrument Status 2/2

• UVCS
• O VI detector appears to develop same symptoms as
  SUMER detector A (row averaging)
• Ly-a detector has been off most of the time since
  1998 because of high HV current has been
  recommissioned in summer 2005 and is fully
  operational.
• LASCO C2 C3 nominal
• Instrument sensitivity decreased less than 3.5
  in 8 years, i.e. lt 0.5 / year
• C1 lost in 1998 (FPI damaged during deep freeze)
• SWAN nominal
• CELIAS
• MTOF, STOF, SEM nominal
• STOF impaired since October 1996 (HV power supply
  hardware failure)
• COSTEP
• EPHIN nominal
• LION impaired since shortly after launch, with
  increased noise.
• ERNE nominal

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Spacecraft Status

• S/C is healthy and performs entirely within
  specifications
• Hardware Failures
• 1997 April 23 Loss of fast loop of receiver 1
• 1998 Sep/Dec Loss of all 3 gyros
• 2002 March 7 Loss of battery 1
• 2003 May High Gain Antenna Z motor stuck
• causes telemetry keyholes every 3 months, but
  manageable with on-board patch for intermittent
  recording of selected packets and extra DSN
  support
• 2004 April 21 Loss of Fine Sun Pointing
  Attitude Anomaly Detector (FSPAAD)
• Reserves
• Remaining fuel 118 kg (yearly use lt 2 kg)
• Current margin 9.83 A (main bus peak current 37
  A)
• Solar array degradation after 123 months 18.25
  (1.79 per year budget was 4 per year)
• Redundant subsystems

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Solar Array Degradation
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Hydrazine Reserve
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SOHO in Popular Magazines
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SOHO and the Popular Imagination
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SOHO and the Popular Imagination
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Lies, Damn Lies, Statistics, Web Statistics

• SOHO Real-time display
• SOHO Real-time Screen Saver
• Hot Shots and Weekly Picks
• Total downloads 150 TByte

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Publications in Refereed Journals

• gt 2400 papers in refereed literature since
  launch, not counting conference proceedings,
  which usually double the number
• gt 2300 authors and co-authors

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Summary

• There are no known limitations which should
  prevent SOHO from operating through the end of
  2009 with almost all of its complement of
  instruments operating at full scientific
  capability.

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10 Years of SOHO

• gt2400 papers in refereed literature
• gt2300 scientists appear in the author lists of
  those papers
• gt140 Ph.D. thesis
• gt1100 comets
• gt2,000,000 command blocks sent to the spacecraft
• gt100,000,000 exposures by MDI
• gt16,000,000 distinct hosts served by SOHO web
  servers
• gt275,000,000 web page requests served by SOHO web
  servers
• gt16 TByte in SOHO archive
• gt150 TByte of data served

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UFOs
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UFOs
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UFO Frenzy on CNN