Outline

1
Outline

• Spacecraft Status (MV)
• Payload Status and Science Highlights (BF)
• SOHO Science Operations (SH)
• SOHO Data System (LS)
• SOHO Science Communication (PB)
• Why keep SOHO going? (BF)
• AOB

2
SOHO Payload Status
3
GOLFPI Alan Gabriel (IAS)

• Instrument is nominal and giving no reason for
  concern.
• Progressive, expected fall-off in throughput is
  not worrying, and will not prevent GOLF
  completing the cycle.
• Continuous observations on red wing since
  recovery
• rotation of quarter-wave plate would require many
  hours of real-time commanding
• noise level in red and blue wing very similar
• GOLF team wants to avoid any risk of getting
  stuck in the middle, therefore continue on red
  wing
• Reserves redundant channel validated, but unused.

4
VIRGOPI Claus Fröhlich (PMOD/WRC)

• All instruments (PMOD, DIARAD, SPM, LOI) are
  nominal.
• Long-term changes of TSI have been re-analyzed.
• With new calibration, the problem with the
  early increase seems to be solved.

5
MDIPI Phil Scherrer (Stanford Univ.)

• Nominal
• Over 58 million exposures since launch (60
  million ground life test shutter moves)
• Instrument performance has been continually
  characterized since launch.
• Changes in MDI Front Window Transmission ? 2.3
  per year
• changes temperature gradient of the front window
  (about 2 per year)
• changes focus
• 9 focus positions
• started at 1, now at 4
• changes plate scale
• annual variations a few parts in 104
• jumps caused by changing focus about 0.1
• important to include these changes in
  helioseismic analyses (mode identification,
  leakage matrix)
• Other calibration details such as image
  distortion, detector misalignment and MTF
  variation now well characterized and documented.

6
MDI Shutter Performance

• Detected in April 2001 that starting on 12 March
  2000 the std dev of the exposure time has grown
  from 12 ?s to about 40 ?s (pre-launch
  requirements 50 ?s)
• Problem started abruptly and has developed slowly
  since (something stuck in a bearing?)
• Now monitoring this quantity daily to see if
  anything needs to be done
• Affects magnetic field noise (slightly up), and
  low degree modes (l0-3)
• Does not affect lgt4 modes

7
MDIPI Phil Scherrer (Stanford Univ.)

• Nominal
• Over 58 million exposures since launch (60
  million ground life test shutter moves)
• Instrument performance has been continually
  characterized since launch.
• Changes in MDI Front Window Transmission ? 2.3
  per year
• changes temperature gradient of the front window
  (about 2 per year)
• changes focus
• 9 focus positions
• started at 1, now at 4
• changes plate scale
• annual variations a few parts in 104
• jumps caused by changing focus about 0.1
• important to include these changes in
  helioseismic analyses (mode identification,
  leakage matrix)
• Other calibration details such as image
  distortion, detector misalignment and MTF
  variation now well characterized and documented.

8
MDI Front Window Transmission
9
MDI Front Window Temperature
10
MDI Focus Changes
11
MDI Plate Scale Changes
12
SUMERPI Klaus Wilhelm (MPAe)

• Both detectors near end of calibrated lifetime
• Operating at highest voltage level
• Campaign-mode observations with off-limb
  targets
• On-disk observations only for special events and
  with express authorization of the PI
• Several years of operation possible, if continued
  to run in campaign mode and careful target
  selection.
• Mechanisms nominal, except
  E-W
  telescope drive.
• Pointing in high-current mode
  possible with constraints, but no
  raster scans allowed.

13
CDSPI Richard Harrison (RAL)

• Continues to operate nominally with
  the detector systems showing no
  signs of degradation above
  what is expected.
• NIS detector
• progressive burn-in in bright lines, which
  is expected
• gives no cause for concern
• burn-in is carefully monitored and folded into
  the intensity calibration
• pre-incident NIS calibration well understood.
• post-recovery change in sensitivity and its
  long-term variation is currently being quantified
  by comparing with SEM, SERTS and quiet Sun data.

14
CDSPI Richard Harrison (RAL)

• GIS
• Detectors nominal
• Slit mechanism anomaly, still under investigation
• Probably software/timing problem with encoder
• Has existed for a number of years without
  noticeable impact
• All voltage levels currents remain stable and
  well within tolerances.
• All critical instrument temperatures remain
  stable. Some temperature monitors close to
  thermal blankets show increases due to expected
  deterioration of the blankets this causes no
  major concern.
• All mechanisms continue to operate
  satisfactorily.
• The ground system is fully functional and was
  recently upgraded.

15
EITPI Jean-Pierre Delaboudinière (IAS)

• EIT is nominal and giving no reason for concern.
• EIT instrument has a decreasing response, but
  understood now and well modeled.
• Two major components
• absorption of EUV by a surface contaminant
• reduction in charge collection efficiency (CCE)
  in CCD due to EUV induced device damage
• Contamination effect has largely disappeared
  after SOHO recovery
• CCE loss can be tracked by calibration lamp exp.
  taken regularly throughout the mission.

16
EITPI Jean-Pierre Delaboudinière (IAS)

• Detector degradation now understood and very well
  modeled.
• Present exposure times range from 7 sec to 2 min,
  with the vast majority taken in Fe XII 195 at 12
  sec.
• The signal-to-noise ration is still very high.
• Expected that future trends in the loss of
  sensitivity will continue as seen over the last 3
  years.
• This would result in another factor 5-8 decrease
  over the next 5 years.
• Possible to mitigate this loss through extended
  CCD bakeouts.
• Even with this loss, reasonable exposure times
  would still yield sufficiently high S/N as to
  have minimal effect upon the quantitative science
  and almost no effect on morphological studies
  (e.g. CME initiation).

17
UVCSPI John Kohl (SAO)

• UVCS is expected to continue performing at full
  scientific capability for many more years.
• O VI Detector
• No significant decrease in efficiency in O VI
  portion of this detector.
• Ly-? portion showed 5 to 10 loss of efficiency
  on parts of detector at a high voltage of 200 EU
• Voltage increase from 200 to 205 EU in January
  2000 restored full efficiency
• Max of 250 EU allows nine additional increases of
  5 EU.
• Voltage increase of 5 EU every 1.2 years is
  expected to keep the efficiency loss at lt 5.
• Ly-? Detector
• Has been turned off since November 1998 because
  it draws about 50 of the maximum current and has
  regions of elevated background.
• This problem is NOT related to the mission
  interruption.
• Still operational and treated as a back-up
  detector for Ly-? observations.

18
UVCSPI John Kohl (SAO)

• All mechanisms nominal, except Ly-? channel
  grating drive, which continues to degrade use is
  restricted, but scientific function is
  redundantly provided by O VI channel grating
  drive.
• Star observations and Spartan 201 have shown the
  UVCS radiometric calibration to be stable within
  lt10 for entire mission.
• No flight software changes have been needed.

19
LASCOPI Russ Howard (NRL)

• C2 and C3 are nominal.
• C1 has been lost (Fabry-Perot wedge defect).
• Telemetry of C1 is used by C2, C3, and EIT,
  greatly enhancing their scientific output.
• No degradation in instrument temperature,
  voltages, or current draws are seen.

20
SWANPI Jean-Loup Bertaux (SA)

• Periscope motors OK
• H Cells absorbing power is decreasing (as
  expected)
• Z sensor 85 of initial value
• -Z sensor 25 of initial value
• continuous calibration efforts

21
CELIAS / COSTEP / ERNEPIs Peter Bochsler (Univ.
Bern), Horst Kunow (Univ.Kiel), Jarmo Torsti
(Univ. Turku)

• All three unaffected by mission interruption
• CELIAS
• MTOF/PM, STOF/HSTOF, SEM nominal
• CTOF impaired since October 1996 due to hardware
  failure in HV supply
• COSTEP
• EPHIN nominal
• LION front detectors noisy (since launch)
• partially operational for higher fluxes
• separation of e and p possible during solar
  events
• ERNE
• Both LED and HED nominal
• Increasing temperatures due to thermal insulation
  degradation a cause for concern, but recent
  X-panel heater changes have improved the
  situation.

22
Summary
? There are no known limitations which should
prevent SOHO from completing an entire solar
cycle with almost all of its complement of
instruments operating at full scientific
capability.

• VIRGO - nominal
• GOLF - nominal
• MDI - nominal
• SUMER - nominal1
• CDS - nominal
• EIT - nominal

• UVCS - nominal
• LASCO - nominal (C1 lost)
• SWAN - nominal
• CELIAS - nominal (CTOF impaired)
• COSTEP - nominal (LION impaired)
• ERNE - nominal

1 SUMERs detectors near end of calibrated life
and restricted pointing capabilities ? campaign
mode observations
23
Science Highlights

• Over 1100 papers in refereed literature
• Representing the work of more than 1500
  scientists

• TSI continuity over two solar cycles
• Continued search for g -modes
• Improved precision of solar interior models
• 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
• The magnetic carpet
• Nanoflares
• Coronal dimming
• Flows as a function of temperature
• Low coronal hole temperatures, MHD wave origin of
  wind
• Source of solar wind in coronal holes
• Lower wind speed in low-latitude coronal holes
• Coronal He abundance
• Low-FIP abundances enhanced in some parts of
  coronal streamers
• Plasma b 1 in some streamers
• Evidence for coronal inflows
• Coronal waves

• Evidence for magnetic reconnection occurring for
  hours after flares
• Evidence for reconnection inflows
• Multi-stage SEP acceleration and CME connection
• Long-period oscillations in polar plumes
• Confirmation of faster wind outflows between
  coronal plumes than in them
• Evidence for reconnection-driven heating in
  post-CME structures
• Spectroscopic determination of helical motions,
  heating in structures trailing CMEs
• Solar wind source scale inferred to be 1 Mm
• No short-supershort FIP effect on wind
  fractionation
• Over 380 comets discovered, over 75 by amateurs
  using freely available LASCO data
• Discovery of a comet, undetected in the visible
  from UV signature of ice sublimation
• Discovery of comets shadow
• Deceleration of H flow at heliopause

24
Subsurface Structure of Sunspots

• How can sunspots last for several weeks without
  flying apart?
• Models inflows
• Observations at surface outflows!
• Applying the new technique of acoustic tomography
  to high quality MDI data provided first images of
  the thermal structure and flows around sunspots
  below the surface.
• Strong inward flows right underneath the surface
• Sunspots surprisingly shallow become warmer than
  surroundings already some 4000 km below surface

Zhao et al. 2001, ApJ 557, 384
25
UV/EUV Spectral Atlas 670 1609Å

• Best ever analysis of the ultraviolet spectrum of
  the Sun from 670 to 1609 Å
• 1100 emission lines identified
• 150 of these had not been recorded or identified
  before
• Particular improvement for ??????Å
• Atlas contains spectra of the quiet Sun, a
  coronal hole, and a sunspot.
• Rich source of new diagnostic tools to study
  physical parameters in the solar atmosphere.
• Important product both for solar and stellar
  communities.

Curdt et al. 2001, AA 375, 591
26
Inflows in the Corona

• LASCO discovery inflows at distances of 2 - 4
  R?
• Speeds 20 km/s to over 100 km/s
• Mostly decelerated or nearly uniform inward
  motion
• Inflow rate correlated with the occurrence of
  non-polar coronal holes and other indicators of
  nonaxisymmetric open flux.
• Origin?
• Gradual closing-down of magnetic flux dragged
  outward by CME? Collapsing field lines?
• Key role for balance of Suns open magnetic flux

Sheeley Wang 2001, ApJ 562, L107
27
CMEs Current Sheets Flux Ropes

• UVCS, EIT, and LASCO observed a CME on 23 March
  1998 that exhibited narrow, extremely hot (gt
  6x106K) plasma emitting in Fe XVIII.
• This emission occurred a the expected location of
  a current sheet predicted by the model of Forbes
  Lin (2000).
• Fe XVIII emission occurs between the post-CME
  arches on the limb and the CME itself.
• The current sheet predicted by Forbes Lin has a
  lifetime and spatial scale that is consistent
  with the spectroscopic constraints.

28
The Event of 5 November 2001Largest Proton
Storm of the Current Solar Cycle

29
SOHO and Comets

• As of 2 Jan 2002, SOHO has discovered a total of
  386 comets (LASCO 385, SWAN 1)
• Over 25 of all comet discoveries since 1760 come
  from SOHO.
• Over 75 of the comets were discovered by
  amateurs in our real-time images freely available
  on the Internet.
• Studies on dust-production of sungrazers
• tails straight and narrow
• no evidence for Lorentz force on charged dust
• tails include a major population of
  sub-micron-sized dielectric grains (most probably
  silicates)
• UV Spectroscopy of a Sungrazing CometComet
  C/2001 C2 (SOHO-294)
• Outgassing rate ? 100 kg/s
• Size of comet nucleus ? 10 m
• Densities
• 10,000 particles/cm3 at 4.82 R?
• 86,000 particles/cm3 at 3.32 R?

Uzzo et al. 2001, ApJ 558, 403
30
Water Production of Comet C/1999 S4
(LINEAR)

• SWAN observed hydrogen coma of comet C/1999 S4
  from end of May through mid August 2000
• Obtained systematic set of water production rates
  for this well documented event of complete
  fragmentation of a cometary nucleus.
• Total amount of water released 3.3x109 kg
• Combining the SWAN measurements with Hubble
  observations of the last fragements yields
  estimate for size of comet r 375 m
• and thus to estimate of density ?15
  kg/m3 (surprisingly low!)

SWAN observations of Comet LINEAR a month before
it disintegrated.
Fragments of Comet Linear seen as mini-comets by
HST on 5 August 2000.
Mäkinen et al. 2001, Science 292, 1326
31
Synoptic Imaging of the
Far Side of the Sun

• Synoptic maps combining observed magnetic flux
  from the near-side of the Sun with proxy flux
  from the far-side inferred from sound travel time
  analysis
• Data medium-l MDI data
• Two-skip helioseismic holography (Lindsey
  Braun, Science 2000)
• Updated daily

32
Synoptic Imaging of Active Regions
on the Far Side of the Sun

• Full sky Ly-? maps by SWAN
• Enhanced UV radiation from active regions make
  interstellar hydrogen glow (searchlights in
  fog)
• CNES sponsored study to make this an operational
  space weather tool

• April 2001 implemented software that produces
  synoptic full sky Ly-? 3 times a week, in which
  new active regions are easily identifiable.

33
Outline

• Spacecraft Status (MV)
• Payload Status and Science Highlights (BF)
• SOHO Science Operations (SH)
• SOHO Data System (LS)
• SOHO Science Communication (PB)
• Why keep SOHO going? (BF)
• AOB