TENACIOUS: Tomographic ENA Comprehensive Ion Optical University Satellite

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TENACIOUS Tomographic ENA Comprehensive
IonOptical University Satellite

• Robert Sheldon, UAH, T.Fritz, H.Spence,
  J.Sullivan, J.Vickers, D.Cotton, M.Alothman, BU
• Oct 29, 1998

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Tomographic ENA?!

• Is this just another fundamental physics globally
  imaging tomographic ENA multiscale constellation
  new millenium mission?
• Well,yes, except for the constellation part.
• ENAs are a new tool that is ALREADY changing the
  way we understand the Msph.
• Tomography is the next logical step.
• Tomography is the next necessary step
• Tomography is the next practical step.

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January 10-11, 1997
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(No Transcript)
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TENA FAQ

• Doesnt tomography require constellations? Not
  if the image rotates rapidly LEO
• Doesnt a rotating image blur? Not if the
  countrate is high, exposures short LEO
• Isnt the ENA flux rather small? Not if one is
  very close to the source region LEO
• Isnt the brightest ENA source at the equator?
  No, its just more photogenic, LEO is brighter.

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Fluxtube Tomography
Parallel Pot. Fluxtube ENA obs. Tenacious
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Comparison between orbits HEO LEO

• Global view of equatorial plane
• Line-of-sight projected on a plane
• Exposures minutes
• Optically thin
• Pixelsize Re
• Observer stationary
• ISEE, GEOTAIL, POLAR, IMAGE, TWINS

• Regional view of both equatorial plane LEO
• Projections on a fluxtube
• Exposures seconds
• Optically thin hgt600km
• Pixelsize 10-100 km
• Observer moving
• TIROS, ASTRID, SAC/B, POLAR

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Logical Step?

• POLAR (and all other) ENA images to date, though
  global, have been 2-D and therefore,
  model-dependent.
• Tomography removes certain ambiguities.
• Tomography enriches the observations with an
  analysis algorithm giving a big return on a small
  investment.
• Tomography complements existing imagers by making
  their data more complete.

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Comparison of ENA Physics HEO LEO

• Equatorial Ring Current 6gtLgt3, 90gtPAgt60
• Substorms (!) 7gtLgt5
• Plasmasheet intrusions (nose events)
• Calculate J from DivJ
• Global perp potentials

• Precipitating R.C. 8gtLgt3, 30gtPAgt0
• Substorms 10gtLgt5
• Ionosphere intrusions (conics, etc)
• Direct J into ionosph
• Field-aligned potentials
• High-latitude auroral ion precipitation
• Low-altitude flux tube mappings

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Necessary Step?

• ENA images are powerful data tools
• absolute Dst (and ASY) correction
• real asymmetric ring current imaged
• substorm initiation region resolved
• global electric potential imaged
• BUT current ENA images
• are projections onto a plane (2-D)
• require deconvolution of H
• can only see rlt7 Re because of H
• from HEO (global) cant resolve footpoints

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ENA Projection Geometry
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Parallel Potential Imaging

• In black(bright) aurora, ions are accelerated
  downward(upward)
• They lose(gain) energy with altitude
• When they charge-exchange with H, they are
  tagged by energy direction
• We can finally image the parallel potentials
  within a flux tube, possibly from 450 - 8000 km.
• Auroral images to complement FAST

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M-I Coupling

• Constellation, as we envision it, will give the
  5ltRlt20 magnetic field geometry with Ngt100
  satellites. (Look under MMM at //buspace.bu.edu/EP
  G/rsheldon)
• BUT the ionosphere mapping needs to connect
  r100km to r20,000 km. This is where multipoles
  errors are largest!
• If TENA can map from 450km-8000km, it can
  complete the fluxline mapping greatly reduce
  the B-field mapping error

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Auroral Imaging withNOAA-TIROS/MEPED
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TIROS AL Correlation
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Practical Step?

• Many ENA imagers have been built, some purposely,
  several flown, and a few have returned data.
• Tomographic imagers have been built (algorithms
  proven, etc.), some have almost flown.
• TENACIOUS combines the proven heritage of the
  POLAR ENA imager with the TERRIERS tomographic
  imager gt TENA

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TERRIERSIPS
Same bus Same optics Same price Swap spec
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Conclusions

• Using existing technologies, we can complete the
  ENA picture with a LEO Tomographic ENA imager.
• The possibility exists for resolving the auroral
  acceleration region, mapping flux tubes,
  observing the RC injections---filling in the
  missing link between the Magnetosphere and
  Ionosphere.
• All for about the price of a UNEX