1. 1 TENACIOUS: Tomographic ENA Comprehensive Ion+Optical University Satellite Robert Sheldon, UAH, T.Fritz, H.Spence, J.Sullivan, J.Vickers, D.Cotton, M.Alothman, BU Oct 29, 1998

2. 2/17 Tomographic ENA?! u Is this just another fundamental physics globally imaging tomographic ENA multiscale constellation new millenium mission? u Well,yes, except for the constellation part. u ENAs are a new tool that is ALREADY changing the way we understand the M’sph. u Tomography is the next logical step. u Tomography is the next necessary step u Tomography is the next practical step.

3. 3/17 January 10-11, 1997

4. 4/17

5. 5/17 TENA FAQ u Doesn’t tomography require constellations? Not if the image rotates rapidly = LEO u D oesn’t a rotating image blur? Not if the countrate is high, exposures short = LEO u I sn’t the ENA flux rather small? Not if one is very close to the source region = LEO u I sn’t the brightest ENA source at the equator? No, it’s just more photogenic, LEO is brighter.

6. 6/17 Fluxtube Tomography Parallel Pot. Fluxtube ENA obs. Tenacious

7. 7/17 Comparison between orbits: HEOLEO u Global view of equatorial plane u Line-of-sight projected on a plane u Exposures ~minutes u Optically thin u Pixelsize ~ Re u Observer ~ stationary u ISEE, GEOTAIL, POLAR, IMAGE, TWINS u Regional view of both equatorial plane +LEO u Projections on a fluxtube u Exposures ~seconds u Optically thin h>600km u Pixelsize ~10-100 km u Observer moving u TIROS, ASTRID, SAC/B, POLAR*

8. 8/17 Logical Step? u POLAR (and all other) ENA images to date, though global, have been 2-D and therefore, model-dependent. u Tomography removes certain ambiguities. u Tomography enriches the observations with an analysis algorithm giving a big return on a small investment. u Tomography complements existing imagers by making their data more complete.

9. 9/17 Comparison of ENA Physics HEOLEO u Equatorial Ring Current 6>L>3, 90>PA>60 u Substorms (!) 7>L>5 u Plasmasheet intrusions (nose events) u Calculate J || from DivJ u Global perp potentials u Precipitating R.C. 8>L>3, 30>PA>0 u Substorms 10>L>5 u Ionosphere intrusions (conics, etc) u Direct J || into ionosph u Field-aligned potentials u High-latitude auroral ion precipitation u Low-altitude flux tube mappings

10. 10/17 Necessary Step? u ENA images are powerful data tools –absolute Dst (and ASY) correction –real asymmetric ring current imaged –substorm initiation region resolved –global electric potential imaged u BUT current ENA images: –are projections onto a plane (2-D) –require deconvolution of [H] –can only see r<7 Re because of [H] –from HEO (global) can’t resolve footpoints

11. 11/17 ENA Projection Geometry

12. 12/17 Parallel Potential Imaging u In black(bright) aurora, ions are accelerated downward(upward) u They lose(gain) energy with altitude u When they charge-exchange with [H], they are “tagged” by energy & direction u We can finally image the parallel potentials within a flux tube, possibly from 450 - 8000 km. u Auroral images to complement FAST

13. 13/17 M-I Coupling u “Constellation”, as we envision it, will give the 5 100 satellites. (Look under MMM at //buspace.bu.edu/EPG/rsheldon) u BUT the ionosphere mapping needs to connect r=100km to r=20,000 km. This is where multipoles & errors are largest! u If TENA can map from 450km-8000km, it can complete the fluxline mapping & greatly reduce the B-field mapping error

14. 14/17 Auroral Imaging with NOAA-TIROS/MEPED

15. 15/17 TIROS AL Correlation

16. 16/17 Practical Step? u Many ENA imagers have been built, some purposely, several flown, and a few have returned data. u Tomographic imagers have been built (algorithms proven, etc.), some have almost flown. u TENACIOUS combines the proven heritage of the POLAR ENA imager with the TERRIERS tomographic imager => TENA

17. 17/17 TERRIERS+IPS Same bus Same optics Same price Swap spec

18. 18/17 Conclusions u Using existing technologies, we can complete the ENA picture with a LEO Tomographic ENA imager. u 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. u All for about the price of a UNEX