Solar and Space Physics Space Science in the Twenty-First Century -- Imperatives for the Decades 1995 to 2015 (1988) / Chapter Skim
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Appendix B: Excerpts from the Final Report of the Jupiter Polar Orbiter Workshop
Appendix B: Excerpts from the Final Report of the Jupiter Polar Orbiter Workshop
Pages 79-108
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From page 79... ...
With polar orbits designed to minimize radiation exposure and with realistically conceivable improvements in radiation hardening, a mission to mine Jupiter's wealth of planetary information might be possible.
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From page 80... ...
The inner jovian system is of interest to a broad range of planetary science; therefore, the workshop participants and contributors represented diverse disciplines. This report describes two mission designs that the workshop participants considered.
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From page 81... ...
~ In support of the above recommendations, NASA should undertake an advanced study project to determine achievable radiation hardening to set total flux limits for mission designs. ~ In view of JPO's likely technical feasibility and its potential for rich scientific yields as assessed by the workshop, NASA should organize a science working team to explore more fully the issues of feasibility and science yields and, if the workshop's preliminary assessment is confirmed, to determine an optimum mission design.
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From page 82... ...
The orbit allows one or more vertical plunges through the northern and southern Alfven wings and To's wake. The orbit thoroughly probes the energetic particle populations and the off-equatorial region where plasma waves grow.
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From page 83... ...
The high-periapsis option fails to provide in situ Jupiter aeronomy data, high-resolution Jupiter atmosphere data, high-order magnetic and gravitation field data, and low-altitude auroral particle, radio, and plasma wave data. Remote sensing cannot supply these.
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From page 84... ...
In situ Io torus G G Off-equatorial plasma waves G G Close Io encounters F G Io-torus coupling F G Torus-Jupiter coupling G F Radiation belts G F "Ring currents" G G Europa G G Amalthea G F Ring G F Low-altitude auroral G B Particles and plasma and radio waves G ~ B Birkeland currents G B Jupiter aeronomy G B High-resolution Jupiter atmosphere G B High-order magnetic field moments G B High-order gravity moments G B Synoptic UV, x-ray aurora and torus F G Imaging fast neutrals F G Reaction time and mission lifetime F G NOTE: G = Good; F = Fair; B = Bad. first-generation scientific problems.
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From page 85... ...
A Jupiter Polar Orbiter mussion will substantially advance comparative planetology by providing in situ data from the atmospheres and ionospheres of Jupiter and lo and by greatly increasing the coverage and resolution of the unaging and remote sensing of these objects. Supplying these data ~s certainly- one of the' remaining major tasks and major challenges confronting NASA.
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From page 86... ...
Europa's cracked, icy surface was observed only poorly by Voyager, and major questions remain concerning the age of the surface, the nature of the processes causing the tectonic patterns evident In the surface, the extent and depth of the ice layer, and whether liquid water can exist beneath the visible surface. The Galileo orbiter wall make several close (<1000 km)
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From page 87... ...
All these numbers are uncertain, based as they are on extensive theoretical modeling of two electron density profiles from Pioneer 10 and the ground-based and Voyager identifications of sulfur dioxide frost and vapor. Many of the remarks about Jupiter's upper atmosphere apply to lo as well.
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From page 88... ...
The torus plasma, whose source is To, corotates with Jupiter and consequently sweeps by To at a relative velocity of more than 50 km/~. The interaction between a flowing plasma and a conducting body can take many forms, as we know from the diverse ways in which planets and the Moon interact with the solar wind.
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From page 89... ...
These sputtered neutrals are expected to form a cloud extending well away from To. Particles in this cloud are ionized to form the plasma torus.
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From page 90... ...
Remote sensing of ions and neutrab when the spacecraft is far from the torus could also be unport ant. Hith-E:nergy Particles The inner magnetosphere of Jupiter contains the highest energy, locally accelerated particles in the solar system and the greatest variety of energetic particle source, acceleration, transport, and loss mechanisms within reach of in situ measurements.
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From page 91... ...
Therefore, it ~ essential to measure angular distributions of all energetic ions as a function of both latitude and radial distance. The highest energy particles in the jovian magnetosphere gain their energy by conserving their first two adiabatic invariants while violating the third and moving inward.
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From page 92... ...
The consequences are radio waves, particle precipitation, and auroras. Besides producing provocative visual and ultraviolet dim plays, auroras can inject significant mnounts of energy to the ups per ionosphere and atmosphere, affecting ionospheric conductivity and atmospheric circulation.
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From page 93... ...
Satellite Sweeping Signatures The molated satellite sweeping signatures obtained by past flybys have served as valuable diagnostics of diffusive particle behavior, and obtaining multiple orbital crominge would allow refinement of this very fruitful method. With repeated crossings of the appropriate ~shells, satellite sweeping signatures from the ring, Mete, Adrastea, Amalthea, Thebe, lo, Europa, Ganymede, and possibly Callmto can be investigated ~ a function of longitude.
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From page 94... ...
Inner Zone With the low-periapsis orbit, the motion of the argument of perigee causes the orbit to intersect the equator at all altitudes from perijove to apojove, and also to cross the ~ ~ 6 lines of force at progressively higher latitudes. It would not take an unreasonable spacecraft lifetime to obtain a complete radial and latitude mapping of particle fluxes and behavior.
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From page 95... ...
, the hectometric wavelength emission (# ~ MHz) , but many major questions such as their variOU8 source locations or enussion mechanisms will not be answered because of the lack of sufficient angular resolution, less than optimal frequency spacing, or lack of simultaneous polarization and direction finding measurements.
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From page 96... ...
The Voyager observations of the jovian rings provided a gross characterization of their spatial location and limited data on the size of the m~cron-s~zed particles. The Galileo spacecraft mission will obtain useful additional information about the Jovian rings by observing the rn~cron-sized population during solar occultation with the imaging system and near-infrared mapping spectrometer and by observing the other two populations at low phase angles.
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From page 97... ...
As a result, it ~ very difficult to discern the true geometry of vertically distended components, such as the halo component. By observing the jovian rings from positions well out of the ring plane, the JPO mission may be able to better elucidate their true three-~nnensional geometry.
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From page 98... ...
The helium abundance was measured only at much higher pressure levels, and thus only extrapolated values are available for the upper atmosphere. The Voyager ultraviolet experiment also provided information on the exospheric neutral gas temperature; this solar occultation measurement gave a temperature of 1100 200°K.
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From page 99... ...
particle fluxes are also required, both in the ionosphere and in the inner magnetosphere. The Voyager UVS exper~rnents observed intense I,yman and Werner band emissions at higher latitudes, implying the precipitation of large auroral particle fluxes into the upper atmosphere of Jupiter.
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From page 100... ...
Cloud structure spatial coverage of the cloud deck at 1~ km resolution (comparable to a pressure scale height) in visible light.
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From page 101... ...
Jupiter's Interior Magnetic Field Jupiter, the largest planet In the solar system, ~ endowed with a powerful and complex magnetic field generated by fluid motion in its interior much like Earth's. Magnetic field measurements sufficient to characterize only the lowest order moments of Jupiter's magnetic field have been obtained by the Pioneer and Voyager spacecraft flybys of the 1970~.
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From page 102... ...
This would allow the precise determination of the radius of Jupiter's dynamo-generating region, using the frozen flux theorem of Bondi and Gold. At the Earth, application of the frozen flux theorem to the secular variation observations leads to a determined core radius within a few percent of that determined seismically.
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From page 103... ...
. The low-altitude polar orbit proposed for JPO is ideal for the measurement and synoptic mapping of these polar Birkeland currents.
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From page 104... ...
One possible area of concern is atmospheric drag during closest approach. B.4 CONCLUSIONS AND RECOMMENDATIONS Scientific J=t~fication · A Jupiter Polar Orbiter mission is scientifically exciting for the number of planetary system processes it will elucidate and because of the basic data it will provide for comparative planetology.
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From page 105... ...
. Measurements of the species, energy spectra, charge state, and angular distributions of energetic particles to determine acceleration and transport mechanisms, sources and sinks over the energy range 10 keV < E < I~0 MeV per nucleon for ions and 10 keV < E < 50 MeV for electrons.
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From page 106... ...
~ To resolve problems concerning the nature of the three pow ulations of ring particles and their interrelationships; the factors controlling ring structure; and the origin of this ring system. Synoptic-scale polar-view images of the to torus and the ~ Fast neutral particle images of the radiation belts and neutral particle torus.
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From page 107... ...
Siscoe (Host) , University of California Workshop Sponsors Henry Brinton, NASA Headquarters William Quaide, NASA Headquarters JPO Workshop Participants and Post-Workshop Contributors Ab~alla, M., UCI,A Bagenal, F., Imperial College Barbosa, D., UCLA Beebe, R., NMSU
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