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| Titel |
JunoCam’s Imaging of Jupiter |
| VerfasserIn |
Glenn Orton, Candice Hansen, Thomas Momary, Michael Caplinger, Michael Ravine, Sushil Atreya, Andrew Ingersoll, Scott Bolton, John Rogers, Gerald Eichstaedt |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250140526
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| Publikation (Nr.) |
 EGU/EGU2017-3926.pdf |
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| Zusammenfassung |
| Juno’s visible imager, JunoCam, is a wide-angle camera (58∘ field of view) with 4 color
filters: red, green and blue (RGB) and methane at 889 nm, designed for optimal imaging of
Jupiter’s poles. Juno’s elliptical polar orbit offers unique views of Jupiter’s polar regions with
spatial scales as good as 50 km/pixel. At closest approach (“perijove”) the images have
spatial scale down to ∼3 km/pixel. As a push-frame imager on a rotating spacecraft,
JunoCam uses time-delayed integration to take advantage of the spacecraft spin to extend
integration time to increase signal. Images of Jupiter’s poles reveal a largely uncharted region
of Jupiter, as nearly all earlier spacecraft except Pioneer 11 have orbited or flown by
close to the equatorial plane. Poleward of 64-68∘ planetocentric latitude, Jupiter’s
familiar east-west banded structure breaks down. Several types of discrete features
appear on a darker, bluish-cast background. Clusters of circular cyclonic spirals are
found immediately around the north and south poles. Oval-shaped features are also
present, ranging in size down to JunoCam’s resolution limits. The largest and brightest
features usually have chaotic shapes; animations over ∼1 hour can reveal cyclonic
motion in them. Narrow linear features traverse tens of degrees of longitude and
are not confined in latitude. JunoCam also detected optically thin clouds or hazes
that are illuminated beyond the nightside ∼1-bar terminator; one of these detected
at Perijove lay some 3 scale heights above the main cloud deck. Tests have been
made to detect the aurora and lightning. Most close-up images of Jupiter have been
acquired at lower latitudes within 2 hours of closest approach. These images aid in
understanding the data collected by other instruments on Juno that probe deeper in the
atmosphere. When Jupiter was too close to the sun for ground-based observers to collect
data between perijoves 1 and 2, JunoCam took a sequence of routine images to
monitor large-scale features, which fortuitously yielded the earliest images of a
very energetic outbreak on the rapid jet at 24∘N. Images taken around perijove 3
(PJ3) allow a closer inspection of the outbreak features in a later state of evolution.
Methane band images covering both polar regions within about four hours, around PJ3,
show the shape and extent of the polar-haze features from favorable vantage points.
Occasional, opportunistic images of the Galilean moons and the ring system were also
acquired. |
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