JIRAM, the Jovian Infrared Auroral Mapper

JIRAM is an imager/spectrometer on board the Juno spacecraft bound for a polar orbit around Jupiter. JIRAM is composed of IR imager and spectrometer channels. Its scientific goals are to explore the Jovian aurorae and the planet's atmospheric structure, dynamics and composition. This paper explains the characteristics and functionalities of the instrument and reports on the results of ground calibrations. It discusses the main subsystems to the extent needed to understand how the instrument is sequenced and used, the purpose of the calibrations necessary to determine instrument performance, the process for generating the commanding sequences, the main elements of the observational strategy, and the format of the scientific data that JIRAM will produce

Coupled Clouds and Chemistry of the Giant Planets— A Case for Multiprobes

In seeking to understand the formation of the giant planets and the origin of their atmospheres, the heavy element abundance in well-mixed atmosphere is key. However, clouds come in the way. Thus, composition and condensation are intimately intertwined with the mystery of planetary formation and atmospheric origin. Clouds also provide important clues to dynamical processes in the atmosphere. In this chapter we discuss the thermochemical processes that determine the composition, structure, and characteristics of the Jovian clouds. We also discuss the significance of clouds in the big picture of the formation of giant planets and their atmospheres. We recommend multiprobes at all four giant planets in order to break new ground.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43766/1/11214_2005_Article_1951.pd

Saturn Atmospheric Structure and Dynamics

2 Saturn inhabits a dynamical regime of rapidly rotating, internally heated atmospheres similar to Jupiter. Zonal winds have remained fairly steady since the time of Voyager except in the equatorial zone and slightly stronger winds occur at deeper levels. Eddies supply energy to the jets at a rate somewhat less than on Jupiter and mix potential vorticity near westward jets. Convective clouds exist preferentially in cyclonic shear regions as on Jupiter but also near jets, including major outbreaks near 35°S associated with Saturn electrostatic discharges, and in sporadic giant equatorial storms perhaps generated from frequent events at depth. The implied meridional circulation at and below the visible cloud tops consists of upwelling (downwelling) at cyclonic (anti-cyclonic) shear latitudes. Thermal winds decay upward above the clouds, implying a reversal of the circulation there. Warm-core vortices with associated cyclonic circulations exist at both poles, including surrounding thick high clouds at the south pole. Disequilibrium gas concentrations in the tropical upper troposphere imply rising motion there. The radiative-convective boundary and tropopause occur at higher pressure in the southern (summer) hemisphere due to greater penetration of solar heating there. A temperature “knee ” of warm air below the tropopause, perhaps due to haze heating, is stronger in the summer hemisphere as well. Saturn’s south polar stratosphere is warmer than predicted by radiative models and enhanced in ethane, suggesting subsidence-driven adiabatic warming there. Recent modeling advances suggest that shallow weather laye

Effects of Hemispheric Circulation on Uranian Atmospheric Dynamics and Methane Depletion

The solar system is filled with meteorological phenomena. For example, geophysical vortices range from hurricanes to the Great Red Spot on Jupiter to the Dark Spots of Uranus and Neptune. These Ice Giant vortices have exhibited unusual dynamical behaviors, such as the shape oscillations and meridional drift of the Great Dark Spot, discovered and observed in 1989 by Voyager II. On the other hand, the Uranian Dark Spot exhibited little to no drift over a similar stretch of observation when it appeared shortly before the spring equinox on Uranus in 2006. Another phenomenon is regions of persistent clouds, common in the banding patterns of the gas giants. The bright companion of the Great Dark Spot is a different type of persistent cloud, arising orographically as the vortex moved through the atmosphere. The Uranian Dark Spot may also have had a similar, although intermittent, cloud companion. Another notable long-lived cloud feature called S34 or the Berg in the southern hemisphere of Uranus, which drifted equatorward covering approximately 30 degrees in latitude over the course of a few years as equinox approached, having previously spent several years in the vicinity of 34 degrees south latitude. While this motion resembles in some ways that of the Great Dark Spot and its Bright Companion, there was no visible vortex associated with the Berg\u27s cloud. A proposed cause of this unexpected drift is the development of a strong meridional, Hadley-cell circulation that caused the cloud (and a possible unseen companion vortex) to drift equatorward. This same circulation may account for observations that showed upper tropospheric methane gas (a primary cloud constituent on Uranus) in the southern hemisphere was preferentially accumulating near the equator while depleting near the south pole. This paper presents the first efforts to examine these phenomena by numerically modeling a full Uranian atmosphere. These simulations are designed to examine these changes in the Uranian atmosphere, probably related to the extreme seasonal change of this planet. While this research will improve our understanding of the Uranian atmosphere and the design of future missions to this system, it will also assist in understanding the similar dynamics on the other Ice Giant planet Neptune, and potentially with similar phenomena in Earth\u27s atmosphere like hurricane drift. © 2012 by by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc

Neptune’s zonal winds from near-IR Keck adaptive optics imaging in August 2001

We present H-band (1.4–1.8 ?m) images of Neptune with a spatial resolution of ?0.06?, taken with the W.M. Keck II telescope using the slit-viewing camera (SCAM) of the NIRSPEC instrument backed with Adaptive Optics. Images with 60-second integration times span 4 hours each on UT 20 and 21 August, 2001 and ?1 hour on UT 1 September, 2001. These images were used to characterize the overall brightness distribution on Neptune, and to determine rotations periods (which translate into wind speeds) of individual cloud features. The images show that the spatial brightness distribution of cloud features, in particular the bright bands at mid-southern latitudes and near 30°N, changed considerably between 1989 (Voyager era) and 2001. The brightest features extend latitudinally over several degrees, and despite the different velocities in different latitude bands, these bright features remain coherent. We show that these features are bright in part because of the foreshortening effect near the limb, which suggests that the features may be composed of small bright clouds that happen to line up near the limb. At certain latitudes (mid-southern and northern latitudes), there is considerable dispersion in relative rotation periods (and hence zonal velocities) of faint and moderately bright features, while there is essentially no velocity dispersion of features at 50°S. While the zonal speeds of the brightest features are consistent with the Voyager-derived zonal-mean wind profile, there are many cloud features that do not appear to move with the flow. The data are further suggestive of oscillations in longitude, with periods > 4 hrs. We suggest that tidal forcing by Triton could play a role in exciting the waves responsible for the velocity variations of the observed period.Space EngineeringAerospace Engineerin