JOVIAN SYSTEM DATA ANALYSIS PROGRAM PROPOSAL SUMMARY

The Galileo Probe Atmospheric Structure Experiment (ASE) provided the first in situ measurements of density, pressure, and temperature in the atmosphere of Jupiter. Accelerometer data from the high speed entry phase provided information on the atmospheric structure down to the 0.35 bar pressure level. From 0.4 bars down to the 22 bar pressure level, sensors directly measured pressure and temperature during the parachute descent phase. In this proposal we request funds to undertake a new analysis of the accelerometer data returned by the ASE with the goal of building upon and extending the previous work reported in Seiff et al (1998). Unlike any previous atmospheric entry, the magnitude of the winds in the upper troposphere at the Galileo Probe Entry Site (PES) is potentially a significant fraction of the probe?s speed at these levels of the atmosphere, resulting in a likely sensitivity of the derived atmospheric structure profile to winds. No winds were included in the analysis of Seiff et al (1998). Due to the very high entry speed of 47 km/s, the reconstruction of the entry profiles is quite sensitive to uncertainties in the entry velocity, particularly to the flight path angle below horizontal. To assess the effects of this uncertainty as well as that due to other sources, we propose to undertake a full error analysis and assess the statistical uncertainties in the atmospheric structure profiles. No such error analysis has previously been undertaken. Our work will use new software recently developed to reconstruct atmospheric structure profiles from the Mars Pathfinder Atmospheric Structure Investigation (ASI). The speed and efficiency of this software allows rapid evaluation of uncertainties in the entry profiles. We will use our new temperature profile to assess the significance of the previously reported 5-10°K difference between the Galileo Probe ASE profile in the upper troposphere and the thermal structure derived from groundbased infrared observations. Such a comparison can provide us with information on the magnitude of the thermal contrasts over small horizontal length scales in the Jovian atmosphere. We will attempt to place constraints on the vertical shear of the horizontal wind in the upper troposphere using the temperature profile and the sensitivity of the reconstruction procedure to atmospheric winds. Lapse rates with uncertainties will be evaluated and checked for regions of neutral or unstable stratification. A search for short wavelength small amplitude periodic structures in the upper troposphere and lower stratosphere will be undertaken and the variation of such structures with pressure and stratification will be compared to analytical linear wave theory.