A Probe to Europa - Abstract
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A PROBE TO EUROPA



For:

Dr. W. T. Fowler


By:

Hector O. Alvidres


Department of Aerospace engineering
and Engineering Mechanics
The University of Texas at Austin




MISSION DESCRIPTION

Mission Objectives

The main objectives of the mission to Europa are: to study the surface of the satellite; to determine any geological activity; to determine the stability of the satellite; to determine the composition of the satellite below the icy surface, to determine the composition of its core, to study the Jupiter-satellite system, and to determine the ability of the satellite to sustain life. The secondary objective is to provide a science platform to study Jupiter.

Feasibility

As explained in the previous section, the mission to Europa has very similar objectives as previous mission to other planets. Voyager traveled from Earth to Jupiter, and on. So the propulsion technology is available. Many of the experiments planned for the surface of Europa are similar to those performed by the Viking spacecraft. The only new experiment that will be performed is the penetration of the three mile thick Europan surface. In the next section, two approaches to this problem are described. The one chosen promises to be a simple and reliable method. The simplicity of the technique selected will add to the reliability of the mission.

Mission Scenarios Explored

Under both mission scenarios presented below a double-vehicle set-up is reviewed. The spacecraft will consist of an orbiting unit and a lander, much in the same way as Viking. This has proven to be a very efficient method of performing a mission. Upon arrival to Europa, the spacecraft will take close-up pictures of the satellite. After arrival into orbit, a series of orbits will be performed to find an orifice on the surface, through which the probe can be introduced. If no such orifice is found, then the best landing site will be selected. Once the landing site has been found, the spacecraft will be prepared to launch the lander. After separation, the orbiter will continue to work as a relay station and to continue analyzing the surface of Europa, or the surface of Jupiter. The lander will descend to the surface and then anchor down. Seismometers will be deployed and measurements will be taken. Other science will be performed before deploying the inner probe. Signals will be recorded or beamed up to the orbiter for transmission to Earth.

The difference of the two scenarios are explained below:

Flying Spike

A high speed projectile was to be launched after a landing site was found. The projectile, or "spike", would have had explosives at the end which would have detonated after the spike had penetrated the surface and stopped moving . This would ensure that spike would penetrate through the three mile layer of ice. The lander would then arrive and drop the probe through the hole created by the spike. The probe would then beam the signals to the lander.

This method seemed highly unreliable, and inefficient. Without having first studied the surface, it is not known what effect the explosion would have on the planet. This method was discarded immediately after the next suggestion was proposed. A mission summary is shown in Figure 2-1.

Warm Feeler

This method promises to be simple and reliable. After a good landing spot has been selected, the lander will separate from the orbiter and land on the surface. There will be two probes which contain a Radioisotope Thermo-electric Generators which will serve to power the probe and create heat to melt the ice. As the ice melts, the probes will sink letting out cable from a reel inside each probe. Since the surface crust is calculated to be three miles deep, the cable will be 4.5 miles long. After all science has been conducted at this depth, the probes will be released so that inner core analysis can be performed. The wire will act as an antenna and collect the data for the lander.

Mission Selected

The mission selected was the Warm Feeler. It is a more reliable mission than the Flying Spike, and most of the equipment and instrumentation can be obtained off the shelf. The Flying Spike would have required the lander to land on a specific area, with a very small margin of error. The Warm Feeler does not have to do this since it is self contained.

The Europa Probe will be launched from the Space Shuttle from Low Earth Orbit (LEO). It will be injected into a non-Hohmann trajectory which will take it to Jupiter in 688 days. It will then fly through the Jovian atmosphere to take advantage of aerobraking. The atmosphere will slow the spacecraft down and place it into a Hohmann like transfer which will take it to an orbit around Europa, at an altitude of 185. km above the Europan surface. The spacecraft will orbit until a suitable landing site is found. Then the lander will separate and proceed to land on the surface of the moon. After conducting seismological studies, the lander will deploy the RTG's which will study the interior of the ice crust. During this time the orbiter will relay the data to Earth, or store it for later transmission. After this portion of the analysis is completed, the RTG's will be released to study the interior of the core.


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