LAPLACE
A mission to Europa and the Jupiter System
for ESA’s Cosmic Vision Programme
Proposal leader: Michel Blanc (F)Japan co-leaders: Sho Sasaki, Masaki Fujimoto
U.S. co-leader: Robert Pappalardo
Russia co-leader: Lev Zelenyi

Working Group leaders and co-leaders:
Yann Alibert (CH)
Nicolas André (F)Sushil Atreya (USA)Reta Beebe (USA)Willy Benz (CH)
Angioletta Coradini (I)Athena Coustenis (F)Véronique Dehant (Be)Michele Dougherty (U.K.),
Pierre Drossart (F)Olivier Grasset (F)Leonid Gurvits (NL)Paul Hartogh (Ge)Hauke Hussmann (Ge)Yasumasa Kasaba (Jpn)
Margaret Kivelson (USA)Krishan Khurana (USA)
Norbert Krupp (Ge)Philippe Louarn (F)Jonathan Lunine (USA)Melissa McGrath (USA)David Mimoun (F)Olivier Moussis (F)Juergen Oberst (Ge)Tatsuaki Okada (Jpn),

Olga Prieto-Ballesteros (Sp)
Daniel Prieur (F)Pascal Regnier (F)Maarten Roos Serote (P)Jerry Schubert (USA)
Christophe Sotin (F)Tom Spilker (USA)Yukihiro Takahashi (Jpn)
Takeshi Takashima (Jpn)
Federico Tosi (I)Diego Turrini (I)Tim Van Hoolst (Be)Team members: full list available at http://jupiter-europa.cesr.fr/
Technical support from CNES PASO, EADS/Astrium, Noveltis and ThalesAleniaSpace to the designof this proposal is kindly acknowledged.

Table of contents:
a °/ Executive summary........................................................................................................................... 3b °/ Introduction: a Cosmic Vision of the Jupiter system ........................................................................ 5c °/ Scientific Objectives ......................................................................................................................... 5
c.1 °/ How did the Jupiter system form? ..............................................................................................5
c.2 °/ How does the Jupiter system work? ...........................................................................................7
c.3 °/ Looking into Europa to assess its habitability ..........................................................................14c.4 °/ From science goals to mission constraints and measurement requirements .............................17d °/ Mission profile necessary to achieve these objectives.................................................................... 20
e °/ Proposed payload instrument complement ..................................................................................... 23
e.1 °/ Observation strategy .................................................................................................................23
e.2 °/ Overview of all payload elements ............................................................................................23
e.3 °/ An example of a possible set of science payload elements ......................................................24
e.4 °/ Recommendations ....................................................................................................................28
e.5 °/ An example of a possible set of highly-integrated science payload elements ..........................29
f °/ Basic spacecraft key factors ............................................................................................................ 29
g °/ Science operations and archiving ................................................................................................... 34
h °/ Key technology areas...................................................................................................................... 35
i °/ Preliminary programmatics and costs.............................................................................................. 36
j °/ Communication and outreach. ......................................................................................................... 38

a°/ Executive summary
The exploration of the Jovian System and its fascinating satellite Europa is one of the priorities
presented in ESA’s “Cosmic Vision” strategic document. The Jovian System indeed displays many
facets. It is a small planetary system in its own right, built-up out of the mixture of gas and icy
material that was present in the external region of the solar nebula. Through a complex history ofaccretion, internal differentiation and dynamic interaction, a very unique satellite system formed, inwhich three of the four Galilean satellites are locked in the so-called Laplace resonance. The energy
and angular momentum they exchange among themselves and with Jupiter contribute to various
degrees to the internal heating sources of the satellites. Unique among these satellites, Europa isbelieved to shelter an ocean between its geodynamically active icy crust and its silicate mantle, one
where the main conditions for habitability may be fulfilled. For this very reason, Europa is one of thebest candidates for the search for life in our Solar System. So, is Europa really habitable, representing
a “habitable zone” in the Jupiter system? To answer this specific question, we need a dedicatedmission to Europa. But to understand in a more generic way the habitability conditions around giant
planets, we need to go beyond Europa itself and address two more general questions at the scale of theJupiter system: to what extent is its possible habitability related to the initial conditions and formation
scenario of the Jovian satellites? To what extent is it due to the way the Jupiter system works?
ESA’s Cosmic Vision programme offers an ideal and timely framework to address these three key
questions. Building on the in-depth reconnaissance of the Jupiter System by Galileo (and the Voyager,
Ulysses, Cassini and New Horizons fly-by’s) and on the anticipated accomplishments of NASA’s
JUNO mission, it is now time to design and fly a new mission which will focus on these three major
questions. LAPLACE, as we propose to call it, will deploy in the Jovian system a triad of orbiting
platforms to perform coordinated observations of its main components: Europa, our priority target, theJovian satellites, Jupiter’s magnetosphere and its atmosphere and interior. LAPLACE will consolidate
Europe’s role and visibility in the exploration of the Solar System and will foster the development oftechnologies for the exploration of deep space in Europe. Its multi-platform and multi-target
architecture, combined with its broadly multidisciplinary scientific dimension, will provide anoutstanding opportunity to build a broad international collaboration with all interested nations andspace agencies.
SCIENTIFIC OBJECTIVESLAPLACE is a multi-platform mission aiming at an in-depth, quantitative study of the Jupiter system
and its moons, which focuses on three major and interrelated scientific questions.
1 - What have been the conditions for the formation of the Jupiter system?
LAPLACE will complement investigation of the origin of Jupiter by focusing on its satellite system,
its origin and evolution. It will study the irregular satellites as witnesses of the early epochs of Jupitersystem evolution. It will study the cratering records of the Galilean satellites and search for signaturesof their formation scenario. LAPLACE will also complement JUNO’s investigations of Jupiter’s coreand internal structure by means of a dedicated seismology experiment.
2 - How does the Jupiter system work?
The diversity of objects composing the Jupiter system forms a complex system coupled by a small
number of universal processes: gravitational interactions, such as the ones locking Io, Europa andGanymede in the LAPLACE resonance responsible for the maintenance of tidal coupling between
them; electrodynamic interactions between the different objects of the system and the plasmas andfields of the magnetosphere; hydrodynamic and radiative coupling processes between the different
layers of Jupiter’s atmosphere, its deep interior and its space environment. LAPLACE will perform aquantitative study of these processes, with special emphasis on their consequences for the evolution
and habitability of Europa.
3 - Is Europa habitable?
To address this central question of the mission, LAPLACE will perform a detailed investigation in
Europa orbit, possibly complemented by a surface experiment. Its Europa orbiter will look for thedifferent habitability conditions: presence of liquid water in a subsurface ocean, possible direct contactof the ocean with a silicate floor, chemical and dynamical characteristics of Europa’s surface and subsurface, exchanges between the surface, sub-surface and ocean, and finally possible bio-signatures.
The other two LAPLACE spacecraft, placed in Jupiter orbit, will place our quest for Europa’s
habitability in the broader context of the origin and evolution processes of the Jupiter system.
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PLATFORM AND MISSION REQUIREMENTS
Our exploration of Europa and the Jupiter System will proceed by successive phases, prepared andsupported by adequate Earth-based observations using the major facilities of the time. The cruise
phase will provide an opportunity for an attempt at detecting the global modes of oscillation of Jupiter.
After Jupiter Orbit Insertion, a multiple-year orbital tour by two or three independent platforms will
follow. The “core” Europa mission will then be performed by one spacecraft injected on a polar
circular Europan orbit to study Europa’s surface, interior and exosphere for a period of at least a few
months. A second spacecraft will be placed in an orbit resonant with Europa to serve as a relay for the
storage and further transmission to Earth of the huge data volume produced by the Europa orbiter. A
third spinning spacecraft will monitor the magnetosphere. After completion of the Europa mission bycrashing on the satellite’s surface, the investigation of the Jupiter system will continue for at least two
years.
Despite the difficulty of implementing a surface element, we recommend to study possible options
during the assessment study phase. As a minimum, the observing program of the Europa orbiter will
help planning future missions to Europa’s surface.
PAYLOAD COMPLEMENT APPROACH
The measurement requirements will be satisfied using three complementary categories of scientificinvestigations:• measurements of Europa’s geometry and its main planetary fields and to a lesser extent those of
the other satellites (gravity, magnetic field, geodesy and surface topography), including their
response to tidal forcing, to retrieve the main characteristics of Europa’s ocean and determine theinternal structure of the different satellites,• multi-spectral remote sensing measurements of the surfaces, atmospheres and gas tori, andpossibly sub-surfaces of the different bodies of the Jupiter system, to retrieve their compositionand dynamics and improve our understanding of the vertical coupling mechanisms between the
different layers,• in situ remote sensing of the plasma, fields, energetic particles gas and dust populations ofEuropa’s exosphere and Jupiter’s magnetosphere, to quantitatively understand the mutualinteractions between the different bodies of the Jupiter system and its space environment.
KEY TECHNOLOGICAL CHALLENGES
A mission to Europa and the Jupiter System offers a set of very stimulating technological challenges
for ESA and its partners, tentatively identified in our proposal which will have to be addressed in
depth during the technology assessment phase. These include high-precision navigation necessary to
retrieve the internal structure of the satellites, on-board solar power and possibly nuclear energy
sources, data transmission and storage capabilities, protection of on-board systems and instruments
against the extremely high radiation doses produced by Jupiter’s radiation belts, and the compliancewith Planetary Protection standards.
INTERNATIONAL COLLABORATIONThe broad spectrum of scientific themes and of technological challenges, its multi-platformarchitecture, and the large community of interested disciplines, scientists and institutes in Europe andabroad, all point to the strong benefit that such a mission will draw from international, possibly
world-wide collaboration. Our proposal will identify potential partners (NASA, JAXA, RosCosmos
and beyond) and propose a limited set of preferred collaborative mission scenarios potentially offering
the best science return, to be validated by a joint assessment study if the mission is selected.
CONTRIBUTIONS TO SCIENTIFIC COMMUNICATION AND EDUCATION
The discovery of Jupiter’s main satellites by Galileo Galilei in 1610 was made possible by theinvention of the telescope – a milestone in the understanding of Cosmos by mankind. The fact that
400 years later the first observational objects of the first telescope are becoming subjects of detailed
in-situ investigation by the LAPLACE mission has a huge educational potential. The mission will
exploit this potential emphasizing the mutually beneficial interaction between astronomy, planetaryand space science on one hand and cutting edge developments in technology on the other hand. It willassociate from its early study and development phases the public and the education bodies in Europe
and beyond, building a bridge across four centuries between one of the founding events of modern
astronomy and one of the most challenging scientific and technological endeavors of our time:
exploring distant words, to better understand our own Solar System, its origin and its destiny.
4b°/ Introduction: a Cosmic Vision of the Jupiter system
Galileo Galilei’s January 1610 observations of the four main satellites of Jupiter represent in a sense
the first time a “planetary system” was ever observed from outside. Today, while we prepare thecelebration of the 400th anniversary of this break-though in our understanding of the Solar System, theplace of the Jupiter System in planetary science and discovery is even more central:• The most recent simulations of the dynamical evolution of the early Solar System show that Jupiterhas played a key role in the formation and early evolution of its sister planets and of the
populations of small bodies and has controlled the amount of water delivered to terrestrial planets,
thus influencing the habitability and emergence of life on our own planet.
• With the discovery of over 200 extrasolar planets since 1995, Jupiter appears as a “template”,
available in our own Solar System, for the numerous gas giants found around other stars. Progressin our understanding of how Jupiter and its satellite system were formed and migrated, and of how
Jupiter works to-day, can therefore be translated into an improved basis for the planning and later
understanding of observations of extrasolar planets.
• Finally, the naïve idea that the Jupiter system is indeed a “mini-solar system” has been only
reinforced by the Pioneer, Voyager, Ulysses, Cassini and recently New Horizons fly-bys of thesystem, and by Galileo’s extended orbital tour. The Voyager fly-by of its moons first revealed theunique aspects of its satellite Europa as a potential “ocean moon”, and opened the possibility forthe existence of a “habitable zone” in the Jupiter system. Moreover, simulation studies strongly
suggest that the formation scenario of the Jupiter system displays many similarities with theformation of the solar system as a whole, involving the dynamical evolution and condensation of a
Jovian sub-nebula.
Thus it is no surprise that the Jupiter System plays such a prominent role in the Cosmic Vision Plan
proposed by the European Agency to build its ambitious scientific programme over the period 20152025. Three key questions about the Jupiter System and its habitability strongly resonate with the
major scientific questions identified by the Cosmic Vision Plan.
They are the Science Goals of our proposed mission :¾ What have been the conditions for the formation of theJupiter system? How do they relate to the formation
scenario of the solar system and other planetarysystems? How do they contribute to the possible
emergence of life? (Cosmic Vision theme 1).
¾ How does the Jupiter system work? How well do weunderstand it at the “system level”? (Cosmic Vision
Theme 2). How does the system contribute to theconditions for habitability?
¾ Is Europa habitable
Does it represent the “habitable zone” of the Jupitersystem? Does Europa actually harbour life? (Cosmic
Vision Theme 1).

c°/ Scientific Objectives
To assess Europa’s habitability, our priority science goal, we first need to understand how the Jupitersystem was formed (question 1), and what coupling processes link its many objects (question 2). We
will then focus on our in-depth exploration of Europa.
c.1°/ HOW DID THE JUPITER SYSTEM FORM?
i°/ Formation scenarios for the Jupiter system
The history of the Jovian system can be divided into three main phases: the formation of Jupiter, theformation of its satellite system and its secular evolution to its present day state.
The first phase (first line in Figure 2), the formation of Jupiter, took place during the nebular epoch ofSolar System history, when the gaseous component was still present and the solid component was
slowly giving birth to planetesimals by means of accumulation processes. Two competing models are
generally proposed to explain the formation of giant planets. In the first approach, the nucleatedinstability model, one assumes that planetary cores form by accumulation of planetesimals, in a way
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similar to the one generally accepted for the formation of terrestrial planets. When a critical mass isreached, the cores start to capture ever increasing quantities of nebular gas, leading to a phase of gas
accretion where the planets grow to their final masses. This scenario has been shown to be compatible
with our present day very limited knowledge of Jupiter’s internal structure and atmosphericcomposition. The second scenario assumes that giant planets are formed by gravitational instabilities
in the massive proto-Solar Nebula, leading to the rapid formation of density enhancements - or clumps- with solar chemical compositions and masses probably larger than the present ones of the giant
planets. Key issues with this model are how to justify the a posteriori formation of a core and the large
amount of heavy elements suspected, but not yet definitely proven, in Jupiter and Saturn.
The second phase (second to fourth lines in Fig. 2) begins when Jupiter’s region of gravitational
influence (quantified by its Hill’s radius) enlarges and exceeds its outer radius. This results from theaccretion of a massive gas envelope, and leads to the generation of a Jovian subnebula, a structure
similar to the Solar Nebula, which had the ability of capturing gas and small planetesimals from it.
The captured planetesimals then can grow further in mass due to mutual collisions and build up theregular Jovian satellites (Fig. 2, second and third lines): the content of ices can vary from satellite tosatellite, since part of the original planetesimal could have lost their volatile species (in particularwater ice) due to the temperature and pressure condition prevailing in the Jovian subnebula. At the endof this process, all of the subnebular gas and the majority of its small scale solids would be accreted
into Jupiter. The formation of the Jovian regular satellite system ended at an epoch between thesubnebular phase and the Late Heavy Bombardment, an event which has recently been suggested tohave been triggered by a chaotic phase of orbital rearrangement of the outer Solar System. Dependingon the capture mechanism, the presence of subnebular gas or the dynamical rearrangement could havesupplied the conditions necessary for the gravitational capture of the irregular satellites of the giant
planets.
Finally, the completely formed Jovian system would have started its evolution phase towards its
present day state, as a consequence of impacts and the various coupling processes acting inside thesystem.
Figure 2 : A scenario of Jupitersystem formation.
First phase: Jupiter forms, its
Hill and outer radii coincide,and no subnebula can exist(first line).
Second phase: formation of thesatellite system. A subnebula
appears, fed in its infancy by
gas and gas-coupled solids
originating from the solar.
Planetesimals, some of themhaving lost their volatile due totemperatureandpressureconditions prevailing in thesubnebula, grow to form
satellites (second and thirdlines). When the subnebula
disappears (fourth line), theirregular satellites are captured.

ii°/ LAPLACE contribution in unveiling the origin of the Jovian system
Understanding the formation of Jupiter and its satellite system therefore requires that we look at thetraces of the first and second phases just described above. The strategies devised for the LAPLACE
mission are presented in the three points below, complemented by composition measurements ofregular satellites (see Sect. c 2 ii).
Probing Jupiter’s interior
In order to determine Jupiter’s internal structure, two approaches are available. The first one, which
will be used by the NASA JUNO mission, relies on the determination of the planet’s gravitational
moments. Since their interpretation in terms of density structure and of the presence or absence of acore is not unique and strongly depends on the correct knowledge of H and He equations of state,
uncertainties in the equations of state will affect the achievable resolution.
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An alternative way to obtain information on Jupiter’s interior is the seismology approach, namely thestudy of the oscillations of the planet. Observations aimed at detecting oscillation modes of Jupiterhave shown promising results, but so far they have been limited by instrumental and windowing
effects and by the effect of Earth’s atmosphere. Combining this method with the gravitational moment
data which JUNO will provide has the potential of determining the whole internal density profile of
Jupiter, thus giving the mass of its internal core and the amount of heavy elements. It can also
constrain the level of homogeneity of Jupiter’s envelope, key information to interpret Galileo
measurements of volatile species in a global context.
Looking for the origins of the irregular satellites
The study of the irregular satellites will allow testing of the capture hypothesis, the reality of the
dynamical families found from Earth and to define their physical nature without having to rely only on
the information-poor colour indexes and the limited spectral range accessible with ground-based
observations. LAPLACE will perform at least one close fly-by of one of the major irregular satellites
and will remotely observe as many of them as possible, with special emphasis on possible family
members of the close fly-by target. It will perform high-resolution imaging and visual-near infrared
spectroscopy of the satellite surfaces and dust collection and analysis (dynamics and composition) in
their orbital region and during the fly-bys. Observing the Jovian irregular satellites also offers thepossibility to look back to the early phases of the evolution of the Solar system and sample theconditions that existed in the primordial planetesimal disk.
Reading the history of the Galilean satellites in their surface morphology.
The study of the cratering history of the Galilean satellites will provide information to date the Jovian
system and the epoch of the Late Heavy Bombardment and the possibly related chaotic orbital
rearrangement of the giant planets. High resolution imaging and visual/near infrared spectroscopy of afew selected site, coupled with coverage of the satellites surfaces at a medium resolution (better than
Galileo) will provide us with new insight into the history of the Jovian and, more generally, the Solar
System.

c.2°/ HOW DOES THE JUPITER SYSTEM WORK?
i°/ A diversity of objects and coupling processes
The Jupiter system comprises a broad diversity of objects, including Jupiter itself, more than 60 outerirregular small satellites (1 to 100 km class objects), the four large Galilean Satellites, Io, Europa,
Ganymede, and Callisto (1000 km class objects), the four inner satellites Metis, Adrastea, Amalthea
and Thebe (10-100 km class objects) and the Jovian ring system, located in the inner region. All theseobjects experience gravitational interactions among themselves, and electrodynamic interactions ofvariable concentration and strengths of Jupiter’s magnetospheric particles and fields. The
magnetosphere itself is strongly coupled to Jupiter’s upper atmosphere and interior by electrodynamic
interactions. The complex interactions between these components (see Figs. 3, 5 and 6) redistributemomentum and energy among them and drive the magnetospheric engine which generates Jupiter‘sradiation belts. Finally, redistribution of momentum and energy among different layers of Jupiter’s
atmosphere is governed by hydrodynamic and radiative processes.
ii°/ Gravitational coupling, structure and composition of Galilean Satellites
The astonishing diversity of features which shape the surfaces, interiors and dynamics of Galilean
Satellites still challenges our understanding: the most intense volcanic and geologic activity in thesolar system is found on Io; subsurface oceans are likely to exist within Europa, Ganymede andCallisto; the smallest solar system magnetosphere is found at Ganymede, comparable only to Mercury.
The diversity of geologic features on Europa and Ganymede, or the incomplete differentiation of
Callisto and the completely different evolutionary paths of all four Galilean moons, are all still waiting
for a satisfactory explanation. Still, all this diversity must result from the same mechanisms whichshaped and still drive the evolution of their interiors and surfaces. Among them, the Laplace resonancebetween Io, Europe and Ganymede plays a particularly important role in dragging energy from Jupiterto maintain tidal heating at these satellites, and to drive their internal dynamics and modify theirsurfaces. Interactions with the exosphere and magnetosphere also shape their surfaces via space
weathering. Understanding and untangling these driving factors is an essential prerequisite to any
attempt at detecting biosignatures at the surface of Europa and - why not - of its sister moons.
7The Laplace Resonance and Tidal Heating
Stable resonances by which orbital periods are kept in a fixed ratio play an essential role in the Jupitersystem. Unique in the solar system is the three-body resonance – the so-called Laplace resonance – bywhich the orbital periods of Io, Europa, and Ganymede are kept in a ratio of 1:2:4.
The resonance maintains the orbital eccentricities of the moons and therefore enables tidal interactions
to operate on geological timescales. The vigorous volcanism of Io, the innermost Galilean satellite, isthe most obvious consequence of internal heating due to tidal friction.

Figure 3: The rotational energy of Jupiter is a huge reservoir of energy for the three inner Galilean satellites.
Orbital energy gained by Io due to tidal torques exerted by Jupiter is distributed among Io, Europa, andGanymede, due to the Laplace resonance. The resonance is therefore essential for ongoing tidal heating inside
Europa, and may allow for the existence of an ocean inside Europa over billions of years.

As illustrated in Figure 3, gravitational coupling redistributes rotational energy and angularmomentum between the three moons and Jupiter. The resulting tidal heating significantly contributes
to the internal heat sources of Io and of Europa. Europa’s tidal deformation and Io’s intrinsic heat flow
derived from mapping surface temperatures will yield constraints for the amount of energy dissipatedinside Io and Europa. The thermal activity of the moons will be inferred from searching fortemperature anomalies at the surfaces. Additionally, astrometric determination of the satellites’
positions will precisely characterize the orbital state of the system. By studying the Laplace resonanceand tidal heating in the Jupiter system, constraints for the habitability of Europa over geologic
timescales can be inferred.
Internal Structure of the Galilean Satellites
Models of the internal structure of the Galilean satellites are mainly based on the determination of themean density and the moment of inertia about the rotational axis by the Galileo mission. However,hydrostatic equilibrium assumed in such models has been directly confirmed only at Io, where polarand equatorial flybys could be analyzed independently. Whereas Io, Europa and Ganymede arestrongly differentiated into an outer ice layer, a rock mantle and an iron rich core, these phases are
only partly separated in Callisto although its size and mean density is very similar to Ganymede’s.
How these different states came to be is still an open question. The low-degree static gravity field of
the Galilean satellites has been determined with a precision of a few percent from flybys by the
Galileo mission. A Europa orbiter as part of the LAPLACE mission will obtain detailed informationon the gravity field of Europa allowing for a great improvement of internal structure models.
Moreover, LAPLACE will measure the topography of Europa, which in case of the absence of gravity
anomalies can constrain ice shell thickness variations. The degree of differentiation of Europa will beinferred from determining the moon’s obliquity, constraining the moment of inertia independently. For
the other satellites an order of magnitude improvement of the gravity field is expected by using radio
and VLBI tracking from the Earth during the flybys, coupled with altimeter, camera and astrometric(both ground-based and space) data. Deviations from hydrostatic equilibrium and local mass
anomalies could be detected and characterized.
One of the most intriguing features with important astrobiological implications is the possible
presence of subsurface oceans inside the icy moons of Jupiter. Evidence for liquid water layers inside
Europa, Ganymede and Callisto has been obtained by Galileo mainly by the detection of induced
magnetic fields generated close to the surface at all three satellites. In the case of Europa observed
8surface features related to tectonics and cryo-volcanic processes (Fig. 8) provide additional evidence.
Possible structures of the H2O shells of Europa, Ganymede and Callisto are shown in Figure 4.
To further constrain these models and to provide unambiguous evidence for these oceans, in particularat Europa, is a key goal of LAPLACE. Whereas the ocean in Ganymede and Callisto is expected to be
enclosed by thick (~100 km) ice layers, the ocean of Europa can be close to the surface (~ 50 – fewkm) and in contact with silicate rock.
Figure 4 : Possible locations of liquid layers
in the icy moons of Jupiter are plotted here asa function of depth : 1) completely frozen; 2)three-layered structures impeding any contact
between the liquid layer and the silicate floor;3) thick upper icy layer (>10 km) and a thickocean; 4) very thin upper icy layer (3-4 km).
Structures 3-4 are the most probable forEuropa (indicated in black in the lower part).
The larger moons Ganymede and Callisto arelocated in the left region (1 or 2) whereinternal pressures are sufficient to allow for
the formation of high-pressure ice-phases.
Oceans in Ganymede and Callisto - if they
exist - should be enclosed between thick ice
layers.

LAPLACE will determine the presence of oceans by measuring the tidal response in addition to thedetection and characterization of the induced magnetic fields of the satellites. The large tides predicted
for Europa, with estimated amplitudes of about 30 m if a subsurface ocean exists and only a few m
without an ocean, will be measured from the gravitational perturbations on the spacecraft and fromaltimeter measurements with a precision of about 1%. In combination with determining the libration
amplitudes (order of 100m at Europa’s equator) this will constrain the thickness of the icy shell.
Independent from tidal interaction LAPLACE will measure the electromagnetic response, i.e. theinduced magnetic fields, of the ocean at multiple frequencies at Europa. This will constrain the
thickness of the ice shell, the thickness of the ocean and its electrical conductivity. Similar
measurements during flybys will allow for the detection and characterization of subsurface oceans at
Ganymede and Callisto with reduced precision as compared to Europa, depending on the number andgeometry of the flybys.
Galileo has found a self generated magnetic field of Ganymede, a unique feature among solar systemsatellites. To better understand the magnetic field generation in the iron core and to constrain interior
structure and evolution models of Ganymede, a detailed characterization of the field structure will beobtained.
Physical Characteristics, Composition and Geology of the Surfaces of the Galilean Satellites
The surfaces of satellites contain valuable information of the moons’ histories. Surface features wereformed by external sources including impacts and particle bombardment and by geologic activity
caused by internal dynamics. Galilean Satellites offer a perfect illustration of these two processes : thesurface of Io is almost completely formed by endogenic activity, whereas Callisto’s surface wasalmost entirely altered externally early in solar system history. At Europa and Ganymede different
phases of endogenic activity have formed the complex icy surfaces of these bodies. The inner satellites
are exposed to stronger radiation in the inner part of the Jovian magnetosphere which leaves its traces
at the surfaces and exospheres of the satellites. LAPLACE will study these surface processes by adiversity of approaches :•Geologic mapping, including significant improvement of global coverage•
Laser altimetry or stereo imaging to derive topographic maps•
Searching for geologic activity from limb scans, thermal anomalies, and image comparison•
Monitoring of Io’s volcanic and thermal activity on day- and nightside•
Determination of global and regional surface ages from the cratering record•
Characterization of the non-ice components and search for organic compounds•
Determination of chemical, elemental and isotopical composition by dust collection andanalysis.
•
Mapping of surface alterations due to the radiation environment9

Our goal is to improve the global coverage of surface imaging and spectroscopy, compared to Galileo,
for all Galilean Satellites (50% of surfaces with 200 m/pxl and 500 m/pxl for total surfaces in thevisible and near infrared ranging from 350 - 5000 nm). High resolution images at local regions at < 10m/pxl will be obtained from close flybys.

iii°/ Electrodynamic coupling and the jovian magnetospheric engine.
Just like gravitational coupling, electrodynamic interactions also operate at a global scale within the
Jupiter system. Magnetospheric charged particles, mainly produced by the ionization of Io’s neutral
torus, populate the whole Jovian magnetosphere and form an extended magnetodisk near the magnetic
equator. This magnetodisk interacts with each satellite in a variety of modes, depending on thesatellite’s internal plasma sources, on the properties of its exosphere and surface, and on its degree ofmagnetization. It is also coupled to Jupiter’s rotation via a system of electric currents which flow
along magnetic field lines and into Jupiter’s upper atmosphere, where they generate the main auroral
oval. The complex interplay between plasma generation at the satellites, satellite-magnetosphereinteractions and Jupiter-magnetosphere interactions, produces the Jovian radiation belts, the harshest
radiation environment in the Solar System, which directly affects habitability on the surfaces of thejovian moons.

Figure 5 :Electrodynamic
interactions
play a variety of roles in the
Jupiter system :generation of plasma at the Io
torus, magnetosphere / satellites
interactions, dynamics of a giant
plasma disc coupled to Jupiter’s
rotation by the auroral current
system, generation of Jupiter’s
intense radiation belts.

The jovian magnetosphere - basically a giant magnetized environment, driven by the fast rotation of its
central spinning object and populated by ions coming mainly its moons - is thus the most accessible
environment for a direct investigation of general astrophysical processes regarding: (i) the dynamics ofmagnetodisks, with different mechanisms of angular momentum exchange and dissipation ofrotational energy ("fast rotator" theme), (ii) the electro-dynamical coupling between a central bodyand its satellites ("binary system" theme) and, (iii) the global and continuous acceleration of particles("giant acceleration" theme).
The fast magnetic rotator
The fast jovian rotation, combined with the continuous creation of ion populations due to Io’s
volcanism, leads to the formation of a magneto-disc. Its structure varies with distance from Jupiter.
Starting at Io’s orbit as a torus of neutrals and ionized particles in rigid co-rotation, the torus
progressively thins and becomes a disc-like system of limited vertical extension. It increasingly
departs from rigid co-rotation with the distance to Jupiter, with magnetic effects as important as thethermal and rotational ones. At 50-60 Rj from Jupiter, in the anti-solar direction, the disc transforms
into a magnetotail with a strong ‘planetary’ wind.
This disk is driven in rotation by an electro-dynamical coupling with Jupiter materialized by a systemof currents circulating along the magnetic field lines and closing at the ionosphere. This current system
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transfers angular momentum from the outer layers of Jupiter atmosphere to the disc. As this coupling
is not perfect, it leads to particle acceleration, resulting in auroras, energy deposition in the upper
layers of the atmosphere and powerful radio emissions. These effects are particularly important where
co-rotation breaks down, at 15-25 Rj.
The structure of the disc and its coupling with Jupiter also strongly vary with local time. Establishingthe 3D structure of this disk, and its variability, is an important goal of a new exploration of Jupiter,
crucial for further analysis of all angular momentum transfer processes in magnetized, ionized media.
Indeed, the disk - this 3D structure - is not a stationary system, it is highly dynamic. Galileo
observations have revealed that it is periodically reconfigured over global scales, with sequences ofloading-unloading of the disk by new plasma and injections of energetic populations both in the innermagnetosphere and the outer disk. Various processes contribute to the radial transport, from the Io
torus to the external magnetosphere and, at the end, the interplanetary medium: microscopic diffusion,
meso-scale interchanges, global sporadic disruptions of the disk and magnetic reconnection. All theseprocesses trigger variations in the transport rate of the iogenic plasma and its radial re-distribution.
The chain of processes involved in the exchanges of angular momentum and the dissipation ofrotational energy, from the global dissipation of the rotational energy to the microscopic mechanisms
responsible for non-ideality is unknown. Determining their spatial/temporal scales, quantifying theirrelative efficiency and how they vary with the activity of Io is a central objective.
As all objects in the solar system, Jupiter interacts with the solar wind which drives a part of themagnetospheric dynamics and possibly triggers major storms when solar perturbations hit themagnetosphere. To what extent is this huge system, endowed with its own powerful dynamics,
affected by and responsive to external perturbation? This question concerning the respective
importance of external and internal processes in the regulation of the activity of a magnetic
environment can also be best studied at Jupiter.
The magnetized Binary system
Different ‘objects’ move in the Jovian environment, each of them interacting with the magnetophericplasma by a large variety of processes. Moons, with their exospheres, are conductive bodies. As they
move trough the Jovian magnetic field, they create a specific current system (the unipolar dynamo).
This electro-dynamical coupling is not stationary. It generates Alfvèn wave structures, called ‘Alfvèn
wings, that couple the jovian ionosphere to the exosphere of the moons. Once again, this coupling is
not perfect. Part of the electromagnetic energy is converted into kinetic energy of accelerated
particles, with the formation of particular auroral features, including the generation of non thermal
radio emissions.
Europa, Ganymede and Callisto are in complementary situations. The interaction at Io is the mostpowerful. It has an extended exosphere, able to fill the environment with matter, and moving in adense and highly magnetized plasma (the inner Io torus). Ganymede, the unique (to date) magnetized
moon, constitutes another remarkable situation. We don’t know how this mini-magnetosphere iscoupled to Jupiter’s huge one. We only know that this interaction is powerful enough to create an
intense auroral footpoint at Jupiter. The coupling with Europa is apparently much less powerful, even
if it seems able to generate intense waves. By contrast, Callisto is the most quiet.
The parameters that determine the strength of the coupling, the way magnetic fields are distorted andlarge–scale fluctuations are generated, are ignored, as are the details of the interaction itself.
Furthermore, the moons are not passive, more or less conductive bodies. Each moon generates a large
level of plasma waves, they locally heat and accelerate the ion populations, enhance the spatial
diffusion and lead to a more efficient assimilation of the exospheric ions by the Jovian magnetosphere.
The Io torus is another original system. In some sense, its innermost region presents similarities with
an ionosphere, where populations of neutrals interact with ionized ones. However, it is fundamentallydifferent in terms of boundary conditions, spatial scales, geometry and forces that regulate theequilibrium. How does this system evolve when the volcanic activity of Io changes? How are thedifferent ion species mixed, and at what scales? What is the importance of turbulence? How does thetorus feed the magneto-disk? Answers to these questions will greatly help to quantify fundamental
mixing, heating, energy exchange processes in dilute, multi-phase media.
All these topics relate to whether a planet immersed in a strong radiation environment can hostcomplex compounds able to react chemically. They are also of central importance for theinterpretation of precise spectral analyses of Europa surface, dedicated to the search for pre-biotic
components.

11

The giant particle accelerator
A further, largely unresolved problem of a fundamental nature regards the Jovian magnetosphere as atremendously efficient particle accelerator. There is no question that Io is the primary source ofparticles in the Jovian environment. The new plasma populations have, however, typical energies of afew 10’s eV at best. At what time and spatial scales, and by what mechanisms, does a significant partof them reach MeV energies and populate the harshest radiating environment of the solar system? The
fact that such environments can exist has direct relevance to the notion of ‘habitability’. A large andhighly variable level of radiation may actually modify or control the emergence of life.
Jupiter is also a ‘prototype’ of powerful exo-magnetosphere, possibly powerful enough in radio to be
detected at stellar distances. One interesting outcome of in-situ measurements in this radio sources isto determine the highest level of wave energy reachable inside the radio sources and then, to better
estimate their possible detection by a very distant observer.
Critical measurements with LAPLACE
The basic magnetospheric measurements concern the characterisation of the different plasma
populations (electrons and ions species) thus, the density, velocity and pressure, including theirdistribution functions. This requires plasma mass spectrometers capable of making measurements at
sufficiently high energies (up to a 100 Kev/q) and dedicated high energy instruments. The
characterisation of electromagnetic field will be done by measuring the static magnetic field, themagnetic and electric components of high frequency fluctuations.
On orbiting spacecrafts, neutrals and dust must be determined, with possibilities of chemical
characterisation. Complementary diagnostic measurements in visible, IR, UV, X that will be used tomonitor the aurora, the energy deposition in Jupiter atmosphere and, the variability of the Io torus areneeded. Sequences of simultaneous in-situ measurements and remote sensing observations of‘magnetospheric’ targets (aurora, torii) are required.
The determination of scales, temporal and spatial, is fundamental. They define the dynamical
processes and guide any theoretical or simulation analysis. LAPLACE, with the possibility of
performing simultaneous measurements in at least two points, will permit completely original analysis.
The first phase of the orbital insertion, with spacecraft exploring the magnetosphere, at variable interspacecraft radial and azimuthal distances, will be fundamental. The main requirement is to broaden as
much as possible the parameters of the exploration, in terms of local time, distances from Jupiter andinter-spacecraft distances.

iv°/ Radiative and hydrodynamic coupling in the jovian atmosphere
Even after the GALILEO mission, some of the most important questions concerning the atmosphere of
Jupiter remain: How does Jupiter radiate its internal energy to space, and what are the dynamics andcoupling in its atmosphere? LAPLACE will address these questions in a very complementing way to
JUNO, extending the measurements to low latitude and equatorial atmosphere and focusing on
different scientific questions. Three different layers will be sounded to address these questions.
The upper atmosphereThis outermost layer is connected to outer space, and its mesospheric, thermospheric andionospheric structure and dynamics must be deciphered. Despite three decades of limited
measurements of Jupiter’s upper atmosphere from ground and space, our knowledge andunderstanding of the region still remains in its early infancy. LAPLACE will address three science
topics which are closely coupled. Firstly, the thermosphere of Jupiter, like those of all gas giants, isfar hotter than expected from solar EUV heating alone. The energy balance on Jupiter and other gas
giants is yet not understood. This problem will remain under-constrained even after JUNO: asystematic measurement of waves on Jupiter at low to mid latitudes is needed, with implications for all
gas giants within our solar system and beyond. Secondly, despite limited observations from theground, observations by Galileo and forthcoming observations by JUNO, the dynamics of thethermosphere at low and mid latitudes will remain poorly known. For example, it is unclear whether
the zonal jets observed in the stratosphere are present also in the thermosphere; the importance ofwave acceleration and ion drag in thermospheric winds is unclear. Knowledge of the dynamics istherefore crucial in order to understand how energy and material are distributed horizontally andvertically in the upper atmosphere. Thirdly, a major unknown on Jupiter is its ionosphere, not only its
structure, but also its relation to the H2 bulge, the nature of the most important ionization processes,
the distribution of ions and the nature of energy deposition processes. Only few vertical profiles of12

Jupiter’s ionosphere are known, and each of them differing substantially from the others, and none ofthem have been reproduced by photochemical models. LAPLACE will perform a systematic
exploration of total electron densities via radio science, and infrared observations at low latitudes will
trace H3+, a key molecule in Jupiter’s ionosphere. LAPLACE will shed light on the nature of coupling
between the thermosphere, ionosphere and magnetosphere of Jupiter at low latitudes, which isessential to understand the processes that drive the entire coupling between the planet and outer Space
as well as the outer atmosphere and deeper interior of Jupiter. This also has key implications for our
understanding of atmospheric loss, and thereby of the atmosphere evolution.

Figure 6 : The three layers of the Jupiter atmosphere studied by LAPLACE:
1) The dynamics of the troposphere will be studied with special emphasis on the source of vorticity, and its
relation to global circulation. Storm activity is suspected of being a major source of vorticity, which is an
important ingredient in the atmospheric circulation, and can also be the source of gravity waves dissipating in theupper atmosphere.
2) The circulation of the stratosphere (image at the cloud top ~100mbar level, as observed at 3.5 micron;
VLT/ISAAC image, P. Drossart, priv. comm..) is poorly known. Doppler resolved spectroscopy can measurewind velocity at the limb and thermal waves can be imaged in the mid-IR and studied in the long term to observe
the spatial and temporal scales (Cassini/CIRS observation).
3) Dynamical changes in the upper atmosphere can be studied by observing H3+ or CH4 emissions in the mid-IR
to visual range (VLT/ISAAC image at 3.2 micron, P. Drossart, priv. comm..), indicating connections to themagnetosphere in the auroral regions or to internal phenomena.

The stratosphere
The stratosphere couples the deeper layers of the troposphere to the upper atmosphere. Its structure,
circulation and composition are still poorly determined. Direct estimation of winds is not possible in
the absence of discrete clouds. However, knowledge of the stratospheric circulation is vital inunderstanding the transport of hazes and minor species. Temperature fields are known from
Voyager/Cassini and ground observations, but temporal variations are organized along many different
time scales, the longer known being the quasi-quadriennal oscillation, observed from the ground.
Wind measurements in the stratosphere are known only from thermal wind equation retrieval, which
unfortunately excludes the equatorial regions where important phenomena take place, and from thedispersion of dust and chemical elements since the Shoemaker-Levy 9 collision in 1994. Missing
elements are, to date, clues on the meridional and equatorial circulations and the vertical structure of13the winds. Moreover, the question of the origin of stratospheric water is still open, and has implicationon the origin of water in the Solar System: latitudinal variations of H2O would provide important clues
on this origin. Finally, the remnants of the Shoemaker-Levy 9 collision (CS, HCN) are still observed
13 years later and used as tracers of stratospheric mixing. LAPLACE will follow up theseobservations, in relation with ground-based or space-borne observations (ALMA, Herschel).
The troposphere
The troposphere will be the deepest level sounded by LAPLACE: its meteorology in a global
sense is poorly understood. In particular, the exact origin of the global circulation of Jupiter, thestructure of the band system, its relation to differential rotation and the connection of thismeteorological system with deep and outer layers are unknown. One way of progressing in this field is
to constrain models by direct measurements of the quantities involved in meteorological equations,such as velocities, thermodynamics quantities and the “potential vorticity”, which is conserved in nondissipative flows like a passive tracer, and which is directly calculated in the models. This latter
quantity can be deduced from observations of the wind field, together with temperature profiles of theatmosphere. Moreover, long term monitoring of Jupiter at medium scales (300 km) with potential
vorticity retrieval at different time scales would constrain the evolution of waves, of atmosphericstructure and of winds from the models. The distribution of lightning storms on Jupiter, detected by
Galileo with a non-uniform density, is still mysterious. The importance of local convection as a source
term for global circulation remains to be proven at a global scale. These convective cells can also be asource of strong gravity waves propagating up to the thermosphere, and contributing to upper
atmosphere heating. Finally, internal waves already described in section C.1 connect the troposphereto the interior of Jupiter and complete the picture that LAPLACE could give of the Jupiter atmospherefrom the uppermost layers to the deep interior.
c.3°/ LOOKING INTO EUROPA TO ASSESS ITS HABITABILITY
i°/ How can an icy moon be habitable?
The potential habitability of Europa rests on the fulfilment of four conditions (Figure 7): the presenceof liquid water, an adequate energy source to sustain the necessary metabolic reactions, a source ofchemical elements (C,N,H,O,P,S, etc), which can be used as nutrients for the synthesis of biomolecules, and relevant pressure and temperature conditions.
The fulfilment of the first condition is directly related to the putative existence of an ocean. The
existence of this ocean has been inferred from the interpretation of the induced magnetic fieldmeasured by the Galileo mission and the interpretation of geological features (Figure 8).
Figure 7 : Present habitability of Europa. Possible locations ofpresent life and biosignatures have been plotted as a function of
depth. Habitability depends on physical and chemical constraints
which are indicated on the right using colour scales (green:highly favourable; red: hostile). Numbers refer to possible
interior structures described in section (c 2).

Europa is not unique among the four Galilean satellites, as
subsurface oceans may also exist at Ganymede and Callisto.
But according to current models, it represents the only casein which liquid water is in contact with a silicate core. Such
conditions are favourable for interactions between theocean and silicates, particularly if a volcanic, andconsequently hydrothermal activity exist. This would

provide a variety of chemicals that could play a role insustaining putative life forms at the ocean floor as
discovered 30 years ago at Earth deep-sea
hydrothermal vents.
Another potential player in Europa’s habitability is its surface, which is exposed to the harshest
radiation environment in the Solar System. This very high level of radiation may modify or alter thedevelopment of sub-surface prebiotic chemistry, and dissociate organic molecules at the surface. But it
may also provide an energy source, via the storage of chemical free energy in the irradiation products.
14ii°/ Assessing Europa’s habitability
Thanks to its Europa Orbiter, LAPLACE will assess all the elements that play a role in Europa’s
potential habitability, focusing on the characterization of its ocean, its sea-floor, and of its surface.
Looking for Europa’s ocean
After the Galileo mission around Jupiter, both geological evidences (tectonic features and surface
composition) and geophysical data (induced magnetic field and gravity field) are strongly in favour ofthe existence of a deep liquid layer below an icy crust. However, although very probable, the existenceof a liquid internal ocean is still not proven. If it exists, its depth is still unknown. It could be very
close to the surface (1-2 kilometers) or much deeper (20 km or more). The most robust method toprove the existence of the ocean is to use an orbiter on which accurate gravimetric and altimetricmeasurements can be achieved. Indeed, the presence of an ocean strongly modifies both the value ofthe periodic Love number k2 and the amplitude of surface libration due to tidal forcing. Suchmeasurements were not achieved with Galileo because of orbital and instrumental constraints (onlyflybys, no altimeter), but may become possible with the LAPLACE Europa orbiter. If the gravity
potential surface is obtained at degree 2 using a precise navigation system, it is possible to estimate thek2 love number value and prove the existence (or absence) of Europa’s ocean. If in addition an
altimeter is added to the system, it is possible to have a direct and independent proof of the existenceof the liquid layer by measuring the amplitude of surface motions due to tidal forcing. The in-situ,
gravimetric and altimetric measurements at Europa will be supplemented by ultra-precise VLBI and
Doppler tracking of the LAPLACE spacecraft by the Earth-based network of radio telescopes.
Characterization of the liquid layer is more challenging. It requires the determination of its depth,
thickness and composition. The interface between the icy crust and the ocean is expected to berelatively flat: since it corresponds to a thermodynamical equilibrium between a solid ice and its liquidcounterpart, temperature and pressure along the interface must be almost constants, which impedes
significant depth variations. Furthermore, the flat topography of Europa is not in favor of large roots ofice below high mountains as we see on Earth. Two specific instruments can be considered forproviding direct constraints on the icy crust thickness. First, a Ground Penetrating Radar (GPR) seems
very attractive. If the icy crust is relatively thin, this instrument will provide a global mapping of theice I / liquid interface, provided that the crust is not thicker than the penetration depth, which is notgaranteed. A GPR is thus challenging but risky. A more robust instrument is a seismometer. If the
final mission can afford a lander or a penetrator, a seismometer will provide without ambiguity the
position of the ocean interface. To our knowledge, this is the only direct measurement of the positionof the ocean that can be envisaged and which will provide information regardless of the internal
structure. A third technique is based on interpretation of topography and gravity field at different
degrees. It requires a laser or radar altimeter in addition to the determination of the gravity field byradio measurements, including VLBI, two-way Doppler and delta-doppler ranging techniques.
Mapping Europa’s seafloor
If an internal ocean exists, Europa probably represents a single case, in which liquid water is in contact
with a silicate core (Figure 7). These unique conditions on Europa allow water-rock interactions,especially if any volcanism exists. The determination of the topography and/or mass anomalies at thesilicate core/liquid interface would provide hints on whether volcanism exists or has existed.
We must keep in mind that this task is a very difficult one mainly because the presence of the icy crust
above the Europa’s liquid layer decouples the surface topography from the ocean floor. But someconstraints will be inferred from the accurate altimetry measurements and the precise determination of
the gravity field at different altitudes. Moreover, magneto-meter measurements will be useful since theconstraints provided on the induced magnetic field of Europa will help to define the depth of themagnetic source.
Small scale features won’t be detectable on the silicate sea-floor, but medium-scale features (200 km)
such as large volcanoes or long ridges will probably be detected if a microgradiometer is embarked on
the Europa Orbiter. All these data (gravimetry, altimetry, magnetometry) will finally be used inmodels of the internal structure that will eventually give constraints on the ocean floor topography.
It should be stressed that, although difficult, the determination of the ocean floor topography and thestate of iron core as well have strong astrobiological implications, and can only be done if the mission
design can provide very precise navigation measurements, and both altimetric, gravity andmagnetometric measurements with very high accuracy.

15

Characterizing its surface dynamics and chemistrySurface composition and chemistry.

Galileo has proven that the surface of Europa is notmade of pure water ice. Whatever the origin of the nonwater components was, either endogenous orexogenous, their characterization is important. The
NIMS (Near Infrared Mapping Spectrometer) onboard
the Galileo mission showed that composition isdifferent along some geological features. Although
there is still some controversy on the nature of non-ice
components, compositional mapping of the interestingareas of the surface must be improved in the futurewith a higher spatial and spectral resolution infrared
mapping spectrometer. With a field of view of 0.5
Figure 8: Surface characteristics of Europa
mrad, a resolution of 1 km/pixel on the region whereobserved with Galileo. Many of these features
non-icy material has been discovered would bestrongly suggest the existence of a deep liquidobtained at 200 km altitude.
layer under the icy crust.
In addition to a NIR mapping spectrometer, the main
neutral species as well as many ion species of Europa’s atmosphere and ionosphere can be easily
measured with a mass spectrometer and dust analyzer on an orbiter at 200 km. Moreover, collecting
dust expelled from the surface of Europa, and analysing their composition will constrain the origins ofbuilding blocks that took part to its formation (via the D:H ratio in ice if we assume that surface
altering can be quantified with LAPLACE) and the thermodynamical conditions prevailing during
Europa’s formation (via the abundance of volatile species like CH4, CO2, NH3).
The composition of the surface, and even of the subsurface ocean (if connections between the interior
and the surface exist or have existed) can then be inferred. However, it should be kept in mind that thesurface environment has very extreme conditions, and materials from interior may be altered bydepressurization, abrupt change in temperature, and particularly exposure to high radiation
environment. These alteration processes must be studied, in particular by inferring the effect ofradiation and energetic particles.
Studying its global surface morphology & dynamics.
The surface of Europa is very young: both crater counting and estimation of erosion rates by sputtering(constrained by the measurements of H2O escape rates by Galileo) suggest an age of Europa’s surface
between 10 millions and one billion years. This surface presents very intriguing tectonic and volcanicfeatures (Figure 8). The size and geometry of linear features suggest surface motions enabled by icecrusted water or soft ice close to the surface. Impact features suggest the existence of a low viscosity
layer at about 5 to 20 km in depth that may be either a liquid layer or a soft ice layer. For some ofthese intriguing features, Galileo also provided topographic estimates using the shadows of theelevated terrains. Interpretations of these features gave some of the strongest arguments in favour of adeep liquid ocean below the icy crust. That is why one of the major goals of the LAPLACE Europa
orbiter will be to study surface structures in more detail was achieved by Galileo.
Both a high-resolution camera, and a laser altimeter will be put on the Europa orbiter. The fullcoverage of the surface from a low orbit will permit the acquisition of high resolution images of every
tectonic/volcanic feature. Laser altimetry measurements will bring new and valuable information on
the topography, which will be of considerable importance for understanding geologic processes, andthus constraining the coupling between the putative ocean and the icy crust.
Finally, such high-resolution analysis of the surface will help to define astrobiologically interestinglanding sites for future space missions.
Unraveling surface/exosphere/magnetosphere interactions.
The atmosphere of Europa is produced mainly from irradiation of its exposed outer surface bymagnetospheric plasma (mainly sulphur and oxygen ions from Io) and UV photons. Its main
component, molecular oxygen, has been indirectly observed by HST. Oxidized constituants producedby irradiation may also provide key components for life support within the subsurface ocean. The
atmospheric composition of Europa is determined by both the water and oxygen photochemistry in thenear-surface region, escape of suprathermal oxygen and water into the Jovian magnetosphere andexchange of radiolytic water products with the porous regolith.
16

Water ice is transformed into its gaseous state by sputtering processes and sublimation. Generally thewater sublimation rate should be extremely low. However, around the dayside equator the observed
increase of the sublimation rate of at least 4 orders of magnitudes than expected means that
sublimation could be a major process for water vapour production. Cryovolcanic activity is anotherpossible source of water vapour around satellites. "Boiling" water which may also exist due to thermal
flexing and cracks in the surface will result in a highly increased supply of water vapour to theatmosphere and thus source regions will be easily detectable.
Europa’s atmopsphere interacts with the magnetospheric plasma by a large variety of processes
including sputtering of the surface and exosphere and resurfacing due to intense bombardments byenergetic particles. Energetic ions and electrons are the principal chemical agents in layers close to thesurface of moons that could alter species originating from the deep interior and migrating to thesurface.
LAPLACE will monitor the incoming and reflected radiations, the structure and composition of theexosphere and ionosphere, surface composition to establish the net production, loss, and exchange of
key chemical species between the magnetosphere, exosphere/ionosphere, surface and subsurface.
Characterization of potential environments and search for biosignatures
If Europa is (or was) habitable, the next exploration step should be the search for any signature of lifethat the environment is able to sustain. Remote detection of reliable biosignatures is very difficult, andin situ exploration is clearly preferable. That is why the mission study includes as an option a surface
module (SE) that will allow to obtain environmental data (radiation, pH, eH, T, redox, chemistry) of
the surface, and possibly of the near-surface.Geological evidences indicate that a link between thesurface and the aqueous layer could have existed. Therefore, examination of endogenous materials,
deep enough to avoid alteration effects by Jupiter’s radiation, may reveal some clues of the aqueous
layer properties.

c.4°/ FROM SCIENCE GOALS TO MISSION CONSTRAINTS AND MEASUREMENT REQUIREMENTS
Our science goals address four different mission targets in the Jupiter system: Europa, the satellite
system, Jupiter’s magnetosphere, and the planetary atmosphere. Through a careful analysis of themeasurements to be performed, we have derived specific requirements for the measurements we needto perform on each of these objects, and specific constraints on the mission profile of LAPLACE.
They are summarized in the following four tables, which represent the traceability matrix of the
LAPLACE mission.

17

LAPLACE MISSION TRACEABILITY MATRIX

18

19

d°/ Mission profile necessary to achieve these objectives
i°/ Platform and orbit requirements
LAPLACE will deploy an observing system to perform the key observations needed at each target. As
shown in figure 9, this observing system will use a hierarchy of observing posts or platforms andstrongly link Earth-based and space-based observations.
How does the system work? How was it formed?
Is it habitable?

Science Goals
Missiontargets

1 - Europa

2 - Satellites

3 - Magnetosphere

4 - AtmosphereEart-based
observations

JWST, ALMA, VLT, ELT’s, radioastronomy
VLBI (includes interaction w. space segment)Interplanetaryorbit

V/E fly-by science, Seismology, gravity, Dust streams,
radio emissions, electron beams, etc,… (IP)Jovian orbit

Jupiter
EuropaOrbiter(JEO)

Satellite orbits

JEO

Surface

Surfaceelement ?
(SE)

Jupiter Magnetosphere Orbiter (JMO)
Jupiter Planetary Orbiter (JPO)
Ganymede orbiter ?
Figure 9: schematic showing how the different science goals and targetsof the mission will be addressed by a comprehensive observing system
including a ground-based segment and a 3-platform space-based segment
progressively deployed on “strategic” orbits and locations inside thejovian world.

Earth-based and Earth-bound observations will be conducted on two distinctive sets of targets: the
LAPLACE mission objects (Jupiter, Europa, other components of the jovian system and theirenvironment) and the LAPLACE mission spacecraft.
The former will help to prepare the mission, and then place space observations in a broader context
during the mission itself, sometimes even providing observational data not achievable by space-based
mission instruments. These astronomical observations will be conducted in a broad range of
wavelengths, from high-energy domain to low radio frequencies.
The latter will include VLBI and Doppler tracking of the spacecraft aimed at achieving very highaccuracy of trajectory characterization of all mission spacecraft in various phases of their operations.
In addition, the radio telescopes involved in VLBI tracking, as well as the Square Kilometre Array(SKA) which will be operational during the LAPLACE orbital mission, will provide a backup“eavesdropping” support to the nominal mission communication scenario enabling receipt of low datarate signals during critical and high scientific value events of the mission.
The space segment will observe the targets at progressively closer distances: from interplanetary
orbit, during the approach to Jupiter; then from Jupiter orbit; finally from satellite orbits, first at
Europa, our priority target, and possibly at Ganymede. If resources and technology allow, a Europa
surface element could be deployed. It will need to be an integrated, multi-platform observing systemof our four target. Ideally, it should include the coordinated operation of three orbiters:
The Jupiter Europa Orbiter (JEO), a nadir-pointing platform optimized for global coverage of thesurface, subsurface and internal structure of Europa, will perform a multi-month mapping of Europa
before impacting its surface.
The Jupiter Planetary Orbiter (JPO), a three-axis stabilized platform optimized for remote sensing
observations of distant objects, will observe Jupiter, its satellites and probe their internal structures.
The Jupiter Magnetospheric Orbiter (JMO), a spinning platform optimized for in-situ fields andparticles measurements, will monitor the magnetosphere, the moons exospheres and their interactions.
These platforms will operate in strong operational synergy, as the JPO will be used as a relay satellite
for the JEO data during the critical period of its operations in Europa orbit. They will also be in strong
scientific synergy: multi-point studies of the magnetosphere; combinations of close, high-resolution
20

observations Europa by the JEO with more distant, synoptic views by the JPO; associations between
ENA or radio imaging of various magnetospheric particle populations by one platform with in situ
characterizations of these same populations by another platform.
Expanded options, to be studied during the assessment phase, include a Europa Surface Element(SE), and possibly a Ganymede Orbiter as the final configuration.

ii°/ Launcher requirements and possible collaborative scenarios
We have identified at least three possible scenarios to launch and deploy this observing system. The
basic mission architecture - a multi-platform, multi-target integrated mission - clearly speaks in favourof a broad international collaboration. This is what our two preferred scenarios (1 and 2) assume.
These scenarios will have to be explored and consolidated with the international partners by means ofa joint assessment study. One stand-alone ESA scenario (3) is also proposed.
Scenario 1 - Two medium capacity launchers (Soyuz/Fregat, HIIA and upgrades, Atlas V-5,…)¾
JPO + JMO on one launch¾
JEO + (optional) SE on the second launch.
Scenario 2 - One heavy launcher (Ariane 5, Atlas 5-5…) with the JEO +1 jovian orbiter (combining
JPO and JMO). Its capacity for carrying SE (with JEO) or separate JPO and JMO spacecraft needs to
be investigated during the assessment study.
Scenario 3 - One Soyuz/Fregat launch (ESA-only mission) with two s/c: JPO/JMO and JEO. This
more constrained scenario will address more limited but more focused objectives, mainly Europa.
iii°/ Trajectories and ∆V budgets
Figure 10 illustrates our basic mission timeline, showing in the top panel how each platform moves
from orbit to orbit with time. Five mission phases can be distinguished, for which the assessment will
have to find the best possible orbits, trajectories and maneuvres, to optimize the science and minimize
the total radiation dose and ∆V budgets. Phase 0 is the interplanetary trajectory. In all studied
scenarios we suggest a 6-year long Venus - Earth - Earth swing-by trajectory with good launch
opportunities in January 2017, March 2020 and June 2023. For Jupiter Orbit Insertion (JOI), theJupiter capture strategy relies on an Io gravity assisted capture with a perijove at 4Rj and a first
apojove at ~400Rj, which is a good compromise between ∆V cost and radiation dose. A Perijove
Raising Manoeuvre (to about 13Rj) is performed at the first apojove, after which the spacecraft are
separated (JPO from JMO in scenario 1, JPO from JEO in scenarios 2 and 3). During phase 1, eachspacecraft then starts its own Jovian tour, with multiple fly-bys of jovian moons (mainly Ganymede,
Callisto and Europa) providing a unique opportunity for multi-spacecraft studies of the jovian system.
For phase 2, the JEO critical Europa mission takes place for a period of 60 to 90 day, to be validated
during the assessment phase. The JPO is placed on a 2:1 resonant orbit with Europa to serve as a relay
satellite. For phase 3, the JPO moves to a safer orbit to reduce radiation doses and relays the JEO data
to the Earth while performing multiple flybys of Ganymede and Callisto. JMO moves to a ~15x70Rj
equatorial orbit to explore the middle magnetosphere and perform multiple satellite fly-bys.

iv°/ Ground segment requirements
The ground segment must support the spacecraft operations through TM/TC links in X/Ka-band andstandard ranging, Doppler and ∆DOR navigation performance for navigating the spacecraft throughthe interplanetary transfer phase and the jovian tours including multiple Moon fly-bys and final
Europa orbit insertion. Optical navigation using a dedicated spacecraft on-board camera willcomplement the ground tracking performance. Once in Europa orbit, precise localisation using a
Huygens type VLBI network support might be necessary to meet the scientific objectives.

21

Phase 0
6 years

JOI

Phase 1(~1.5 years)

Phase 2(60-90 days)

Phase 3~2 years

Initial tour
Europa mission
Multiple Satellite flybys
Data relay
Multiple point measurements Impact observations

Cruise science
VGA/EGA

Post-Europa mission tour

time

JMO
JPO
JEO

Interplanetary cruise

Jovian orbit

Ganymede Orbiter ?

Ganymede orbit
Europa orbit

Release of
an impactor ?

Europa surface

Release of
impact impact
a penetrator ?
Scenario 1

Expanded options

Scenario 2

Scenario 3

20000000-25000000-20000000-15000000-10000000-50000000-2000000

Phase 0-4000000-6000000-8000000

Phase 1-10000000-12000000-14000000-16000000-18000000

Phase 2JMO science orbit

JPO relay
orbit

JEO
scienceorbit
aroundEuropaFigure 10: A generic timeline of mission phases for the different flight components
and the different mission scenarios and trajectory geometries for phase 0,1 and 2.

In terms of ground station, at least one ESOC station must be dedicated to support the mission in theroutine phases. One JAXA station will support the JMO once separated from JPO. In all mission
critical phases, and especially during the JEO 3-month orbiting phase, support from another ESOC
ground station and from NASA DSN stations will be needed. Additional support from the Square
Kilometer Array, foreseen to be operational (including X-band) in the 2020s, will be of great interest.
22v°/ Special Requirements
The overall scientific optimisation of the Jovian tours of the different spacecraft will have to be donetaking into account the two main special requirements affecting the mission: keeping the radiation
doses received by the three spacecraft below an acceptable level, and fulfilling Planetary Protection
requirements. The severe radiation environment forces one to optimise the spacecraft trajectories andflight system radiation tolerance such that the radiation doses remain acceptable. This affects the ∆Vbudget, the shielding mass to be considered to meet a given radiation hardening level for platform
equipment and science instruments, and the spacecraft lifetime in operational orbit. This trade-off at
mission / system level will have to be performed during the assessment phase. The PlanetaryProtection requirements of COSPAR for Europa flybys, orbiters and landers, including bio-burden
reduction, shall be applied in order to reduce the probability of inadvertent contamination of an
europan ocean to less than 1 x 10-4 per mission. In the case of JEO which impacts Europa at the end ofits mission this will likely require bio-burden reduction. In the case of JPO and JMO, the option of
reducing the probability of impacting Europa below 10-4 can relax or eliminate the need forcontamination control and sterilization.
vi°/ Critical issues
The tight mass budget limited by two medium sized (scenario 1) or one single heavy launcher(scenario 2), though much better than in scenario 3, requires stringent management of the mass
allocations. The severe Jovian radiation environment and the remoteness from the Sun and the Earthalso have implications for the mission and system design. Power must be provided with either highefficiency solar cells with concentrators or RTGs (an option that will have to be considered duringassessment). The remoteness from the Earth and the limited power resources and lifetime of JEO
poses a data volume and communications challenge which has been partly addressed by relaying datafrom JEO to JPO where it is stored and returned to Earth at a later time. This eliminates the need for ahigh gain antenna and high power transmitter on JEO mitigating the mass and power challenge for thatspacecraft. Even so, relaying back to Earth the important data volume to be generated by the mission
will require a specific strategy: design of on-board data compression and storage capacities with theappropriate robustness to radiations, data link capacities between spacecraft and to Earth, optimal use
of Earth-based reception capacities, careful sequencing of observation phases to share the resources
between all instruments and data acquisition and data relay sequences, will be major tasks for theassessment study phase.

e°/ Proposed payload instrument complement
e.1°/ OBSERVATION STRATEGYLAPLACE addresses a broad spectrum of scientific objectives covering all themes of planetarysciences. Let us now propose a possible payload instrument complement to meet these objectives.
Three complementary categories of scientific investigations satisfy the measurement requirements of
LAPLACE• measurements of the main planetary fields of Europa, and to a lesser extent of the other satellites(gravity, magnetic field, geodesy and surface topography), including their response to tidal
forcing, to retrieve the main characteristics of Europa’s ocean and determine the internal structureof the different satellites,• multi-spectral remote sensing measurements of the surfaces, atmospheres and gas tori, andpossibly sub-surfaces of the different bodies of the Jupiter system, to retrieve their compositionand dynamics and improve our understanding of the vertical coupling mechanisms between the
different layers,• in situ remote sensing of the plasmas, fields, energetic particles gas and dust populations ofEuropa’s exosphere and Jupiter’s magnetosphere, to quantitatively understand the mutualinteractions between the different bodies of the Jupiter system and its space environment.
e.2°/ OVERVIEW OF ALL PAYLOAD ELEMENTS
An overview of the detailed list of instruments which address the objectives of LAPLACE is given in
Table 1. The table shows how the instruments meet the stated scientific objectives listed in Section (c)and summarizes key resources for each of the instruments, in terms of mass, power and telemetry23

(when possible) budget. It also provides a synthesis in terms of pointing and alignment requirements
and design constraints on mission elements. Instrument heritage is also shown, clearly revealing thatthe necessary experience and expertise is in place in order to design, build and fly such
instrumentation. The resource figures rely mainly on state-of-the art and current technologies
developed in European and foreign laboratories but the significant progress in instrument design andperformances expected in the coming years will help in reducing the load on spacecraft resources(mass, power), as will be discussed later. In term of technology readiness level, most of these types of
instrumentation have successfully flown on several planetary missions, including previous missions toJupiter. A limited set of foreseen instruments are new and deserve feasibility studies during theassessment phase, as detailed in Section (e.3.iii). The stringent jovian radiation environment around
Europa however places much higher constraints on spacecraft and instrument subsystems, as describedin Section (e.4).
e.3°/ AN EXAMPLE OF A POSSIBLE SET OF SCIENCE PAYLOAD ELEMENTS
Using the list of instruments from Table 1 as our starting point, and a realistic estimate of spacecraft
resources for each mission scenario and each platform, we have identified a possible payload
complement, given for illustrative purposes.
It consists of core scientific instruments, addressing high-priority science objectives, plus
complementary instruments, for each scenario and mission elements.
In addition, our payload complement includes specific high-priority instruments which requirefeasibility studies in order to demonstrate their ability to achieve the required science performance.
Finally, we recommend inclusion of scenario-dependent instruments in case it is demonstrated during
the assessment phase that our proposed expanded options are achievable.
i°/ Scientific payload mass allocation and shielding strategy
Preliminary investigations have been carried out in order to assess the scientific payload mass
allocation on each platform and for each scenario. The outputs of these studies are detailed in Section(f). The resulting minimum/maximum achievable payload mass allocations including shielding aredetailed in Table 2. The lower values arise from the consideration of a 5% launch mass margin at
platform level and are the ones taken into account for the definition of our core payload complement.
Our proposed additional complementary instruments, listed in order of priority, should be considered
together with the maximum payload mass allocations. The stringent radiation environment around
Jupiter forces us to consider high shielding masses for each of the instruments. This critical issue
clearly will deserve further dedicated studies, both at platform and instrument levels, and will require a
unified approach and an access to integrated and common facilities for all instruments in order toreach the required level of protection against radiation. Since definitive specification levels are not yet
available, we choose to introduce realistic shielding coefficients in order to ensure we do notunderestimate this issue. Therefore, we reduce payload mass allocations by 20% both on JPO and
JMO, and by 40% on JEO in the case of scenarios 1 and 2, and by 20% on JPO and 30 % on JEO in
the case of scenario 3 since we target a shorter lifetime for the latter spacecraft. At the end, these
reductions enable us to consider the instrument masses given in Table 2 in order to fit our proposedcore payload complement with the resulting mass budget.
ii°/ Mission Element strategy
The science objectives of LAPLACE will only be met by a combination of measurements from thevarious instruments onboard all the mission elements. In order to optimize scientific return, we haveselected our list with the objective of maximizing complementarities and synergies between individual
instruments, between different platforms and to each specific target. We have also made use of thespecific pointing requirements of each platform (e.g. section d), by allocating preferably nadirpointing instruments to JEO, remote sensing instruments to JPO, and particles-and-fields instruments
to JMO.
Our payload mass allocations and shielding strategy result in similar payload mass allocations on the
JEO for all three scenarios. Therefore, we propose at this stage to include the same core payload
complement independently of the scenario considered. This is also valid in the case of our proposed
additional instruments, except that these additional instruments are only considered for scenarios 1 and2 owing to the strict limited achievable payload mass allocation for scenario 3. In the case of the JPO,
our proposed core payload complement is very similar between scenarios 1 and 2 except on two
counts. First, we propose to include a more reduced plasma package for scenario 1 compared to24scenario 2 since the former scenario enables us to include the JMO with a complete magnetosphericinstrument suite. Second, we choose to allocate more mass to the cameras for scenario 1 compared toscenario 2 in order to achieve a better resolution. Whereas our core payload complement does notdiffer significantly between scenarios 1 and 2, this is not the case for our proposed additional
instruments, notably in term of prioritization. In the case of scenario 1, our first priority is given to ahigh-energy neutral atom imager on the JPO since this instrument will provide the overall context ofthe magnetospheric in-situ measurements taken from the instruments on the JMO. In the case of
scenario 2, our first priority is given to supplementary mass allocation for the cameras. Finally, ourproposed payload complement on the JPO for scenario 3 is severely constrained by the limited
achievable payload mass allocation.

Table 1 : Comprehensive list of instruments to be considered for LAPLACE, meeting the scientific objectives
listed in section (e) and showing key specifications, resources and design constraints. The actual core payloads
for each spacecraft can be extracted from this list once the available p/l resources are determined. The color codeused is the same as in traceability matrix. Instruments that have never flown in the jovian environment areunderlined, new ones are indicated.
A detailed description of these instruments is available at http://jupiter-europa.cesr.fr/

25

Table 3 :Proposed set of science payload elements for eachspacecraft and for each scenario.

Compared to Table 2, highly-integrated instrument packages havenow been introduced and make it possible to include as core payload
several of the additional complementary instruments listed in Table
2, for the same payload mass budgets.

Table 2 :Proposed set of science payload elements
for each spacecraft and for each scenario.

Core scientific instruments have been chosen to ensure the prime scienceobjectives of LAPLACE are addressed,as well as fitting with the preliminary
lower mass budget offered by each mission element. Additional
complementary instruments are also proposed, if higher mass budgets areachievable.
To be studied and scenario-dependent instruments are also included.
Color codes are used to designate the three main categories of instruments.

One last justification for our proposed payload complement needs to be highlighted. The LAPLACE
mission will enable for the first time multi-point measurements of the jovian system to be obtained.
To take advantage of this unique opportunity, we need to include similar instruments on-board several,
if not all, of our mission elements, independent of the scenario considered. This concerns particularly
the magnetospheric in-situ instruments. Magnetometers are essential instruments since they address
both the planetary and magnetospheric objectives of the LAPLACE mission. It seems therefore logicalto include such instrumentation on each platform. Charged-particle detectors covering energy range
from a few eV to several MeV will be carefully designed to provide detailed information oncomposition and charge state of the jovian magnetospheric plasma. These key measurements will
enable us to go beyond the limited or incomplete measurements provided by the various spacecrafts
which previously investigated the jovian magnetosphere. It is particularly appropriate to include such
instruments on each platform, even with reduced capabilities. Second, such an opportunity concerns
also the cameras since they will enable us to observe simultaneously different or similar locations onto
the surfaces of the jovian satellites, at different resolutions. Since the JPO will spend most of its orbital
time at moderate but not close distances from the jovian satellites, we ensure that onboard framing
cameras will be able to observe these objects with enough resolution and allocate them in consequencea larger mass than on the JEO. As a general rule, the more payload mass is available, the more isallocated to the cameras.

26

iii°/ Specific instruments to be studied during the assessment phase
Penetrating radar
A ground penetrating radar is a very attractive but challenging instrument that could provide adefinitive answer concerning the presence of a sub-surface ocean at Europa as well as a unique
diagnosis of the structure of the ice shut. Following the promising conclusions of the dedicated ESA
CDF study ‘Europa Low Resource Radar’, a further instrument assessment study is recommended. On
scientific aspects, a full-scale sensitivity study is required to estimate the effects of the external andinternal structure of Europa (ionospheric effects, radio noise, radiation environment, surface
properties, temperature profiles and ice dielectric properties) that can affect significantly the radar
performances. Current models should be consolidated by analyzing all related data returned by the
Galileo spacecraft. On technical aspects, further studies on the design, accommodation, deployment
and data commissioning of the instrument are required. The feasibility study should also analyse thepossibility of using the altimetric mode of this instrument.
Micro-gradiometer
A micro-gradiometer is expected to bring strong scientific added-value for the study of the internal
structure of Europa by obtaining high-resolution gravity field information. But its implemention on the
JEO imposes strong constraints on the spacecraft design. An instrument assessment study, following
the dedicated ESA study ‘Gravity Sensor Technology for Future Planetary Mission’, is required todemonstrate that it can meet its science requirements: the instrument has to be exactly at the centre ofmass of the spacecraft, or, alternatively, the position of its centre of mass has to be precisely
monitored. Moving parts in the spacecraft (e.g., propellant in the tanks) must be precisely monitored inorder to correct the gravity gradient measurements. This instrument requires a very accurate
knowledge of the attitude (angular velocities and angular accelerations, which are part of themeasurements), and an in-flight calibration system/strategy. In case this instrument can not be
implemented on JEO, we will rely on a conservative approach based on classical Earth-based tracking(Radio Science experiment) in order to determine the gravity field of Europa and its time variation due
to tidal deformation.
Doppler spectro-imager
The roadmap we are planning for jovian seismology will include a feasibility study, both to assess thefeasibility of a space version of a Doppler velocity imager (with possible heritage from very similar
helioseismic experiment) and to prove the capability of the space instrument to achieve the required
performance for detection of the jovian oscillations. We are also considering the possibility to apply forsupport from the Framework Programme 7 Space Theme - Strengthening of Space Foundations
Activity. The feasibility study will also include the analysis of the possibility to integrate the Doppler
imager as a specific visible channel within a fully integrated spectrograph/camera package, allowing toconsider it as a possible option for scenario 2.
Penetrators
For penetrators for the Europan surface the feasibility of such instrumentation requires analysis;
confirming survival to very high-speed impacts and operations lifetime issues (thermal concerns due
to cold conditions, insulation, batteries, RHU); communications (surface material transparency toradio, need for a trailing aerial). The ruggedness of seisometers is an issue as is heat flow
measurement feasibility. An initial study of a mineralogy/astrobiology instrument should be carriedout as well as miniature attitude control systems and selection and development of a de-orbit motor.
iv°/ Summary
A possible set of desired payload elements for each scenario and each platform has been identified anddescribed in the previous section, which fits within the anticipated payload mass and power budgets,
using inputs from Table 1 and outputs from Section (f). In addition, a tentative list of complementary
instruments, ordered in term of priority, has been considered in case the payload mass budgets
increase. These critical issues will require further study during the assessment study, which will alsoneed to revisit the prioritization of payload elements on the basis of technical and scientificperformance analysis.
In order to maximize the science return of LAPLACE it would be highly desirable to include thecomplementary instruments identified over and above the core payload already described. Our study
has been performed using a rather conventional approach that considers the scientific payload as27

independent passengers. It is clear that the best way to optimize the science return with respect to thelimited available resources (mass, power, telemetry) is to follow an integrated payload approach,where individual instruments share common subsystems such as DPU, electronics, and power, as
described below.
e.4°/ RECOMMENDATIONS
i°/ Proposed procurement approach and international partners.
In order to design the best possible payload, and to open its scientific utilization to the best scientificteams, we strongly favour selection of all payload elements on all platforms to the broad scientificcommunity, by the way of an open call to at least all countries contributing to LAPLACE, followed byinternational peer review and subsequent final selection decision according to the internal rules of eachof the funding space agencies. This international opening of all platforms will also reinforce theinternational collaboration on LAPLACE, and is likely to push for instrument teams with broad
geographical base and scientific expertise.
ii°/ Critical issues - The radiation environment and a highly integrated payload approach
A mission to the Jupiter system presents important technical and engineering challenges. The limited
payload mass coupled with low power levels and the harsh radiation environment dictate that thedesign of both the spacecraft and the accommodation of science instruments follow a new approach. A
Robust, Efficient, Autonomous Payload approach hereafter referred to as a highly integrated
payloadwill maximize the LAPLACE mission science return in two ways: (1) by minimisingoverlapping resources and optimising the sharing and utilisation of available hardware within the
payload (mass and power savings will be translated directly into increased accommodation for science
instruments and enhanced flexibility of on-orbit operations); (2) the risks of premature instrument or
mission failure due to radiation effects will be minimised by the design of spacecraft electronics
including autonomous redundancy implementation and optimal use of instrument accommodation andspacecraft shielding.
Survival for an extended period of time in the jovian radiation environment rests upon the careful
design and selection of the components and materials of both spacecraft and instruments. Space
electronics and in particular mass memory and processors, are susceptible to a number of radiationinduced effects which can lead to a variety of performance reduction and failure modes. Theseradiation effects are broadly separated into two categories: a) Total Ionising Dose (TID) damage andb) Single Event Effects (SEE). TID damage presents itself as a gradual degradation in operation andperformance of electronic components and can have a considerable effect on the power production
efficiency of solar panels. It is the less serious of the two effects and can be minimised and evenreversed by various strategies such as minimal component power-on time and thermal annealing
cycles. Also of concern is the SEE rate of mission critical components. A radiation induced SEEsuch as Single Event Latchup (SEL) could lead to a mission critical failure due to component burnout
in the power or communications system for example and a SEE within a mission critical segment of
the spacecraft memory could lead to software corruption with associated serious effects. It should be
noted that the use of silicon-on-insulator (SOI) substrates can reduce component sensitivity to SEE’s.
As an example of the radiation environment, the TID behind 8 mm of Al shielding accumulated from a
66 day tour of Europa is of the order of 1 Mrad. A comfortable level of margin will therefore demandhardware that is hardened to the several Mrad level. This dose is well beyond the level at whichcurrent space qualified mass memory, processors and other components are rad hardened. The full
realisation of the Jupiter mission science goals and those of the Europa orbiter (JEO) in particular, will
rely on a trade off between spacecraft shielding and the radiation tolerance of the electronics. Any
reduction in shielding requirements can be translated into an increased instrument capacity and thus
science return. The use of alternative shielding materials such as Ta coupled with a multi-layered
approach with different materials can serve to both reduce mass and increase the radiation resistanceover a broader range of particle energies. Previous studies have shown that solar cells are also
susceptible to degradation in an intense radiation environment with the result being an appreciable
decrease in output power. A 1 MeV electron flux at Europa (9.3 RJ) of ~1013 cm-2.day-1 integrated
over a 60 day tour will lead to a 20 % reduction of the solar cell output. It is thus clear that mission
planning and operations will have to account for the inevitable reduction in available power over the
mission lifetime.
28

It is clear that the jovian environment drives the REAP instrument accommodation architecture whereseparation of the sensor from the rest of the instrument (instrument electronics, interfaces etc.) is acentral feature and offers several distinct advantages. In order to minimize the risk of instrument
failure, as much of the instrument as possible should be enclosed within a shielded environment with
only the front end sensor exposed to the environment. This co-location of a large portion of the
instruments also provides the opportunity to share resources; centralized DC/DC conversion forcommon electronic component standard voltages being one example. This resource requirement
reduction is complementary with the second benefit of the REAP approach which is a high level of
hardware redundancy.
This co-location of the majority of the instrument components provides an opportunity for a departurefrom the traditional instrument accommodation approach where each individual instrument isallocated a dedicated processor and mass memory. The instruments under the REAP approach will
instead have access to multiple processors with a single processor at a time being operational(depending on the overall instrument suite processing load). This approach offers significant resourcesavings and ensures a high level of redundancy against radiation induced instrument loss. If a
processor displays signs of radiation induced degradation then a replacement will be automaticallyassigned to service the instruments. A mechanism providing automatic switch over of the failed
components without damaged in the switchover operations will be central to the implementation of the
REAP architecture.
e.5°/ AN EXAMPLE OF A POSSIBLE SET OF HIGHLY-INTEGRATED SCIENCE PAYLOAD ELEMENTS
Table 3 illustrates the mission benefits gained from including a possible highly integrated payload
approach. Such an approach will make it possible to include as core payload a number of theadditional complementary instruments introduced in Table 2, thereby increasing significantly thescience return of the LAPLACE mission. A specific study during the re-assesment phase of the
BepiColombo payload of the Mercury Planetary Orbiter identified a possible mass reduction of about
60 % by designing instruments towards a highly integrated payload suite.
Without addressing this issue at the level of the entire payload, here we introduce in Table 3 twocategories of highly-integrated instrument package, a remote sensing one (consisting of optical andspectroscopic instruments) and a magnetospheric one (consisting of fields and particles instruments),
for illustration purposes. We also propose an attempt to combine the laser altimeter receiver with acamera, for a targeted mass of 7 kg.
Our proposed camera and spectrometer compact packages (N.B.: each with different resolutions,hence different focal lengths) could be similar to the various approaches used in the case of the
BepiColombo SIMBIO-SYS or proposed in the case of the Pluto Express HIPPS or Deep Space 1
MICAS packages. The latter attempted to combine two cameras, an ultraviolet imaging spectrometerand an infrared imaging spectrometer plus all the thermal and electronic control for 12 kg, all its
sensors sharing a single 10-cm diameter telescope.
Our proposed magnetospheric packages (N.B.: each with different performances, without including amagnetometer) could be similar to the approach developed and used in the case of the Rosetta-RPC
package, which combines five sensors - ion and electron sensors, an ion composition analyzer, aLangmuir probe, a mutual impedence probe together with a magnetometer - for 7.45kg and 12.1W.
We strongly recommend to study the feasibility and design of highly-integrated payload elements
during the assessment phase, to ensure that this approach will preserve the expected science
performances of individual instruments while providing additional resources. A clearly identified
outcome of this assessment study could be the definition of a generic multi-mission concept for otherfuture planetary missions, enabling more frequent launches and reducing the schedules.

f°/ Basic spacecraft key factors
The preliminary spacecraft design presented here is mostly derived from the recent ESA studies (JMEand JSE) that have been performed by Astrium. Some new investigations and updates have been
carried out especially for scenario 1 in order to assess more precisely the science payload mass
allocation on each of the three orbiters : JPO, JMO and JEO. For scenario 2 a dedicated study should
be carried out in the assessment phase when the potential heavy launcher and international partners are
more precisely identified. If an Ariane 5 is assumed, then the payload mass allocations of JPO andJEO will probably be about the same as in scenario 1, with however the JPO payload combining now
29the payload of JPO and JMO. For scenario 3 the JPO and JEO payload mass allocations are known
from the JME ESA study results which have not been updated here.
i°/ Spacecraft Configuration
The three spacecraft configurations proposed in scenario 1 are shown in Figure 11. The JPO is basedon the same concept as during the ESA studies, a square tube structure in CFRP fitting four Eurostar
2000+ propellant tanks and an Astrium-ST 500N main engine at the bottom . It also holds a fixed
1.5m X/Ka-band antenna and two 1dof articulated solar arrays supporting in total 18m2 of LILT solar
cells and twice this area of solar concentrators, which are mandatory to provide enough power (350W
EOL) at a reasonable weight. A small area of solar cells and OSRs is implemented at the back of thesolar arrays to provide power when too close to the Sun, where using the solar concentrators is
prohibited due to cells over-heating. The platform electronics, embedded in a radiation vault, and the
payload instruments can be accommodated on one lateral wall that stays always in shadow during thetransfer phase, thus optimising the thermal control system. The JMO spacecraft is a squared structurethat interfaces with JPO though its four upper corners. It contains a small hydrazine propulsion systemand two large solar arrays equipped of LILT solar cells (without concentrators because they can not be
pointed exactly to the Sun due to the constraint to point the antenna boresight, aligned with the spin
axis, to the Earth). The JEO is actually mounted on a carrier propulsion stage which is a recurrent JPO
platform. This enables to optimise the JEO for its final Europa orbiting mission while minimising
spacecraft development costs. JEO uses a bi-liquid propulsion system with four small tanks and acentral ATV-like 250N thrusters of Isp around 300s. The JEO solar arrays are the same as JPO andcan provide 300W at EOL. JEO accommodates a 2-axis articulated antenna which supports a morerobust and flexible link with the Earth, allowing to maximise the science data acquisition and thespacecraft monitoring from the ground (full ground station coverage is assumed during the threemonths orbiting Europa). The platform electronics, embedded in a radiation vault, and the payload
instruments can be accommodated on the upper wall (below the antenna) and on the Nadir pointed
lateral wall.

JPO + JMO

JMO
Figure 11 : Spacecraft Configurations

JEO + propulsion stage

30

ii°/ Spacecraft Functional Architecture
A preliminary functional architecture is shown in Figure 12 for JPO. The JEO one is quite similar butwith an articulated antenna and less thrusters. It is based on a highly integrated centralised avionics
architecture embedding the processors, mass memory, Power Control and Distribution Unit, star
tracker electronics, reaction wheels electronics, and Inertial Measurement Unit. This new
development, which could be based on the ESA Highly Integrated Control and Data System predevelopment performed (but finally not retained) for Bepi-Colombo, is an essential enabling
technology for reducing the mass, volume, power consumption, and shielding mass required on JPO
and JEO. A common digital processing and power distribution unit is also foreseen for the payload
instruments for the same reasons. The AOCS architecture based on gyros, autonomous star trackers,
Sun sensors and reaction wheels is classical of interplanetary missions but requires adaptations andupgrades for the radiation shielding of star tracker optics and reduction of gyros power consumption.
The RCS thrusters configuration relies on 24 10N bi-liquid thrusters which provides pure torqueattitude control and omnidirectional thrust capability, very useful near Venus to perform TCMs
without exposing critical spacecraft faces to the Sun. The RF system uses a X/Ka-band system withmultiple antenna (one HGA, two MGA and two LGA). The second MGA is used during the earlycruise phase when the Sun – Spacecraft – Earth angle excursion is very large and there are stringent
pointing limitations due to the high Sun flux. Indeed it is intended to restrict Sun illumination to only
two spacecraft faces in order to optimise the thermal control concept for the near Jupiter phase.
According to JAXA, the differences between JPO and JMO are: (1) JMO is a spinner and has anattitude control system including Sun sensor, star scanner, and nutation damper. (2) Integrated DataManagement Controller (DMC), which is under development for BepiColombo, will take care of data
flow, attitude, orbit, thermal, and power delivery control. (3) The propulsion system consists of 8~16
thrusters (3~10N-class) capable of 6-directional orbit control and pure-torque attitude control (monopropellant hydrazine system)

Figure 12: JPO Functional Architecture31

iii°/ Spacecraft Budgets
Details of the spacecraft mass and power budgets preliminary estimates can be found at
http://jupiter-europa.cesr.fr/
The estimated dry and wet mass budgets for the three spacecraft in scenario 1 (assuming two SoyuzFregat launchers) include classical maturity margins and a 20% system margin, as well as substantial
allocations for shielding mass (15kg for JPO, 70kg for JEO, i.e. 2 to 3 times more than in the previous
JME study). The maximum achievable payload mass allocations are about 75kg for JPO and JEO, and25kg for JMO, including a provision for shielding (20% on JPO & JMO, 40% on JEO) and maturity
margins. If a 5% launch mass margin is targeted, then the payload mass allocations drop to 50kg on
JPO and JEO, along with a 20% reduction in shielding mass at platform level.
A preliminary power budget including a 20% system margin gives payload power allocations of 50W
for JEO, from 20 to 100W for JPO (depending on the Earth communications mode), and 20W for
JMO. Obviously the power budget is very tight and deserves a careful consolidation during theassessment phase. The JPO and JEO solar arrays are sized to produce respectively 350W and 300W at
EOL, which just fit the needs. The JEO orbit around Europa shall avoid eclipses, otherwise a strong
limitation in payload allocations or spacecraft lifetime will result. This means that the orbit local solar
time shall be higher than typically 4:30pm on a 200km altitude circular orbit. At EOL the JEO power
resources are just enough to recharge the battery in-between two eclipses by Jupiter, which can not be
avoided. The JEO power budget supports simultaneous Nadir pointed science and Earthcommunications, using the articulated antenna, except during the Jupiter eclipse when science must be
reduced for power saving purposes.
JPO can provide up to 50W of power to JMO while attached, which is expected to satisfy thermal
control needs only. Full JMO check-outs at Jupiter will have to be done on battery power or without
Earth communications. The JPO power budget can not support simultaneously full remote sensing
science and high data rate Earth communications, which is not a real problem as JPO remote sensing
science phases will be mostly during short duration jovian moons fly-bys, with the fixed HGA offpointed from the Earth. The rest of the time 20W is allocated for low power in-situ field and plasma
instruments.
The RF link budgets are not detailed here but they are expected to be quite similar to those studied in
the recent ESA studies.
iv°/ Critical Issues and Open Points
There are several critical issues that deserve more detailed investigations in the future assessment
phase. Radiation shielding and hardening is probably the most serious one. It has been computed withthe latest radiation model developed for ESA, based on Divine & Garett, GIRE and Salammbô; thatthe three spacecraft would experience the following doses on their respective orbits:•
JPO : 600krads behind 4mm Al or 300krads behind 6mm Al•
JEO : 1100krads behind 12mm Al or 850krads behind 14mm Al•
JMO : 250krads behind 4mm Al
The shielding mass allocations (15kg on JPO and 70kg on JEO) are enough to shield a volume about
0.15m3 with 4mm and 14mm thick Aluminium walls respectively on JPO and JEO. Therefore if it canbe proven in the future assessment phase that this volume covers all platform electronics equipment,
then a radiation hardening qualification level up to ~600-800krads should be targeted for electronics
parts. Actually a dedicated study and technology predevelopment program is required to adequately
prepare the LAPLACE mission with respect to radiation issues. Possibly the most critical electronics
part deserving the highest attention are memory components, for which state-of-the-art is very far
from those levels. It is recommended to investigate alternative solutions like hard discs, to be spacequalified. The preliminary estimates of the needed mass memory sizes amount to typically 50Gbits for
JEO, which represents a week worth of science data volume, and about 500Gbits for JPO, whichcorresponds to the accumulated JEO science data during its 3-month mission, assuming a limited JPO
downlink capacity during that same time due to the required sharing of the same ground stations, andthe priority given for the monitoring and commanding of JEO.
The 1MeV equivalent fluences experienced on the spacecraft trajectories have been computed with thesame radiation models, assuming coverglass thicknesses of 500µm for JEO and JPO, and 130µm for
JMO. The results amount to 2.75.1015#/cm2 for JEO, 5.75.1014#/cm2 for JPO and 3.1015#/cm2 for JMO,
which, using recent LILT test results from ESA, Astrium and JPL, correspond to radiation degradation
32

factors of 0.86 for JEO, 0.92 for JPO and 0.86 for JMO. Accounting for some margins and otherfactors, the sizing of the solar arrays has been done with EOL degradation factors of 0.75 for JEO,
0.85 for JPO and 0.8 for JMO, and assuming a LILT solar cell efficiency of 34% at low temperature,
which is the best state-of-the-art today. Here again, a dedicated pre-development program is required
to confirm the availability of such LILT solar cells for the LAPLACE mission.
solar concentrators are strictly mandatory for JEO and JPO. The V-trough reflectors concept proposedin the baseline design, already flown by Hughes or JAXA with different outcomes, are expected to
improve the solar array efficiency by 75% for an over-weight of less than 7%. Other concepts like
Fresnel lens systems could also be envisaged in the future assessment phase. Furthermore it can not be
excluded that next generation US RTGs with high specific power efficiencies become available forEuropean spacecraft in international cooperation missions like LAPLACE. Therefore this option shallalso be studied in the assessment phase.
Highly integrated centralised avionics systems are also necessary to reduce the overall mass andvolume of the Data Handling System. A relevant ESA pre-development initiative was the Highly
Integrated Control and Data System performed for Bepi-Colombo even if it was finally not selected at
project start. This effort shall be resumed with even more ambition, to integrate the star sensor andreaction wheels electronics, and the Power Distribution Unit.
v°/ Other Mission Scenarios
The previous description of the basic spacecraft key factors applies to the mission scenario 1 with twolaunches by medium launchers. The second envisaged scenario consists in a single launch by a heavy
launcher like Ariane 5 ECA or Atlas 5. In that case the launch composite would consist in a JPO-likespacecraft carrying a JEO. The JPO-like orbiter could be very similar to the one in Scenario 1, exceptthat its payload should integrate the JMO payload as much as possible. The JEO spacecraft mass
allocation (nearly 2 tons) would be typically twice the current mass estimate of the wet JEO (~1 ton)
on top of its propulsion stage in Scenario 1, but the required propellant load would also double.
Overall a small increase of the JEO payload mass allocation can therefore be anticipated. This mission
scenario could well support an international collaboration with NASA through a NASA-provided JEO
spacecraft on top of the ESA JPO orbiter in an Ariane 5. Open issues are the possibility to launch US
RTGs from Kourou and the adequation of the JEO mass allocation to NASA Europa Orbiter concepts.
The back-up all-European scenario consists in the JME scenario where JPO and JEO are launched by asingle Soyuz-Fregat. This scenario has been studied by ESA and Astrium, and its characteristics arewell known. Its major drawback is the limited payload mass and power allocations (less than 35kg /20W on JEO and 20kg / 15W on JPO). Its main other technical limitations, which are all mitigated by
the selected Scenario 1 with two Soyuz-Fregat launches, are the requirement for radhard electronics up
to 1Mrads (because of limited shielding mass), a shorter life-time around Europa, less flexibility androbustness in the communications concept (no 2-axis articulated antenna on JEO, less frequent JEO –JPO relay), and in the AOCS (less capable reaction wheels, no pure torque thrusters configuration),and less conservative mass and power budgets.
Finally two other mission options were considered. The first one consists in inserting JPO in orbit
around Ganymede after its JEO relay mission is over. However it has been checked that ellipticalorbits around Ganymede are instable, and the ∆V cost to acquire a circular orbit around Ganymede is
too high and not compatible with carrying the JMO spacecraft to Jupiter, unless a more powerfullauncher than Soyuz-Fregat is used, for example the H-II(A), .. Indeed JAXA has checked that if the
H-II(A) is used for the JPO-JMO launch, an estimate shows that the total mass (wet) after the Jupiterorbit insertion can be increased by 400kg. There are several options to utilize this increased resource
to enhance the science of the mission. To list a few of them :(1) Increase the payload mass on JPO and/or JMO.
(2) Increase the power supply to the payloads.
(3)Use it to load the propellant on JPO so that the spacecraft will be inserted into a stable circular orbit
around Ganymede in its final stage.
The last mission option consists in carrying a small Europa surface impactor on JEO, but this seems
not feasible unless a heavy launcher is selected and the penetrator weight is much less than 100kg,
which deserves a dedicated study in the future assessment phase.

33g°/ Science operations and archiving
i°/ Mission Operations concept
The precise mission operation scenario will mainly depend on the level of international cooperation:
the general principle is that after spacecraft separation, each Agency controls the spacecraft under its
responsibility, with its own means. ESA will be responsible for the coordination of all groundinfrastructures. Dedicated communication links shall be considered. ESOC will have theresponsibility for the mission operations of ESA-led spacecraft elements (JEO and JPO). ESAC will
perform the scientific payload operations on ESA-led elements, in relation with the PI teams.
ii°/ Ground Segment Facilities
The ground facilities will consist of:• The ground stations and communication network of involved agencies and partners (radio
astronomers)• The Mission Operations Centre (MOC): hosted at ESOC, responsible for all spacecraft-related
issues, which includes mission planning, orbiter monitoring and control, orbit and attitude
determination and control, communications with the spacecrafts, data downlink• The Spacecraft Operations Centre (SOC): hosted at ESAC, responsible for the coordination of
the long- and short-term scientific planning of the mission, preparing with the PI teams thedetailed operational timelines and delivering them to the MOC
The
PI teams: interacting with the SOC, to prepare operational timelines for their instrument•
and to provide high-level scientific data for long-term archiving.
iii°/ Mission Operations
The operations of simultaneous spacecrafts will take advantage of the methods of interplanetary
mission operations developed for Rosetta, as well as of the collaboration schemes developed for
Cassini-Huygens and BepiColombo.
In the frame of the recent Jupiter System Explorer study, the specific impacts of operating two
spacecraft flying to Jupiter at a one-week interval was assessed with ESOC and considered feasible
with a modest increase in ground station coverage. The mission operations will also be adapted to thehigh level of autonomy foreseen for the spacecrafts, especially for the JEO.
The orbit determination during all the mission phases will use two-way range and coherent two-way
Doppler tracking data with the help of ground stations. During the critical phases of the mission, an
overall support of all Agencies ground facilities should be foreseen, in partnership with other groundfacilities, such as SKA radio telescopes, for direct-to-Earth downlink or radio science. The
coordination between ESOC and radio astronomers will require a dedicated operational interface tobe specified.
iv°/ Data Processing and archiving
The data processing and archiving strategy will be defined at a later stage of the mission design.
However, the multidisciplinary scientific aspects of the mission will require a coordinatedapproach to ensure full data availability to interdisciplinary studies.
v°/ Proprietary data policy
The proprietary data policy will comply with the rules of each international partner, and defined in
the MOU signed between all agencies contributing to LAPLACE. The proprietary data period
should be just long enough to allow for the validation of the data by the PI teams, but as short as
possible to allow quick access of all data to the broadest possible community of users via the longterm ESA archive (the Planetary Science Archive) and international data centers.

34

Jupiter Europa : Laplace Mission
Ground Segment Overview
JPO

Scientific data

JEO

Scientific data

Scientific data

JMO

TT&C

TT&C

(TBC)

Command & Data
Acquisition Element

Command & Data
Acquisition Element

SKA radiotelescope
(TBC)

USERS
Science Data Center

Processing & Archiving
Element (PAE)

Mission Operation& Satellite Control
Element

JAXA Mission Center

Figure 13: Preliminary Ground Segment overview

h°/ Key technology areas
As any deep space projects, the LAPLACE mission will have to deal with several critical technologies
such as intelligent on-board data processing and storage, long distance communications (which require
low noise receivers and large Earth stations), resources minimisation (mass, volume, power).
The Galileo mission and the JUNO mission under development demonstrate that U.S. technologies are
suitable for the jovian environment. For Europe a number of specific key technologies will have to be
developed, particularly for overcoming the radiation issues and planetary protection aspects while
keeping the mass low, and high accuracy navigation required for the science.
Radiation issues
A first step to be done in the short term is to assess the sensitivity of the foreseen instruments,
particularly for detectors and electronics. On the other hand, the mass issue is such that miniaturized
instruments are also necessary. Unfortunately, highly integrated electronics is quite often very
radiation sensitive and trade-off will have to be done to optimise the instruments. The correct
identification of these difficulties is vital for the national agencies funding the instruments to start new
developments as early as possible.
In parallel, the same radiation assessment is to be done on the existing European technologies used forplatform subsystems (power generation is a critical example). This step is also essential to identify thefields where new developments are necessary or collaborations must be discussed.
At spacecraft level, sectorial analysis will also play a major role to optimize the shielding where
necessary/possible, with acceptable mass penalty. To cover these analyses, accurate radiation models,
powerful simulation tools and later on test facilities will be required.
In case of the use of radioactive devices (RHUs or RTGs), a specific analysis will also be required.

35

Planetary protection
A careful early analysis of the problem is there also necessary to size the requirements to the realneeds, because they may have a huge impact on the technical definition of the spacecrafts and their
mission. However, on this field, European expertise exists at ESA level and partly at national level.
Precision navigation
The science return expected on the internal structure of the moons and planet requires very accurate
navigation, in an environment characterised by the radiation aspects, the presence of numerous bodies
and a large distance from the Earth. Early modelling studies are to be performed immediately to assess
the criticality of the problem and extract constraints on the orbits, the spacecrafts and other mission
elements.

i°/ Preliminary programmatics and costs
i°/ Overall proposed mission management structure
The following organization is proposed, based on the BepiColombo organization scheme, is illustrated
in Figure 14. Each Space agency has its own management office, composed of a program manager, aproject manager and a project scientist. This “core” management team constitutes the LAPLACE
Program Board.
Each Project Scientist manages the Science Working Team (SWT) which is the assembly of all
instrument PIs, namely JEO/SWT, JPO/SWT, JMO/SWT. All pI instruments are also under the
responsibility of a Payload Manager of the spacecraft engineering team. The assembly of all
instrument’s pIs constitute the LAPLACE Science Working Team.

Figure 14 : Proposed LAPLACE mission management structure(1) The ESA project manager will also manage the launch segment and the ground segment
facilities.
(2) The JAXA project manager will also manage the Japanese Ground Segment facilities and thelaunch segment if JAXA provides a H-II(A) launcher.
(3) Depending on the US contribution, NASA will also manage, in addition to its groundsegment, any launch segment contribution to the LAPLACE mission.
(4) Roscosmos will also be included at the high-level of the management of the cooperation, andwill monitor its own flight elements while sharing the conduct of science with other partners.
ii°/ Mission schedule drivers.
Technology developments (identified in section h) will be the first driver in the mission development
timeline. According to the ESA plan for implementation of L-class missions, the corresponding
studies and developments will come very early, being actually part of the selection process. On theside of JAXA, which plans to develop solar-power sail technology for outer planets exploration, the
PrePhase-A study of the technology demonstration mission has been completed. Its launch is expected36

to be in the middle 2010’s, in time for possible application to LAPLACE. So everything indicates thatin the early 2010’s substantial upgrades in the readiness of some of the new technologies usable forthe LAPLACE mission will have been accomplished.
As the mission preparation develops, lessons from JUNO will become available at the level of
mitigation techniques against radiations through the NASA partnership.
Good planetary windows are available starting in 2017, with additional ones in 2018 and later, so thatmeeting a launch window will not very strongly constrain the mission.
iii°/ Overall mission cost analysis.
The assessment study will identify the ESA-funded contribution to this mission, limited to the 650 M€
envelope ceiling, through discussions with identified partners (JAXA, NASA and RosCosmos). The
cost on the JAXA side is estimated to be lower than the largest science mission managed by JAXA todate (SELENE). NASA’s current plans for a mission to Europa and/or the Jupiter system are for aflagship-class mission, before consideration of a possible international cooperation for this mission.
Table 4 shows a very preliminary estimate of the cost break-down and total ESA costs for eachscenario, if ESA provides the two launchers and all orbiting platforms except JMO. Provision of asurface element by Roscosmos would be a separate budget item, not charged to ESA.
Scenario 1

Scenario 2

Scenario 3

Spacecraft : JPO+JEO

320 Spacecraft : JPO+JEO

320 Spacecraft : JPO+JEO

270

Spacecraft : JMO

tbd

Planetary protection

24 Planetary protection

24 Planetary protection20

Pre-implementationphase

6 Pre-implementationphase

6 Pre-implementation
phase

6

Launchers : 2 S/F
Groundsegment
operations

100 Launcher : 1 AR5&

98 Ground segment
operations

150 Launcher : 1 S/F&

98 Ground segment
operations

50
&

98

ESA internal costs

70 ESA internal costs

70 ESA internal costs

70

Contingency

130 Contingency

130 Contingency

130

Total

748 Total

798 Total

644

Table 4

Cost estimates are given in M€, e.c. 2007

Scenario 3, the most studied so far, adds up to just 646 M€, and could therefore be a viable, standalone mission option, should all international partnerships fail to materialise.
Scenarios 1 and 2, although they exceed the cost cap for L-class missions, represent the opportunityof a large international cooperative mission, with a high level scientific return. In this context, NASA
cooperation would lead to the procurement of one spacecraft, thus leading to a cost for ESA lower
than the L-class cap. The cost of JMO is not estimated at this time, since it is procured and funded by
JAXA. The spacecraft industrial activities costs are ROM costs, including the H/W, systemengineering, management/PA, AIT and facilities, ground support equipment, and some common
developments for the spacecrafts. Planetary protection is explicitly addressed in the form of extra costs
for sterilisation procedures and induced system-level studies and techniques. The cost estimates do notinclude technology development that must be led to be able to manufacture the various spacecrafts(particularly: development of 1Mrad-class radiation hardened electronics, high power solar arrays):they are supposed to be funded by R&D programs carried out for Space Science needs. Groundsegment and operation costs need to be assessed in the next phases, in order to take into accountexisting facilities to be reused for the LAPLACE mission. In the meantime, an estimate of 15-20% of
the mission cost seems realistic. Launchers costs are the current costs for European launchers. Finally,
payload costs are not included in the ESA-funded budget estimates since, as proposed, instruments
will be procured and funded by national agencies after an international call for instruments.
This very preliminary estimate validates the choice of scenario 1 as our favourite, with scenario
3 as a back-up ESA-only option. A joint assessment study between ESA and all its international
partners will explore and compare additional scenarios to optimize the total budget and the use of theresources and expertise areas of each partner.
37

j°/ Communication and outreach.
i°/ Content
Exploration of planets is a highly interdisciplinary field. We propose to use the framework of the
LAPLACE mission to develop educational products that relate closely to the curriculum of european
schools in the area of science and technology (physics, chemistry, biology, technology), but also in theareas of art, languages and history. As examples: 400 years of the discovery of the galilean satellites,
exobiology (extremophiles), celestial mechanics (travel to Jupiter, travel in the jovian system),atmospheric physics, formation of the solar system (historic models like the one by LAPLACE, thecurrent view, the importance of the formation of Jupiter for our understanding of the formation of thesolar system), exoplanets...
ii°/ Organisation
Public Education is a very important issue for all space exploration missions. Therefore, it must be
done professionally and as a consequence does require a full time dedicated person, the Public
Education Person (PEP). The PEP must have experience in outreach / education and a strong scientificculture and interest. The PEP will co-ordinate the core group for Public Education Activities of themission. This group will consist of the PEP and the National Public Education Persons (NPEP), one
for each of the participating countries. The NPEPs can be scientists with experience in and enthusiasm
for education, but do not need to be full time dedicated. The NPEPs will play an active role in theoutreach activities in their country and will organise, co-ordinate and report on national activities.
They will also translate news and education products into their national langage.
The web site must be centralized and present a homogeneous and clear structure throughout. It willcontain the standard information on the mission, as well as news and be a place to download
educational materials. Similar to the ESA web site, the mission’s web site will contain links to national
sections. In these sections is presented the basic information about the project and news flashes, all in
the national language (translated by the NPEP) and a calendar of national activities. A tool for asking
questions to team scientists will also be included. As the project grows, the web site will hosteducational material (presentation, suggestions for experiments).
iii°/ Activities• Press Office activities: It is very important to have professional contacts with the media, and the
PEP will be experienced in this area. The press office activities will include (1) Production of press
releases and other printed packages, (2) Actively contact and pass information to science journalists,(3) Organisation of interviews with the team, (4) Support exhibitions and other public events
throughout Europe (and elsewhere if possible). This last activity includes (a) the organisation of an
exhibition about jovian exploration, moving through different places in Europe, (b) the organisationof yearly intense international seven day summer schools about jovian exploration (international
jovian Exploration Summer School, iJOSS) at the level of tertiary and secondary education, (c) theorganisation of seminars in the different countries, visits to schools.
• Production of printed materials for a general public: All kind of printed/printable material(leaflets, posters, lesson plans, gadgets) will be produced during the different phases of the mission(and translated into different languages). This material will be published on the web site fordownloading. Printed packages will be prepared in different languages for distribution during
activities.
• Production of educational films: The film media (DVD, internet) is becoming a more and morecommon tool to communicate science and education. We propose to produce (1) a suite of shorter(up to about 15 minutes) educational films on topics related to the mission and that closely connects
to the curriculum in science taught at schools, (2) several larger documentaries aimed at the generalinterested public about topics related to the mission (possible topics are 2010: 400 years of jovian
studies, the life of LAPLACE).

38