International Colloquium and Workshop "Ganymede Lander: scientific goals and experiments"

International Colloquium and Workshop "Ganymede Lander: scientific goals and experiments"


Ganymede
is
composed of rock and ice. It has intrinsic
magnetic field, that makes it an exciting object for investigation.



Its plasma composition is c consists of Jupiter
magnetospheric

particles and ions originated from the surface of
Ganymede. Interaction of Ganymede’s and Jovian magnetospheres
leads to acceleration of ions and complicated transport.



Analysis of ion flux, composition and velocity distribution
provides important tool for Ganymede’s soil composition and
characteristics, not only on local scale but also on planetary scale,
due to transport within Ganymede’s environment.

International Colloquium and Workshop "Ganymede Lander: scientific goals and experiments"

FOOTPRINT OF GANYMEDE

International Colloquium and Workshop "Ganymede Lander: scientific goals and experiments"

Auroral

footprint

of

Ganymede

i
s

produced

by

electric

currents

generated

by

motion of
the

satellite

relative Jovian
magnetic field. This current
flow
s

along

Jupiter's

magnetic

field

lines and
exites

the glow
of

the

upper

atmosphere
.
This

ultraviolet

image

of

Jupiter

was

taken

with

the

Hubble

Space

Telescope

Imaging

Spectrograph

(STIS)
on

November

26,
1998
.

T
enuous oxygen
atmosphere of
1.2

×

10
8
–
7

×

10
8

cm
−3

and hydrogen atoms
of ~
1.5

×

10
4

cm
−3

Intrinsic magnetic moment
is about 1.3

×

10
13

T∙m
3
directed against the
Jovian magnetic moment. 720
nT

at equator (Jovian magnetic field 120
nT
).

M
oves
relative to
Jovian
magnetic field with
subsonic velocity. Its
magnetosphere
has diameter
is 4
–
5

R
G

(
R
G

=

2,631.2

km)

Ganymede has
airglow
near
±

50
°

latitude, which is exactly the boundary
between the open and closed field lines of the
Ganymedian

magnetosphere

Relative motion induces magnetic field that suggests
highly conducting
ocean.

Energetic electrons and ions
(tens and hundreds
of
kiloelectronvolts
)
hit
Ganymede’s
surface that leads to
sputtering

International Colloquium and Workshop "Ganymede Lander: scientific goals and experiments"

International Colloquium and Workshop "Ganymede Lander: scientific goals and experiments"

Measurements requirements

International Colloquium and Workshop "Ganymede Lander: scientific goals and experiments"

Combination of internal and induced magnetic fields
-
> open magnetosphere

Ganymede’s
surface and atmosphere



Atmospheric/ion composition and its losses to the

magnetosphere


Fluxes of accelerated ions and electrons near
Ganymede
and/or
at its

surface
.


Surface sputtering and implantation of energetic ions


Mapping of surface composition


Jovian magnetosphere and its interaction with
Ganymede


Ion composition of plasma and accelerated particles


Ganymede’s
role in
magnetospheric

plasma population


Magnetospheric

plasma dynamics


Electromagnetic interaction with Jupiter

International Colloquium and Workshop "Ganymede Lander: scientific goals and experiments"

Measurements of flux and velocity distribution of
suprathermal

and
energetic
ions,
and mass/charge ion composition for investigation:


-

influence on
Ganymede’s
surface


-

surface composition


-

Ganymede’s
atmospheric losses


-

composition of
Ganymede
and its atmosphere



-

Jovian
magnetospheric

plasma dynamics and the
role of

Ganymede
in Jovian magnetosphere


International Colloquium and Workshop "Ganymede Lander: scientific goals and experiments"


1

2

3

4

8

6

7

9

5

1
–

collimator
,
2
–

electrostatic analyzer
,
3
–

light trap
,

4
–

diaphragm
,
5
–

wedge magnet
,
6
–

drift tube
,

7
–

grids
,
8
–

secondary electron multiplier (SEM)
,

9
–

DC amplifier
,

10
–

pulse counter

Velocity distributions of proton
-

and
α
-
s
measurements in May 1972.

International Colloquium and Workshop "Ganymede Lander: scientific goals and experiments"

1

2

3

4

5

6

Structure of the instrument
:

1
–

angular scanner
,

2
–

electrostatic analyzer
,

3
–

drift tube,

4
–

magnet
,

5
–

focusing electrode
,

6
–

MCP detector

S
imulation results for solar wind ions
Fe
+7
-

Fe
+12

and
O
+5

and O
+6

with E/Q =
1
keV


(1…20
keV
/Q capability)

International Colloquium and Workshop "Ganymede Lander: scientific goals and experiments"

Energy range
,
keV
/Q

1
…20

Mass range
,

M/Q

2…9

Mass resolution,

M/
Δ
m

10
-
40

for

E/Q = 1
keV

Full

angle of view

30
0
х
30
0

for

E/Q = 1
keV

Angular resolution

~2
0

Analyzer

dimensions
,

mm

230х170х120

Estimated mass
,
kg

3.5

International Colloquium and Workshop "Ganymede Lander: scientific goals and experiments"

—
Measurements of ions, electrons and
s
econdary neutral
particles provide important tools for investigation of
Ganymede’s surface characteristics and composition


—
Ion spectrometer under development can
b
e considered as
candidate for plasma suite developed by MSSL and IKI for
exploration of planetary surfaces and planetary
magnetospheres

International Colloquium and Workshop "Ganymede Lander: scientific goals and experiments"