Transcript Presentation - Centre for Mechanical and Aerospace Science and

Plasma in the solar system:
science and missions
Stas Barabash
Swedish Institute of Space Physics (IRF)
Kiruna, Sweden
Swedish Institute of Space Physics
• Established 1957
• A governmental research institute under the auspice
of Ministry of Education. Annual budget ~ 9 M€
• Basic research in the area of space physics, space
technology/instrumentation, atmospheric physics,
and long-term observations (geophysical
observatory)
• Division of Space engineering of Luleå Technical
University and EU Erasmus Mundus SpaceMaster
program
PI missions since 1978
Experiment
PROMICS-1
PROMICS-2
V3
ASPER A
TICS/MATE
PROMICS-3
PIPPI/EMIL/MIO
ASPER A- C
IMI
MEDUSA, P IA
MEDUSA, DINA
ASPER A- 3
NUADU (Co-PI)
ICA
ASPER A- 4
SARA
PRIMA
YPP
DIM
MINA
LINA
MIPA
ENA
Mission
Prognoz-7
Prognoz-8
Viking
Phobos-1/2
Freja
Interball-1/2
Astrid-1
Mars-96
Nozomi
Astrid-2
Munin
Mars Express
Double Star
Rosetta
Venus Express
Chandrayaan-1
PRISMA
Yinghuo
Phobos-Grunt
Mars 2013
Luna-Globe
BC MP O
BC MM O
Launch, Org/Country
1978, USSR
1980, USSR
1986, Sweden
1988, USSR
1992, Sweden
1995/96, Russia
1995, Sweden
1996, Russia
1998, Japan
1999, Sweden
2000, Sweden
2003, ESA
2004, China
2004, ESA
2005, ESA
2007, ISRO
2010, Sweden
2011, China
2011, Russia
2013, China
2014, Russia
2014, ESA
2014, ESA
Target
Earth's magnetosphere
Earth's magnetosphere
Earth's magnetosphere
Mars / Phobos
Earth's magnetosphere
Earth's magnetosphere
Earth's magnetosphere
Mars
Mars
Earth's magnetosphere
Earth's magnetosphere
Mars
Earth's magnetosphere
Comet Churyumov-Gerasimenko
Venus
Moon
Technol.
Mars
Mars
Mars
Moon (lander)
Mercury
Mercury
Swedish missions
Magnetospheric physics: Viking, Freja, Astrid-1/2, Munin
Technology demonstrator: PRISMA
Atmospheric physics / Astronomy: Odin
Odin 2001
PRISMA, 2008
Astrid-2, 1999
Viking, 1986
Astrid-1, 1995
Munin, 2000
Freja, 1992
Solar wind
• Solar wind is a plasma flow blowing
away from the Sun.
• The complicated wave - particle
interaction near the photoshere (“Sun
surface”), which is not well understood, results in the heating of
the solar corona plasma from 6·103 K
to 106 K.
• The thermal expansion of the solar
corona in the presence of the
gravitation field converts the thermal
energy to the direction flow
(“gravitational nozzle”).
• Solar wind is a supersound flow of
plasma (95% p+, 5% a-particles) with
a velocity of 450 km/s and density
about 70 cm-3 (Mercury) to 3 cm-3 at
Mars
QuickTime™ and a
Sorenson Video decompressor
are needed to see this picture.
What defines the type of the solar wind interaction
• Charge particles of the solar wind can be only affected by a magnetic
field at an obstacle
• The magnetic field may originates from:
• Intrinsic field of an obstacle
• Currents induced in a conductive obstacle as a result of the
interaction
• The obstacle’s magnetic field:
• Intrinsic dipoles (Earth, Mercury, Jupiter, Uranus, Neptune)
• Local crust magnetizations (Moon, Mars)
• Conductivity of the obstacle (Mars, Venus)
• Conductivity of rocks low
• The presence of the conductive material (ionosphere, an ionized
part of the atmosphere) increases conductivity ( s ~ne , for
magnetized plasmas we >> nc)
Types of the solar wind interactions
Corotating Jovian magnetosphere
Induced magnetospheres of
Mars and Venus
Earth magnetosphere
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Terrestrial magnetosphere
Interaction with the Moon
Field of the solar wind interactions. Why is it important?
• The fundamental scientific questions to address:
• Space plasma physics: What is the structure and characteristics of the nearplanet environment? What physics governs the interaction?
• Planetology: What is the impact of the interaction (environment) on the
central body?
• Non-thermal atmospheric escape (non-magnetized planets)
• Auroral phenomena and influence on thermospheres
• Surface space weathering (airless bodies)
Magnetic field measurements. Why are they important?
•
Magnetic field measurements are essential to organize and understand energetic charged
particle and plasma measurements.
•
Magnetic field measurements also represent one of the very few remote sensing tools that
provide information about the deep interior.
• Magnetic field of Earth, Jupiter, Saturn are generated by currents circulating in their
liquid metallic cores.
• Uranus’ and Neptune’s magnetic fields are generated closer to the surface by
electrical currents flowing in high-conductivity crustal ‘‘oceans.’’
• Mercury is currently magnetized by the remains of an ancient dynamo
• Subsurface oceans on Europa, Ganymede, Callisto were first sensed by a
magnetometer
Instrumentation to study near-planet space. Particles
• Particle distribution functions: amount of particles of a
certain kind from a certain direction at a certain energy in
each measurement point
f  f (M, , , E, x, y, z)
• Types of instruments
• Ion and electron spectrometers
• Ion mass analyzers
• Energetic neutrals imagers
• Energetic particle telescopes
• Radiation monitors
• Energy ranges
• meV - 10s eV: thermal plasma
• 10s eV - 10s keV: hot plasma
• 10s keV - Mev: energetic particles
• MeV - 100s MeV: radiation flux
Mars-96 / ASPERA
Instrumentation to study near-planet space. Field and waves
• Thermal plasma density and temperature
• Langmuir probes
• Density 0.1 - 100 cm-3
• T ~ 0.1 - 10 eV
• Magnetic and electric field vectors and
magnitude. Frequency spectra
• Typical instruments
• Magnetometers
• Electric field experiments
• Correlators with particle fluxes
• Typical magnitudes
• B-field: 0.01 nT - few 10 000 nT
• E-field: 0.01 - 10 mV / m
Ørsted satellite (1999)
Basic platform requirements
• Particle measurements (energetic particles)
• Unobscured omnidirectional (4p) field of view
• Avoidance of thruster plumes and firing
• Spacecraft potential control
• Thermal plasma measurements (plasma density/temperature)
• Minimizing effect of the spacecraft on thermal plasma: booms/sticks
• Fields and plasma wave measurements
• Minimizing effect of the spacecraft
• Magnetic cleanliness
• Booms
• Electro-Magnetic Compatibility (EMC) programs. Some what more
stringent than usual (not discussed here)
Unobscured omnidirectional field of view
Lewis et al., 2009
• The main and the most challenging
requirement
• Can be fully (4p) fulfilled only on
spinning platforms
• Possible solutions for 3-axis
stabilized platforms
• 2 hemispheric identical sensors:
mass increase!
• Fan-type field of view (180° over
polar angle) on mechanical
scanners and attenuators:
attitude disturbances
• Spun sections on 3-axis
stabilized platforms: enormously
expensive
Galileo despun platform
Mechanical scanners (1)
• Typical moving mass 4 kg, L ~ 0.1 m, w ~ 1 rpm
• Typical spacecraft mass 0.5 - 1 tons, L ~ 1 m, w ~ 10-4 rpm
Spin axis
Mechanical scanners (2)
0.02°
Spin-stabilized platforms (spinners)
• Mission examples
• JAXA Mercury Magnetospheric Orbiter
• ESA Cluster (Earth magnetosphere)
• Swedish Freja (Earth magnetosphere)
• Typical spin rates 10 - 20 rpm
• Only limited imaging experiments can be
carried out
• High intensity emissions / large fields
of view
• Auroral / EUV imaging
• Scanning photometers
Freja
MMO
Cluster
Thruster plumes and firing
• Operating even attitude thrusters
(1 - 10 N) increase gas pressure
around spacecraft.
• It may result in discharge in
instruments ion optics using high
voltage of few kV
• Hydrazine / Nitrogen thetroxide
may contaminate open particle
detectors
• Usually weak requirement
• Can be fulfilled by proper
accommodation and thruster
shields (conflict with blocking of
field-of-view)
Rosetta / Schläppi et al., 2010
Attitude maneuver
Spacecraft potential
• Due to release of photoelectrons (discharging) and accommodation of
electrons and ions from the ambient plasmas (charging), spacecraft
surfaces get charged and are under a potential relative to the ambient
plasma
• Typical values between -10..-20 to +30…+50 V
• In energetic plasma on night side the potential may reach -500…-1000 V
• The spacecraft potential affects the particle measurement at the
respective energies: energy cut-off at ~q Vsc
• Differential charging over the spacecraft affects particle trajectories
• The surfaces (MLI) surrounding instruments must be conductive.
• Spacecraft potential control systems (electron emitters) may be required.
• If not possible, the spacecraft potential should be measured.
Thermal plasma measurements (1)
• Langmuir probes: small spheres (5-10 cm diam.) biased at different
voltages. The measurable is the current to the sphere (volt-amp
characteristics)
• From voltage - current curve one deduces:
• Plasma density and temperature
• Spacecraft potential (voltage when the current = 0)
• Spacecraft potential affects the surrounding plasma and the influence
should be minimized
Rosetta simulations / Sjögren, 2009
32 m
Thermal plasma measurements (2)
• Rigid (quasi-rigid) booms / sticks are required
• The length depends on the spacecraft size and plasma parameters (the
denser plasma, the shorter boom)
• The longer, the better. Minimum 1 m
Cassini Langmuir probe
Magnetic field measurements
• It is practically impossible to reduce the stray
spacecraft magnetic field from a platform to
the smallest required levels.
• Solar arrays, motors, actuators, power
systems, magnetic materials, etc
• The magnetic cleanliness programs on the
early planetary missions were enormously
expensive (will never repeat again).
• Pioneer 10 / 11 (launched 1973) achieved
0.01 nT at the 3 m distance (practical limit)
• Long booms are required: B ~ 1/r3
• Double magnetometer techniques: shorter
booms with two magnetometers to obtain the
spacecraft stray field (extra mass)
Voyager-1 (1977)
14 m
Electric field measurements
• A space voltmeter: the potential difference between two terminals (probes)
is measured.
• The electrostatic spacecraft potential (1 - 10 V) and V ~ Vsc Dsc/r
• To measure fields of Emin ~ 0.01 mV/m
L~
DscVsc
~ 30m
E min
• Booms of 30m are required!

V = V1 - V2 (measured), E = V / L
General boom designs (1)
• Rigid tubular booms max. 3 segments
mostly for magnetometers
• Scissor booms on MAGSAT (1979)
• Optical mirrors are mounted on the
magnetometer sensor platform to
‘‘transfer’’ its orientation to the main
body of the spacecraft using infrared
beams.
• Truss-like “astromast” designs (Polar /
WIND)
6m
MAGSAT
6m
General boom designs (2)
• Wire booms deployed by centrifugal force for E-field experiments and
Langmuir probes
Magnetometer
and star camera
Langmuir probe
E-field wire booms
Swedish Astrid-2
A typical plasma science spacecraft
ESA-JAXA BepiColombo / Mercury Magnetospheric Orbiter
Plasma instruments vs. remote sensing
Requi rement
Space plasma measurements
Unob scur ed hemis pher ic FoV
Spin-stabili zed p la tforms /
scanne rs
Thru ster avo idanc e
Spacecraft potentia l
Minimi zing spacecraft
influence (boo ms )
Magne tic cleanli nes s
EMC progra m
Criti cal. Chall eng ing to fulfill
Criti cal. Chall eng ing to fulfill
Remote sensing
instruments
Not requir ed
Not comp atible
Moderate. Easy to fulfill
Minor
Criti cal. Chall eng ing to fulfill
Criti cal. Easy to fulfill
Not requir ed
May not be comp atibl e
Criti cal. Chall eng ing/exp ensive to fulfill
Criti cal. Rela tively ea sy to fulfill
Not requir ed
Moderate. Easy to fulfill
• Main conclusion: Requirements (and thus platform design drivers) are
different and in general not compatible.
• Trade-off may not be always possible
Very few dedicated space plasma missions (planetary)
• Mars: Nozomi (ISAS, Japan, 1998)
• Mars: MAVEN (NASA, 2013)
• Not a spinner!
• Mercury: BepiColombo MMO Mercury
Magnetospheic orbiter (JAXA, 2014)
• Piggy-backing on ESA BepiColombo
Mercury Planetary Orbiter
MAVEN
Nozomi
Possible “main stream” solutions
• Piggy-backing on “planetary-proper” missions
• Small scale national / bilateral dedicated missions
• Proposals from the Swedish Institute of Space Physics
• 3 missions to Mars
• MOPS, a microsat on Phobos-Grunt (discussions with NPO Lavochkin)
• Mjolnir, a microsat on the ESA Cosmic vision MEMOS (proposal)
• Solaris, a microsat on a NASA discovery mission (proposal)
• 2 missions to the Moon
• Lunar Explorer, a Swedish microsat (proposal)
• A mission within the Chinese space program (under discussion)
• A microsat on Venus Express (mission idea)
Moon space plasma mission (1)
• A small space plasma mission to the Moon: Swedish Space Corporation
feasibility study of 1996
• Payload: Particle instruments, magnetic and electric field measurements
including waves
• Study conclusion: a small space plasma mission at the Moon is doable
and can be conducted on the moderate (national) level.
• Estimated cast: ca. 23 M€ (229 MSEK) in 1996
Moon space plasma mission (2)
Basic mission characteristics from the feasibility study
• Launch: Kosmos-3M/Tsiklon
• TTI (Translunar Trajectory Injection)
• From an eccentric LEO
• DV = 1300 - 2200 m/s (depending on
launcher)
• Lunar Orbit Insertion (LOI)
• Direct insertion from TTI
• DV = 1200-1600 m/s depending on the
final orbit
• Propulsion system for TTI/LOI (2 alternatives)
• Solid (STAR 24A) /Mono-propellant
• Bi-propellant/ Bi-propellant
Moon space plasma mission (3)
Basic mission characteristics from the feasibility
study
• A spinning platform with spin axis pointing
to the Sun
• 166 kg total mass at the Moon inc. 36 kg
of payload with booms
• Equatorial orbit 400 x 5000 km to sample
the lunar wake
• Communications
• Omnidirec. LGA S-band to 9-m G/S
antenna (ESRANGE): 5-6 kbps
• 40 cm HGA S-band to 9-m G/S
antenna (ESRANGE): 133 kps
Mars Orbiting Plasma Surveyor (MOPS). Overview
•
•
•
•
•
•
Dedicated space plasma mission to Mars
Earth - pointing spin stabilized platform
Direct communication with the Earth
Wet mass: 76.1 kg
Dry mass: 60.0 kg (inc. 5% margin)
Payload mass: 10 kg
•
•
•
Piggy-back on a mission to Mars
Separation right after MOI
Hohmann transfer onto a working orbit (500 km
x 10000 km, equatorial)
Life time: 1 Martian year (687 days)
Operations in the eclipse
•
•
•
•
Pre-phase A technical study completed by
Swedish Space Corporation, Solna, Sweden.
Example mother ship - Russian Phobos-Grunt
The project is technically feasible
“Art house” ideas. Impact probes
• A small (nano) satellite to conduct measurements until not- surviving
impact
• Greatly reduced platform masses
• Only for airless bodies (Moon, Callisto, Ganymede, Pluto)
• Feasible for fly-by missions or scientific objectives requiring
measurements at the surface
Pluto probe (proposal). 2.8 kg / ø22 x 7 cm
Chandrayaan-1 / MIP
Feasible AND interesting new targets (beside the Earth)
• Mercury, Mars, comets, Saturn covered
• Venus: A dedicated space plasma mission on a spin-stabilized platform
• Jupiter. Jupiter Magentospheric Orbiter (JAXA)
• Solar sail
• Combined with a mission to Trojans
• Uranus orbiter: Identified in the recent the 2011 Planetary and Astronomy
Decadal Survey
• Mission to a new type of object “Icy Giants”
• Not a dedicated space plasma mission but the Uranus’ magnetosphere is
unique: magnetic moment rotates around solar wind direction