Transcript Solar Orbiter

Solar Orbiter
A high-resolution mission to the Sun and
inner heliosphere
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Study team
E. Marsch
E. Antonucci
P. Bochsler
J.-L. Bougeret
R. Harrison
R. Schwenn
J.-C. Vial
Max-Planck-Institut für Aeronomie, Germany
Osservatorio Astronomico di Torino, Italy
University of Bern, Switzerland
Observatoire de Paris, France
Rutherford Appleton Laboratory, UK
Max-Planck-Institut für Aeronomie, Germany
Institut d’Astrophysique Spatiale, France
ESA:
Study Scientists: B. Fleck, ESA/GSFC and R. Marsden, ESA/ESTEC
Study Manager: O. Pace, ESA/ESTEC
Solar System Mission Coordinator: M. Coradini, ESA/HQ
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Solar Orbiter rationale


The Sun's atmosphere and heliosphere are
- uniquely accessible domains of space,
- excellent laboratories for studying in detail
fundamental processes common to astrophysics,
solar and plasma physics
Remote sensing and in-situ measurements,
- much closer to the Sun than ever before,
- combined with an out-of-ecliptic perspective,
promise to bring about major breakthroughs in
solar and heliospheric physics
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Close-up observations of the Sun

Imaging and spectroscopy, due to proximity, with an
order of magnitude improvement over past missions
SOHO/EIT
1850 km pixels
TRACE
Solar Orbiter
350 km pixels
35 km pixels
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Linking corona and heliosphere

Sources of solar wind and magnetic network
Solar wind emanates
from supergranular
cell boundaries in
coronal hole.
•The Solar Orbiter line-
of-sight allows detailed
analysis of the polar
outflows
• Co-rotation will
enable steady magnetic
linkage
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Basic questions

Why does the Sun vary and how does the solar
dynamo work?

What are the fundamental processes at work in the
solar atmosphere and heliosphere?

What are the links between the magnetic field
dominated regime in the solar corona and the
particle dominated regime in the heliosphere?
These questions are basic to
astrophysics in general
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Solar Orbiter firsts

explore the uncharted innermost regions of our solar
system

study the Sun from close-up (45 solar radii or 0.21
AU)

fly by the Sun tuned to its rotation and examine the
solar surface and the space above from a co-rotating
vantage point

provide images of the Sun’s polar regions from
heliographic latitudes as high as 38°
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Novel orbital design

Projected trajectory
XY-plane trajectory plot including extended mission
1.5
1
0.5
Y [AU]
Satellite
Earth
0
-1.5
-1
-0.5
0
0.5
1
1.5
thrust
Venus
-0.5
-
-1
closer to the Sun
- out of the ecliptic
-1.5
X [AU]
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Scientific goals
determine in-situ the properties and dynamics of
plasma, fields and particles in the near-Sun
heliosphere
 investigate the fine-scale structure and dynamics of
the Sun’s magnetised atmosphere, using close-up,
high-resolution remote sensing
 identify the links between activity on the Sun’s
surface and the resulting evolution of the corona and
inner heliosphere, using solar co-rotating passes
 observe and fully characterise the Sun’s polar
regions and equatorial corona from high latitudes

Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
New perspectives

Co-rotation remote-sensing observations

In-situ diagnostics of the innermost heliosphere

Close-up high-resolution imaging and spectroscopy

Observations from out of the ecliptic plane
These unique scientific perspectives
form the basis for our scientific case
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Co-rotation observations:
linking corona and heliosphere
 Global solar corona and solar wind
SOHO
Ulysses
Solar Orbiter will discriminate spatial from temporal variations
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Co-rotation observations:
linking corona and heliosphere

Boundaries and
fine structures
Solar Orbiter will
• determine relationships
between coronal and solar
wind structures on all scales
• correlate in-situ particle
characteristics with coronal
sources
• identify ion compositional
boundaries
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
In-situ measurements of the
inner heliosphere
Plasma microstate
• Temperature anisotropies
• Ion beams
• Plasma instabilities
• Interplanetary heating
Solar Orbiter will make
high-resolution plasma
measurements (10 ms)
Proton velocity distributions (Helios)
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
In-situ measurements of the
inner heliosphere
Magnetohydrodynamic
waves and turbulence
Solar Orbiter will show
• how MHD turbulence
varies and evolves spatially,
• what generates Alfvén
waves in the corona,
Spectrum of Alfvénic fluctuations:
• how the turbulence is
dissipated.
Steepening and dissipation!
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
In-situ measurements of the
inner heliosphere
Solar energetic particles
Solar Orbiter will provide
novel information on shock,
flare and CME related
particle acceleration, by
virtue of
• proximity to the Sun
• co-rotating orbit (long-
term magnetic linkage)
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Close-up observations of the
solar atmosphere
Solar Orbiter will resolve the highly structured solar atmosphere an order
of magnitude better than presently possible (both images and spectra)
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Close-up observations of the
solar atmosphere
An illustration of
the multi-thermal
nature of the solar
atmosphere
Solar Orbiter will
observe loops and
• resolve their fine
structure and
• map plasma flows
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
The Sun’s polar regions and
equatorial corona

The polar magnetic fields and the dynamo
What are the detailed flow
patterns in the polar regions?
What is the magnetic field
structure in the polar regions?
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
The Sun’s polar regions and
equatorial corona

Coronal mass ejection longitudinal extent and global
distribution
Viewing from out of the
ecliptic plane allows the
Solar Orbiter to study
- CME longitudinal
spreads
- CME directions
- the global distribution
of CMEs
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
The Sun’s polar regions and
equatorial corona

Solar luminosity variations
The Sun is the only star for which we can determine the 3-D luminosity
contribution.
Solar Orbiter will address
questions such as:
• Does luminosity vary
globally, or is brightening
at the equator balanced
by polar darkening?
• What is the angular
distribution of radiance
from active regions?
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Solar Orbiter payload

The science goals require a sophisticated suite of
remote sensing and in-situ instruments.

The mission profile demands that the instruments be
low-mass, autonomous and thermally robust.

The thermal aspects have demanded quite mature
instrument concepts at this early stage.
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Heliospheric in-situ package
Mass
kg
6
Power
W
5
Radio & Plasma Waves Analyser (RPW)
10
7.5
5
Coronal Radio Sounding (CRS)
0.2
3
0
Magnetometer (MAG)
1
1
0.2
Energetic Particle Detector (EPD)
4
3
1.8
Dust Detector (DUD)
1
1
0.05
Neutral Particle Detector (NPD)
1
2
0.3
Neutron Detector (NED)
2
1
0.15
Instrument
Solar Wind Plasma Analyser (SWA)
Solar Orbiter
kb/s
5
F2/F3 Presentations, 12 Sep 2000
Heliospheric in-situ package

First in-situ detection
of neutral (hydrogen)
atoms from the Sun

First measurement of
near-Sun dust (e.g.,
from grazing comets)

First detection of
low-energy solar
neutrons from flares
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Remote-sensing instruments
Instrument
Visible Light Imager &
Magnetograph (VIM)
Extreme UV Spectrometer (EUS)
Mass Power kb/s
kg
W
26
25
20
22
25
17
Extreme UV Imager (EUI)
36
20
20
UV & Visible Light Coronagraph
(UVC)
Radiometer (RAD)
17
25
5
4
6.5
0.5
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Visible-light Imager and
Magnetograph (VIM)
High-resolution images (35 km pixels),
Dopplergrams (helioseismology) and
magnetograms of the photosphere
Vector magnetograph
consisting of:
- 25 cm diameter
Gregorian telescope
- 5 cm diameter full
disc telescope
(refractor)
- Filtergraph optics
(two 50 mm FabryPerot etalons)
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Extreme UV Spectrometer (EUS)
High-resolution plasma diagnostics (75 km pixels)
- 120 mm RitcheyChretien feeding
spectrometer
- light-weight carbon
fibre structure with
SiC optics
- thermal control
includes radiators,
light rejection and
shield
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Extreme UV Imager (EUI)
High-resolution imaging (35 km pixels) of the corona
- EUV imaging, simultaneously
in 3 part-Sun and and one fullSun Gregorian 20 mm
telescopes
- long baffle system for
thermal control of each
telescope
- common pointing mechanism
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
UV and Visible Light
Coronagraph (UVC)
Imaging of the visible and UV emission
line corona
- imaging of visible, H I
and He II corona using
off-axis Gregorian with
external occulter
- resolving element down
to 1200 km. Stray light
<10-8 (visible)
- principal thermal
approach through
occultation and optical
rejection of unwanted
light
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Main mission features
 Orbit :
• solar orbits achieving high heliographic latitudes
(goal over 30°)
• perihelion inside 0.3 AU
• co-rotation
 Launch windows:
• as early as 2007, compatible with ESA F 2/3
• in principle every ~ 19 months:
May 2007, Jan. 2009, Aug. 2010
 Mission duration:
• cruise phase
~1.9 years (3 orbits)
• nominal mission
~2.9 years (7 orbits)
• extended mission ~2.3 years (6 orbits)
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Main mission features
 3-axis stabilised satellite:
• always Sun-pointing
• pointing accuracy (rms):
- absolute pointing error
± 3 arcmin
- relative pointing error
± 0.7 arcsec /15 min
 Payload resources:
• Mass
130 kg
• Power
127 W
• Total data rate (in observation)
74.5 kbit/s
 Spacecraft:
magnetically clean
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Programmatic assumptions
 Mission financed by ESA
 Mars Express programmatic approach (model philosophy,
industrial organisation, AIV approach, and launcher type)
 Payload, e.g. instruments, booms, antennas, etc. supplied
by the scientific community (PI approach), with science
operations directed by Project Scientist, supported by the
Science Team and Data Centre(s)
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Programmatic assumptions
 Maximum use of already developed (or to-be-developed)
hardware (e.g. technology qualified by 2004) and new
technologies planned for BepiColombo considered available
 Orbit injection by Soyuz-Fregat, launched from Baikonur
 Operations done by ESOC, only one 15m ground station
(Perth), single shift of 8 h/day, 7 days/week
 Observation during cruise phase possible, consistently with
spacecraft operation plan and radio link capability
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Schematic presentation
of the orbit
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Mission phases
XY-plane trajectory plot including extended mission
1.5
Earth
departure
Earth 1.5
swing-by
Subsequent
Venus
swing-by’s
1
0.5
Satellite
Y [AU]
X-Y-plane
trajectory
plot
including
extended
mission
Earth
0
-1.5
-1
-0.5
0
0.5
1
1.5
thrust
Venus
-0.5
-1
First Venus
swing-by
-1.5
X [AU]
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
S/C heliographic latitude
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
S/C perihelion distance
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Spacecraft design approach
 Mission lifetime:
4.7 years (extended 7.1 years)
 Solar aspect angle:
0° (Sun pointing)
 Spacecraft:
3-axis stabilised
 Observations:
30 days around each perihelion
 Lift-off mass:
1296 kg, with 130 kg payload
 Power:
7500 W, on cruise
457 W, on nominal mission
 Science data rate:
according to data dumping strategy
(science data at 74.5 kb/s in observation, stored on 240 Gb
on-board memory, dumped through HGA at max 750 kb/s)
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Spacecraft design approach
 Configuration:
Modular concept (SVM, PLM) at structural level
 Structure:
S/C body: 3 m x 1.2 m x 1.6 m,
compatible with Soyuz-Fregat type-S fairing
 Stabilisation:
3-axis, pointing accuracy for imaging,
thermal, and High Gain Antenna (HGA)
Sensors: star sensors, sun sensors, and gyros
Actuators: reaction wheels (3+1) and hydrazine
thrusters ( 2 x 6, 5 N) as main actuators
 Propulsion:
Solar Electric Propulsion (SEP) for transfer
orbit and cruise phase, with 4 x 0.15 N
Stationary Plasma Thrusters (SPT),
commercially available in 2003
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Launch configuration
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Spacecraft in cruise phase
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Spacecraft in observation mode
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Spacecraft in data-dump mode
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Spacecraft design approach
 Power supply:
2 solar arrays, 50 V bus regulated, with 2 Li-ion, 200 Wh batteries
Cruise solar array (for SEP):
- two steerable wings of 4 panels, 14 m2 each (7500 W at 0.33 AU)
- dual junction GaAs solar array, jettisoned at end of cruise phase
- standard telecom technology, with edges protection
Orbiter solar array (for S/C):
- two rotating wings (0° - 90°), 86% OSR, 14% GaAs cells, 10 m2,
(500 W at 0.89 AU) to power orbiter in nominal operation
- BepiColombo technology
 Data handling:
- standard ESA TT&C with centralised control unit for S/C operations,
attitude and orbit control, thermal control
- 240 Gb on-board mass memory
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Spacecraft design approach
 Thermal Control: Combination of active and passive devices
- Front sunshield (5 Ti foils + 20 Ka/Dacron net and upper Ti foils
coated with white paint), covering S/C main body and mechanisms
- Use of radiators and heat pipes, also for PLM CCDs cooling
- Variable Orbiter solar array/Sun angle (0°-80°) according to Sun-S/C
distance
 Communications:
TT&C:
Standard ESA X-band up- and down-links, omni-directional
by 4 LGAs, 20 W
Science Telemetry:
- 20 W, Ka-band, for up to 750 kb/s (at 0.7 AU, turbo code) science
data dump rate
- Dump strategy as from 0.5 AU (S/C-Sun distance) by 1.5 m,
Cassegrain, HGA antenna, mounted on deployable boom and shielded
for distance < 0.5 AU
- BepiColombo technology for HGA
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Spacecraft budgets
Budgets
Mass / kg
Power /W
Baikonur
Launch
Cruise
Power / W
Orbiter**
Payload module
130
0
127
Service module*
806
7500
330
7500
457
System margin
Fuel
89
271
Spacecraft
1296
* Including 50 kg for L/V adapter; ** System margins included
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Cost at completion
Cost estimate
Million Euro
- Procurement
(ESA + industry +
overheads + contingency)
- Spacecraft operations
- Science operations
- Launch
Total project
149.4
35.3
3.9
35.0
223.7
Current (year 2000) flexible mission budget envelope = 181.7 M Euro
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Technical summary
 The mission design concept meets all the scientific
requirements for solar and heliospheric observations
close to the Sun (0.21 AU) and at high inclination
with respect to the solar equatorial plane (38°).
 The spacecraft design concept is feasible with the
assumption that all the required technologies would
be available off-the shelf or from the BepiColombo
programme.
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000
Conclusions: Solar Orbiter...
will explore unknown territory near the Sun
 will deliver the first images of the solar poles
 will provide unprecedented high-resolution
observations of the Sun (> 35 km)
 will correlate in-situ & remote-sensing measurements
at 45 Rs from a co-rotational vantage point
 is technically feasible (using electric propulsion)
 will maintain ESA’s position at the forefront of solar
and heliospheric physics

...is the next logical step towards
understanding our star, the Sun.
Solar Orbiter
F2/F3 Presentations, 12 Sep 2000