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TRANSCRIPT
1Final Presentation, August 2nd 2012
Alpbach Summer School 2012
iTOURInvestigative Tour Of URanus
TEAM ORANGE
2Final Presentation, August 2nd 2012
Outline
• Science case
• Mission analysis
• System engineering
• Outreach
3Final Presentation, August 2nd 2012
Mission Statement
The iTOUR mission will study the Uranus system to give crucial
answers about its current state and evolution, paying particular
regard to the unusual inclination and characteristics of the
magnetosphere by flying a slave satellite in addition to the main
orbiter.
4Final Presentation, August 2nd 2012
What do we know about Uranus?
Facts from Voyager 2 fly-by in 1986:
– 14.5 times as big as Earth
– Rotational period 17 hrs, 14 mins
– Each pole has 42 years sunlight, 42 years darkness
– 27 known satellites, 5 larger moons
– 11 rings
– High winds in upper atmosphere
© NASA
5Final Presentation, August 2nd 2012
Composition of Uranus
• Coldest planetary
atmosphere
• Density of 1.27 g/cm3
• Various ices (water,
ammonia)
• Rocky core, icy mantle
and an outer gaseous
helium / hydrogen
envelope.
6Final Presentation, August 2nd 2012
Striking aspects of Uranus’ atmosphere
• The unexpected high
velocities winds in the upper
atmosphere.
• The latitudinal wind profile
that presents a prograde
wind jet at equator and
retrograde wind jets at mid
latitudes (~ 50°).
7Final Presentation, August 2nd 2012
Magnetosphere of Uranus
• Axial tilt of 97.77o
• Magnetic field 59o from
axis of rotation
• Magnetic field does not
originate from geometric
centre
• Sun will be on opposite
side to this diagram for
our selected arrival date© Atmosphere of Uranus
8Final Presentation, August 2nd 2012
Uranus’ Magnetosphere
9Final Presentation, August 2nd 2012
Aurora of Uranus
• Around both magnetic poles
• Strong aurorae radio emissions at frequency (1–1,000
kHz)
10Final Presentation, August 2nd 2012
Uranus’ five largest moons
• Four show signs of
internal geological
processes on their
surfaces
• Miranda shows
evidence of a surface
impact
• Titania & Oberon may
harbour liquid water
undergroundEncylcopedia of Science website
11Final Presentation, August 2nd 2012
ESA’s cosmic vision 2015 - 2025
• How does the solar system work?
• What are the conditions for life and planetary formation?
• What are the fundamental laws of the universe?
• How did the universe begin and what is it made of?
• NASA’s decadal survey specifically recommended a mission
to Uranus
12Final Presentation, August 2nd 2012
Science Objectives
• Characterise Uranus’ interior
• Characterise Uranus’ atmosphere
• Characterise & investigate
Uranus' magnetosphere
• Study Uranus' satellite
and ring system
© NASA
13Final Presentation, August 2nd 2012
Interior?
Rotation rate?
Bulk composition & internal
mass distribution
Gravity field &
aggregation?
Radio emissions to provide a
proxy measure of the rotation,
gravity and two point
observations of magnetic field
High resolution imaging,
multispectral
spectrometry and gravity
field close to the planet
Visible
Infra-red
Spectrometer
Radio Science
Instrument
Radio Plasma
Wave Instrument
Magnetometer
Characterise Uranus‘ interior
Magnetic field?
Two point
observations of
magnetic field close
to the planet
14Final Presentation, August 2nd 2012
Structure & composition Dynamics Thermal
What are the condensables? Winds? Heating effect of Aurora?
Imaging
sample of
atmosphere
IR, NIR, UV
Vertical
structure of
horizontaly
propagating
waves, top
velocity winds,
IR and NIR
Charcterize
dynamics,
IR and NIR
Composition,
IR and NIR for
traces in the
troposphere
Pressure
Profile,
Radio
occultation
(X-Band)
Velocity,
vertical
temperature
profiles,
submm
Doppler
Browaden-
ing
Vertical
temperature
profile,
submm,
Aurora
imaging UV
and NIR
Ultra
stable
Oscillator
Visible
Infra-red
Spectrometer
Submm
Wave
Instrument
Camera Ultraviolet
spectrometer
Clouds?
Characterise Uranus‘ atmosphere
15Final Presentation, August 2nd 2012
Different altitude approaches for
Sounding Uranus’ atmosphere
Upper atmosphere - µbar pressure level – UV from Rayleigh
scattering + aurora features: Ultraviolet spectrometer
Visible – Reflected solar radiation at cloud tops:
Camera Visible
Thermal IR + Spectral: Visible and IR
spectrometer
Sub mm – Collision induced transition
absorption of H2 gas and aerosol particles: Sub
millimeter spectrometer
Radio – deep atmosphere and ice layer
sounding: Ultra Stable Oscilator
16Final Presentation, August 2nd 2012
StructureInteraction with
solar windDynamics
Boundaries? Plasma
population?
Aurora?
Measure inner
magnetosphere ions
& electrons
distribution function
and magnetic field
at < 20Ru
Measure outer
magnetosphere ions &
electrons distribution
function and possible
two point observations
of magnetic field at
about 20Ru.
Radio
emission
Imaging of
aurora and
solar wind
monitoring in
UV
Radiation belts,
ionosphere and
near tail?
Plasma
Package
Ultraviolet
Spectromet
er
Radio
Plasma
Wave
Instrument
Visible
Infra-red
Spectrometer
Plasma
circulation &
current system?
Simultaneous remote and in situ
observations of magnetosphere
& solar wind monitoring: ions &
electrons distribution function at
two points observation of
magnetic field at < 20Ru, and
UV Imaging aurora & ENA
imaging
Magnetometer
Characterise & investigate Uranus' magnetosphere
Interaction
with moons
& rings?
Measuring
neutral particles
near the rings &
moon
interaction
ENA
imager
17Final Presentation, August 2nd 2012
Structure &
composition
Dynamics &
interactions
Geology, age and
surface processes
Shape, size of
known and new
discoveries?
Surface
properties?
Shape &
size?
Interior?
High spatial surface
imaging <5m for
Miranda and
Titania to identify
crater rates &
cracks
Gravity and
magnetic field
anomalies,
Miranda and
Titania
High spectral
resolution
imaging of
Miranda, VIS
(<200m), IR
(spectral ?)
Specific structures, high
spatial resolution at the
beginning of the
mission & several
images at the end of the
mission; 50ms-200s
exposures
Global mapping
<1km, NAC + UV +IR
at the beginning of
the mission &
several images at
the end of the
mission
Camera
Radio
Science
Instrument
Visible
Infra-red
SpectrometerUltraviolet
Spectrometer
Tectonics &
subsurface
activities?
Surface
imaging for all
satelites, low
spatial
resolution
<1km
Structure &
composition
Temporal
variation?
Plastma
Package
Magneto
meter
Study Uranus' satellites and ring system
18Final Presentation, August 2nd 2012
Requirements – Highlights (1)
• Imaging of Uranus for atmospheric dynamics
– High spectral resolution � High data volume (4 Mbits/line)
– Large spatial coverage with spatial resolution < 100��
– Good illumination-viewing conditions � ~3.5��
• Atmospheric and � profile soundings
– Few numbers (10 − 20) of Sun Occultation measures
• Atmospheric chemical composition sounding
– Day & night-side sounding distributed around Uranus surface
– Acquisition time: 1��� per measurement
19Final Presentation, August 2nd 2012
Requirements – Highlights (2)
• Magnetic field and Charged Particles
– High variability of magnetosphere � Measures every orbit
– Close to recombination points
– Continuous measurement of magnetic field with Magnetometers
• Imaging of the aurora
– Night-side observation + Near cusp region (~4 hours observation time)
– Total Data Volume (UVIS+RPWI): 120 Mbits
• Uranus Gravity field
– RSI operations close to pericentre � No Remote Sensing on the night-
side due to HGA operation constraints
20Final Presentation, August 2nd 2012
Requirements – Highlights (3)
• Moon Imaging and Gravity field
– High-spatial res. multispectral/PAN imaging (<10m)
– High-spectral res. with moderate spatial res. (<100m)
• Rings characteristics and dynamics
– 10 PAN images with resolution <500 m + 1 Multiband (6 bands) � 200
Mbits
– Good illumination conditions
21Final Presentation, August 2nd 2012
Why two spacecraft ?
● Several designs not realistic (balloon, cubesats etc)
● Feasible designs: Orbiter & Probe vs Two orbiters
● The two orbiters design is the best compromise to fit the
science case and the engineering requirements.
Design For Against
Orbiter & Probe- In situ measurements of the surface
(noble gazes)
- The magnetic field become
secondary
Two Orbiters
- Two simultaneous measurement
points
- Main orbiter: 3 axes stabilized for
remote sensing measurements
- Slave orbiter: spinning for
magnetospheric study.
- In situ measurements of the
surface impossible
- Data rate of the spinner
may be low
22Final Presentation, August 2nd 2012
Instrument specifications
VIRHIS (Visible and InfraRed Hyperspectral Imaging)
FOV [°]:
Spectral Range [nm]:
Filters:
Image Format:
Pixel Size [μm]:
Exposure Time [ms]:
Spatial Scale TELE:
Spatial Scale WIDE:
Operating Temperature [°C]:
Mass [kg]:
Peak Power [W]:
Data Volume [MB/s]:
Heritage:
3.4
400 – 5200
2
480 x 480
27
0 – 60 000
62 m/pixel @ 500 km
125 m/pixel @ 500 km
< - 143
17
20
5
JUICE
UVIS (UltraViolet Imaging Spectrometer)
FOV [°]:
Spectral Range [nm]:
Spatial scale:
Exposure Time [ms]:
Pixel Size [μm]:
Operating Temperature [°C]:
Mass [kg]:
Peak Power [W]:
Data Volume [KB/s]:
Heritage:
0.1 x 2
50 – 320
512 x 512
1000
80
0 – 30
6.5
24
34
JUICE
Main Spacecraft
UltraViolet Imaging Spectrometer
23Final Presentation, August 2nd 2012
Instrument specifications
SWI (Submm Instrument)
FOV [°]:
Spectral Range [μm]:
Filters:
Exposure Times [s]:
Operating Temperature [°C]:
Mass [kg]:
Average Power [W]:
Data Volume [GB/year]:
Heritage:
0,15 – 0,065
550 – 230
CTS
1 – 300
- 20 to +20
9.7
48.5
5
JUICE
LORRI (Narrow Angle Camera)
FOV [°]:
Spectral Range [nm]:
Filters:
Image Format:
Pixel Size [μm]:
Pixel Binning:
Mass [kg]:
Electrical Power [W]:
Heater Power [W]:
Data Volume [MB/s]:
Heritage:
0,29
350 – 850
None (Filter wheel used from
Mars Pathfinder)
1024 x 1024
13
4 x 4
8.6
5
10
12
New Horizons
RSI (Radio Science Instrument)
Operating Temperature [°C]:
Mass [kg]:
Power [W]:
Data Volume [MB/s]:
Heritage:
-25 till 60
4.5
26
5
JUICE
RPWI (Radio Plasma & Wave Instrument)
Operating Temperature [°C]:
Mass [kg]:
Power [W]:
Range [RWI}:
Range [Search Coil Mag]
Heritage:
-20 to +50
6.8
7.0
10 kHz – 45 MHz
0.1 Hz – 600 kHz
CASSINI
24Final Presentation, August 2nd 2012
Instrument specifications
Plasma Package:
ELS (Electron
Spectrometer)
HPS (Hot Plasma
Spectrometer)
DPU (Digital
Processing Unit
Scanner
Heritage:
0.7kg
1 – 20,000 eV
0.8kg
1 – 30,000 eV
2.0kg
1.5kg
JUICE
INCA ENA Imager
Operating [keV]:
Mass [kg]:
Power [W]:
Data Volume [KB/s]:
Heritage:
3 - 300
16
14
7
CASSINI
INCA
25Final Presentation, August 2nd 2012
Instruments specifications
Search Coil Magnetometer (SCM)
Operating Frequency [Hz]:
Mass [kg]:
Power [W]:
Heritage:
0.1 – 8,000
2.0
0.090
THEMIS
FGM (Flux Gate Magnetometer)
Range:
Resolution: (lowest-
highest range)
Mass [kg]:
Peak Power [W]:
Data Volume [B/s]:
Heritage:
±128nT to ±32764nT
15pT - 4nT
3.1
3.6
1211
DOUBLESTAR
Search Coil Magnetometer
Flux Gate Magnetometer
26Final Presentation, August 2nd 2012
Model Payload - orbiter
Instrument Mass [kg] Margin
Total
mass [kg] Heritage
Main Spacecraft
VIRHIS (Visible and InfraRed Hyperspectral Imaging
Spectrometer) 17 20% 20.4 JUICE
UVIS (UltraViolet Imaging Spectrometer) 6.5 20% 7.8 JUICE
RSI (Radio Science Instrument) 4.5 10% 4.95 JUICE
SWI (Submm Instrument) 9.7 30% 12.61 JUICE
NAC (Narrow Angle Camera) 8.6 20% 10.32 LORRI
- Filter wheel for NAC 0.5 20% 0.6 Mars Pathfinder
Radio & Plasma Wave instrument (inc Search Coil Magnetometer) 6.8 5% 7.14 CASSINI
FGM (Flux Gate Magnetometer) 3.1 5% 3.255 DOUBLESTAR
MENA (Medium Energy Neutral Atom imager) 16 5% 16.8 CASSINI
Plasma package:
ELS - 1 (Electron Spectrometer) 0.7 30% 0.91 JUICE
HPS - 1 (Hot Plasma Spectrometer) 0.8 30% 1.04 JUICE
Scanner 1.5 30% 1.95 JUICE
DPU (Digital Processing Unit) 2 30% 2.6 JUICE
ELS - 2 (Electron Spectrometer) 0.7 30% 0.91 JUICE
HPS - 2 (Hot Plasma Spectrometer) 0.8 30% 1.04 JUICE
D-DPU (Digital Processing Unit) 1.5 30% 1.95 JUICE
Total: 94.3
27Final Presentation, August 2nd 2012
Model Payload – Slave satellite
Slave Satellite Mass [kg] Margin
Total
mass [kg] Heritage
FGM (Flux Gate Magnetometer) 3.1 5% 3.26 DOUBLESTAR
SCM (Search Coil Magnetometer) 2 20% 2.4 THEMIS
Plasma package (Juice)
ELS - 1 (Electron Spectrometer) 0.7 30% 0.91 JUICE
HPS - 1 (Hot Plasma Spectrometer) 0.8 30% 1.04 JUICE
DPU (Digital Processing Unit) 2 30% 2.6 JUICE
Total: 10.2
Total payload for orbiter & slave satellite: 104.5
28Final Presentation, August 2nd 2012
Model Payload – Power consumption
Instrument
Peak Power
[W] Margin Peak Power [W] Heritage
Main Spacecraft
VIRHIS (Visible and InfraRed Hyperspectral Imaging Spectrometer) 20 20% 24 JUICE
UVIS (UltraViolet Imaging Spectrometer) 24 20% 28.8 JUICE
RSI (Radio Science Instrument) 26 10% 28.6 JUICE
SWI (Submm Instrument) 46.8 30% 60.84 JUICE
NAC (Narrow Angle Camera) 15 20% 18 LORRI
- Filter wheel for NAC n/a Mars Pathfinder
Radio & Plasma Wave instrument (inc Search Coil Magnetometer) 7 5% 7.35 CASSINI
FGM (Flux Gate Magnetometer) 3.6 5% 3.78 DOUBLESTAR
MENA (Medium Energy Neutral Atom imager) 14 5% 14.7 CASSINI
Plasma package (Juice) 18.6 20% 22.29 JUICE
Slave satellite
Magnetometer package
FGM (Flux Gate Magnetometer) 3.6 5% 3.78 DOUBLESTAR
SCM (Search Coil Magnetometer) 0.09 20% 0.108 THEMIS
Plasma package
ELS - 1 (Electron Spectrometer) 18.6 20% 22.29 JUICE
HPS - 1 (Hot Plasma Spectrometer) JUICE
DPU (Digital Processing Unit) JUICE
29Final Presentation, August 2nd 2012
Observation scheduling: Constraints
• Limit data volume 2 Gbits/orbit (average)
• Simultaneous payload operation limited by available ASRG
power (110Wmaster, 25W slave)
• Best solar viewing angles achieved when the orbiter is ~ 3.5
R� from the planet
• Magnetosphere measures to be taken in-situ within the
magnetopause (< 20R�)
• Mission operations for 5 years
30Final Presentation, August 2nd 2012
Observation scheduling: Proposal
Operation schedule and observation modes for best scientific
return, fulfilling downlink, power and time constraints:
1) First scientific phase: 2 years in the baseline orbit for
reconnaissance of the Uranus system
2) Second scientific phase: Uranus satellites & magnetic field
exploration
31Final Presentation, August 2nd 2012
Observation scenario: Proposal
Proposed observation modes :
• Uranus System Survey (USS) mode: Reconnaissance of the
Uranus system by imaging the planet, rings and
measurements of the magnetic field and magnetosphere
• Atmosphere & Interior (A&I) mode: Thorough analysis of
Uranus atmosphere composition and dynamics together with
gravity field & magnetic field measurements
• Magnetosphere Research (MR) mode: Exhaustive study of
Uranus magnetic field and magnetosphere
• Moon Flyby (MF) mode: Detailed observation and analysis of
each Moon, focusing on surface and inner composition
32Final Presentation, August 2nd 2012
Observation Scenario
33Final Presentation, August 2nd 2012
Observation scenario: Proposal
USS mode: Uranus System Survey
Operations Data
Volume
[Mbits]
Peak
Power [W]
1) 120 VIRHIS samples on the day-side with along-track
scanning and 30 soundings with SWI
2) NAC imaging of the rings from 4 ��3) Continuous acquisition by Plasma Package (both
satellites) when s/c @4-20 ��4) 20 VIRHIS samples with Sun-occultation technique
5) UVIS & RPWI measuring the aurora region and 30
soundings of atmosphere with SWI
VIRHIS: 600
SWI: 960
NAC: 200
Plasma
Package: 20
UVIS: 100
RPWI: 20
70
Total Data
Volume:
1.9 Gbits
34Final Presentation, August 2nd 2012
Observation scenario: Proposal
A&I mode: Atmosphere & Interior
Operations Total Data
Volume
[Gbits]
Peak
Power [W]
1) 240 VIRHIS samples on the day-side with along-track
scanning and 80 soundings with SWI
2) UVIS & RPWI measuring the aurora region together
with magnetosphere study (Plasma Package)
3) 40 frames high spatial res. frames with PAN (NAC) at
same area previously scanned with VIRHIS
4) 10 Sun-occultation technique measures using the HGA
(Ultra-Stable Oscillator)
VIRHIS: 1040
SWI: 1280
NAC: 500
Plasma
Package: 15
UVIS: 100
RSI: n/a
100
Total Data
Volume:
3 Gbits
35Final Presentation, August 2nd 2012
Observation scenario: Proposal
Operations Total Data
Volume
[Gbits]
Peak
Power [W]
• High resolution measures (Plasma Package) for 2 days
between 4-20 ��• Medium resolution measures (Plasma Package)for 2
days near perapsis
• Low resolution measures (Plasma Package) outside
the bow-shock & MENA imaging
• Imaging (UVIS & RPWI) of the aurora regions for a
total time of 4 hours
0.8 50
MR mode: Magnetosphere Research mode
36Final Presentation, August 2nd 2012
Mission Profile
• Two spacecraft
– Master
– Slave
• Transit to Uranus: 18.5 years
• Science operations: 5 years
– Uranus Science Phase: ~2 years (1.5 x 70 Ru, polar orbit)
– Moons Science Phase: ~3 years (similar orbit, increasingly larger apocenter)
37Final Presentation, August 2nd 2012
Interplanetary Trajectory
Interplanetary Trajectory Data
Launch Date Sep 11, 2026
Arrival Date Mar 20, 2045
Gravity Assists VEEJ
AR 5 ECA Launch Capacity 4300 kg (5160 kg)
Mass at Launch needed 4100 kg
Comments:
• Jupiter rad. Belts
• Could use VVEE
38Final Presentation, August 2nd 2012
Choice of Science Orbits
Orbit Scientific Requirements
• Master
– Small periapsis
– Elliptical orbit
– High inclination
– Sun illumination
• Slave
– Elliptical orbit
– Cross the dayside
magnetopause
– Visit the magneto tail
Orbit Engineering Constraints
– Small periapsis for gravity
assist during Uranus orbit
insertion
– Small angle between
incoming orbit vector and
Uranus orbit apoapsis vector
– Slave cannot perform ∆V
(no propulsion)
Design orbits to satisfy
Requirements and Constraints!
39Final Presentation, August 2nd 2012
Considered Orbits
# Advantages Disadvantages
1
- Magneto tail
- Close to Uranus
in the day side
- Night side all the
time
- No time for remote
measurements
(at dayside)
2
- Bow shock
- Time for remote
measurements
- Long enough in
the magnetosphere
- We can’t study the
magneto tail
- Part of the time
outside the
magnetosphere
3
- Bow shock
- Time for remote
measurements
- Spends too much
time outside of the
Magnetosphere
- We can’t study the
magneto tail
Id Magnet. Remote Total
1 10 50 60
2 90 70 160
3 70 80 150
90 deg. Incl.
40Final Presentation, August 2nd 2012
Chosen Baseline Orbit
Intermediate Orbit:
• Good illumination conditions for remote sensing
• Crosses bowshock at dayside & close to reconnection points
• Spends enough time in the magnetosphere
41Final Presentation, August 2nd 2012
Uranus Science Phase
• Starts after Uranus orbit insertion
• Both Master satellite and Slave satellite are inserted at the same orbit
• Separation after insertion
• Science operations at baseline orbit for both satellites: 1 – 2 yr
• Once the science requirements are sufficiently fulfilled, go to Moons
Science Phase
Master
Slave
Comments
1.5 x 70 RU orbit feasible
42Final Presentation, August 2nd 2012
Moons Science Phase
• Follows Uranus Science Phase
• Slave stays on baseline orbit
• Master allocated 650 m/s total
∆V for moon tour
• Raise orbit of Master to cross
moon orbit (e.g. Miranda)
• Resonant Master – moon orbits
to perform flybys
• Move on to outer moon once
done
• Repeat!
43Final Presentation, August 2nd 2012
∆V Budget
Maneuver ∆V (km/s)
Interpl. navigation 0.125
Uranus OI 0.92
Miranda orbit 0.08
Ariel orbit 0.12
Umbriel orbit 0.1
Titania orbit 0.18
Oberon orbit 0.15
Moon tour navigation 0.17
TOTAL + MARGIN 1.93
44Final Presentation, August 2nd 2012
The Spacecraft Design
Cassini
BepiColombo© ESA
© NASA
45Final Presentation, August 2nd 2012
Overview
• Study Flow
• Science Driven Mission Architecture Selection
• System design trades and choices
• Programmatic issues and constraints
46Final Presentation, August 2nd 2012
SYSTEM DESIGN
BASELINE
Study Flow/Systems Engineering
Science
Requirements
Options for the
Architecture
First Estimation
for Trajectories
Trade-Off and
Selection
Concept
ExplorationTrade-Off
Systems Design
Top-down
Bottom-up
Systems
Integration
47Final Presentation, August 2nd 2012
Possible Architectures
• Orbiter only
– „Standard“ configuration, low complexity
– Science: no simultaneous measurements
• Two orbiters, smaller
– Less common design, but with heritage: BepiColombo
– Science: magnetospheric package and observations at multiple locations possible simultaneously
• Orbiter and „slave satellites“
– No heritage
– Science return insignificant because of limited lifetime
• Orbiter probe
– Heritage: Cassini, Galileo
– Probe is not required for defined science requirements
48Final Presentation, August 2nd 2012
Architecture trade-off
• Todo: Add table
• Outcome of trade-off: 1 main orbiter, 1 slave spinner
– Science driven result, needed for observations
– Feasible engineering wise
49Final Presentation, August 2nd 2012
Top Down Estimation
y = 6.952x + 212.1
R² = 0.800
0
500
1000
1500
2000
2500
3000
0 50 100 150 200 250 300 350 400
To
tal
Dry
Ma
ss [
kg
]
Payload Mass [kg]
Mission Heritage
Mission Heritage
Linear (Mission Heritage)
50Final Presentation, August 2nd 2012
Configuration
• BepiColombo heritage, fits in AR 5
• Antenna side mounted for science operations
51Final Presentation, August 2nd 2012
Communication with Earth
Design
• Required data downlink/orbit: 2 Gbit
• High Gain (with radio science package) and Low Gain Antenna
• Cassini like system 3.6 m HGA incl. LGA (100 kg)
– Size limited by launcher fairing
• Data rate from Uranus to Earth 3200 bps (X-band)
Ground Segment
• ESA ESTRACK 35 m Deep Space Antennae
– Cerebros (Spain), New Norcia (Australia)
• ESOC Mission Operations Centre
• NASA DSN compatible
• ESA ESAC data centre,
science operation planning
© ESA
52Final Presentation, August 2nd 2012
Communication Master / Slave
- Low Gain Helical Antenna (Huygens heritage)
- Transmitting in orbit plane to HGA (main)
- Max. distance is 2 Mkm, data rate is 12 kbps
- 4 h of transmission per orbit
- 2 Redundant systems
- Mass of antenna 0,5 kg
- Amplifiers and subsystems (40 W / 5 kg)
Fig.: S-Band QFH Antenna
© SSTL
Requirements from instrument on-time:
minimum is 80 Mbit per orbit
Uranus
2 million km
53Final Presentation, August 2nd 2012
Propulsion System
• Master satellite
– NH4/MMH bipropellant system
– 500N/>321s EAM of EADS Astrium
– 1/1 tanks for Lox/Fuel, 2 He tanks
~ 0.6 m spherical radius, ~ 60 kg
– Total mass: 187 kg
• Slave satellite
– No main propulsion unit
– AMPAC DSD-12 NH4 monopropellant
RCS system
– Used for spin-up, adjustments
54Final Presentation, August 2nd 2012
Thermal Control System
Temperature range for instruments/electronics 273 - 293 K
Instrumentation with low temperature:
1. NAC 217K (passive cooling)
2. UVIS 173 K (passive cooling)
3. VIRHIS 73 K (active cooling)
Power input• RTG: 480 W (3x160W) for Master
(363 W after 23 years)
• RTG: 160 W for Slave satellite (121 W after 23 years)
• Power at Venus flyby (just bus):• 150 W for Master satellite
• 70 W for Slave satellite
• Power at Uranus with margin (bus and instrumentation):
• 247 W for Master satellite
• 92.4 W for Slave satellite
Heat shields
55Final Presentation, August 2nd 2012
Thermal Control System
Cold case (Normal operation at Uranus):
- High emittance (ε): Master 0,74, Slave 0,9
- Solar Radiation: 3,4 W/m2
- Heat is generated by subsystem and instruments: Master 247 W/m2, Slave 92,4 W/m2
- Radiator: Master 0,84 m2, Slave A = 0,3 m2
Hot case (Flyby at Venus):
- Low absorptance (α): Master 0,07 Slave 0,12
- Solar Radiation: 2657 W/m2
- Heat is generated by subsystem: Master 150 W/m2, Slave 69,6 W/m2
- Master is shielded by the HGA, Slave is shielded by dedicated shield
- Radiator can never be directed towards the sun
- Multiple layers of isolation
56Final Presentation, August 2nd 2012
Power System
• TODO (Fabian)
57Final Presentation, August 2nd 2012
Driven by 0.8 arc/sec (1 sigma) pointing accuracy and 0.01˚/h pointing stability.
Master Satellite
(AOCS DV = 1700 m/s)
• 3-axis stabilised
• 3 EADS HYDRA star trackers
• 2 Honeywell MIMUs
• 4 RSI 25 Nms reaction wheels
• 24 EADS 5N hydrazine reaction
control thrusters
Slave Satellite
(AOCS DV = 700 m/s)
• Spin stabilised
• 2 EADS HYDRA star trackers
• 2 Honeywell MIMUs
• Dutch Space nutation damper
• 12 EADS 5N hydrazine reaction
control thrusters
© Rockwell Cullins© EADS Astrium
AOCS
58Final Presentation, August 2nd 2012
Load Bearing Hexagonal/Octagonal Structure
• Hexagonal inner structure:
– Improved resistance to propulsion
system loads
– Ease of propellant tank mounting
• Octagonal outer structure:
– Improved resistance to launch stress
– Ease of instrumentation, antenna
and RCS mounting
– Weight saving truss structure
59Final Presentation, August 2nd 2012
Power consumption
Base load Watt
AOCS 40
OBDH 8
Thermal Control 15
Communication (receiving) 50
Power 12
Base load at any time 125
Base load with 20% margin 150
Payload Operation Mode I 80
Communication X-band Operation Mode 90
Orbiter Slave
Base load Watt
AOCS 16
OBDH 8
Thermal Control 5
Communication (receiving) 17
Power 12Base load at any time 58
Base load with 20% margin 70
Payload Operation Mode I 60
Communication X-band Operation Mode 35
Degradation/Year %/Year Years Total Watt after 23 Y
Orbiter 1,20% 23 363,62
Slave 1,20% 23 121,21
Power sourcesOrbiter: 3 x ASRG with total power of 480 W
Slave satellite: 1 x ASRG with total power of 160 W
60Final Presentation, August 2nd 2012
Separation Mechanism (Huygens Probe Heritage)
• The separation mechanism for the Cassini/Huygens mission was developed by RUAG Space
• Separation via Pyro-nuts and bolt-cutters
• Ejection by means of compressed springs
• Spin-up of Slave satellite via helical tracks and rollers
• Umbilical connectors separation system
• Small volume and low mass (23 kg)
© Dr. Udo R. Herlack et al.
61Final Presentation, August 2nd 2012
Antenna Articulation Mechanism
Mission Requirements
• Allows for simultaneous optical,
particle and gravitational field
measurements
• High shock and vibration resistance –
Ariane 5 launch platform
• Low temperature performance: 50K
min and 343K max (reflective coating
on antenna) i.e. design for lower limit
• High pointing accuracy: ≈ 0.1°
• If mechanism failure occurs moment
arm programmed to return to
optimal static configuration
62Final Presentation, August 2nd 2012
Challenging Lifetime
Cassini
• Planned lifetime 20 years
• Launch date: 1997
• Saturn’s radiation level is
worse than Uranus
iTOUR
• 23 years duration (expected)
• 18,5 years journey
• ~5 years mission (expected)
• Launch date: 2026 (expected)
• Cold environment
• Technology improvements may
be expected
Life time infered in comparison with Cassini:
Conclusion: 23 year life-time is possible
63Final Presentation, August 2nd 2012
Mass Budget
Sub-systemMass without
margin (kg)
Total mass
(kg)
AOCS 60,2 66,2
Power 110,0 121,0
Comm 170,0 187,0
Propulsion 294,8 324,3
OBDH 65,0 71,5
Thermal 60,0 66,0
Structure 200,0 220,0
Payload 94,3 113,2
Boom 3,0 3,3
Sub-system total 1057 1171
System margin 20 %
Dry mass Orbiter 1407
Slave Satellite Wet 409
Total Dry mass 1407
Propellant 2285 2285
Launch mass 4100
Orbiter Slave
Sub-systemMass without
margin (kg)Total mass (kg)
AOCS 36,7 40,4
Power 38,0 41,8
Comms 30,0 33,0
Propulsion 14,7 16,2
OBDH 23,0 25,3
Thermal 15,0 16,5
Structure 65,0 71,5
Payload 11,0 13,2
Boom 6,0 6,6
Sub-system total 240 265
System margin 20 %
Dry mass 317
Propellant 82,9 91
Wet mass 409
64Final Presentation, August 2nd 2012
Risk Management
Mission profil
What Likelihood Impact Mitigation activities
1 Failure @ Orbit insertion C 5
simulations, inhibit safe mode,
residual risk remains
2 Collision with unknown object C 5 early investigation of equatorial disk
3 Large gradiant hot/cold case B 5 design issue
4 RTG risk on launch B 5
5 RTG risk on earth fly-by B 5
6 Failure of Ejecting Slace Satillite C 4 redundant ejection mech.; qualification
7 Failure of Boom deployment B 4
8 Failure of HG Antenna deplyoment C 4 extensive qualifications
9 Low dose rate failure C 4
10 Reaction wheel failure C 2
InstrumentsWhat Likelihood Impact
1 Failure of LORRI B 4
2 Failure of VIRHIS B 4
Comination of Severity and Likelihood
E Low Medium High Very High Very High
D Low Low Medium High Very High
C Very Low Low Low Medium High
B Very Low Very Low Low Low Medium
A Very Low Very Low Very Low Very Low Low
1 2 3 4 5
65Final Presentation, August 2nd 2012
Mission end of life
• Uranian system planetary protection: Class II
• Brief Planetary Protection Plan required
• At end of life: shut down systems, leave vehicles in orbit
– Reinvestigate if compromising discovery is made
• Mission extension may be investigated in 2050, RTGs will still
deliver sufficient power for reduced operations
© NASA
66Final Presentation, August 2nd 2012
Vehicle Disposal
• Uranian system planetary protection: Class II
• Primary option:
– Controlled collision into Titania (last moon visited) in 2050
– Allows for remote science from Earth (orbit)
– Slave’s orbit remains unchanged
• Secondary option:
– Extend operations
• Choice can be deferred
© NASA
67Final Presentation, August 2nd 2012
Mission Phases
Phase 0
• 2012 - 2013
Phase A/B1
• 2013 - 2015
Phase B2/C/D
• 2015 - 2024
Margin
• 2024 - 2026
Interplanetary Flight
• 2026 - 2045
Science Operations
• 2045 - 2050
End of life
Extension?
• 2050 - ??
68Final Presentation, August 2nd 2012
Mission Critical Items
Issues
• Thermal environments Venus/Uranus
• Low solar flux dictates use of RTGs
• Distance from sun requires big antenna
• RTG availability
To be investigated in further detail
• Interface Master/Slave
– in stacked configuration, on orbit
• Impact of RTG radiation on instrumentation
• Low data rate, European foldable antennae?
• Reduce radiation at Jupiter flyby by trajectory optimisation
• Optimise mission analysis, especially tour of moons
• RTG in Arianespace launcher, launch approval
69Final Presentation, August 2nd 2012
Cost Estimation Assumptions
Model based on expert analysis, rough order of magnitude output:
Estimation Paramater Input
Launcher Ariane 5 ECA
Number of Spacecraft 2
Cruise Duration 18 years
Operational Phase 5 years
Number of Ground Stations 1 x 8 hrs, 35 m DSA
Master Dry Mass/Payload Mass 1280 kg/ 100 kg
Slave Dry Mass/Payload Mass 308 kg/ 20 kg
Master/ Slave Propellant Mass 2000 kg/ 91 kg
Master/ Slave Total Power 430 W, 3 RTGs/160 W, 1 RTG
Specific Needs 4 Gravity Assists, Intercomms.
70Final Presentation, August 2nd 2012
Total Lifecycle Cost Estimate
Contributor Cost/M€
Ariane 5 with RTG mods. 175
Master: Platform 1150
Master: Payload 100
Slave: Platform 200
Slave: Payload 20
Total 1750
• Typical L- class mission: M€1000 (including payload)
• Payload usually covered by member states
• Thanks to Denis Moura!
71Final Presentation, August 2nd 2012
Descoping Options/Cost Reduction
• Downgrading the launcher to Soyuz only possible if 50 % of
payloads are dropped
• Slave satellite
– Saves 500 kg, M€ 220
– Should be last resort, slave satellite is needed for magnetospheric
science
• Try implementing high level of operations autonomy to
reduce costs
72Final Presentation, August 2nd 2012
Firsts achieved by iTOUR/Outreach
1. First orbiter of an ice giant
2. First detailed study of the Uranus system
3. First detailed investigation of Uranus’ atmosphere
4. First detailed study of Uranus´ magnetic field
5. First outer planet mission with two orbiters
• Exploration of an underexplored system
– We expect Cassini- like public outreach
• University and school involvement
73Final Presentation, August 2nd 2012
Announcement Of Opportunity!
• 700 kg Launch capacity remaining
• International project involvement by adding a probe?
74Final Presentation, August 2nd 2012
investigative Tour Of URanus - iTOUR
Thanks to all tutors and lecturers for your help.
We are looking forward to your questions!
75Final Presentation, August 2nd 2012
Appendix
76Final Presentation, August 2nd 2012
Ground Segment Infrastructure
iTOUR Operations
77Final Presentation, August 2nd 2012
Radiation
Electrons (dominating) & protons up to 4 MeV
Uranus Pathfinder (1UR / 16y):
Using SPENVIS (SHIELDDOSE-2) estimate a total
mission radiation dose of 20 kRad (18 krad from
cruise) behind 4 mm of aluminium.
iTOUR has its closest approach at 2UR but has
18.5 y until Uranus TID > 20 krad
Fly-by at Jupiter within 15 RJ / 42 h
�� Single Event Effects
© B
. H
. M
au
k
78Final Presentation, August 2nd 2012
Studied configurations
Cassini heritage BepiColombo heritage
Fixed antenna
SlaveInstruments
Instruments
Slave
Movable antenna
79Final Presentation, August 2nd 2012
Studied configurations
Config Hexagonal -simple manufacuring
-easy accommodation
of the instruments
HGA top - stable
- high
reliability(previous
mission)
- shielding the main
structure
- low risk , less
mechanism
- resistance to launch
stresses
- easy stacking in the
fairing volume
Sub-sat side - Requires heat shield
(Huygens Probe)
- unbalanced after
discarding
Constraints/To do Main engine must be
gimbaled
(stability complexity
and implies
mechanism for engine
maneuvers )
The orbiter and sub-
sat release
mechanism
Tube inner structure
for distribution of
stresses
Config Hexagonal - simple manufacuring
- easy accommodation of the
instruments
HGA side - easier pointing for
communication with ground
station
- less propellant required
- no complex stability
problems with the sub-sat on
top
- difficult to fit in fairing
- detailed analysis of stresses
during launch (future work)
- required reinforcement of
the primary structure
- risks of mechanisms failure
of the retractable arm
- balanced with instruments
Sub-sat top - better stacking sequence for
stress behaviour
- shielding by pointing the
HGA
To do cylinder and arm attachement
the shielding of the sub-sat by
the HGA is always possible (?)
Cassini heritage BepiColombo heritage
80Final Presentation, August 2nd 2012
Thermal Design• Selection of material for radiator in the worst case with consider absorptance (low (α) for Venus)
and emmitance( high (ε) for Uranus) where the second value is more important, because distance
from Sun increase during travel
• Uranus environment was first consider during selection, where area for radiator include
temperature of inside of satellite, power of system and environment of Venus during flyby.
• Radiator can never be face direct to Sun.
• Warming system in orbit of Uranus with switch on/off instrument and subsystem.
• 23 Kapton layers of isolation
• OSR for Master satellite and white paint silicate for slave satellite
Planet Satellite
Solar
radiationAlbedo
Albedo
radiation
Planetary
radiationPower of system Absorptance Emittance Temperature Area
- - - K
Uranus
Master
3.4 0.2820(~) 0(~)
247 0.07 0.74 293 0.84
Slave 92.4 0.12 0.9 293 0.30
Venus
Master
2657 0.820(~) 0(~)
150 0.07 0.74 303 0.84
Slave 70 0.12 0.9 281 0.30
81Final Presentation, August 2nd 2012
Possible Add-on Science
Jupiter flyby
• The interaction between the Jovian magnetospheric plasma with Europa’s
torus can be investigated through the detection of energetic neutral atoms
(measurements during the Jupiter approach (Krimigis et al., 2004) with the
ENA imager instrument).
• During the close flyby to Jupiter VIRHIS and SWI can be used to measure
the composition and density of some molecular species (already tuned in
the SWI instrument for Venus).
• Additionally, the VIRHIS instrument is also able to perform cloud tracking
at high spatial resolution.
82Final Presentation, August 2nd 2012
AOCS Delta V budget
• 100 % margin on AOCS DV budget
• Assumptions: Master satellite
– Every orbit one 10 m/s manoeuvre
– 5 x 50 m/s for safe mode recovery
• Assumptions: Slave satellite
– Every two orbits one 10 m/s manoeuvre
– 1 x 50 m/s for safe mode recovery
83Final Presentation, August 2nd 2012
Material for Radiator OSR for Master Satellite White Paint Silicate for Slave Satellite
Planet Satellite
Solar
radiationAlbedo
Albedo
radiation
Planetary
radiation
Power of
systemAbsorptance Emittance Temperature
Area of
radiator
- - - K
Uranus
Master
3.4 0.2820(~) 0(~)
247 0.07 0.74 293 0.84
Slave 92.4 0.12 0.9 293 0.30
Venus
Master
2657 0.820(~) 0(~)
150 0.07 0.74 305 0.84
Slave 70 0.12 0.9 281 0.30
84Final Presentation, August 2nd 2012
AOCS Block Diagram