Alpbach Summer School 2012
iTOUR
Investigative Tour Of URanus
TEAM ORANGE
Final Presentation, August 2nd 2012
1
Outline
•
•
•
•
Science case
Mission analysis
System engineering
Outreach
Final Presentation, August 2nd 2012
2
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.
Final Presentation, August 2nd 2012
3
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
Final Presentation, August 2nd 2012
4
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.
Final Presentation, August 2nd 2012
5
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°).
Final Presentation, August 2nd 2012
6
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
Final Presentation, August 2nd 2012
© Atmosphere of Uranus
7
Uranus’ Magnetosphere
Final Presentation, August 2nd 2012
8
Aurora of Uranus
• Around both magnetic poles
• Strong aurorae radio emissions at frequency
kHz)
Final Presentation, August 2nd 2012
(1–1,000
9
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
underground
Final Presentation, August 2nd 2012
Encylcopedia of Science website
10
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
Final Presentation, August 2nd 2012
11
Science Objectives
• Characterise Uranus’ interior
• Characterise Uranus’ atmosphere
• Characterise & investigate
Uranus' magnetosphere
• Study Uranus' satellite
and ring system
© NASA
Final Presentation, August 2nd 2012
12
Characterise Uranus‘ interior
Bulk composition & internal
mass distribution
Gravity field &
aggregation?
High resolution imaging,
multispectral
spectrometry and gravity
field close to the planet
Visible
Infra-red
Spectrometer
Rotation rate?
Magnetic field?
Two point
observations of
magnetic field close
to the planet
Radio Plasma
Wave Instrument
Final Presentation, August 2nd 2012
Interior?
Radio emissions to provide a
proxy measure of the rotation,
gravity and two point
observations of magnetic field
Magnetometer
Radio Science
Instrument
13
Characterise Uranus‘ atmosphere
Structure & composition
What are the condensables?
Pressure
Profile,
Radio
occultation
(X-Band)
Velocity,
vertical
temperature
profiles,
submm
Doppler
Browadening
Ultra
stable
Oscillator
Winds?
Composition,
IR and NIR for
traces in the
troposphere
Submm
Wave
Instrument
Final Presentation, August 2nd 2012
Dynamics
Clouds?
Thermal
Heating effect of Aurora?
Vertical
structure of
horizontaly
propagating
waves, top
velocity winds,
IR and NIR
Imaging
sample of
atmosphere
IR, NIR, UV
Visible
Infra-red
Spectrometer
Camera
Charcterize
dynamics,
IR and NIR
Vertical
temperature
profile,
submm,
Aurora
imaging UV
and NIR
Ultraviolet
spectrometer
14
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
Final Presentation, August 2nd 2012
15
Characterise & investigate Uranus' magnetosphere
Interaction with
solar wind
Structure
Boundaries?
Radiation belts,
ionosphere and
near tail?
Measure outer
magnetosphere ions &
electrons distribution
function and possible
two point observations
of magnetic field at
about 20Ru.
Plasma
Package
Plasma
population?
Measure inner
magnetosphere ions
& electrons
distribution function
and magnetic field
at < 20Ru
Magnetometer
Final Presentation, August 2nd 2012
Interaction
with moons
& rings?
Measuring
neutral particles
near the rings &
moon
interaction
ENA
imager
Dynamics
Aurora?
Radio
emission
Imaging of
aurora and
solar wind
monitoring in
UV
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
Ultraviolet
Spectromet
er
Radio
Plasma
Wave
16
Instrument
Study Uranus' satellites and ring system
Structure &
composition
Interior?
Gravity and
magnetic field
anomalies,
Miranda and
Titania
Radio
Science
Instrument
Geology, age and
surface processes
Shape, size of
known and new
discoveries?
High spectral
resolution
imaging of
Miranda, VIS
(<200m), IR
(spectral ?)
Plastma
Package
Final Presentation, August 2nd 2012
Surface
properties?
Surface
imaging for all
satelites, low
spatial
resolution
<1km
Magneto
meter
Structure &
composition
Tectonics &
subsurface
activities?
High spatial surface
imaging <5m for
Miranda and
Titania to identify
crater rates &
cracks
Camera
Dynamics &
interactions
Shape &
size?
Global mapping
<1km, NAC + UV +IR
at the beginning of
the mission &
several images at
the end of the
mission
Ultraviolet
Spectrometer
Temporal
variation?
Specific structures, high
spatial resolution at the
beginning of the
mission & several
images at the end of the
mission; 50ms-200s
exposures
Visible
Infra-red
Spectrometer
17
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
Final Presentation, August 2nd 2012
18
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 nightside due to HGA operation constraints
Final Presentation, August 2nd 2012
19
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
Final Presentation, August 2nd 2012
20
Why two spacecraft ?
●
Several designs not realistic (balloon, cubesats etc)
●
Feasible designs: Orbiter & Probe vs Two orbiters
Design
Orbiter & Probe
Two Orbiters
●
For
Against
- In situ measurements of the surface
(noble gazes)
- The magnetic field become
secondary
- 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
The two orbiters design is the best compromise to fit the
science case and the engineering requirements.
Final Presentation, August 2nd 2012
21
Instrument specifications
Main Spacecraft
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:
Final Presentation, August 2nd 2012
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
UltraViolet Imaging Spectrometer
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
22
Instrument specifications
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:
SWI (Submm Instrument)
0,29
350 – 850
None (Filter wheel used from
Mars Pathfinder)
1024 x 1024
13
4x4
8.6
5
10
12
New Horizons
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
RSI (Radio Science Instrument)
RPWI (Radio Plasma & Wave Instrument)
Operating Temperature [°C]:
Mass [kg]:
Power [W]:
Range [RWI}:
Range [Search Coil Mag]
Heritage:
Final Presentation, August 2nd 2012
-20 to +50
6.8
7.0
10 kHz – 45 MHz
0.1 Hz – 600 kHz
CASSINI
Operating Temperature [°C]:
Mass [kg]:
Power [W]:
Data Volume [MB/s]:
Heritage:
-25 till 60
4.5
26
5
JUICE
23
Instrument specifications
Plasma Package:
ELS (Electron
Spectrometer)
0.7kg
1 – 20,000 eV
HPS (Hot Plasma
Spectrometer)
0.8kg
1 – 30,000 eV
DPU (Digital
Processing Unit
2.0kg
Scanner
1.5kg
Heritage:
JUICE
INCA
INCA ENA Imager
Operating [keV]:
Mass [kg]:
Power [W]:
Data Volume [KB/s]:
Heritage:
Final Presentation, August 2nd 2012
3 - 300
16
14
7
CASSINI
24
Instruments specifications
FGM (Flux Gate Magnetometer)
Range:
Resolution: (lowesthighest range)
Mass [kg]:
Peak Power [W]:
Data Volume [B/s]:
Heritage:
±128nT to ±32764nT
15pT - 4nT
3.1
3.6
1211
DOUBLESTAR
Flux Gate Magnetometer
Search Coil Magnetometer (SCM)
Operating Frequency [Hz]:
Mass [kg]:
Power [W]:
Heritage:
0.1 – 8,000
2.0
0.090
THEMIS
Search Coil Magnetometer
Final Presentation, August 2nd 2012
25
Model Payload - orbiter
Instrument
Mass [kg]
Margin
Total
mass [kg]
17
6.5
4.5
9.7
8.6
0.5
20%
20%
10%
30%
20%
20%
20.4
7.8
4.95
12.61
10.32
0.6
JUICE
JUICE
JUICE
JUICE
LORRI
Mars Pathfinder
6.8
3.1
16
5%
5%
5%
7.14
3.255
16.8
CASSINI
DOUBLESTAR
CASSINI
0.7
0.8
1.5
2
0.7
0.8
1.5
30%
30%
30%
30%
30%
30%
30%
0.91
1.04
1.95
2.6
0.91
1.04
1.95
JUICE
JUICE
JUICE
JUICE
JUICE
JUICE
JUICE
Heritage
Main Spacecraft
VIRHIS (Visible and InfraRed Hyperspectral Imaging
Spectrometer)
UVIS (UltraViolet Imaging Spectrometer)
RSI (Radio Science Instrument)
SWI (Submm Instrument)
NAC (Narrow Angle Camera)
- Filter wheel for NAC
Radio & Plasma Wave instrument (inc Search Coil Magnetometer)
FGM (Flux Gate Magnetometer)
MENA (Medium Energy Neutral Atom imager)
Plasma package:
ELS - 1 (Electron Spectrometer)
HPS - 1 (Hot Plasma Spectrometer)
Scanner
DPU (Digital Processing Unit)
ELS - 2 (Electron Spectrometer)
HPS - 2 (Hot Plasma Spectrometer)
D-DPU (Digital Processing Unit)
Total:
Final Presentation, August 2nd 2012
94.3
26
Model Payload – Slave satellite
Mass [kg]
Margin
Total
mass [kg]
3.1
5%
3.26
DOUBLESTAR
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
2
30%
2.6
JUICE
Slave Satellite
FGM (Flux Gate Magnetometer)
SCM (Search Coil Magnetometer)
DPU (Digital Processing Unit)
Total:
10.2
Total payload for orbiter & slave satellite:
104.5
Final Presentation, August 2nd 2012
Heritage
27
Model Payload – Power consumption
Instrument
Main Spacecraft
VIRHIS (Visible and InfraRed Hyperspectral Imaging Spectrometer)
UVIS (UltraViolet Imaging Spectrometer)
RSI (Radio Science Instrument)
SWI (Submm Instrument)
NAC (Narrow Angle Camera)
- Filter wheel for NAC
Radio & Plasma Wave instrument (inc Search Coil Magnetometer)
FGM (Flux Gate Magnetometer)
MENA (Medium Energy Neutral Atom imager)
Plasma package (Juice)
Slave satellite
Magnetometer package
FGM (Flux Gate Magnetometer)
SCM (Search Coil Magnetometer)
Plasma package
ELS - 1 (Electron Spectrometer)
HPS - 1 (Hot Plasma Spectrometer)
DPU (Digital Processing Unit)
Final Presentation, August 2nd 2012
Peak Power
[W]
Margin Peak Power [W]
Heritage
20
24
26
46.8
15
n/a
7
3.6
14
18.6
20%
20%
10%
30%
20%
24
28.8
28.6
60.84
18
5%
5%
5%
20%
7.35
3.78
14.7
22.29
JUICE
JUICE
JUICE
JUICE
LORRI
Mars Pathfinder
CASSINI
DOUBLESTAR
CASSINI
JUICE
3.6
0.09
5%
20%
3.78
0.108
DOUBLESTAR
THEMIS
18.6
20%
22.29
JUICE
JUICE
JUICE
28
Observation scheduling: Constraints
• Limit data volume 2 Gbits/orbit (average)
• Simultaneous payload operation limited by available ASRG
power (110W master, 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
Final Presentation, August 2nd 2012
29
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
Final Presentation, August 2nd 2012
30
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
Final Presentation, August 2nd 2012
31
Observation Scenario
Final Presentation, August 2nd 2012
32
Observation scenario: Proposal
USS mode: Uranus System Survey
Operations
Data
Volume
[Mbits]
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 70
SWI:
960
NAC: 200
Plasma
Package: 20
UVIS: 100
RPWI:
20
Final Presentation, August 2nd 2012
Peak
Power [W]
Total Data
Volume:
1.9 Gbits
33
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
Final Presentation, August 2nd 2012
34
Observation scenario: Proposal
MR mode: Magnetosphere Research mode
Operations
Total Data
Volume
[Gbits]
• High resolution measures (Plasma Package) for 2 days 0.8
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
Final Presentation, August 2nd 2012
Peak
Power [W]
50
35
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)
Final Presentation, August 2nd 2012
36
Interplanetary Trajectory
Interplanetary Trajectory Data
Comments:
• Jupiter rad. Belts
• Could use VVEE
Final Presentation, August 2nd 2012
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
37
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
Final Presentation, August 2nd 2012
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!
38
Considered Orbits
#
Advantages
- Magneto tail
- Close to Uranus
1 in the day side
Disadvantages
- Night side all the
time
- No time for remote
measurements
(at dayside)
- Bow shock
- We can’t study the
- Time for remote
magneto tail
measurements
- Part of the time
2 - Long enough in
outside the
the magnetosphere magnetosphere
- Bow shock
- Time for remote
3 measurements
Final Presentation, August 2nd 2012
- Spends too much
time outside of the
Magnetosphere
- We can’t study the
magneto tail
90 deg. Incl.
Id
Magnet.
Remote
Total
1
10
50
60
2
90
70
160
3
70
80
150
39
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
Final Presentation, August 2nd 2012
40
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
Final Presentation, August 2nd 2012
41
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!
Final Presentation, August 2nd 2012
42
∆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
Final Presentation, August 2nd 2012
43
The Spacecraft Design
BepiColombo
Final Presentation, August 2nd 2012
© ESA
© NASA
Cassini
44
Overview
• Study Flow
• Science Driven Mission Architecture Selection
• System design trades and choices
• Programmatic issues and constraints
Final Presentation, August 2nd 2012
45
Study Flow/Systems Engineering
Options for the
Architecture
Science
Requirements
Trade-Off and
Selection
First Estimation
for Trajectories
BASELINE
Concept
Exploration
Trade-Off
Systems Design
Top-down
Bottom-up
Systems
Integration
SYSTEM DESIGN
Final Presentation, August
2nd
2012
46
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
Final Presentation, August 2nd 2012
47
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
Final Presentation, August 2nd 2012
48
Top Down Estimation
Mission Heritage
y = 6.952x + 212.1
R² = 0.800
3000
2500
Total Dry Mass [kg]
2000
1500
Mission Heritage
Linear (Mission Heritage)
1000
500
0
0
50
100
Final Presentation, August 2nd 2012
150
200
Payload Mass [kg]
250
300
350
400
49
Configuration
• BepiColombo heritage, fits in AR 5
• Antenna side mounted for science operations
Final Presentation, August 2nd 2012
50
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
Final Presentation, August 2nd 2012
© ESA
51
Communication Master / Slave
Requirements from instrument on-time:
minimum is 80 Mbit per orbit
- 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)
Uranus
Fig.: S-Band QFH Antenna
© SSTL
2 million km
Final Presentation, August
2nd
2012
52
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
Final Presentation, August 2nd 2012
53
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)
Heat shields
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
Final Presentation, August 2nd 2012
54
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
Final Presentation, August 2nd 2012
55
Power System
• TODO (Fabian)
Final Presentation, August 2nd 2012
56
AOCS
Driven by 0.8 arc/sec (1 sigma) pointing accuracy and 0.01˚/h pointing stability.
Master Satellite
(AOCS DV = 1700 m/s)
Slave Satellite
(AOCS DV = 700 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
© EADS Astrium
Final Presentation, August
2nd
2012
Spin stabilised
2 EADS HYDRA star trackers
2 Honeywell MIMUs
Dutch Space nutation damper
12 EADS 5N hydrazine reaction
control thrusters
© Rockwell Cullins
57
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
Final Presentation, August 2nd 2012
58
Power consumption
Power sources
Orbiter:
Slave satellite:
3 x ASRG with total power of 480 W
1 x ASRG with total power of 160 W
Orbiter
Slave
Base load
AOCS
OBDH
Thermal Control
Communication (receiving)
Power
Watt
40
8
15
50
12
Base load at any time
Base load with 20% margin
125
150
Payload Operation Mode I
Communication X-band Operation Mode
Degradation/Year
Orbiter
Slave
Final Presentation, August 2nd 2012
%/Year
1,20%
1,20%
80
90
Years
23
23
Base load
AOCS
OBDH
Thermal Control
Communication (receiving)
Power
Watt
16
8
5
17
12
Base load at any time
Base load with 20% margin
58
70
Payload Operation Mode I
Communication X-band Operation Mode
60
35
Total Watt after 23 Y
363,62
121,21
59
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
© Dr. Udo R. Herlack et al.
• Spin-up of Slave satellite via
helical tracks and rollers
• Umbilical connectors separation
system
• Small volume and low mass (23
kg)
Final Presentation, August 2nd 2012
60
Antenna Articulation Mechanism
Mission Requirements
Final Presentation, August 2nd 2012
•
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
61
Challenging Lifetime
Life time infered in comparison with Cassini:
iTOUR
Cassini
• Planned lifetime 20 years
• Launch date: 1997
• Saturn’s radiation level is
worse than Uranus
•
•
•
•
•
•
23 years duration (expected)
18,5 years journey
~5 years mission (expected)
Launch date: 2026 (expected)
Cold environment
Technology improvements may
be expected
Conclusion: 23 year life-time is possible
Final Presentation, August 2nd 2012
62
Mass Budget
Orbiter
Sub-system
Slave
Mass without Total mass
margin (kg)
(kg)
AOCS
Power
Comm
Propulsion
OBDH
Thermal
Structure
Payload
Boom
Sub-system total
System margin
Dry mass Orbiter
Slave Satellite Wet
Total Dry mass
Propellant
Launch
mass August 2nd 2012
Final Presentation,
60,2
110,0
170,0
294,8
65,0
60,0
200,0
94,3
3,0
1057
2285
66,2
121,0
187,0
324,3
71,5
66,0
220,0
113,2
3,3
1171
20 %
1407
409
1407
2285
4100
Sub-system
AOCS
Power
Comms
Propulsion
OBDH
Thermal
Structure
Payload
Boom
Sub-system total
System margin
Dry mass
Propellant
Wet mass
Mass without
Total mass (kg)
margin (kg)
36,7
40,4
38,0
41,8
30,0
33,0
14,7
16,2
23,0
25,3
15,0
16,5
65,0
71,5
11,0
13,2
6,0
6,6
240
265
20 %
317
82,9
91
409
63
Risk Management
Mission profil
What
1
2
3
4
5
6
7
8
9
10
Failure @ Orbit insertion
Collision with unknown object
Large gradiant hot/cold case
RTG risk on launch
RTG risk on earth fly-by
Failure of Ejecting Slace Satillite
Failure of Boom deployment
Failure of HG Antenna deplyoment
Low dose rate failure
Reaction wheel failure
Instruments
What
1 Failure of LORRI
2 Failure of VIRHIS
Final Presentation, August 2nd 2012
Likelihood
Impact
C
C
B
B
B
C
B
C
C
C
Mitigation activities
simulations, inhibit safe mode,
5 residual risk remains
5 early investigation of equatorial disk
5 design issue
5
5
4 redundant ejection mech.; qualification
4
4 extensive qualifications
4
2
Comination of Severity and Likelihood
Likelihood Impact
B
4 E Low Medium High Very High Very High
Low Medium
High Very High
B
4 D Low
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
64
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
Final Presentation, August 2nd 2012
65
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
Final Presentation, August 2nd 2012
66
Mission Phases
Phase
0
• 2012 - 2013
Phase A/B1
• 2013 - 2015
Margin
• 2015 - 2024
Interplanetary Flight
• 2024 - 2026
• 2026 - 2045
Science Operations
• 2045 - 2050
Final Presentation, August 2nd 2012
Phase B2/C/D
End of life
Extension?
• 2050 - ??
67
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
Final Presentation, August 2nd 2012
68
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.
Final Presentation, August 2nd 2012
69
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!
Final Presentation, August 2nd 2012
70
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
Final Presentation, August 2nd 2012
71
Firsts achieved by iTOUR/Outreach
• Exploration of an underexplored system
– We expect Cassini- like public outreach
• University and school involvement
1.
2.
3.
4.
5.
First orbiter of an ice giant
First detailed study of the Uranus system
First detailed investigation of Uranus’ atmosphere
First detailed study of Uranus´ magnetic field
First outer planet mission with two orbiters
Final Presentation, August 2nd 2012
72
Announcement Of Opportunity!
• 700 kg Launch capacity remaining
• International project involvement by adding a probe?
Final Presentation, August 2nd 2012
73
investigative Tour Of URanus - iTOUR
Final Presentation, August 2nd
Thanks to all tutors and lecturers for your help.
We are looking forward to your questions!
74
2012
Appendix
Final Presentation, August 2nd 2012
75
Ground Segment Infrastructure
iTOUR Operations
Final Presentation, August 2nd 2012
76
Radiation
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.
© B. H. Mauk
Electrons (dominating) & protons up to 4 MeV
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
Final Presentation, August 2nd 2012
77
Studied configurations
Slave
Fixed antenna
Slave
Instruments
Cassini heritage
Final Presentation, August 2nd 2012
Instruments
Movable antenna
BepiColombo heritage
78
Studied configurations
Cassini heritage
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
Constraints/To do
Final Presentation, August 2nd 2012
BepiColombo heritage
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
- Requires heat shield
(Huygens Probe)
- unbalanced after
discarding
Main engine must be
gimbaled
(stability complexity
and implies
mechanism for engine
maneuvers )
The orbiter and subsat release
mechanism
Tube inner structure
for distribution of
stresses
To do
cylinder and arm attachement
the shielding of the sub-sat by
the HGA is always possible (?)
79
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
Solar
radiation
Planet
Albedo
Albedo
radiation
Planetary
radiation
Power of system
Absorptance
Emittance
Temperature
Area
-
-
K
247
0.07
0.74
293
0.84
92.4
0.12
0.9
293
0.30
150
0.07
0.74
303
0.84
70
0.12
0.9
281
Satellite
-
Master
Uranus
3.4
0.282
0(~)
0(~)
Slave
Master
Venus
2657
Slave
Final Presentation, August 2nd 2012
0.82
0(~)
0(~)
80
0.30
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.
Final Presentation, August 2nd 2012
81
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
Final Presentation, August 2nd 2012
82
Material for Radiator OSR for Master Satellite White Paint Silicate for Slave Satellite
Solar
radiation
Planet
Albedo
Albedo
radiation
Planetary
radiation
Power of
system
Area of
radiator
Absorptance
Emittance
Temperature
-
-
K
247
0.07
0.74
293
0.84
Slave
92.4
0.12
0.9
293
0.30
Master
150
0.07
0.74
305
0.84
70
0.12
0.9
281
0.30
Satellite
-
Master
Uranus
3.4
Venus
2657
Slave
Final Presentation, August 2nd 2012
0.282
0.82
0(~)
0(~)
0(~)
0(~)
83
AOCS Block Diagram
Final Presentation, August 2nd 2012
84