Jupiter Europa Orbiter and Geant4 - Insoo Jun
←
→
Page content transcription
If your browser does not render page correctly, please read the page content below
Jupiter Europa Orbiter
The NASA Element of the Europa Jupiter System Mission
Jupiter Europa Orbiter and Geant4
Insoo Jun
Jet Propulsion Laboratory
California Institute of Technology
Copy Right 2009 California Institute of Technology.
ACKNOWLEDGEMENT: The research described in this presentation was carried out at the Jet Propulsion
Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space
Administration
EJSM Baseline Mission
Overview
• NASA & ESA share
mission leadership
• Two independently
launched and operated
flight systems with
complementary payloads
– Jupiter Europa Orbiter (JEO):
NASA-led mission element
– Jupiter Ganymede Orbiter
(JGO):
ESA-led mission element
• Mission Timeline
– Nominal Launch: 2020
– Jovian system tour phase: 2–3
years
– Moon orbital phase: 6–12
months
– End of Prime Missions: 2029
• ~10–11 Instruments on
each flight system,
including Radio Science
For Planning and Discussion Purposes Only 2
JGO Baseline Mission Overview
• ESA-led portion of EJSM
• Objectives: Jupiter System, Callisto, Ganymede
• Launch vehicle: Arianne 5
• Power source: Solar Arrays
• Mission timeline:
– Launch: 2020
• Uses 6-year Venus-Earth-Earth gravity assist trajectory
– Jovian system tour phase: ~28 months
• Multiple satellite flybys
– 9 Ganymede
– 21 Callisto
– Ganymede orbital phase: 260 days
– End of prime mission: 2029
– Spacecraft final disposition: Ganymede surface impact
• 10 Instruments, including radio science
• Radiation: Current estimated TID for whole mission after 260 days in
Ganymede orbit ~85 krad behind 320 mils of Al (requirement to keep it below
100 krad)
For Planning and Discussion Purposes Only 3
JGO Key Objectives
• In-depth post-Galileo exploration
of the Jupiter system,
synergistically with JEO
– En route to Callisto and
Ganymede
• In-depth study and full mapping of
Callisto
– Multiple flybys using a resonant
orbit
• Detailed orbital study of
Ganymede
– Two successive dedicated moon
orbits (elliptical first, then circular)
For Planning and Discussion Purposes Only 4
JGO Science Highlights
A major step forward in our understanding of
the two “icy” Galilean satellites, Ganymede and
Callisto:
• Ocean detection/characterisation
• State of internal differentiation
• Global surface mapping: morphology and chemistry
• Comprehensive study of Ganymede’s magnetism
• Relations between thermal history, geology,
oceans and the Laplace resonance
The first global description of the Jovian World
as an “integrated system”, together with JEO:
• Jupiter’s atmosphere 3D meteorology and coupling
processes,
• Jupiter’s magnetosphere as an “astrophysical
object”,
• A major step toward untangling the history of the
chemical evolution of the Jupiter system, from
formation to potential habitability
For Planning and Discussion Purposes Only 5
JGO Reference Model Payload
73 kg core payload:
¾ Wide Angle and Medium Resolution Camera
Imaging ¾ V/NIR Imaging Spectrometer
¾ EUV/FUV Imaging Spectrometer
¾ Ka-band transponder
Planetary
fields and
¾ Ultra Stable Oscillator
internal ¾ Magnetometer
structure ¾ Radar Sounder
¾ Micro Laser Altimeter
Atmosphere
¾ Thermal IR Mapper
¾ Sub-millimeter wave sounder
Magnetosphere ¾ Plasma Package
For Planning and Discussion Purposes Only 6
Heritage of Europa Mission Concepts
• Europa Orbiter (1997–2001)
• Jupiter Icy Moons Orbiter (2002–2005)
• Europa Geophysical Explorer (2005)
• Europa Explorer (2006)
• Europa Explorer (2007)
• Jupiter System Observer (2007)
• Laplace Cosmic Vision Proposal (2007)
• Jupiter Europa Orbiter
– Combines EE 2007, JSO 2007, and
Europa flight element of Laplace
For Planning and Discussion Purposes Only 7
JEO Baseline Mission Overview
• NASA-led portion of EJSM extensively studied in 2007–2008
• Objectives: Jupiter System, Europa
• Launch vehicle: Atlas V 551
• Power source: 5 MMRTG or 5 ASRG
• Mission timeline:
– Launch: 2018 to 2022, nominally 2020
• Uses 6-year Venus-Earth-Earth gravity assist trajectory
– Jovian system tour phase: 30 months
• Multiple satellite flybys: 4 Io, 6 Ganymede,
6 Europa, and 9 Callisto
– Europa orbital phase: 9 months
– End of prime mission: 2029
– Spacecraft final disposition: Europa surface impact
• 11 Instruments, including radio science
• Optimized for science, cost, and risk
• Radiation dose: 2.9 Mrad (behind 100 mils of Al)
– Handled using a combination of rad-hard parts and tailored component shielding
– Key rad-hard parts are available, with the required heritage
– Team is developing and providing design information and approved parts list for
prospective suppliers of components, including instruments
For Planning and Discussion Purposes Only 8
JEO Mission Design Overview
• Interplanetary trajectories feature gravity assists to greatly reduce the
required specific energy of launch
• Jupiter Orbit Insertion occurs low in Jupiter's gravity well, significantly
reducing ΔV
• Gravity-assist tour of Jovian satellites greatly reduces size of Europa
Orbit Insertion maneuver
For Planning and Discussion Purposes Only 9
JEO Goal: Explore Europa to Investigate Its
Habitability
Objectives:
• Ocean and Interior
• Ice Shell
• Chemistry and Composition
• Geology
• Jupiter System
– Satellite surfaces and interiors
– Satellite atmospheres
– Plasma and magnetospheres
– Jupiter atmosphere
– Rings
Europa is the archetype of icy world habitability
For Planning and Discussion Purposes Only 10JEO Model Payload
JEO Instrument Similar Instruments
Radio Science New Horizons USO, Cassini KaT
Laser Altimeter MESSENGER MLA, NEAR NLR
Ice Penetrating Radar MRO SHARAD, Mars Express MARSIS
VIS-IR Spectrometer MRO CRISM, Chandrayaan MMM
UV Spectrometer Cassini UVIS, New Horizons Alice
Ion & Neutral Mass Spectrometer Rosetta ROSINA RTOF
Thermal Instrument MRO MCS, LRO Diviner
Narrow-Angle Camera New Horizons LORRI, LRO LROC
Camera Package MRO MARCI, MESSENGER MDIS
Magnetometer MESSENGER MAG, Galileo MAG
Particle and Plasma Instrument New Horizons PEPSSI, Deep Space 1 PEPE
For Planning and Discussion Purposes Only 11JEO Baseline Flight System
• Three-axis stabilized with instrument
deck for nadir pointing
• Articulated HGA for simultaneous
downlink during science observations
• Data rate of 150 kbps to DSN 34m
antenna on Ka-band
• Performs 2260 m/s ∆V with 2646 kg of
propellant
• Five MMRTGs would provide 540 W
(EOM) with batteries for peak modes
• Rad-hardened electronics with
shielding to survive 2.9 Mrad (behind
100 mil Al) environment
• 9-year lifetime
• Healthy mass and power margins
(43%, >33% respectively)
JEO would be built upon minor modifications to a strong EE2007 design
For Planning and Discussion Purposes Only 12JEO Flight System Block Diagram Telecom
KaT HYB
*Note: All C&DH interfaces are SDST (2)
SDST (2)
C&DH* cross-strapped. T
X/Ka-band
X/Ka-band HYB WTS
Computer Chassis (2) Exciter 25W RF Ka-
Exciter
XX44
Computer Chassis (2)
AACS TWTA
Band TWTA Ka Diplexer
Diplexer(2) 3m Ka/
CEPCU X-band Ka-band
(2) X HGA
CEPCU X-band HYB
Exciter
Sun Acquisition
Wheel Exciter
WheelDrive
Drive WTS (2)
WTS
Detectors (3)
Electronics 25W RF
MREU Electronics(4)
(4) TWTA
MREU X-band X-band X Diplexer
Diplexer(2)
X-band Filter X-band
Receiver TWTA (2)
4-Channel
2-ChannelGimbal
Gimbal Receiver X-Band
Custom JEO Card Drive
DriveElectronics
Electronics(2)
(3)
Custom JEO Card LGA (2)
CTS
U/L, D/L WTS
cPCI Backplane
cPCI Backplane
MTIF
MTIF USO
SIRU (1) X-Band
BAE RAD TELECOM ENCLOSURES BEHIND HGA
BAE
750 (2 slotRAD
width) MGA
750 (2 slot width)
Star Trackers
Wheel Drive
(2)
Electronics (4)
Mechanical & Thermal Main Linear Separation
Hybrid SSR: Engine Louvers Atlas V 551
HGA Assembly
1Gb CRAM 25 Nms Temp Sensors
Gimbal Gimbal
16 Gb SDRAM RWA (4) w/ 10m Magnetometer Boom & Heaters
Science Memory electronics RHUs 3m HGA Boom
Variable LV Adapter
Shunt Radiator (20)
RHUs (24) (LV provides)
MLI
Rad Monitoring To MTIF Card
in C&DH
Rad Monitoring Sensor 1 Low-Rate Instruments
Power Waste T-0 Umbilical
6U Electronics Heat Power Distribution Unit
Card (Physically Sensor 3 Ion and Neutral Mass
in C&DH Spectrometer (INMS) MMRTG
MMRTG Power Bus
Chassis) Sensor 2 MMRTG
(5)
MMRTG Controller
MMRTG
(5)
(5)
(5)
Propulsion
(5)
Remote
Remote
Model Payload Ultraviolet Engineering GHe Pressure GHe
Engineering Transducers (10)
Spectrometer (UVS) Unit
Unit(2)
(2)
High-Rate Instruments Power Assembly
Power
Power
Wide Angle & Medium Shunt Limiter Conditioning
Conditioning Ox Fuel
Angle Cameras Laser Altimeter (LA) FETs Unit
(WAC + MAC) Unit(2)
(2) Tank Tank
RPS Protection Prop
Prop Drive
Drive
Prop
PropDrive
Drive
Lightning Diodes Electronics
Electronics (4)
(4)
Narrow Angle Camera Thermal Instrument Electronics
Electronics(4)
(4)
Suppression L
(NAC) (TI) Assembly
Balanced Bus
Grounding Pyro
Pyro Driver
Driver
Pyro
PyroDriver
Driver
Hardware Pyro
Cards
Cards Driver
Pyro(6)
Driver
(6)
Cards
Cards (6)
(6)
IR Spectrometer Particle and Plasma Cards
Cards(6)(6) To S/C
16 (8 coupled
(VIRIS) Instrument (PPI) Loads
Pyro and Prop clusters) 4.5 N
Enable Relays Power
Power Switch
Switch ACS Thrusters
Power
Power Switch
Switch
Power
Cards
Power
Cards Switch
(8)
Switch
(8)
12 A-Hr Li- Power
Cards
Power
Cards Switch
(8)
Switch
(8)
Ice Penetrating Radar Dual Magnetometer Battery Control Cards
Cards (8)
(8)
Ion Cards
Cards(8)(8)
(IPR) (MAG) FET Board
Batteries (2)
Gimbaled 890 N HiPAT
Main Engine
For Planning and Discussion Purposes Only 13Europa Science Campaigns
JOI to EOI Jul 2028 Aug 2028 Sep 2028 Oct 2028
Observing Strategies for Europa Campaigns 1−3
• Always on: LA, MAG, PPI, TI, INMS (50%)
JOI EOI • 2-orbit ops scenario permits power/data rate equalization:
Satellite/Jupiter Science - Even orbits emphasize optical remote sensing:
- Odd orbits emphasize radar sounding to locate water
• Targets collected with residual data volume
Eng Assessment (6 d)
Initial Europa Orbit
Altitude: 200 km 1A 1B Europa Science Campaigns
Inclination: 95−100 deg
(~85° N lat) 2A 2B
Lighting: 2:30 PM LST
Repeat: 4 Eurosols 3
After Campaign 1 4
Altitude: 100 km
Repeat: 6 Eurosols
WAC
context MAC
80x20 km
10° x 10°
IRS
Europa Campaigns Global Framework Regional Processes
10x10 km
1−3 total 99 days 200 km altitude 100 km altitude Targeted Processes
(200 m/pixel WAC) IPR + LA
8 eurosols ≈ 28 days (100 m/pixel WAC) 100 km altitude
12 eurosols ≈ 43 days 8 eurosols ≈ 28 days
For Planning and Discussion Purposes Only 142008 JEO Design Baseline End of Prime Mission
JOI EOI
Jovian Tour Europa Science
2026 2027 2028 2029
D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A
Radiation Design Factor
Radiation Dose (Mrad)
Io Encounters System Survival
99%
Europa Encounters
Ganymede Encounters 80%
Callisto Encounters
2.9 Mrads (Si)
(Design Point)
Estimated Mean Total Ionizing Dose (TID)
• Using traditional methodologies
– Current design has an RDF = 7 when JEO begins Endgame
– RDF is ~1.25 at end of Prime Mission
Current design practices produce significant margins
and high probability of success through end of mission
For Planning and Discussion Purposes Only 15System Design Process
Analysis
Input Variables Dependent Components
• Science Objectives • Shielding Design
• Instrument and Circuit Design
• Mission Design—Environment
• Margin Assessment
• Launch Vehicle Capabilities • Risk Analysis
• Part Capabilities • Cost Analysis
Iteration
• System design iterative process continues through Phase B as capabilities
evolve and science instrument capabilities solidify
• Acceptable cost and risk posture is a joint discussion between project and
NASA Headquarters
For Planning and Discussion Purposes Only 16Mission Design—Environment
• The JEO mission design takes advantages of better radiation
knowledge than available for Galileo design
– The JEO dose-depth curve is similar to that of Galileo at end of its
mission (J35)
– Environment is modeled statistically based primarily on Galileo data
– The JEO peak flux is comparable to or lower than that of Juno
– Data available from Juno will be incorporated when available
• Io flyby strategy is a better engineering solution than the Ganymede
strategy used in 2007 Europa Explorer Mission Study
– ΔV savings of 200 m/s at first-flyby altitude of 1000 km
– Tour strategy involves ~0.4 Mrad increase
– A net dry-mass increase to Europa orbit of approximately 100 kg
For Planning and Discussion Purposes Only 17JEO vs. GLL vs. Juno Mean Dose-Depth Curves
1.E+08
JEO 2008 Reference
Mis
sio nD
urat GLL End of Mission (J35)
1.E+07 ion
: 39
mon Juno
ths
Mis
1.E+06 sion
Dur
atio
rad(Si)
n:
14
mo
nth
1.E+05 s
1.E+04
1.E+03
10 100 1000 10000
aluminum shield thickness, mil
The estimated TID radiation design environment for JEO is similar to
the estimated end-of-mission Galileo environment
For Planning and Discussion Purposes Only 18Peak Flux Comparison: JEO vs. Juno
The radiation flux design environment for JEO is less than that for Juno
For Planning and Discussion Purposes Only 19Detector Radiation Effects Analysis
• A Detector Working Group (DWG) comprised of experienced detector,
instrument, and radiation experts from JPL and APL was formed to evaluate
the radiation tolerance of existing detector technologies
• The DWG also assessed the response of detectors to incident electron and
proton radiation to determine the impact on science measurement quality
• Silicon used by NAC, MAC, WAC
• HgCdTe (MCT) used by VIRIS
• Microchannel plate (MCP) used by PPI, INMS, UVS
• Avalanche photodiode (APD) used by LA
– The incident radiation flux reaching the detector through various levels of radiation
shielding, with the response of the detector to that radiation flux, was used to
determine the amount of radiation shielding required for acceptable science
measurement quality
• The DWG found that detector radiation shielding requirements are driven by
electron-induced transient noise, not total dose
– Shielding to mitigate transient noise effectively mitigates total-dose effects
Existing detectors, shielded to mitigate background radiation noise,
meet JEO mission dose and science measurement requirements
For Planning and Discussion Purposes Only 202008 JEO Detector Working Group Insoo Jun For Planning and Discussion Purposes Only 21
Detector Working Group Summary Information
Total Dose Survivability Transient Noise Effect
Expected TID Expected DDD Required Instru- Notional Transient Radiation Response at 9 Rj
Recom-
Tolerance Tolerance Shielding ment Detector With Given Shielding mended
Sensor Conclusions
with Characteristics 0.3- cm 0.6-cm 1.0-cm 1.5-cm 3.0-cm Shield (Assumes Recommended Shield)
Technology
RDF=2 Relevant to Ta Ta Ta Ta Ta
Transient
(krad Si) (MeV/g Si) (cm Ta) Effects (cm Ta)
CCD/CMOS n-CCD: n-CCD MPP: 1.0 WAC 13 µm pixel 35.66% 11.4% 5.6% 2.2% 0.6% 1.0 • Shielding: 1.0-cm Ta (requires TID
Tested to 80 Tested 4 to 6E7 DDD, 77 ms exposure of pixels tolerance to 70 krad Si, DDD tolerance to
krads, Id=920 Id=56 to 240 pA/cm2 @ corrupted 1.3E8 MeV/g Si)
pA/cm2 @ 20˚C. 25 ˚C. MAC 13 µm pixel 3.6% of 1.1% 0.6% 0.2% 0.06% 1.0 • Shielding driven equally by total dose
Tested to 1.4E8 DDD, 7.7 ms exposure pixels survivability and transient noise
CTE=0.9993 @ -118 ˚C. corrupted • Dark current increases from TID and
DDD mitigated by cooling detector
p-CCD: NAC 13 µm pixel 0.4% of 0.1% 0.06% 0.02% 0.01% 1.0
• CMOS is favored (hardened by design
Tested 5 to 14E7 DDD, 0.77 ms exposure pixels
and/or process), but TID and DDD
Id=1–4 nA/cm2 @ 25 ˚C corrupted
requirement allows for CMOS, p-CCD,
Tested to 7.4E8 DDD, and possibly n-CCD.
CTE=0.99995 @ -93 ˚C.
CMOS: CMOS:
Tested to 100 Tested to1.3E8 DDD,
krads, Id=200 Id=50 pA/cm2 @ 27 ˚C.
pA/cm2 @ 27 ˚C
HgCdTe MWIR HgCdTe LWIR HgCdTe detector 1.0 VIRIS 27 µm pixel 307% of 98% 48% 19% 5% 3.0 • Shielding: 3.0-cm Ta (requires TID
detector tested to tested up to1E9 DDD 154 ms exposure pixels tolerance to 20 krad Si, DDD tolerance to
1 Mrad, no with no change in R0 @ corrupted 1.9E6 MeV/g Si)
change in R0. 78 K. • Shielding driven by transient noise, which
CMOS readout mitigates total dose survivability concerns
similar to visible • No dark current data available; mitigation
detector above by focal plane cooling
For Planning and Discussion Purposes Only 22Parts Capabilities
Radiation Requirements Comparison
Aspect Military GEO* Military MEO* JEO
Mission Duration 15 yr 6 to 10 yr 9 yr
Parts TID CapabilityGeant4 for JEO
• Simulation of signal to noise ratios in sensors and
detectors in high energy electron environment
• Computation of response function (e.g., geometric factor)
for particle detectors
• Shielding analysis
– Material selection criteria (e.g., low-Z, high-Z, or combination of
them
• Particle trajectory analysis in the Jovian magnetosphere
(or in the vicinity of Europa)
Insoo Jun For Planning and Discussion Purposes Only 24Example: Model Layers for Transient
Estimates
• 5 Layers in GEANT4
Electron beam
Initial Beam
• Detector Array with 7 (mono-energetic)
elements
– Cylindrical Geometry Assumed
Shield Material
– Initial results similar to results in
Pickel’s 2005 NSREC paper D D D D D D D
• Semi-infinite shielding slabs Alumina Backing
Copper Layer
• Shield Material Shield Material
– WCu, Al, Ta
– Thickness ∼ 1.6, 8 and 16g/cm2
• Ceramic and Cu layers used Courtesy of D. Roth (APL)
to account for backscatterExample: Geant4 Simulation of Shields
• One dimensional analysis to define the shield thickness of
a dosimeter “channel”.
– For example, we’d like to obtain the shield thickness, behind which
a “RadFET” will predominantly measure >10 MeV electrons.
100k
electrons
incident
Courtesy of D. Haggerty (APL) 26Summary
• An overview of Jupiter Europa Orbiter is presented.
• The challenges associated with harsh radiation
environment were discussed.
– Mission fluence
– Peak flux
• It is emphasized that detector survivability (or operability)
in this environment is a key for the mission success.
– Early identification of the problems through analyses and tests is
important.
– Geant4 can be very useful for this purpose with its comprehensive
physics packages and modeling capabilities.
– Geant4 will be one of the tools that the Project plans to use heavily
in the detector modeling effort.
Insoo Jun For Planning and Discussion Purposes Only 27You can also read
