g4suws 2009 Jun Jeoandg4

Jupiter Europa OrbiterThe NASA Element of the Europa Jupiter System Mission

Insoo JunJet Propulsion Laboratory

California Institute of Technology

Jupiter Europa Orbiter and Geant4

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

2For Planning and Discussion Purposes Only

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)


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)


JGO Science HighlightsA 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


73 kg core payload:

Wide Angle and Medium Resolution CameraV/NIR Imaging SpectrometerEUV/FUV Imaging SpectrometerKa-band transponderUltra Stable Oscillator Magnetometer Radar SounderMicro Laser Altimeter Thermal IR Mapper Sub-millimeter wave sounder Plasma Package

JGO Reference Model Payload

Imaging

Planetary fields and internal

structure

Atmosphere

Magnetosphere


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, andEuropa flight element of Laplace


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 instruments8For Planning and Discussion Purposes Only

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


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 10For Planning and Discussion Purposes Only

JEO Model PayloadJEO Instrument Similar InstrumentsRadio Science New Horizons USO, Cassini KaTLaser Altimeter MESSENGER MLA, NEAR NLRIce Penetrating Radar MRO SHARAD, Mars Express MARSISVIS-IR Spectrometer MRO CRISM, Chandrayaan MMMUV Spectrometer Cassini UVIS, New Horizons AliceIon & Neutral Mass Spectrometer Rosetta ROSINA RTOFThermal Instrument MRO MCS, LRO Diviner Narrow-Angle Camera New Horizons LORRI, LRO LROCCamera Package MRO MARCI, MESSENGER MDISMagnetometer MESSENGER MAG, Galileo MAGParticle and Plasma Instrument New Horizons PEPSSI, Deep Space 1 PEPE


JEO 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 design12For Planning and Discussion Purposes Only

Power Assembly

Balanced Bus Grounding Hardware

RPS Protection Diodes

Battery Control FET Board

Pyro and Prop Enable Relays

Shunt Limiter FETs

Wheel Drive Electronics (4)

Star Trackers (2)

25 Nms RWA (4) w/ electronics

2-Channel Gimbal Drive Electronics (3)4-Channel Gimbal

Drive Electronics (2)

SIRU (1)

12 A-Hr Li-Ion

Batteries (2)

Lightning Suppression

Assembly

Power Distribution Unit

Power Bus Controller

Power Switch Cards (8)








Prop Drive Electronics (4)




Pyro Driver Cards (6)






Remote Engineering

Unit (2)

Remote Engineering

Unit (2)

Power Conditioning

Unit (2)

Power Conditioning

Unit (2)

Temp Sensors & Heaters

MLI

Model Payload

C&DH*

Power

Telecom

GHe GHe

Fuel Tank

Gimbaled 890 N HiPATMain Engine

L

16 (8 coupled clusters) 4.5 N ACS Thrusters

Ox Tank

Propulsion

To S/C Loads

U/L, D/L

10m Magnetometer Boom

HGA Gimbal

Variable RHUs (24)

Linear Separation AssemblyLouvers

Main Engine Gimbal

X 4 TWTA

Ka-band

TWTAX-band

25W RF Ka-Band TWTA

(2)

25W RFX-band

TWTA (2)

HYB

X 4

Filter

WTS (2)

WTS

X-Band LGA (2)

3m Ka/X HGA

WTS

HYB

X-Band MGA

WTS

CTS

USO

T

TELECOM ENCLOSURES BEHIND HGA

High-Rate Instruments

IR Spectrometer (VIRIS)

Ice Penetrating Radar (IPR)

Wide Angle & Medium Angle Cameras (WAC + MAC)

Narrow Angle Camera (NAC)

Low-Rate Instruments

Ultraviolet Spectrometer (UVS)

Laser Altimeter (LA)

Ion and Neutral Mass Spectrometer (INMS)

Dual Magnetometer (MAG)

Thermal Instrument (TI)

Particle and Plasma Instrument (PPI)

Shunt Radiator

Computer Chassis (2)cP

CI B

ackp

lane

CEPCU

MTIF

BAE RAD750 (2 slot width)

Custom JEO Card

MREU

Computer Chassis (2)cP

CI B

ackp

lane

MTIF

BAE RAD750 (2 slot width)

Custom JEO Card

MREU

CEPCU

Wheel Drive Electronics (4)Wheel Drive

Electronics (4)Sun Acquisition

Detectors (3)

SDST (2)

X/Ka-bandExciter

X-bandExciter

X-bandReceiver

SDST (2)

X/Ka-bandExciter

X-bandExciter

X-bandReceiver

MMRTG (5)

MMRTG (5)

MMRTG (5)

MMRTG (5)

MMRTG (5)

Waste Heat

Mechanical & Thermal

KaT

Rad Monitoring

Rad Monitoring 6U Electronics Card (Physically

in C&DH Chassis)

3m HGA Boom

Pressure Transducers (10)

DiplexerKa Diplexer (2)

HYB

DiplexerX Diplexer (2)

Sensor 1

Sensor 3

Sensor 2

Hybrid SSR:1Gb CRAM

16 Gb SDRAM Science Memory

JEO Flight System Block Diagram

RHUs (20)

*Note: All C&DH interfaces are cross-strapped.

To MTIF Card in C&DH

Atlas V 551

LV Adapter (LV provides)

T-0 Umbilical

AACS


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%)• 2-orbit ops scenario permits power/data rate equalization:

- Even orbits emphasize optical remote sensing:- Odd orbits emphasize radar sounding to locate water

• Targets collected with residual data volume

4

10° x 10°

Eng Assessment (6 d)Initial Europa OrbitAltitude: 200 kmInclination: 95−100 deg

(~85° N lat) Lighting: 2:30 PM LSTRepeat: 4 Eurosols

After Campaign 1Altitude: 100 kmRepeat: 6 Eurosols

3

Targeted Processes100 km altitude

8 eurosols ≈ 28 days

MAC80x20 km

IRS10x10 km

IPR + LA

WAC context

Europa Campaigns 1−3 total 99 days

Europa Science Campaigns

Regional Processes100 km altitude

(100 m/pixel WAC)12 eurosols ≈ 43 days

2A 2B

Global Framework200 km altitude

(200 m/pixel WAC)8 eurosols ≈ 28 days

1A 1B Europa Science Campaigns

EOIJOISatellite/Jupiter Science


2008 JEO Design Baseline

Current design practices produce significant marginsand high probability of success through end of mission

• Using traditional methodologies– Current design has an RDF = 7 when JEO begins Endgame– RDF is ~1.25 at end of Prime Mission

A2026 2027 2028

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

JOI EOI

Ganymede Encounters

Callisto Encounters

Europa Encounters

Io Encounters

End of Prime Mission

Europa Science

J F M

Estimated Mean Total Ionizing Dose (TID)

2029Jovian Tour

2.9 Mrads (Si)(Design Point)

System Survival

99%

80%

Rad

iatio

n D

esig

n Fa

ctor

Rad

iatio

n D

ose

(Mra

d)


System Design Process

Input Variables

• Science Objectives

• Mission Design—Environment

• Launch Vehicle Capabilities

• Part Capabilities

Dependent Components• Shielding Design• Instrument and Circuit Design• Margin Assessment• Risk Analysis• 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

Analysis


Mission 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


JEO vs. GLL vs. Juno Mean Dose-Depth Curves

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

10 100 1000 10000aluminum shield thickness, mil

rad(

Si)

JEO 2008 Reference

GLL

Juno

End of Mission (J35)

Mission Duration : 14 months

Mission Duration : 39 months

The estimated TID radiation design environment for JEO is similar tothe estimated end-of-mission Galileo environment


Peak Flux Comparison: JEO vs. Juno

The radiation flux design environment for JEO is less than that for Juno


Detector 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


2008 JEO Detector Working Group

Insoo Jun For Planning and Discussion Purposes Only 21

Detector Working Group Summary Information

Sensor Technology

Total Dose Survivability Transient Noise Effect

Conclusions (Assumes Recommended Shield)

Expected TID Tolerance

(krad Si)

Expected DDD Tolerance

(MeV/g Si)

Required Shielding with RDF=2

(cm Ta)

Instru-ment

Notional Detector Characteristics Relevant to Transient Effects

Transient Radiation Response at 9 Rj With Given Shielding

Recom-mended Shield

(cm Ta)

0.3- cm Ta

0.6-cm Ta

1.0-cm Ta

1.5-cm Ta

3.0-cm Ta

CCD/CMOS n-CCD:Tested to 80 krads, Id=920 pA/cm2 @ 20˚C.

CMOS:Tested to 100 krads, Id=200 pA/cm2 @ 27 ˚C

n-CCD MPP: Tested 4 to 6E7 DDD, Id=56 to 240 pA/cm2 @ 25 ˚C. Tested to 1.4E8 DDD, CTE=0.9993 @ -118 ˚C. p-CCD: Tested 5 to 14E7 DDD, Id=1–4 nA/cm2 @ 25 ˚C Tested to 7.4E8 DDD, CTE=0.99995 @ -93 ˚C.

CMOS:Tested to1.3E8 DDD, Id=50 pA/cm2 @ 27 ˚C.

1.0 WAC 13 µm pixel77 ms exposure

35.66% of pixels corrupted

11.4% 5.6% 2.2% 0.6% 1.0 • Shielding: 1.0-cm Ta (requires TID tolerance to 70 krad Si, DDD tolerance to 1.3E8 MeV/g Si)

• Shielding driven equally by total dose survivability and transient noise

• Dark current increases from TID and DDD mitigated by cooling detector

• CMOS is favored (hardened by design and/or process), but TID and DDD requirement allows for CMOS, p-CCD, and possibly n-CCD.

MAC 13 µm pixel7.7 ms exposure


1.1% 0.6% 0.2% 0.06% 1.0

NAC 13 µm pixel0.77 ms exposure


0.1% 0.06% 0.02% 0.01% 1.0

HgCdTe MWIR HgCdTe detector tested to 1 Mrad, no change in R0. CMOS readout similar to visible detector above

LWIR HgCdTe detector tested up to1E9 DDD with no change in R0 @ 78 K.

1.0 VIRIS 27 µm pixel154 ms exposure

307% of pixels corrupted

98% 48% 19% 5% 3.0 • Shielding: 3.0-cm Ta (requires TID tolerance to 20 krad Si, DDD tolerance to 1.9E6 MeV/g Si)

• Shielding driven by transient noise, which mitigates total dose survivability concerns

• No dark current data available; mitigation by focal plane cooling


Parts CapabilitiesRadiation Requirements Comparison

JEO parts requirements are similar to MEO Military Satellites, though shielding limitations and planetary protection pose significant challenges

Aspect Military GEO* Military MEO* JEO

Mission Duration 15 yr 6 to 10 yr 9 yr

Parts TID Capability <100 krad 100 to 300 krad 300 krad desired

Mission Dose 500 krad@100 mil Al

800 krad@100 mil Al

2.9 Mrad@100 mil Al

Shielding Effectiveness Down to <10 krad Down to ~20 krad <100 krad

very massive

DD Dose Up to 6x1011 eq.N/cm2 >2x1012 eq. N/cm2 2x1012 eq. N/cm2

Planetary Protection No Requirement No Requirement Required

* GEO: Geostationary Earth Orbit; MEO: Medium Earth Orbit


Geant4 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 24

Example: Model Layers for Transient Estimates

• 5 Layers in GEANT4

• Detector Array with 7 elements– Cylindrical Geometry Assumed– Initial results similar to results in

Pickel’s 2005 NSREC paper

• Semi-infinite shielding slabs

• Shield Material– WCu, Al, Ta– Thickness ∼ 1.6, 8 and 16g/cm2

• Ceramic and Cu layers used to account for backscatter

Shield Material

D D D D D D D

Alumina Backing

Copper Layer

Shield Material

Initial BeamElectron beam (mono-energetic)

Courtesy of D. Roth (APL)

Example: 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.

26

100k electronsincident

Courtesy of D. Haggerty (APL)

Summary• 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 27

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