THEMIS INSTRUMENT PDR OVERVIEW-1 UCB, October 15, 2003
THEMIS SYSTEM OVERVIEWDr. Vassilis Angelopoulos, Science Overview
Dr. Ellen Taylor, Mission and Requirements OverviewUniversity of California - Berkeley
THEMIS INSTRUMENT PDR OVERVIEW-2 UCB, October 15, 2003
THEMIS was selected on March 20, 2003as the next NASA/MIDEX mission (#5) to study the:
Onset and evolution of magnetospheric substormsOnset and evolution of magnetospheric substorms
•Addresses a 30yr old question (the holy grail) in magnetospheric physics•A 5 spacecraft (probe) mission•Single launch vehicle (Delta 2925)•Launch in August of 2006•In Tail (midnight) on February 21, 2007/2008•Two year nominal duration•Extended phase of 2 years possible (overlap with Cluster and MMS)•Details at: http://sprg.ssl.berkeley.edu/themis
THEMIS INSTRUMENT PDR OVERVIEW-3 UCB, October 15, 2003
Auroral eruptions and substorms
Auroral eruptions…
Aurora
…are a manifestation ofmagnetospheric substorms
MAGNETOSPHERESO
LARW
IND
EQUATORIAL PLANE
THEMIS INSTRUMENT PDR OVERVIEW-4 UCB, October 15, 2003
Compelling science driver
Substorms are:
• Sun-Earth-Connections Objective #1: “Understand the changing flow of energy and matter through … planetary magnetospheres”
• US National Academy of Sciences:“A strategic question in space physics”
SEC Objective#2: Explore fundamental physical processes of plasma systems
• SEC Objective #3: “Define origins and societal impacts of variability in SEC”
Fundamental processes… …and important for space science• …for understanding magnetospheric transport
• … for basic physics
• … for space weatherand society
THEMIS INSTRUMENT PDR OVERVIEW-5 UCB, October 15, 2003
Most important science resultand its science impact
Answers how substorms operate
– Explains how magnetospheres process solar wind energy
– Explains how auroras erupt
MERCURY: 10 min EARTH: 3.75 hrs JUPITER: days
ASTROSPHERE
GALACTIC CONFINEMENT
SUBSTORM RECURRENCE:
THEMIS INSTRUMENT PDR OVERVIEW-6 UCB, October 15, 2003
Events occuring during a substorm
CurrentDisruptionAuroral
Eruption
Reconnection
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Flows
Primary Objectives, Goals and Means
Onset and evolution of substormsTime History of Events (Onset)…
– Delineate cause and effect
• Measure WhenWhere
… and Macroscale Interactionsduring Substorms (Evolution)– Coupling in the magnetosphere
• Measure plasma flows and waves
– Coupling to the ionosphere
• Measure currents and structures
Distinguishes among competing models: impartially answers a well-posed question…
Current Disruption Model
timeEvent
0 secCurrent Disruption
30 secAuroral Eruption
60 secReconnection
Reconnection Model
time Event
0 sec Reconnection
90 sec Current Disruption
120 sec Auroral Eruption
?
?Rarefaction wave
?
P1P2P3P4P5
GBO
…as implied by Themis,goddess of impartial justice
THEMIS INSTRUMENT PDR OVERVIEW-8 UCB, October 15, 2003
Mission elements
Probe conjunctions along Sun-Earth line recur once per 4 days over North America.
Ground based observatories completely cover North American sector; determine
auroral breakup within 1-3s …
… while THEMIS’s space-based probes determine onset of Current Disruption and
Reconnection each within <10s.
: Ground Based Observatory
THEMIS INSTRUMENT PDR OVERVIEW-9 UCB, October 15, 2003
.THEMIS’s goal is to study >10 substorms w/ 4- or 5–probe alignments along X [limit case]. Met w/ >50% margin by a fault-tolerant orbit strategy.
• Need 188hrs; have 300hrs/yr (>50% margin)– computation includes lunar, solar, drag, J2 terms
– Conditions: YP1,2,3,4,5<±2RE; ZP2,3,4/NS<±2RE
• Ascent:– minimizes shadows and post-L&EO ops
– maximizes science (conjunction durations)
• Mission immune to probe insertion errors– RCS capability of V<8cm/s exceeds rqmt V<80cm/s
• … 3rd stage insertion errors– long duration piece-wise major Vs with ground contact
Extensive orbit study shows high event yield
THEMIS INSTRUMENT PDR OVERVIEW-10 UCB, October 15, 2003
Mission overview: Fault-tolerant design hasconstellation and instrument redundancy
D29
25-1
0 @
CC
AS
Instrument I&TUCB
Mission I&TSwales
Encapsulation
& launch
BGS
OperationsUCB
Probe instruments:ESA: Thermal plasma (UCB)SST: Super-thermal plasma (UCB)FGM: Low frequency magnetic field (TUBS/IWF)
SCM: High frequency magnetic field (CETP)EFI: Electric field (UCB, LASP)
Ground
SST
ESA
EFIa
EFIs
FGM
SCM
Tspin=3s
THEMIS INSTRUMENT PDR OVERVIEW-11 UCB, October 15, 2003
– Ideal overlap of objectives and orbits
Synergy with Cluster and MMS
With Cluster/DoubleStar (2006)With MMS (2008)
THEMIS INSTRUMENT PDR OVERVIEW-12 UCB, October 15, 2003
THEMIS Instruments
Radial EFIs ESA
IDPUFGM
SCM
Axial EFIs
FGM
Axial EFIs
Radial EFIs
SCM
SSTs
THEMIS INSTRUMENT PDR OVERVIEW-13 UCB, October 15, 2003
Requirement Development
Top-Level requirements developed during Phase A • Concept Study Report provides basic mission concept• Outlines top-level requirements imposed by science and programmatic
objectives
Mission requirements flown down (to subsystem level), formalized and documented early in Phase B• All elements of the THEMIS CSR concept and mission requirements reviewed
by development team• Mission Requirements Database (MRD) developed and reviewed• MRD finalized and put under Configuration Control at System Requirements
Review (SRR), July 2003
Subsystem Interfaces and Component Requirements further detailed in Phase B• Interface Control Documents between Subsystems and Institutions• System and Subsystem Specifications (Electrical Spec, SOWs, etc)• Mission Plans and Policies (Safety Plan, Risk Mitigation Plan, etc)• Control Plans (Magnetics, Electrostatic Cleanliness, Contamination)
THEMIS INSTRUMENT PDR OVERVIEW-14 UCB, October 15, 2003
Requirement Verification
Requirement Verification Plans developed in Phase B and C• Development of Verification Matrix ensures a test or analysis is scheduled for all
Mission Requirements in MRD• Performance Verification and Environmental Test Plan provides launch and
space environments and outlines comprehensive component, subsystem and system level test program
Requirements Compliance and Verification Matrices completed in Phase D• Mission Requirements Document evolves into summary of test program as run• Documents Verification and Compliance Status of all Requirements• Provides direct trace-ability from requirements to test procedures and reports
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Key Requirement DocumentsInterface Control Plans: Sign-off by PDR
• Instruments-to-IDPU ICDs (covers software, data, electrical)• Instruments-to-Probe ICDs (covers mechanical, thermal, contamination)• Probe-to-IDPU ICD (electrical and mechanical)• Probe-to-Probe Carrier ICD• Launch Vehicle ICD (Boeing Mission Specification)• Ground System ICDs (Space-to-Ground link, Ground Station, Data System)
Contamination Control Plans: Draft by PDR, Sign-off by CDR• Separate Plans for Magnetics, Electrostatic Cleanliness (ESC) and Molecular Contamination• Provides contamination budgets, best design practice guidelines and verification plans
Verification Plan and Environmental Specification: Draft by PDR, Sign-off by CDR• Performance Verification Plan• Qualification Philosophy and Test Levels (Acceptance, Qualification, Protoflight)• Vibration/Loads/Shock Environments• Thermal Vacuum/Balance Environments• EMI/EMC/Magnetics/ESC Test Requirements• Mission Simulations and RF Compatibility Testing
THEMIS INSTRUMENT PDR OVERVIEW-16 UCB, October 15, 2003
Radiation RequirementsIN-1 The Instrument Payload shall be designed for at least a two-year lifetimeIN-2 The Instrument Payload shall be designed for a total dose environment of 33
krad/year (TBR) (66 krad for 2 year mission, behind 5mm of Al, RDM 2)• Initial estimate in Phase A• GSFC Radiation Report and Innovative Concept (IC) Report validation
IN-3 The Instrument Payload shall be Single Event Effect (SEE) tolerant and immune to destructive latch-up
• GSFC Radiation Report environment will be provided (est. Nov 2003)• Innovative Concept (IC) Report environment provided• Part analysis being done for upset rate on specific parts
Parts list provides an assessment of the THEMIS radiation environment; determination of the radiation susceptibility of the THEMIS flight component parts lists; leading the radiation test regime required for any parts; and working with Product Development Leads and the Parts Engineer to assess any implementation measures that need to be applied to mitigate radiation concerns.
THEMIS INSTRUMENT PDR OVERVIEW-17 UCB, October 15, 2003
Mass AllocationIN-6 The Instrument Payload shall not exceed a mass of 23.6 kg.
IN-7 No component of the Instrument Payload shall exceed the allocated mass budget (documented in THM-SYS-008 THEMIS Mass Budget)
Project Margin for Probe Dry Mass is 26%Project Margin for Probe Carrier Assembly is 25%
Instrument Allocations AllocationsSubsystems Mass Mass Cont. Mass Mass Cont.
(kg) (kg) % (kg) (kg) %FGM 1.46 1.35 8.15% 1.59 1.47 7.94%SCM 1.68 1.50 12.00% 1.58 1.40 12.86%ESA 2.24 2.08 7.69% 2.24 2.13 5.55%SST 1.42 1.26 12.70% 1.04 0.95 10.03%EFI 12.40 11.20 10.71% 12.40 10.70 15.95%IDPU 4.43 3.54 25.08% 4.77 4.48 6.57%TOTAL 23.63 20.94 12.89% 23.63 21.12 11.90%
Phase A Predict Rev K Oct-03
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Power Allocation
IN-8 The Instrument Payload shall require less than 14.7 W (on-orbit average)
IN-9 No component of the Instrument Payload shall exceed the allocated power budget (documented in THM-SYS-009 THEMIS Power Budget)
Instrument Allocations AllocationsSubsystems Power Pwr Cont. Power Pwr Cont.
(W) (W) % (W) (W) %FGM 0.01 0.01 11.11% 0.01 0.01 11.11%SCM 0.09 0.08 12.50% 0.09 0.08 12.50%ESA 2.01 1.87 7.49% 2.01 1.88 6.91%SST 1.06 0.85 24.71% 0.00 0.00 N/AEFI 0.54 0.48 12.50% 0.53 0.48 10.42%IDPU 11.06 8.85 24.97% 12.12 9.20 31.74%TOTAL 14.77 12.14 21.67% 14.76 11.65 26.79%
Rev K Oct-03Phase A Predict
Project Margin for Probe Power is 40%
THEMIS INSTRUMENT PDR OVERVIEW-19 UCB, October 15, 2003
Thermal RequirementsIN-13 The Instrument Payload shall survive the temperature ranges provided in the ICDs
IN-14 The Instrument Payload shall perform as designed within the temperature ranges provided in the ICDs
IN-15 The Instrument Payload shall be able to cold start as provided in the ICDs
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Contamination RequirementsIN-16 The Instrument Payload shall comply with the Magnetics Cleanliness standard described in the THEMIS Magnetics Cleanliness Plan
• THM-SYS-002 THEMIS Magnetics Cleanliness Plan, Rev A, In Progress• Bi-weekly meetings with Swales, UCLA, UCB• Swales Solar Array Specification reviewed by UCB and UCLA• Magnetics Modeling (AC and DC) to be done by UCLA• Magnetics Budget at preliminary stage• Magnetics Verification and Test planning at preliminary stage
IN-17 The Instrument Payload shall comply with the THEMIS Electrostatic Cleanliness Plan• THM-SYS-003 THEMIS Electrostatic Cleanliness Plan, Rev A, In Review• Swales Solar Array Specification Reviewed by UCB
IN-18 The Instrument Payload shall comply with the THEMIS Contamination Control Plan• THM-SYS-004 THEMIS Contamination Control Plan, Draft, In Progress
THEMIS INSTRUMENT PDR OVERVIEW-21 UCB, October 15, 2003
Interface RequirementsIN-20 The Instrument Payload shall be compatible per IDPU-Instrument ICDs
• THM-SYS-101 IDPU-to-Probe ICD Rev E In Progress
IN-21 The Instrument Payload shall be compatible per the IDPU-Probe Bus ICD• THM-SYS-103 EFI Digital Fields Board-to IDPU ICD Rev B In Progress• THM-SYS-104 EFI Boom Electronics Board-to-IDPU ICD Rev A In Review• THM-SYS-105 ESA and SST I/F Card Spec (ICD) Draft In Progress• THM-SYS-106 FGM I/F Requirement Document (ICD) Rev B In Review• THM-SYS-107 SCM I/F Requirements Document (ICD) Rev B In Progress
IN-22 The Instrument Payload shall be compatible per Instrument-Probe Bus ICDs• THM-SYS-108 Radial EFI Booms-to-Probe ICD Rev D2 In Review• THM-SYS-109 Axial EFI Booms-to-Probe ICD Rev D2 In Review• THM-SYS-110 ESA-to-Probe ICD Rev D2 In Review• THM-SYS-111 SST-to-Probe ICD Rev D2 In Review• THM-SYS-112 FGM Mag Boom-to-Probe ICD Rev D2 In Review• THM-SYS-113 SCM Mag Boom-to-Probe ICD Rev D2 In Review
THEMIS INSTRUMENT PDR OVERVIEW-22 UCB, October 15, 2003
Test RequirementsIN-23 The Instrument Payload shall verify performance requirements are met per the THEMIS Verification Plan and Environmental Test Specification
IN-24 The Instrument Payload shall survive and function prior, during and after exposure to the environments described in the THEMIS Verification Plan and Environmental Test Specification
• THM-SYS-101 THEMIS Verification Plan and Test Specification, Draft, In Progress• Mechanical Design Specifications have been provided
Environments and Test Matrix will be presented during IDPU PDR (Oct 16)