themis instrument pdroverview- 1 ucb, october 15, 2003 themis system overview dr. vassilis...

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 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


Auroral eruptions and substorms

Auroral eruptions…

Aurora

…are a manifestation ofmagnetospheric substorms

MAGNETOSPHERESO

LARW

IND

EQUATORIAL PLANE


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


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:


Events occuring during a substorm

CurrentDisruptionAuroral

Eruption

Reconnection


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


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’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


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


– Ideal overlap of objectives and orbits

Synergy with Cluster and MMS

With Cluster/DoubleStar (2006)With MMS (2008)


THEMIS Instruments

Radial EFIs ESA

IDPUFGM

SCM

Axial EFIs

FGM

Axial EFIs

Radial EFIs

SCM

SSTs


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)


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


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


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.


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


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%


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


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


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


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)