THEMIS FDMO Review Introduction − 1 October 5, 2004 MISSION OVERVIEW AND STATUS Vassilis Angelopoulos THEMIS was selected on March 20, 2003 as the next NASA/MIDEX mission (#5) to study the: Onset 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 on October 19 of 2006 In Tail (midnight) February 21, 2007/2008 Two year nominal duration Details at:

THEMIS FDMO Review Introduction − 2 October 5, 2004 Covered in this presentation Mission objectives Redundancy and resilience Overview of launch and placement RCS, ACS and Operational modes Outline

THEMIS FDMO Review Introduction − 3 October 5, 2004 Status PDR – peer: Oct 8/9/15/16, 2003, Mission: Nov 13-14, 2003 Confirmation: April 22, 2004: Launch reset request to October 19, CDR – peer: Apr – Jun 2004, Mission CDR: Jul 13-18, Delta thermal review: Aug 10, st MIWG held at Boeing, Huntington Beach: Aug 30, 2004 Instrument status All ETUs tested Flight production started EM IDPU I&T to be completed by Oct 18, 2004 Instrument Suite EM test review: November 5, 2004 F1 instruments ready by end of December, 2004 Bus status Flight production started Bus I&T starts: March 2004

THEMIS FDMO Review Introduction − 4 October 5, 2004 T IME H ISTORY OF E VENTS AND M ACROSCALE I NTERACTIONS DURING S UBSTORMS (THEMIS) RESOLVING THE PHYSICS OF ONSET AND EVOLUTION OF SUBSTORMS Science Team Principal Investigator Vassilis Angelopoulos, UCB Program Manager Peter Harvey, UCB Mission Operations Manager Manfred Bester, UCB GSFC technical partnership Mark Beckman, MESA (former GN&C) Industrial Partner SWALES Aerospace, Inc., Beltsville MD

THEMIS FDMO Review Introduction − 5 October 5, 2004 Auroral eruptions and substorms Auroral eruptions… Aurora …are a manifestation of magnetospheric substorms MAGNETOSPHERE SOLAR WIND EQUATORIAL PLANE

THEMIS FDMO Review Introduction − 6 October 5, 2004 Most important science result and 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 FDMO Review Introduction − 7 October 5, 2004 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 FDMO Review Introduction − 8 October 5, 2004 First bonus: What produces storm-time “killer” MeV electrons? Affect satellites and humans in space Source: – Radially inward diffusion? – Wave acceleration at radiation belt? THEMIS: –Tracks radial motion of electrons Measures source and diffusion Frequent crossings –Measures E, B waves locally ANIK telecommunication satellites lost for days to weeks during space storm

THEMIS FDMO Review Introduction − 9 October 5, 2004 Second bonus: What controls efficiency of solar wind – magnetosphere coupling? Important for solar wind energy transfer in Geospace Need to determine how: – Localized pristine solar wind features… – …interact with magnetosphere THEMIS: – Alignments track evolution of solar wind – Inner probes determine entry type/size

THEMIS FDMO Review Introduction − 10 October 5, 2004 THEMIS is unique and timely Solves major long-standing question in magnetospheric physics (NAS) –Self-sufficient, ideally complements current SEC line –Global context for Cluster (2006/7), MMS (2010), LWS (Rad. Belt Storm Probes: 2012) A scientific and technological pathfinder for future SEC missions –Pre-requisite to Space Weather prediction –Identifies causal relationships for MagCon –Low cost highly integrated probes in anticipation of future Constellations Inspires K-12 students –Hands-on involvement of high-school students: ground magnetometer curators First University-managed multi-satellite project –Expands NASA partnership with Academia –Trains scientific, technological and industrial workforce of future

THEMIS FDMO Review Introduction − 11 October 5, 2004 Covered in this presentation Mission objectives Redundancy and resilience Overview of launch and placement RCS, ACS and Operational modes Outline

THEMIS FDMO Review Introduction − 12 October 5, 2004 Identical instrumentation provides high science margins and fault tolerance Instrument redundancy: –SST-ESA energy overlap –FGM-SCM frequency overlap –P1/P2 redundant instrumentation (only directional flux needed in one of two). Each probe has: 1FGM 1ESA (i/e) 2SSTh (2heads, i/e) 1SCM 4EFIs (4spin plane) 2EFIa (2axials) Selected instruments built en masse before Instruments required to achieve Primary Mission Objective Measurement goalsP1P2P3P4P5 Time History of Events P3,4&5 monitor CD P1,2 bracket Rx t res <30s,  Y<±2R E FGM 1SSTh 2EFIs FGM ESA 2SSTh 2EFIs FGM ESA 1SSTh FGM ESA 1SSTh FGM ESA 1SSTh Macroscale Interactions Track rarefaction wave, inward flows, Poynting with  B<1nT,  V/V~10% FGM ESA FGM ESA FGM ESA FGM ESA Radial/cross-sheet pressure, velocity and current gradients require  P/P~  V/V ~  B/B ~10%, non-MHD FGM ESA FGM ESA 2EFIs FGM ESA 2EFIs FGM ESA 2EFIs Cross-tail pairs measure FLRs, KH, ballooning on B, V, 10s and fast modes on B xyz and E 60 Hz FGM ESA SCM FGM ESA SCM 4EFIs 2EFIa FGM ESA 2EFIs FGM ESA SCM 4EFIs 2EFIa TOTAL Minumum mission (Red) Baseline add-ons (green) FGM 1SSTh 2EFIs FGM ESA 2SSTh SCM 2EFIs FGM ESA 1SSTh SCM 4EFIs 2EFIa FGM ESA 1SSTh 2EFIs FGM ESA 1SSTh SCM 4EFIs 2EFIa

THEMIS FDMO Review Introduction − 13 October 5, 2004 Probe conjunctions well understood BASELINE: >10 substorms/yr i.e., 188hrs/yr (achieved w/ 5 probes in 2 yrs). MINIMUM: >5 substorms in 1 year, i.e., 94hrs in 1 year (w/ 4 probes, x2 margin). – computations include lunar, solar, drag, J2 terms –  Y P1/2/3/4/5 <±2R E ;  Z P3,4,5/NS <±2R E ;  Z P1,2/NS <±5R E Ascent design is optimal for science – maximizes conjunctions, minimizes shadows … immune to launch insertion errors – small, piece-wise  Vs increase placement fidelity … and immune to probe insertion errors. – Can withstand insertion error of  V=40cm/s on any probe (  V control is 100 times better; knowledge requirement is 3 times better, capability is >10times better) Actual conjunction times in 1 st year

THEMIS FDMO Review Introduction − 14 October 5, 2004 Descope list and science-related risk mitigation factors Re-positioning allows recovery from failure of critical instruments on some probes Graceful degradation results from partial or even full instrument failures –Instrument frequency and energy range overlaps –Complete backup option for EFI radials (need 2 in most probes but have 4) –Relaxed measurement requirements (1nT absolute is not permitted to drive team, but rather a nicety) –Substorms come in wide variety; can still see large ones with degraded instruments Minimum mission can be accomplished with a reduced set of spacecraft requirements –EMC and ESC requirements important for baseline but less severe for minimum mission –Observation strategy can be tuned to power loss (turn-on/off) and thermal constraints (tip-over/back) –Fuel and mass margins for 1 st year (minimum) are 30% larger than for a two year (baseline) mission

THEMIS FDMO Review Introduction − 15 October 5, 2004 Covered in this presentation Mission objectives Redundancy and resilience Overview of launch and placement RCS, ACS and Operational modes Outline

THEMIS FDMO Review Introduction − 16 October 5, 2004 Probe Carrier Assembly (PCA = 5 Probes + Probe Carrier) on L/V Probe Carrier Assembly (PCA = 5 Probes + Probe Carrier) on L/V Probe Carrier Assembly (PCA) on Delta 3 rd Stage Delta II Launch From KSC Dedicated Delta ’ Composite Fairing required to accommodate five Probes on the Probe Carrier in the “Wedding Cake” configuration PC stays attached to Delta 3 rd stage after probe dispense minimizing orbital debris Each probe dispense from the PCA is coordinated with but independent of the other probes No single probe anomaly precludes dispense of remaining probes Boeing provided ordnance fired from 3rd stage blows all clampbands to initiate separation Standard Delta 10 ft. Fairing Static Envelope 3712 PAF THEMIS Launch Configuration Star 48 3 rd Stage

THEMIS FDMO Review Introduction − 17 October 5, 2004 Mission profile is robust Pre-Launch (6hrs) Launch (25min) Check-out & ascend (60days) Science ops (2yrs) Re-entry Checkout Countdown 2 nd stage burn Spin-up 3 rd stage burn Spin-down Probe dispense Bus check-out, reor Dply mags/check instr. Place to Orbit. - 6 side thrustings - 6 reor/fire/reor sequences Deploy EFI Minor ctrl ops (all): – 22 side-thrustings – 2 inclination changes Minor ctrl ops (Side-thrusts, finish by EOM+9mo) - 8 side-thrustings Passive re-entry thereafter (1-10yrs) Fuel consumption, maneuvers and contacts during ascend: validated with GMAN.

THEMIS FDMO Review Introduction − 18 October 5, 2004 Probe power positive under any release season/orientation Except for a subset of February/March launch, which (with current elements) can result in longer shadows

THEMIS FDMO Review Introduction − 19 October 5, 2004 Mission overview: Fault-tolerant design has constellation and instrument redundancy CCAS Instrument I&T UCB Mission I&T Swales Encapsulation & launch BGS Operations UCB 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 T spin =3s

THEMIS FDMO Review Introduction − 20 October 5, 2004 Covered in this presentation Mission objectives Redundancy and resilience Overview of launch and placement RCS, ACS and Operational modes Outline

THEMIS FDMO Review Introduction − 21 October 5, 2004 Probe bus is a single string design with selected redundancy Power positive in all attitudes with instruments off (launch, safe hold modes) Passive thermal design using MLI and thermostatically controlled heaters tolerant of longest shadows (3 hours) –Spin stabilized probes point within 13° of ecliptic south and have inherently stable thermal environment S-Band communication system always in view of earth every orbit at nominal attitude. In view for greatest part of orbit in any attitude Passive spin stability achieved in all nominal and off-nominal conditions Monoprop blow down RCS (propulsion) system is self balancing on orbit Antenna 4x Side Solar Panels Top Deck 4x Radial EFIs Axial EFI Booms SCM Boom FGM Boom 2x Top Solar Panels 2x SSTs 2x Tang. Thruster RCS Fill / Drain Valves ESA Shunt 2X Propulsion Tanks Transponder Battery Sun Senor ESA/IDPU BAU IRU Single Point Ground Harness Bridge (harness not shown) Radial EFIs Bus Overview

THEMIS FDMO Review Introduction − 22 October 5, 2004 Blowdown N2H4 system design Two Interconnected tanks Lightweight, High Performance System Robust, self-balancing fuel management (as on ISEE, ACE) Components flown on dozens of missions, integrated by Aerojet Readily Available Components Arde Inconel propellant tanks on order Carleton P/N 7149 pressurant tank from ST5 All other components are off the shelf Robust Thruster arrangement provides for partial redundant function with degraded performance Meets all Range Safety Requirements Heritage design based on ISEE-3 and ACE Reaction Control System (RCS): A Hydrazine Orbit/Attitude Control System

THEMIS FDMO Review Introduction − 23 October 5, 2004 Propulsion System Recent Upgrade for Additional Fuel Tanks are launched 93% full Initial blowdown occurs quickly One time actuation of pressurant tank Repress back to full pressure Larger volume depressurizes slowly Profile-averaged Isp= 223s for continuous thrusting 210s for pulsed at +/-30deg pulse

THEMIS FDMO Review Introduction − 24 October 5, 2004 Thruster Placement Two axial, parallel thrusters for reors, and major orbit changes Two radial, parallel thrusters for spin control and minor orbit changes

THEMIS FDMO Review Introduction − 25 October 5, 2004 ACS sensors Sun Sensor provides spin pulse and elevation angle FGM science sensor doubles up as TAM ACS sensor Two Solid State Gyros (Inertial Reference Units) for tactical use; provide  x,  y

THEMIS FDMO Review Introduction − 26 October 5, 2004 Slew/precession control –Sun synchronous thrusting –Major circle reor performed by piece-wise continuous Rhumb line reor Spin up/down –Continuous and/or sun synchronous Axial thrust –Continuous Side thrust –Sun synchronous thrusting None of the above (i.e., no thrusting) = “safe mode” –Fault protection to return to “none of the above” if anomaly is detected Thrusters commanded off under following conditions: –Sun aspect angle out of bounds –Spin rate out of bounds –Thruster control electronics Watch Dog Timer time out –Processor reboot RCS operational modes

THEMIS FDMO Review Introduction − 27 October 5, 2004 Replaced check valve with solenoid valve –Prevents hydrazine fuel from condensing into (colder) pressurant tank at a needed 10^-6 scc/se Open trade to negate mass growth since CDR: –Utilize the same RCS components but in a repress-then-regulate mode –Solenoid valve to perform regulation at 300psi, increasing Isp to 224.4s –By increasing fill to 97.5% the system also improves deltaV by 36m/s Design modifications since CDR

THEMIS FDMO Review Introduction − 28 October 5, 2004 Backup Slides

THEMIS FDMO Review Introduction − 29 October 5, 2004 Baseline L1 Req’s pertaining to orbit design S-2 Current Disruption Onset Time –Determine current disruption onset time with t_res<30s, using two near-equatorial (within 2Re of magnetic equator) probes, near the anticipated current disruption site (~8-10 Re). Current disruption onset is determined by remote sensing the expansion of the heated plasma via superthermal ion flux measurements at probes within +/-2Re of the measured substorm meridian and the anticipated altitude of the current disruption. S-3 Reconnection Onset Time –Determine reconnection onset time with t_res<30s, using two near-equatorial (within 5Re of magnetic equator) probes, bracketing the anticipated reconnection site (20-25Re). Reconnection onset is determined by measuring the time of arrival of superthermal ions and electrons from the reconnection site, within dY=+/-2Re of the substorm meridian and within <10Re from the anticipated altitude of the reconnection site. ….. S-4 Simultaneous Observations –Obtain simultaneous observations of: substorm onset and meridian (ground), current disruption onset and reconnection onset for >10 substorms in the prime observation season (September-April). Given an average 3.75hr substorm recurrence in the target tail season, a 2Re width of the substorm meridian, a 1Re requirement on probe proximity to the substorm meridian (of width 2Re) and a 20Re width of the tail in which substorms can occur, this translates to a yield of 1 useful substorm event per 18.75hrs of probe alignments, i.e, a requirement of >188hrs of four-probe alignments within dY=+/-2Re.

THEMIS FDMO Review Introduction − 30 October 5, 2004 S-6 Earthward Flows –Track between probes the earthward ion flows (400km/s) from the reconnection site and the tailward moving rarefaction wave in the magnetic field, and ion plasma pressure (motion at 1600km/s) with sufficient precision (dV/V=10% or V within 50km/s whichever is larger, dB/B=10%, or B within 1nT whichever is larger, dP/P=10%, or P within 0.1nPa whichever is larger) to ascertain macroscale coupling between current disruption and reconnection site during >10 substorm onsets (>188hrs of four-probes aligned within dY of +- 2Re). S-7 Pressure Gradients –Determine the radial and cross-current-sheet pressure gradients (anticipated dP/dR, dP/dZ ~0.1nPa/Re) and ion flow vorticity/deceleration with probe measurement accuracy of 50km/s/Re, over typical inter-probe conjunctions in dR and dZ of 1Re, each during >10 onsets. The convective component of the ion flow is determined at 8-10Re by measurements of the 2D electric field (spin-plane to within +-30degrees of ecliptic, with dE/E=10% or 1mV/m accuracy whichever is larger) assuming the plasma approximation at t_res<30s. S-8 Cross-Current Sheet changes –Determine the cross-current-sheet current change near the current disruption region (+/-2Re of meridian, +- 2Re of measured current disruption region) at substorm onset from a pair of Z-separated probes using the planar current sheet approximation with relative (interprobe) resolution and interorbit (~12hrs) stability of 0.2nT. S-10 Cross-Tail Pairs –Determine the presence, amplitude, and wavelength of field-line resonances, Kelvin-Helmholz waves and ballooning waves on cross-tail pairs (dY=0.5-10Re) with t_res 10 substorm onsets. … continued: Baseline L1 Requirements

THEMIS FDMO Review Introduction − 31 October 5, 2004 Minimum L1 Req’s pertaining to orbit design Current Disruption Onset Time –Determine current disruption onset time with t_res<30s, using two near-equatorial (within 2Re of magnetic equator) probes, near the anticipated current disruption site (~8-10 Re). Current disruption onset is determined by remote sensing the expansion of the heated plasma via superthermal ion flux measurements at probes within +/-2Re of the measured substorm meridian and the anticipated altitude of the current disruption Reconnection Onset Time –Determine reconnection onset time with t_res<30s, using two near-equatorial (within 5Re of magnetic equator) probes, bracketing the anticipated reconnection site (20-25Re). Reconnection onset is determined by measuring the time of arrival of superthermal ions and electrons from the reconnection site, within dY=+/-2Re of the substorm meridian and within <10Re from the anticipated altitude of the reconnection site. … Simultaneous Observations –Obtain simultaneous observations of: substorm onset and meridian (ground), current disruption onset and reconnection onset for >5 substorms in the prime observation season (September-April). Substorm statistics discussed in S-4 point to a requirement of >94hrs of four probe alignments. Lifetime –THEMIS instrument and spacecraft shall be designed for at least a 2-yr lifetime Launch –THEMIS will be launched into an orbit with R a =12Re, R p =1.1Re and INC=9.5deg, prior to 03/2007. –Launch window = 40 min –Prefered (not required) launch season = August /- 2 months (now October 19, 2006).