1. UCB, November 12-14, 2003THEMIS Mission PDR/CAR 1 Probes and Probe Carrier Overview Mission PDR Tom Ajluni Swales Aerospace Systems Engineering Team Tom Ajluni, tajluni@swales.com, 301.902.4077tajluni@swales.com Kevin Brenneman Mike McCullough

2. UCB, November 12-14, 2003THEMIS Mission PDR/CAR 2 Standard Delta 10 ft. Fairing Static Envelope 3712 PAF Probe Carrier Assembly (PCA = 5 Probes + Probe Carrier) on L/V Probe Carrier Assembly (PCA = 5 Probes + Probe Carrier) on L/V THEMIS Launch Configuration Probe Carrier Assembly (PCA) on Delta 3 rd Stage Delta II Launch From KSC  Dedicated launch accommodated within standard Delta 7925-10 vehicle configuration and services  PC permanently attached to Delta 3rd stage –Minimizes orbital debris –Meets < 25 yr. re-entry requirement –Desire unique 3 rd Sep Signal  10’ Composite Fairing required to accommodate five Probes on the Probe Carrier in the “Wedding Cake” configuration  Each probe dispense from the PCA is coordinated with but independent of the other probes  No single probe anomaly precludes dispense of remaining probes Star 48 3 rd Stage

3. UCB, November 12-14, 2003THEMIS Mission PDR/CAR 3 Probe Bus Design Based on Simple Single String Approach  Power positive in all attitudes with instruments off (launch, safe hold modes) –Exception is top deck pointed at the sun where the steady state heater power drives bus power negative, this issue is being actively worked  Passive thermal design tolerant of longest shadows (3 hours) –Steady state sun on the bottom deck drives hot case, this issue being actively worked  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 –Full boom deployment attitude not meeting requirements  Monoprop blow down RCS (propulsion) system is self balancing on orbit

4. UCB, November 12-14, 2003THEMIS Mission PDR/CAR 4 THEMIS Instruments

5. UCB, November 12-14, 2003THEMIS Mission PDR/CAR 5 Orbital Geometries  Probe Constellation Aligned for Winter Science: Apogee alignment of elliptical orbits at local midnight over North America in the winter  Probe orbits designed to provide spatial and temporal sampling of the local plasma, electric field, and magnetic field

6. UCB, November 12-14, 2003THEMIS Mission PDR/CAR 6 First Axial Mode: 72.4 Hz First Lateral Mode: 43.7 Hz Probe Fundamental Natural Frequencies Probe Mechanical Design  Mechanical design is based on an industry standard simple “unibody “ structure composed of panels with an Al honeycomb core and composite face sheets –Standard size panels are pinned and bolted together for easy assembly / disassembly  Bottom deck is the primary mounting surface and load path –Side panels are independently removable for easy access  Design is based on extensive analysis with high stiffness and ample margins –Inertia ratio control key to passive stability

7. UCB, November 12-14, 2003THEMIS Mission PDR/CAR 7 Probe GN&C  Attitude control scheme based on a passively stable spinner that is fault tolerant and has graceful degradation –Sensor complement consists of Sun Sensor, Two transverse mounted single axis gyros, and FGM –Actuators consist only of four thruster complement  Attitude determination and control done on the ground –Sensor data telemetered to the ground –All thruster commands generated on the ground, firings are planned only during real time contact –THEMIS flight and ground configuration closely mimics ST-5 (also operated by UCB)

8. UCB, November 12-14, 2003THEMIS Mission PDR/CAR 8 Hydrazine RCS  Simple, high heritage RCS design and components –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 All other components are off the shelf –Robust Thruster arrangement provides for redundant function with degraded performance Meets all Range Safety Requirements Heritage design based on ISEE-3 and ACE Figure RCS1: Probe RCS Schematic Design

9. UCB, November 12-14, 2003THEMIS Mission PDR/CAR 9 Probe Power Subsystem  Power design is a direct energy transfer system with the battery and solar array connected directly to the power bus –Solar array power control and battery charging are performed using linear and sequential switching shunts, minimizing EMI / EMC  Solar array consists of eight panels, one on each side (59W EOL) and two each on the top and bottom decks (21W EOL) –Arrays have conductive cover glass to minimize surface charging  At nominal attitude the min load power available is 41.7W, easily accommodating the required load power of 29.2W (includes reserves) –Energy balance accounts for battery recharging, increased eclipse heater power, and power control inefficiencies –Heritage (Mars Rover) triple junction GaAs cells from EMCORE baselined (27.5% efficiency) –Heritage (Mars Rover) Lithium Ion battery from Yardney baselined (10.5A-hr), has maximum DoD of approximately 50% for worst-case 180 minute eclipse

10. UCB, November 12-14, 2003THEMIS Mission PDR/CAR 10 Probe RF Communications  Probes S-Band system fully compatible with existing UCB ground station (BGS), USN, DSN, and TDRSS networks  L-3 Conic CXS-610 transponder a strong heritage baseline –Supports Tx, Rx, and ranging  Antenna is a spin axis omni directional low gain microstrip patch –3dB beam width about 45° cone centered about spin axis –Antenna design study underway at Ball  Link is closed at all orbital positions –BGS primary, USN/Perth backup –Downlink rate selectable from 1, 4, 8, 16, 32, 64, 128, 256, 512, and 1000 kbps –Uplink fixed at 1 kbps –Downlink closed at P1 apogee (31 Re, max range) at 4 kbps with 6.03 dB margin Table RFCS1: Uplink Budget EIRP66.0dBWUCB Ground Station Space Loss-204.5dBR a = 30.943R e Receive Antenna Gain-5.0dBi Receive Circuit Loss-0.5dB Other LossesdB Polarization, pointing, etc. Received Power-145.0dBW Required Power-151.0dBW1kbps, 10 -6 BER Margin6.77dB Table RFCS2: Downlink Budget EIRP3.5dBW Space Loss-185.5dBRange = 20 kkm Other LossesdB Polarization, pointing, etc. Data/Total PowerdB1.1 radian mod index Ground station G/T24.0dB/KUCB Ground Station Data Rate512kbps Received E b /N o 12.6dB Required E b /N o 3.1dBRS+Conv, 10 -6 BER Implementation Loss1.5dB Margin6.61dB

11. UCB, November 12-14, 2003THEMIS Mission PDR/CAR 11 THEMIS Sensor Orbit Positions and Downlink Rates

12. UCB, November 12-14, 2003THEMIS Mission PDR/CAR 12 Probe Bus Avionics Unit (BAU)  Processor card is procured from GDDS and utilizes a Coldfire processor –Standard features include EDAC, watchdog timer, memory checksum, limit checking with action, and memory dwell diagnostics  Comm card based on SMEX-Lite (Triana) –Incorporates CCSDS and both convolutional and Reed-Solomon encoding  Power card is derived from Swales EO-1 power controller –Provides power control, conditioning, switching, analog circuitry, separation, gyros, and temp sensors  Existing in-house avionics testbed for rapid hardware and software development

13. UCB, November 12-14, 2003THEMIS Mission PDR/CAR 13 Flight Software Minimal, Brains on the Ground  Software based on past SMEX missions including SAMPEX, FAST, SWAS, TRACE, WIRE, SMEX-Lite / Triana, and EO-1  With attitude determination and control command generation all done on the ground, flight software is significantly simpler than any of these missions –Hammers Company is our strategic partner, THEMIS teammate and the bus software developer on these past missions listed above and is also supporting the ST-5 mission flight software development (very similar to THEMIS)  Software developed in C and Assembly and runs on RTEMS operating system. Code is modular and table driven to minimize software development, testing and maintenance  Coldfire processor CPU clock speed is 8.38 MHz, board clock sized to allow a doubling in capacity if required. Software development based on proven approaches such as incremental builds and COTS development and CM tracking tools

14. UCB, November 12-14, 2003THEMIS Mission PDR/CAR 14 Figure TCS-2: Probes 3/4/5 and Probe 1 Transient Thermal Response of Avionics Deck Probe 3/4/5 Longest Shadow Probe 1 Full Sun Response Probe and Instruments Utilize Passive Thermal Control  Passive thermal design using MLI and thermostatically controlled heaters maintains thermal environment for bus, avionics, propulsion, and deck mounted instruments. Design selected as the best balance to achieve lowest mass, cost, and design simplicity –External instruments (EFI, SCM, FGM) move with environment –SST and ESA moderated by bus –Conductive and radiative energy coupling paths isolated to minimize heater power in eclipse  Spin stabilized probes orbit within 13° of ecliptic plane have inherently stable thermal environment  Geometric Math Model- Thermal Desktop version 4.5 (Contains about 1000 surfaces)  Thermal Math Model – SINDA/FLUINT version 4.5 (Contains about 3000 nodes, 10,000 linear couplings, and 150,000 radiative couplings) –Conservative assumptions and EOL properties used

15. UCB, November 12-14, 2003THEMIS Mission PDR/CAR 15 PAF Adapter Ring/Tube & Attach to Launch Vehicle Main Deck Center Spool (4) Lower Probe Standard Separation Fittings (1) Upper Probe Standard Separation Fitting (8) External Struts Probe Carrier (PC) Probe Carrier is a Simple Dispenser  Simple probe carrier utilizes –Machined aluminum structure –Standard heritage payload attach fittings for Probes –Straight-forward umbilical interconnect harness –Multi layer insulation blanketing as required  Detailed design supported by comprehensive analysis –NASTRAN model used to recover material stresses and fundamental frequencies –Base drive analysis used to verify strength and recover component loads  Probe layout on carrier maximizes static and dynamic clearances –Design is the best balance between deployment clearances and probe structural mass First Axial Mode: 48.27 Hz First Lateral Mode: 18.29 Hz Probe Carrier Fundamental Natural Frequencies: Displacements Not to Scale

16. UCB, November 12-14, 2003THEMIS Mission PDR/CAR 16 ADAMS Dispense Model Dynamic Simulation Image Split screen Probe Dispense is Passively Stable  Design study and analysis major results –Deploy sequence of P1 then P2-P5 simultaneously –15 rpm nominal PCA spin rate –Probe separation velocity of.35 m/s  Results of evaluating off-nominal conditions –No collisions or close approaches due to combinations of ‘stuck’ Probes, timing errors and tip-off –Reasonable nutation and pointing angles that Probe ACS can easily accommodate –Separation initiation is two fault tolerant  Visualization –Used actual output files from ADAMS to make the animation –No “airbrushing” or touch up  Flexibility for tuning deployment later in the design process includes; carrier spin rate, deployment spring stiffness, deployment order, and timing

17. UCB, November 12-14, 2003THEMIS Mission PDR/CAR 17 Operational States and Flow Definition

18. UCB, November 12-14, 2003THEMIS Mission PDR/CAR 18 Fault Detection and Correction  Based on limited spacecraft autonomy  Primary action during normal or eclipse operation is to load shed for overcurrent or under voltage conditions –Instrument low power mode first –Instruments Off last resort  During thruster firing gyros and sun sensor must remain “in the box” or burn is autonomously terminated –Restarted only by ground command

19. UCB, November 12-14, 2003THEMIS Mission PDR/CAR 19 Major Trade Studies TRADESTATUS Larger propellant tanks vs. mass and volume Larger tanks on order, x% increase in fuel Clampband vs. Lightband separation system Timing errors too large in light band system, clamp band baselined Thruster placement Baseline that brackets CG adopted pending final plume impingement study Thruster size increase from 1N to 5N Cost / Benefit analysis ongoing by Mission Systems at UCB Separate from 3rd stage or stay attached Trade completed, baseline remains attached Processor TypeSwitched from 80C196 to Coldfire Processor Speed vs. power consumption Clock increased to 8.38 MHz, 58 mW max increase in power acceptable, capability increase up to 16.77 MHz retained Auto sun acquisition after ELV separation On hold, evaluation of need not fully justified

20. UCB, November 12-14, 2003THEMIS Mission PDR/CAR 20 System Change Notice (SCN)  SCN is a formal mechanism for capturing changes that cross interface boundaries or affect the project baseline design. Process is documented in the Mission Level Systems Engineering Management Plan  SCN 001 Propulsion Tank Size –Initiated on 7/17/03 by SAI to improve propellant margins by 11.5% –Increase propellant load from 34.52 to 38.7 kg –Approved 9/23/03  SCN 002 Probe Carrier Mass Increase –Initiated on 9/9/03 by SAI –Increase Probe Carrier mass from 103 kg to 122 kg, to account for heavier pyro activated clamp band –Approved 11/04/03  SCN 003 Thruster Size –Initiated 10/31/03 by UCB –Increase all thrusters from 1N to 5N –Approved 11/05/03  Future SCNs that have been informally discussed but have not been submitted include SST Envelope Increase and Thruster Placement

21. UCB, November 12-14, 2003THEMIS Mission PDR/CAR 21 Probes and Probe Carrier Overview Mission PDR Resource Summary Tom Ajluni Swales Aerospace Red = increased from previous month Green = decreased from previous month

22. UCB, November 12-14, 2003THEMIS Mission PDR/CAR 22 Probe Bus Mass Budget

23. UCB, November 12-14, 2003THEMIS Mission PDR/CAR 23 Probe Bus Power Budget

24. UCB, November 12-14, 2003THEMIS Mission PDR/CAR 24 Probe Carrier Mass Budget

25. UCB, November 12-14, 2003THEMIS Mission PDR/CAR 25 Probe Carrier Assembly and Propellant Budget