UCB, November 12-14, 2003THEMIS Mission PDR/CAR 1 Probes and Probe Carrier Overview Mission PDR Tom Ajluni Swales Aerospace Systems Engineering Team Tom

THEMIS Mission PDR/CAR 1 UCB, November 12-14, 2003

Probes and Probe Carrier Overview

Mission PDRTom Ajluni

Swales Aerospace

Systems Engineering Team

Tom Ajluni, [email protected] , 301.902.4077

Kevin Brenneman

Mike McCullough


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

THEMIS Launch Configuration

Probe Carrier Assembly (PCA) on Delta 3rd StageProbe Carrier Assembly (PCA) on Delta 3rd Stage

Delta II Launch From KSCDelta 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 3rd 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 3rd Stage


Probe Bus Design Based on Simple Single String Approach

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


THEMIS InstrumentsTHEMIS Instruments


Perigee, Re Apogee, Re Inclination, Deg1 4 1.500 31.645 7.02 2 1.168 19.770 7.03 1 1.118 12.127 9.04 1 1.118 12.127 9.05 0.8 1.350 10.044 4.5

Orbital Period, Days

Orbit GeometryProbe

Orbital GeometriesOrbital 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


First Axial Mode: 72.4 HzFirst Lateral Mode: 43.7 Hz

Probe Fundamental Natural Frequencies

Probe Mechanical DesignProbe 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


Probe GN&CProbe 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)

ACS Sensors

Actuators

Bus Avionics Unit (BAU)

Flight Software

Ground Data System

SS Interface Electronics

IRU Interface Electronics

Sun Sensor

Magnetometer (FGM Instrument)

Y-Axis Angular Rate

Sun Crossing Pulse Sun Sensor Processing

(1 Hz)

TAM Processing

(1 Hz)

3-Axis Magnetic Field

IRU Processing (20 Hz) ACS Telemetry

Processing (1 Hz)

Thruster Command Processing

(10 Hz)

Thruster Operations Monitoring

GTDS Orbit Detemination

MSASS Attitude

Determination

GMAN Maneuver Planning

Disable Thrusters

Thruster Commands

Fault Limits

Thruster Control Electronics

Start Count, Stop Count

ThrusterThruster

ThrusterThruster

Rate Gyro

Thruster Valve

Open/Closed

Rate Gyro

X-Axis Angular Rate

Spin rate, Sun Aspect Angle, Sun Crossing Time

Instrument Data Processing Unit

(IDPU)

Sun Aspect Angle

Status Bit

Status Bit

Spin Rate

Sun Crossing Count

Fault Protection (1 Hz)


Hydrazine RCSHydrazine 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

F/D Valves

T1 A1 T2 A2

Tank1 Tank 2

Thrusters

PGSE PressureTransducer

P

P/V Valve

20 m20 m 20 m 20 m

40 m

40 mSystemFilter15 m

LatchValve

1mm

Orifice

Flight PressureTransducer


Probe Power SubsystemProbe 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


Probe RF CommunicationsProbe 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

EIRP 66.0 dBW UCB Ground Station

Space Loss -204.5 dB Ra = 30.943Re

Receive Antenna Gain -5.0 dBi

Receive Circuit Loss -0.5 dB

Other Losses -1.0 dB Polarization, pointing, etc.

Received Power -145.0 dBW

Required Power -151.0 dBW 1kbps, 10-6 BER

Margin 6.77 dB

Table RFCS2: Downlink Budget

EIRP 3.5 dBW

Space Loss -185.5 dB Range = 20 kkm

Other Losses -1.0 dB Polarization, pointing, etc.

Data/Total Power -1.0 dB 1.1 radian mod index

Ground station G/T 24.0 dB/K UCB Ground Station

Data Rate 512 kbps

Received Eb/No 12.6 dB

Required Eb/No 3.1 dB RS+Conv, 10-6 BER

Implementation Loss 1.5 dB

Margin 6.61 dB


THEMIS Sensor Orbit Positions and Downlink Rates

THEMIS Sensor Orbit Positions and Downlink Rates

P1P2

P3

32 kbps

4Kbps

4Kbps

P44Kbps

4Kbps

32 kbps

32 kbps

32 kbps

32 kbps64 kbps

64 kbps

64 kbps

64 kbps

64 kbps

32 kbps

64 kbps

128 kbps

128 kbps

128 kbps

128 kbps

128 kbps

128 kbps

256 kbps256 kbps

256 kbps

256 kbps

256 kbps

256 kbps

DEPICTION OF ORBIT POSITIONS AND DOWNLINK RATES

512 kbps

512 kbps

512 kbps

512 kbps

16 kbps

8 kbps

16 kbps

16 kbps

16 kbps

8 kbps

8 kbps 8 kbps

1 M bps

1 M bps


Probe Bus Avionics Unit (BAU)

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

DirectPower

ShuntRegulation

UmbilicalSAS

Interface

PowerDistribution

UplinkCommandInterface

CommandVerification

LVPS+5V, +3.3V

DiscreteCommandGenerator

DownlinkTelemetryInterface

TelemetryProcessor

HardwareCmd

Interface

CommandFIFO

TelemetryFIFO

RS&ConvEncoding

FPGA

33.554MHz

ColdFireProcessor

256 KBEEPROM

PowerControlCard

CommunicationInterface Board

ProcessorBoard

LVPS+5V

SepInterface

HardlineTlm

+28V Bus

512 KBRAM

16 KBPROM

BulkMemory

LVPS+/-5V 8.388 MHz

256 KBEEPROM3.3V

Switch /8 /8

Sel

ect

Add

r

Da

ta

Standby

2Mbps

RS-422Dvrs/Rcvrs

I2CInterface

RS-422

FPGA

54AC

Baud Clk

8.388MHz

ClockData

RS-422

BDM TestPort

UART TestInterface

I2CInterface

I2CInterface

SeparationCommand

SeparationInputs

InstrumentData Processing

Unit (IDPU)

Solar Arrays (6)

Battery

SunSensor

TransmitterReceiver

Diplexer

Thrusters &Latch Valves

PressureTransducers

S-BandAntenna

SST

SCM

ESA

FGM

EFIEFI EFIEFIEFIEFI

+28V to IDPU,XPNDR,& Heaters

BatteryOff Cmd

+28V

+28V

Thermistors& PRTs

1 PPS

Hardline Command

Inst CmdsS/C TLMTime

Inst StatusInst TLM

+28V

To SunSensor

+5V

ToGyros

+28V

+28V

SolidState

Gyros(2)

+5V -5V

SunPulse

BatteryOn Cmd


Flight Software Minimal, Brains on the Ground

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


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

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


PAF Adapter Ring/Tube & Attach to Launch Vehicle

PAF Adapter Ring/Tube & Attach to Launch Vehicle

Main DeckMain Deck

Center SpoolCenter Spool

(4) Lower Probe

Standard Separation

Fittings

(4) Lower Probe

Standard Separation

Fittings

(1) Upper Probe Standard Separation Fitting(1) Upper Probe Standard Separation Fitting

(8) External Struts(8) External Struts Probe Carrier (PC)Probe Carrier (PC)

Probe Carrier is a Simple Dispenser

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


ADAMS Dispense Model Dynamic Simulation Image

ADAMS Dispense Model Dynamic Simulation Image

Split screen

Probe Dispense is Passively Stable

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


Operational States and Flow Definition

Operational States and Flow Definition


Fault Detection and Correction

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


Major Trade StudiesMajor Trade Studies

TRADE STATUS

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 placementBaseline that brackets CG adopted pending final plume impingement study

Thruster size increase from 1N to 5NCost / Benefit analysis ongoing by Mission Systems at UCB

Separate from 3rd stage or stay attachedTrade completed, baseline remains attached

Processor Type Switched from 80C196 to Coldfire

Processor Speed vs. power consumptionClock 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 separationOn hold, evaluation of need not fully justified


System Change Notice (SCN)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


Probes and Probe Carrier Overview

Mission PDR

Resource Summary

Tom Ajluni

Swales Aerospace

Red = increased from previous month

Green = decreased from previous month


Probe Bus Mass BudgetProbe Bus Mass Budget

Probe Bus Allocations CommentsSubsystems Mass Mass Contingency Mass Contingency

(kg) (kg) % (kg) %

STRUCTURAL 24.20 21.05 14.99% 21.05 14.99% No new estimates

Bottom Deck 6.05 6.05Top Deck 2.38 2.38Solar Side Panels 2.61 2.61Corner Panels 1.44 1.44Top & Bottom Solar Panels 0.76 0.76RCS Accommodation 1.19 1.19Separation Ring 1.71 1.71Misc. Mechanical (Balance, Ant. Boom, etc.) 2.72 2.72Fasteners 2.18 2.18ACS 0.41 0.37 10.81% 0.37 10.81% No new estimates

ELECTRICAL 7.12 5.90 20.68% 6.30 13.02%Avionics 2.05 2.20 Latest GD Estimate

Comm 2.60 2.85 Added 25g for diplexor

Harness (Pwr., Data) 1.25 1.25POWER 6.62 5.42 22.15% 5.57 18.86%Solar Panel Side Cells 1.97 1.97Solar Panel Top & Bottom Cells 0.50 0.50Battery (inc. harness) 2.95 3.10 Added Battery Enable Relay Box &

Updated Battery Est

THERMAL 2.11 1.83 15.55% 1.83 15.55%Blankets (Bus + Tanks) 1.48 1.48Control (Bus + Tanks) 0.34 0.34PROPULSION 9.40 10.02 -6.17% 10.02 -6.17% Need allocation of 10.40

Tanks 4.90 4.90RCS 5.12 5.12

Probe Bus Total 49.86 44.58 11.85% 45.13 10.48%

Rev 3 October-03 Rev 3 November-03


Probe Bus Power BudgetProbe Bus Power Budget

Probe Bus Allocations CommentsSubsystems Power Pwr Contingency Pwr Contingency

(W) (W) % (W) %

STRUCTURALBottom DeckTop DeckSolar Side PanelsCorner PanelsTop & Bottom Solar PanelsRCS AccommodationSeparation RingMisc. MechanicalFASTENERSACS 0.16 0.13 23.08% 0.13 23.08% No new estimates

ELECTRICAL 12.04 10.25 17.46% 11.34 6.17%Avionics 5.00 6.24 Updated Eng Estimates

Comm 5.25 5.10 Updated info for 610 transponder

HarnessPOWERSolar Panel SideSolar Panel Top & BottomBatteryTHERMAL 2.30 2.00 15.00% 2.00 15.00% No new estimates

BlanketsControl 2.00 2.00PROPULSIONTanksRCS

Probe Bus Total 14.50 12.38 17.12% 13.47 7.65% No new estimates



Probe Carrier Mass BudgetProbe Carrier Mass Budget

Probe Carrier Allocations CommentsSubsystems Mass Mass Contingency Mass Contingency

(kg) (kg) % (kg) %

Structure 117.00 101.46 -1.08% 101.46 15.31% SCN 002 Approved- new allocation

Deck 43.18 43.18Struts 8.23 8.23Center Adapter 8.26 8.26PAF Assembly 14.11 14.11Seperation System 24.26 24.26Hardware 0.57 0.57Balance Weights 2.50 2.50Click-Bond Tie Downs 0.09 0.09Clips, etc 0.18 0.18Connector Brackets 0.08 0.08Thermal 2.60 2.10 -82.38% 2.10 23.81% SCN 002 Approved- new allocation

Electrical 2.40 1.81 24.86% 1.81 32.60% SCN 002 Approved- new allocation

Probe Carrier Total 122.00 105.37 -2.25% 105.37 15.78%



Probe Carrier Assembly and Propellant Budget

Probe Carrier Assembly and Propellant Budget

Probe Carrier Assembly Allocations Comments Mass Mass Contingency Mass Contingency (kg) (kg) % (kg) %

Probe A Bus 49.86 44.58 11.85% 45.13 10.48%Probe A Instruments 23.66 20.95 12.94% 20.95 12.94%Probe B Bus 49.86 44.58 11.85% 45.13 10.48%Probe B Instruments 23.66 20.95 12.94% 20.95 12.94%Probe C Bus 49.86 44.58 11.85% 45.13 10.48%Probe C Instruments 23.66 20.95 12.94% 20.95 12.94%Probe D Bus 49.86 44.58 11.85% 45.13 10.48%Probe D Instruments 23.66 20.95 12.94% 20.95 12.94%Probe E Bus 49.86 44.58 11.85% 45.13 10.48%Probe E Instruments 23.66 20.95 12.94% 20.95 12.94%

Probe Carrier 122.00 105.37 -2.25% 105.37 15.78%PCA Dry Mass Total 489.60 433.02 -144.69% 435.77 12.35%

Probe A Fuel (Full) 38.70Probe B Fuel (Full) 38.70Probe C Fuel (Full) 38.70Probe D Fuel (Full) 38.70Probe E Fuel (Full) 38.70LV Capability 807.00Total Dry Mass Capability & Margin 613.50 433.02 41.68% 435.77 40.79%

Propellant Margin Allocations CommentsCalculation Components Mass Est. Contingency Est. Contingency

(kg) % %

ACS Maneuvers 1.84 1.40 31.43% 2.04 -9.80% Latest Estimate



Documents

UCB, November 12-14, 2003THEMIS Mission PDR/CAR 1 Probes and Probe Carrier Overview Mission PDR Tom Ajluni Swales Aerospace Systems Engineering Team Tom