Section 9.0

Power Subsystem

Karen CastellPower Subsystem

ST5 PDR June 19-20, 2001

GSFC 5Space Technology

“Tomorrow’s Technology Today”

ST5 PDR June 19-20, 2001 9 - 2

GSFCAgenda

• Requirements

• Documentation

• Power Diagrams

• Power System Electric (PSE)

• Umbilical Interfaces

• Li-Ion Battery Analysis

• Budgets

• Risk Mitigation

ST5 PDR June 19-20, 2001 9 - 3

GSFCRequirements (1 of 3)

• 3 Month Mission Life.

– EOL budgets for 3 month requirement

• Energy storage with Li-ion batteries.

– Through necessary usage in Eclipse, Sun Acquisition and Sunlight

• Telemetry for monitoring battery performance.

– Cell level performance (voltage monitoring)

• Validate Flexible Circuitry.

– With solar array string backwiring on all panels

• Power available in sunlight: 18W at PSE output connector.

– Triple junction solar cells, 27% efficient

– Solar panels normal to the sun within 5 degrees nominally

ST5 PDR June 19-20, 2001 9 - 4

GSFCRequirements (2 of 3)

• 30 Watt-hours from battery.

– One 7.5 Amp-hour Lithium Ion Battery

• Spacecraft powered off until released from the deployer structure.

– Fly-Away Connector initiates the Power System Enable Switch

ST5 PDR June 19-20, 2001 9 - 5

GSFCRequirements (3 of 3)

• Provide Regulated (+5V+/-4%) Power Bus- Regulated power to smaller services and C&DH

• C&DH board space is very constrained

• Provide Unregulated (7.2V, +/-1.2V) Power Bus- Unregulated power to larger or noisier services

• Provide switched, over-current protected services- Trip level tailored to each component (H/W selectable)

• Provide “unfused” services to essential loads- Essential services are not over-current protected-- S/C Receiver, C&DH- Sun sensor --over-current protected service that powers up ON;

Can be commanded OFF in eclipse, otherwise always ON

• Provide C&DH Special Command - Power on reset

• Radiation (Assuming 80mil Al shielding)- TID is 40 krad-Si (with margin); LETth is 35Mev/cm2-kg

• Magnetic Field Requirement- Drives power and signal routing in order to minimize current loop area

ST5 PDR June 19-20, 2001 9 - 6

GSFCDocumentation

• Battery SOW, Spec under CM

• Solar Array SOW/Spec under CM

• Power System Spec - Preliminary

• Preliminary ICDs- Battery Mech, Elec ICD

- PSE ICDs

- Solar Panel and string layout drawing

ST5 PDR June 19-20, 2001 9 - 7

GSFCPower System Interfaces

Analog Mux

C&DHControl

Telemetry

Power System Electronics (PSE)Power

Telemetry

Telemetry

Power

Power

Telemetry

Power to Spacecraft

Power

Solar ArrayVoltageRegulator/BatteryCharger

Umbilical/SkinConnectors

Solar Array

Battery

+5V Regulation

Power SystemTelemetry

Breakwire (Loop)to Enable Switch

DPC Power

Telemetry

SwitchCommands/Status

Switching/Distribution

+5VRegulation

UnregulatedBus

ST5 PDR June 19-20, 2001 9 - 8

GSFCNanosat Mockup

~60% of ST5 volume

ST5 PDR June 19-20, 2001 9 - 9

GSFC

Power Distribution Diagram

NOTES:** Essential Over-current Protected Services

Bus Regulation,Distribution& Switching

Li-Ion Battery

EPS Enable Switch

.Solar Array

7.2V Services

5V Services

Transponder (Receive Mode)

C&DH (Always ON)**

Essential Unfused Service

Switched Services

TransmitterCCNTMag ElectronicsMag Boom ActuatorS band Antenna ActuatorPressure TransducerSpare

Sun Sensor (Always ON)**Propulsion Control ElecThermal Technology 1Thermal Technology 2

SpecialCmd

C&DH Reset Sp. Cmd.(From Transponder)

+5VRegulator

+5V Regulator

SHD539274

SHD539274

SwitchCommands

Fly Away Connector

. .

.

Regulator

ST5 PDR June 19-20, 2001 9 - 10

GSFCPSE Features

• Solar Array Regulator/ Battery Charging Circuitry combined for efficiency

• Regulated Bus– +5V +/- 4%

• Unregulated Bus– +7.2V, +/-1.2V

• Over current protected services– Each switch has a trip point that is individually tailored

– Commandable, resettable circuit breakers in surface mount package

• Designed by GSFC engineer-- MAP, EO-1 Evolution

• Power Bus Enable Switch– Turns spacecraft on after separation from deployer structure

• Power System Health and Safety Monitoring

ST5 PDR June 19-20, 2001 9 - 11

GSFC

Power System Functional Diagram

Solar Array:Triple Junction Cells8 PanelsEach string on every panel has its own isolation diode.

Bus Regulation,Distribution& Switching

Li-Ion Battery

TelemetrySignalConditioning

EPS Enable Switch(Break-away, Loop Back)

Power System Telemetryto C&DH

Regulator/Charge Control

Switchcommands

7.2V

x 8

5.0V+5V

+5V

Sp. Cmd

.

FETDrive

Ref

Vsense

VoltageClamp

Redundant FET

VDD

VDD

BatteryHealth &Safety Telm To C&DH

VCC

VCC

VDD

ST5 PDR June 19-20, 2001 9 - 12

GSFCPSE Breadboards

ST5 PDR June 19-20, 2001 9 - 13

GSFCPSE Telemetry

PSE Telemetry

Fast Telemetry Medium Telemetry Slow TelemetryCritical Voltages, Currents Other Voltages, Currents, Other Status,

Status Signals Temperaturesevery 4 sec (TBR) every 8-32 sec (TBR) every 32+ sec (TBR)

Bus V, unregulated Solar Array Voltage Battery Temperature-Hot CellBus Current, unregulated Solar Array Current Battery Temperature-Cold CellBattery Voltage Battery Voltage Solar Array Temperature (2)Battery Current +5V Bus Monitor Battery Midstring VoltagesBattery Current Polarity Battery Charger TemperatureBattery State of Charge PSE Card Temperature (TBD)

PSE Reference Resistor

ST5 PDR June 19-20, 2001 9 - 14

GSFCPSE Packaging

• C&DH and PSE located in same Card Cage Assembly (CCA) with common backplane

• CCA stretches across the diameter of the spacecraft

• Tight Magnetics requirement drives the design:

Signals and Power are bundled together and routed to individual components

• Temperature range

Operating-10 to 40 C

Survival -20 to 50 C

ST5 PDR June 19-20, 2001 9 - 15

GSFCPSE/C&DH Card Cage

ST5 PDR June 19-20, 2001 9 - 16

GSFCPSE/C&DH Interface

PSE C&DH

C&DH +5V Power

C&DH Power Return (GND)

Data Write Strobes

MUXed PSE Telemetry

Non-MUXed Bus & Battery Telemetry

MAG +7.2V Power & Return

Analog MUX Select/Enable

Digital Data Bus

110-pinbackplaneconnector

Note that signals (between C&DH and other sub-systems) that go throughthe Back-plane but NOT through the PSE are NOT shown in this figure.

8

8

16

4

Data Read Strobes 2

5

5

1

4

MAG Boom Power & Return 4

VEC1 +5V Power & Return 4

4VEC2 +5V Power & Return

4DSS +5V Power & Return

110-pinbackplaneConnector

164-pinbackplaneconnector

164-pinbackplaneconnector

ALL signals between the C&DH and the PSE are over the back-plane. Switched power from PSE to sub-systems on C&DH side of S/C goes over back-plane and “through” C&DH board.

ST5 PDR June 19-20, 2001 9 - 17

GSFC

Umbilical Interfaces (1 of 2)

• Power to PSE- Direct Power Conditioner (DPC) / Solar Array Simulator

• PSE Test Connector- Battery Voltage/Current, Polarity- Bus Voltage and Current- Solar Array Voltage/ Current - PSE Ground Reference- Battery Midstring Voltages- Separation Signal to LV(TBR)- Separation Wire Loop (2)

• Umbilical to Battery Interface- Power (Battery Charging)- Battery Temperature- Battery Voltage and Cell Midstring Voltages

ST5 PDR June 19-20, 2001 9 - 18

GSFC

Figure 1: Proposed Direct Access (DA) Connector Signals from PSE side of S/C

PSE

DA J1

DA Test (Skin) Connector #1

J1J2_dia.ppt

DPC +7.2V Pwr and Rtn

Analog Voltage & Current Telemetry

CCNT Test CTS in

CCNT Test Data In

CCNT Test Data Out

DS 2 May 01

CCNT Test RTS out

Direct Access (DA) test connectors are “Skin” Connectors, butNOT T-0 Umbilical connectors.

2

2

2

2

Copy of SE Warning Pulse 2

4

10

CCNT

Separation Signals (AB pairs) 4

Fly-Away (SEP J1) connectorwith 3 wire “loops”

Battery

To Launch Vehicle

Battery Temperature (thermistor)

Battery Voltage Telemetry

2

10

Battery Charging 6

Fly-Away Loop Signals (AB pairs) 4

4

SAFE-ing connector ???with 2 wire “loops”

Safing Signals TBD 4

ARM loops (4) here orTEST Harness here.

(Might be 66-pin circular TBD)

Umbilical Interfaces ( 2 of 2)

ST5 PDR June 19-20, 2001 9 - 19

GSFC

• Heritage:

– Cells passed space flight qualification testing

– Similar Battery (same cells) flown on STRV1-c,d

– Monitoring performance of cells as battery cycles

• Dimensions– 4.6” x 2.3” x 3.3” (10 cell)

• Mass – 525 grams (10 cell)

– 625 gram mass allocation

Lithium Ion Battery

ST5 PDR June 19-20, 2001 9 - 20

GSFC

Battery Electrical Analysis Results

• Battery analysis indicates insufficient voltage margin (for regulation) at 60% DOD, -10 deg C with 10 cell battery

• Options:– Add 1 more string to battery (2 cells, approx. 85 grams)

– Relax DOD requirement to < 60% DOD

– Add small, thermostatically-controlled heater to warm battery above -10 deg C

• 10 cell battery baselined– Qualifying 12 cell battery for risk mitigation

ST5 PDR June 19-20, 2001 9 - 21

GSFC

Battery Level Charging• Charging at the Battery level• Monitoring at the Cell level

.

x 8

FETDrive

Ref

VsenseVoltageClamp

+

V

V

V

V+

+

+

+. . .

5 Strings of 2 series cells

ST5 PDR June 19-20, 2001 9 - 22

GSFCBattery Operation

• Battery Charge Method– Full taper charge to clamp

– Redundant over charge protection (redundant hardware)

– Battery level charge control, rather than cell level control

• Due to small, highly matched cells

• Battery Interface Temperature– Operating: -10 to 40 C (Battery is always operating)

– Qualification: -20 to 50 C

• Telemetry for Flight Validation– Battery Voltage

– Battery Midstring Voltages (Cell Voltages on ground)

– Battery Current

– Battery Temperature - hot cell, cold cell

ST5 PDR June 19-20, 2001 9 - 23

GSFC

ST5 Prototype Lithium Ion Battery

• Mech, Elec ICD complete

• Prototype battery in test at GSFC Battery Lab

• Performed initial magnetics testing

• AEA Technology preparing to build 12 cell Qualification model

• Flight Batteries to be delivered in Jan 02

Battery Status

ST5 PDR June 19-20, 2001 9 - 24

GSFCBattery Cell Safety Features

• Overcharge Protection Device– Non-reversible, triggered on over 100% overcharge

– Internal pressure rises and breaks internal connection

– Ensures that the cell fails open circuit

• Shut-down Separator– Non-reversible

– Pores contract and shut down reaction at T>90 deg C

• Over Pressure Vent – Operates to release internal pressure if safety mechanisms described above fail

+

+

+

+. . .

5 Strings of 2 series cells

+

+ +. .

Battery after cell failure

+

+

ST5 PDR June 19-20, 2001 9 - 25

GSFC

ST5 Solar Array Requirements

• Provide 18 Watt orbit average load at 8.4V at the end of a three month mission

• Off-Pointing Angle of ±5°

• Solar Array Temperature Range

Operating -50 to 55 C

Survival -75 to 95 C

• Panel Volume Constrained by Fairing Envelope

– Limits cell area for solar array; impacts power margin in sunlight; thus limiting spacecraft operations

ST5 PDR June 19-20, 2001 9 - 26

GSFCSolar Array Design

•8 Identical Panels

•Triple junction cells

•27% efficient

•4 cells per string, 4 strings per panel

•Conductive Coating on cell covers– To prevent surface charging

11.14” (28.30cm)

6.49” (16.48cm)

ST5 PDR June 19-20, 2001 9 - 27

GSFCFlex Technology on ST5

• TRL 7- Prototype demonstration in a space environment

– Flex circuitry used on prior missions in different application

• ST5 use to reduce the stray magnetic fields on the solar array

• Flex will have wide copper traces for the return path of each solar array string in order to mirror the current through strings

• Flex bonded onto panel substrate, then cells are laid down

Panel substrate

Flex circuitSolar Cells

Completed solar array

ST5 PDR June 19-20, 2001 9 - 28

GSFC

Solar Array Design Factors

ISC VOC VMP PMAX IMP

MEASUREMENT UNCERTAINTY 0.98 0.99 0.99 0.97 0.98

COVERGLASS LOSS 1 1 1 1 1

ASSEMBLY LOSS 1 1 1 1 1

UV IRRADIATION DARKENING 0.976 1 1 0.976 0.976

THERMAL CYCLING, RANDOM

FAILURE, MICROMETEOROIDS,SPACE DEBRIS, ETC. 0.97 0.985 0.985 0.955 0.97

TOTAL BOL LOSS FACTOR 0.98 0.99 0.99 0.9702 0.98

TOTAL EOL LOSS FACTOR 0.928 0.975 0.975 0.905 0.928

MINIMUM SOLAR INTENSITY 0.967 1 1 0.967 0.967

MAXIMUM SOLAR INTENSITY 1.033 1 1 1.033 1.033

ST5 PDR June 19-20, 2001 9 - 29

GSFC

Solar Array Power Estimate, BOL• Beginning of Life• 27% efficient cells• Temp = 30 deg C• Panels normal to sun within 5 deg

Max BOL Spin Average Array ParametersPerihelionNo shadow Shadow

ISC 3.45 Amps 3.25 AmpsVOC 10.05 Volts 10.05 VoltsVMP 9.05 Volts 9.05 VoltsIMP 3.35 Amps 3.16 AmpsPMAX 29.96 Watts 28.26 WattsPVMPREQ 28.81 Watts 27.18 WattsVMPREQ 8.4 Volts 8.4 Volts

ST5 PDR June 19-20, 2001 9 - 30

GSFC

Solar Array Power Estimate, EOL

• End of Life (3 months)• 30 Degrees C nominal• 27% efficient solar cells• Panels normal to sun within 5 deg

Min EOL Spin Average Array ParametersAphelionNo shadow Shadow

ISC 3.01 Amps 2.84 AmpsVOC 9.65 Volts 9.65 VoltsVMP 8.69 Volts 8.69 VoltsIMP 2.92 Amps 2.76 AmpsPMAX 25.11 Watts 23.70 WattsPVMPREQ 24.9 Watts 23.49 WattsVMPREQ 8.4 Volts 8.4 Volts

ST5 PDR June 19-20, 2001 9 - 31

GSFC

Power Management Assumptions• Energy Balance per Orbit

– Project Power Management Plan includes meeting energy balance at EOL with only essential loads powered on

– Battery is required to operate transmitter or CCNT in sunlight, even at BOL

• Assume 100% Battery State of Charge when entering Eclipse

• Essential loads only are powered during Battery charging

• Essential loads only are powered during Thruster firing

Eclipse

Charge BatteryEssential Loads Only

Charge BatteryEssential Loads Only

ST5

ValidationOperations forremainder of the orbit,if energy balance can be met.

Sunlight

ST5 PDR June 19-20, 2001 9 - 32

GSFCSun Acquisition Budget

• Spacecraft Powered OFF at Launch• Spacecraft turns ON after separation from deployer structure• Battery SOC at launch = 95%• Magnetometer is deployed after sun acquisition• BOL solar cells, 27% efficient• Temp = 30 deg C, Solar panels normal to sun within 5 deg• 25% power load contingency, 30 minutes to acquire the sun

ST5 Sun Acquisition for 30 Minutes Batt C= 7.5 Ah C&DH Trans SunSens Magn. VECsEclipse duration = 40 minutes Batt C_eclipse= 6.2 Ah CBE CBE CBE CBE CBEBOL Solar Array Batt T eclipse= 8 C 5.50 3.75 0.15 0.55 0.4

S/C Total Solar Trans SunTime Load S/C S/C Pwr Array Batt Batt C&DH pondrSensorThruster

Mission Modes min w/conting Load Avail Avail V I BSOC PSE w/Reg w/Regw/Reg Harness

1 Deploy S/C 1000 15.7 13.3 0 0 8.2 -1.91 95% 1.17 9.05 3.75 0.25 0.2 0.12 Steady State Loads 1000 15.7 13.3 0 0 8.2 -1.91 95% 1.17 9.05 3.75 0.25 0.2 0.13 30 minute Sun Acq 1030 25.4 23.1 0 0 8.1 -3.15 82.2% 1.17 8.92 3.75 0.25 10 0.24 Sun Acq Complete 1030 25.4 23.1 0 0 8.1 -3.15 82.2% 1.17 8.92 3.75 0.25 10 0.25 Start Mag Deploy 1031 15.6 13.2 14.5 20.4 8.1 -0.14 81.5% 4.75 8.92 3.75 0.25 0.2 0.16 Mag Deploy Complete 1035 15.6 13.2 14.5 20.4 8.1 -0.14 81.3% 4.75 8.92 3.75 0.25 0.2 0.17 Transmit to Gnd, 30 min 1035 23.6 21.3 21.3 27.2 8.1 -0.29 81.3% 4.75 8.92 11.75 0.25 0.2 0.28 End Transmit 1065 15.4 13.1 21.3 27.2 7.9 0.74 79.4% 4.75 8.76 3.75 0.24 0.2 0.19 Charge Battery 1065 15.2 12.9 21.3 27.2 7.9 0.76 79.4% 4.75 8.76 3.75 0.24 0 0.1

10 Charge Batt/ End Orbit 1655 15.5 13.1 21.3 27.2 8.2 0.70 100.0% 4.75 9.05 3.75 0.25 0 0.111 Start Eclipse, 40 min 1655 15.5 13.1 0 0 8.2 -1.89 100.0% 1.17 9.05 3.75 0.25 0 0.112 End Eclipse 1695 15.2 12.9 0 0 7.9 -1.91 79.8% 1.17 8.76 3.75 0.24 0 0.113 Charge Battery 1695 15.2 12.9 21.3 27.2 7.9 0.76 79.7% 4.75 8.76 3.75 0.24 0 0.114 Charge Battery 1825 15.5 13.1 21.3 27.2 8.2 0.70 100% 4.75 9.05 3.75 0.25 0 0.1

Sun Acquistion Recovery 2.20 Hours to Charge DOD= 20.6%followed by transmit Margin to Max Allowable DOD= 66%

Eclipse DOD= 20.3%Eclipse Recovery 2.16 Hours to Charge Margin to Max Allowable DOD= 66%

Sun Acquisition SummarySun acquisition duration 30 MinutesTransmit duration 30 MinutesCharge Battery 2.2 HoursTime remaining in orbit 7.3 Hours

ST5 PDR June 19-20, 2001 9 - 33

GSFCWorst Case Eclipse Budget

• Worst Case Inclination, Worst Case Eclipse Duration (1 Hour)• EOL solar array• Power to Essential Loads Only

ST5 Worst Case Eclipse Orbit (1 Hour) Batt C= 7.5 Ah C&DH Trans SunSens Magn.VECsEOL Solar Array Batt C_eclipse= 6.2 Ah CBE CBE CBE CBE CBE10.5 hour orbit Batt T eclipse= 8 C 5.50 3.75 0.15 0.55 0.4Transmit every orbitEssential Loads only Powered On S/C Total Solar Trans Sun

Time Load S/C S/C Pwr Array Batt Batt C&DH pondr Sensor Thruster

Mission Modes min w/conting Load Avail Avail V I BSOC PSE w/Reg w/Reg w/Reg Harness

1 Steady State Loads 0 15.3 12.9 0 0 8.0 -1.91 100% 1.17 8.83 3.75 0.25 0 0.12 Start Eclipse, 60 min 0 15.3 12.9 0 0 8.0 -1.91 100% 1.17 8.83 3.75 0.25 0 0.13 60 minute Eclipse 60 14.7 12.4 0 0 7.5 -1.96 74.5% 1.17 8.30 3.75 0.23 0 0.14 End Eclipse/Enter Sunlight 60 14.7 12.4 0 0 7.5 -1.96 74.5% 1.17 8.30 3.75 0.23 0 0.15 Transmit to Gnd, 30 min 60 22.8 20.4 18.8 23.49 7.5 -0.53 74.4% 3.78 8.30 11.75 0.23 0 0.26 End Transmit 90 14.7 12.4 18.8 23.49 7.5 0.54 70.9% 3.78 8.30 3.75 0.23 0 0.17 Charge Battery 91 14.7 12.4 18.8 23.49 7.5 0.54 70.9% 3.78 8.30 3.75 0.23 0 0.18 Charge Batt/ End Orbit 630 15.3 12.9 18.8 23.49 8.0 0.44 100.0% 3.78 8.83 3.75 0.25 0 0.19 Charge Battery 630 15.3 12.9 18.8 23.49 8.0 0.44 100.0% 3.78 8.83 3.75 0.25 0 0.1

Battery Recovery 5.0 Hours to Charge DOD= 29.1%Eclpise followed by transmit Margin to Max Allowable DOD=51%

Orbit Plan SummaryEclipse duration 60 MinutesTransmit duration 30 MinutesCharge Battery 5.0 HoursTime remaining in orbit 4.0 Hours

ST5 PDR June 19-20, 2001 9 - 34

GSFCBOL with CCNT Operation

ST5 BOL Nominal Eclipse Orbit (40 Minutes)BOL Solar Array Batt C= 7.5 Ah C&DH Trans SunSens Magn. VECsCCNT Operation Batt C_eclipse= 6.2 Ah CBE CBE CBE CBE CBETransmit every orbit Batt T eclipse= 8 C 5.50 3.75 0.15 0.55 0.4Nominal Loads Powered On25% contingency on loads

S/C Total S/C Solar Trans SunTime Load S/C Pwr Array Batt Batt C&DH pondr Sensor Thruster VECs

Mission Modes min w/conting Load Avail Avail V I BSOC PSE w/Reg w/Reg w/Reg Magn.w/Reg CCNT Harness

1 Steady State Loads 0 16.7 14.1 0 0 8.0 -2.09 100% 1.17 8.83 3.75 0.25 0 0.55 0.65 0 0.12 Start Eclipse 0 16.7 14.1 0 0 8.0 -2.09 100% 1.17 8.83 3.75 0.25 0 0.55 0.65 0 0.13 40 minute Eclipse 40 16.3 13.8 0 0 7.7 -2.12 81.4% 1.17 8.50 3.75 0.24 0 0.55 0.62 0 0.14 End Eclipse/Enter Sunlight 40 16.3 13.8 0 0 7.7 -2.12 81.3% 1.17 8.50 3.75 0.24 0 0.55 0.62 0 0.15 Transmit to Gnd, 30 min 40 24.4 21.8 21.3 27.2 7.7 -0.41 81.3% 4.75 8.50 11.75 0.24 0 0.55 0.62 0 0.26 End Transmit 70 16.1 13.5 21.3 27.2 7.5 0.68 78.6% 4.75 8.30 3.75 0.23 0 0.55 0.61 0 0.17 CCNT On for 40 min 70 28.6 26.0 21.3 27.2 7.5 -0.97 78.6% 4.75 8.30 3.75 0.23 0 0.55 0.61 12.38 0.28 End CCNT Operation 110 16.0 13.4 21.3 27.2 7.4 0.71 69.9% 4.75 8.17 3.75 0.23 0 0.55 0.60 0 0.19 Charge Battery 110 16.0 13.4 21.3 27.2 7.4 0.71 69.9% 4.75 8.17 3.75 0.23 0 0.55 0.60 0 0.1

10 Charge Batt/ End Orbit 630 16.7 14.1 21.3 27.2 8.0 0.57 100.0% 4.75 8.83 3.75 0.25 0 0.55 0.65 0 0.111 Charge Battery 630 16.7 14.1 21.3 27.2 8.0 0.57 100.0% 4.75 8.83 3.75 0.25 0 0.55 0.65 0 0.1

Battery Recovery 4.0 Hours to Charge DOD= 30.1%Eclpise followed by transmit Margin to Max Allowable DOD= 50%

Orbit Plan SummaryEclipse duration 40 MinutesTransmit duration 30 MinutesCharge Battery 4.0 HoursTime remaining in orbit 5.4 Hours

• Magnetometer, VECs powered on• CCNT Operates for 40 minutes

ST5 PDR June 19-20, 2001 9 - 35

GSFCEOL with Nominal Loads

• Magnetometer, VECs powered on

ST5 EOL Nominal Eclipse Orbit (40 Minutes)EOL Solar Array Batt C= 7.5 Ah C&DH Trans SunSens Magn. VECs10.5 hour orbit Batt C_eclipse= 6.2 Ah CBE CBE CBE CBE CBETransmit every orbit Batt T eclipse= 8 C 5.50 3.75 0.15 0.55 0.4Nominal Loads Powered On

S/C Total Solar Trans SunTime Load S/C S/C Pwr Array Batt Batt C&DH pondr Sensor Thruster VECs

Mission Modes min w/conting Load Avail Avail V I BSOC PSE w/Reg w/Reg w/Reg Magn. w/Reg CCNT Harness

1 Steady State Loads 0 16.7 14.1 0 0 8.0 -2.09 100% 1.17 8.83 3.75 0.25 0 0.55 0.65 0 0.12 Start Eclipse 0 16.7 14.1 0 0 8.0 -2.09 100% 1.17 8.83 3.75 0.25 0 0.55 0.65 0 0.13 40 minute Eclipse 40 16.3 13.8 0 0 7.7 -2.12 81.4% 1.17 8.50 3.75 0.24 0 0.55 0.62 0 0.14 End Eclipse/Enter Sunlight 40 16.3 13.8 0 0 7.7 -2.12 81.3% 1.17 8.50 3.75 0.24 0 0.55 0.62 0 0.15 Transmit to Gnd, 30 min 40 24.4 21.8 18.8 23.5 7.7 -0.73 81.3% 3.78 8.50 11.75 0.24 0 0.55 0.62 0 0.26 End Transmit 70 16.1 13.5 18.8 23.5 7.5 0.35 76.4% 3.78 8.30 3.75 0.23 0 0.55 0.61 0 0.17 Charge Battery 71 16.1 13.5 18.8 23.5 7.5 0.35 76.4% 3.78 8.30 3.75 0.23 0 0.55 0.61 0 0.18 Charge Batt/ End Orbit 630 16.7 14.1 18.8 23.5 8.0 0.26 100.0% 3.78 8.83 3.75 0.25 0 0.55 0.65 0 0.19 Charge Battery 630 16.7 14.1 18.8 23.5 8.0 0.26 100.0% 3.78 8.83 3.75 0.25 0 0.55 0.65 0 0.1

Battery Recovery 6.9 Hours to Charge DOD= 23.6%Eclpise followed by transmit Margin to Max Allowable DOD= 61%

Orbit Plan SummaryEclipse duration 40 MinutesTransmit duration 30 MinutesCharge Battery 6.9 HoursTime remaining in orbit 2.4 Hours

ST5 PDR June 19-20, 2001 9 - 36

GSFC

Power System Mass Estimate

• Battery Mass Limit: 625g

• Solar Array in Mechanical Budget

• PSE Card Mass Estimates (g):

PSE Card 942

Conf Coating 100Total 1042Requirement 1300Margin 258

ST5 PDR June 19-20, 2001 9 - 37

GSFCPSE Power Summary

Power System Dissipation and ConsumptionSunlight Sunlight Eclipse EclipseBOL EOL BOL EOL

Consumption 1.17 1.17 1.17 1.17Dissipation 3.58 2.61 0.89 0.69

Total 4.75 3.78 2.06 1.86

ST5 PDR June 19-20, 2001 9 - 38

GSFCPower System Status

• Hardware Development Status

– Breadboard testing of PSE circuits since July 2000

– Ordering Flight Parts Now

– Deliverable Breadboards to FSW and C&DH by September 2001

– Qual. Battery by October 2001; Flight batteries by January 2002

– Solar panels by Fall 2002

• Reviews

– PSE Schematic Review held April 26, 2001

– Power System Peer Review held May 30, 2001

ST5 PDR June 19-20, 2001 9 - 39

GSFCRisk Mitigation (1 of 2)

• Risk: Power Budget with small margin– Components are new designs; concerns that power demand may increase– Power balance achieved through operational constraints– Solar panels size constrained due to fairing size in Delta IV – no room for growth

• Mitigation:– Considering replacing linear regulator with switching regulator to improve efficiency

(Issues with magnetic cleanliness, volume, mass, EMI, parts, schedule to be worked)– Working to see if additional volume in the launch fairing is possible (Growing diameter of

S/C by 1.5” could result in power increase of 25%)– Project Power Management Plan includes meeting energy balance at EOL – All mission

requirements met– Baseline contingency of 25% held on all loads

• Risk: Aggressive Schedule/Development Plan– Schedule contains breadboards but no ETU development – Proto-flight development– Risk due to potential increases in rework on flight units during test

• Mitigation:– Experienced development team– Working schedule issues to allow PSE ETU build– More rigorous testing of breadboards to compensate for lack of ETU

ST5 PDR June 19-20, 2001 9 - 40

GSFCRisk Mitigation (2 of 2)

• Risk: Launch Vehicle Uncertainty– Exact orbital parameters not known – Uncertainty in Interface to Power System– Uncertainty in allowable Pre-launch battery operations

• Mitigation: – Launch Vehicle Study Task completed– Orbital constraints, including maximum eclipse duration, defined– Interface requirements defined– Baseline launch site processing scenario with acceptable battery access during flow defined

ST5 PDR June 19-20, 2001 9 - 41

GSFC

Efficiency: Switching vs. Linear Regulator

C&DH Converter Trade Min MaxInput Voltage 7.2 8.4 VoltsPower Required 5.5 5.5 Watt

Regulator Dissipation 2.4 3.7 Watt

Converter Dissipation 1.6 1.6 Watt

Additional Power Avail 0.8 2.1 Watt

Additional Power AvailIf Receiver is included 3.2 Watt

• Other factors:- Volume increase - Mass increase - EMI considerations- Use of Magnetic components- Schedule delay

ST5 PDR June 19-20, 2001 9 - 42

GSFC

Topology Trade: How to get more power to the spacecraft without compromising the quality of the bus and reliability?

+5VLoads

Unreg.Loads

9.05V-8.6V

Regulated to 8.4V

Regulated to 4.8-5.2V

Regulator

+5VLoads

Unreg.Loads

9.05V-8.6V Regulated to 8.4VRegulated to 4.8-5.2V

LinearOr SwitchingRegulator•Lower Impedance Bus

•Noise Immunity•Fewer Elements in Power Path

•Efficiency improvement•Higher Impedance Bus•More Elements in Power Path

LinearOr SwitchingRegulator

LinearOr SwitchingRegulator

Topology Trade for Improving Efficiency