rocsat-2 topic: thermal analysis results - isual scientific payload (with str and iru) jeng-der...

ROCSAT-2

Topic:

Thermal Analysis Results- ISUAL Scientific Payload

(with STR and IRU)

Jeng-Der Huang

(黃正德 )

ROCSAT-2Contents

Thermal Design Description

Configuration

Power Dissipation

Thermal Analysis Results

Thermal Analysis Results Discussion

ROCSAT-2

ISUAL, STR and IRUThermal Design Description

ISUAL, STR (Star Tracker) and IRU (Inertial Reference Unit) are thermal isolated from the payload platform to reduce the platform’s thermal distortion.

ISUAL, STR and IRU have the independent thermal control to keep the temperatures within their limits.

Thermal control devices such as the radiator, MLI and heater are used to maintain the temperatures within their operating/non-operating limits.

ROCSAT-2Configuration

STR

CCDImager

ArrayPhotometer

Spectrophotometer

IRU

AEP

ROCSAT-2

Nominal hot (operating EOL)

Power Dissipation

Power Dissipation (W)Phase Number 1 2 3 4 5 6 7 8 9 Mean

ISUAL-CCD Imager 9.05 6.90 6.90 6.90 6.90 6.90 6.90 6.90 9.05 7.57

Spectrophotometer 1.75 1.75 1.75 1.75 1.75 1.75 1.75 1.75 1.75 1.75

Array Photometer 11.88 4.77 4.77 4.77 4.77 4.77 4.77 4.77 11.88 6.97

AEP 19.38 16.60 16.60 16.60 16.60 16.60 16.60 16.60 19.38 17.46

Bus-IRU 22.7 22.7 22.7 22.7 22.7 22.7 22.7 22.7 22.7 22.7

STR 13.0 13.0 13.0 13.0 13.0 13.0 13.0 13.0 13.0 13.0

ROCSAT-2

Nominal cold (stand-by BOL)

Power Dissipation (Continued)

Power Dissipation (W)Phase Number 1 2 3 4 5 6 7 8 9 Mean

ISUAL-CCD Imager 6.9 6.9 6.9 6.9 6.9 6.9 6.9 6.9 6.9 6.9



AEP 11.3 11.3 11.3 11.3 11.3 11.3 11.3 11.3 11.3 11.3

Bus-IRU 21.3 21.3 21.3 21.3 21.3 21.3 21.3 21.3 21.3 21.3

STR 11.0 11.0 11.0 11.0 11.0 11.0 11.0 11.0 11.0 11.0

ROCSAT-2

ASH mode

Power Dissipation (Continued)

Power Dissipations (W)Phase Number 1 2 3 4 5 6 7 8 9 Mean

ISUAL-CCD Imager 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0



AEP 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Bus-IRU 22.7 22.7 22.7 22.7 22.7 22.7 22.7 22.7 22.7 22.7

STR 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

ROCSAT-2

Radiator area requirement

Thermal Analysis Results

PIP Units Area(m2)ISUAL-

CCD Imager 0.029Spectrophotometer 0.001Array Photometer 0.017

AEP 0.089Total 0.136

Bus-IRU 0.121STR 0.062

ROCSAT-2

Radiator

STRIRU

Radiator

Radiator Locations

• Bus units

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Array Photometer CCD Imager

Spectrophotometer AEP

RadiatorRadiator

RadiatorRadiator

Radiator Locations (Continued)

• ISUAL units

ROCSAT-2

Orbit averaged heater power requirement

Thermal Analysis Results (Continued)

Units NominalHot

NominalCold

ASH Mode(W)

ISUAL-CCD Imager - - 1.2

Spectrophotometer - - -

Array Photometer - - 1.5

AEP - - -

Total - - 2.7

Bus-IRU 2.9 12.0 9.3

STR 3.1 8.3 2.6

ROCSAT-2

Predicted temperatures for nominal hot case

Temperature (oC)Computed Operating Non-Operating Predicted Margin

Min. Max. Min. Max. Min. Max. Min. Max.ISUAL-

CCD Imager 16.1 18.7 -20.0 30.0 - - 36.1 11.3Spectrophotometer 17.1 17.9 -20.0 30.0 - - 37.1 12.1Array Photometer 18.7 20.3 -20.0 30.0 - - 38.7 9.3

AEP 36.6 38.9 -40.0 50.0 - - 76.6 11.2Bus-

IRU 20.2 21.3 20.0 30.0 - - 0.2

8.7

STR 20.2 20.2 18.0 22.0 - - 2.2 1.8*


The actual minimum operating temperature limit for IRU is 10oC, but 20oC is an optimal lower limit. The heater load margin (25% excess control authority) instead of heater temperature margin (6oC above the temperature limit) is applied.* The STR radiator sizing is based on 14oC with considering thermal uncertainty margin of 8oC although its predicted margin is only 1.8oC.

ROCSAT-2

Predicted temperature for nominal cold case (stand-by mode)

Temperature (oC)Computed Operating Non-Operating Predicted MarginMin. Max. Min. Max. Min. Max. Min. Max.

ISUAL-CCD Imager 4.2 6.0 -20.0 30.0 - - 24.2 24.0

Spectrophotometer 6.3 7.7 -20.0 30.0 - - 26.3 22.3Array Photometer -1.9 -0.4 -20.0 30.0 - - 18.1 30.4

AEP 8.8 10.6 -40.0 50.0 - - 48.8 39.4Bus-

IRU 20.2 20.2 20.0 30.0 - - 0.2

9.8

STR 20.1 20.1 18.0 22.0 - - 2.1 1.9*


The actual minimum operating temperature limit for IRU is 10oC, but 20oC is an optimal lower limit. The heater load margin (25% excess control authority) instead of heater temperature margin (6oC above the temperature limit) is applied.* The STR radiator sizing is based on 14oC with considering thermal uncertainty margin of 8oC although its predicted margin is only 1.8oC.

ROCSAT-2

Predicted temperature for ASH case


Minimum temperature (oC)Computed Operating Non-operating Predicted Margin

ISUAL-CCD Imager -28.9 - -35.0 6.1

Spectrophotometer -19.3 - -35.0 15.7Array Photometer -28.8 - -35.0 6.2

AEP -36.4 - -55.0 18.6Bus-

IRU 20.2 20.0 - 0.2

STR -33.8 - -40.0 6.2

The actual minimum operating temperature limit for IRU is 10oC, but 20oC is an optimal lower limit. The heater load margin (25% excess control authority) instead of heater temperature margin (6oC above the temperature limit) is applied.

ROCSAT-2

Orbital Temperature Profiles of PIP Equipments for Nominal Imaging, LTDN = 10:00

Time (min.)

0 20 40 60 80 100

Te

mp

. (oC

)

17

18

19

20

21

Array PhotometerSectrophotometerCCD Imager

Time (min.)

0 20 40 60 80 100

Te

mp

. (oC

)

15

20

25

30

35

40

STR Base PlateSTR 1IRUAEP

Eclipse Energe Storage Imaging

Energe StorageEclipse




ROCSAT-2

Orbital Temperature Profiles of PIP Equipments for Nominal Standby, LTDN = 10:00

Time (min.)

0 20 40 60 80 100

Tem

p. (

oC

)

-2

0

2

4

6

8

10


Time (min.)

0 20 40 60 80 100

Tem

p. (

oC

)

8

10

12

14

16

18

20

22

24


Eclipse Energe Storage

EnergyStorage& Com.

Energe Storage Eclipse Eclipse Energe Storage

EnergyStorage& Com.

Energe Storage Eclipse


ROCSAT-2

Orbital Temperature Profiles of PIP Equipments for ASH mode, LTDN = 10:00

Time (min.)

0 20 40 60 80 100

Tem

p. (

oC

)

-30

-28

-26

-24

-22

-20

-18


Time (min.)

0 20 40 60 80 100

Tem

p. (

oC

)

-40

-30

-20

-10

0

10

20

30


Eclipse Energe Storage Eclipse Eclipse Energe Storage Eclipse


ROCSAT-2

Orbital Temperature Profiles of PIP Equipments for Nominal Imaging, LTDN = 9:30

Time (min.)

0 20 40 60 80 100

Te

mp

. (oC

)

16

17

18

19

20


Time (min.)

0 20 40 60 80 100

Te

mp

. (oC

)

15

20

25

30

35

40







ROCSAT-2

Orbital Temperature Profiles of PIP Equipments for Nominal Standby, LTDN = 9:30

Time (min.)

0 20 40 60 80 100

Tem

p. (

oC

)

-2

0

2

4

6

8


Time (min.)

0 20 40 60 80 100

Tem

p. (

oC

)

8

10

12

14

16

18

20

22

24


Eclipse Energe Storage

EnergyStorage& Com.

Energe Storage Eclipse Eclipse Energe Storage

EnergyStorage& Com.

Energe Storage Eclipse


ROCSAT-2

Orbital Temperature Profiles of PIP Equipments for ASH mode, LTDN = 9:30

Time (min.)

0 20 40 60 80 100

Tem

p. (

oC

)

-30

-28

-26

-24

-22

-20

-18


Time (min.)

0 20 40 60 80 100

Tem

p. (

oC

)

-40

-30

-20

-10

0

10

20

30


Eclipse Energe Storage Eclipse Eclipse Energe Storage Eclipse


ROCSAT-2

ISUAL Portion:

Three ISUAL units (including Spectrophotometer, Array Photometer, and CCD Imager) were put together on a stack on the top of PIP and the other unit - AEP inside Bus during the SDR. However, all units have been moved to the top of PIP separately during the PDR.

The total radiator areas of ISUAL have changed from 0.059 m2 for SDR to 0.136 m2

(include AEP) for PDR due to the configuration and the uncertainty margin changes (from 11oC to 8oC).

The heater margin was changed from 10oC to 6oC in the PDR thermal analysis. Besides, the change in ISUAL layout. The total heater power requirements are effectively reduced as follows:

SDR PDR Nominal imaging: 0.0 Watt 0.0 Watt Nominal standby: 0.0 Watt 0.0 Watt ASH: 12.6 Watt 2.7 Watt

Thermal Analysis Results Discussion

ROCSAT-2

Thermal Analysis Results Discussion(Continued)

Both worst hot and cold predicted temperatures of ISUAL are within the maximum and minimum operating/non-operating limits with proper margins by applying radiators and heaters.

There is no heater power required to keep the ISUAL above the minimum temperature limits in nominal operation. For ASH mode, two ISUAL units, i.e., CCD Imager and Array Photometer, are controlled by heaters to maintain the minimum temperatures above their non-operating lower limits with proper margin.

The built-in survival heaters of Array Photometer, Spectrophotometer and CCD Imager are strongly suggested for temperature control.

ROCSAT-2

Thermal Analysis Results Discussion(Continued)

IRU and STR:

The IRU and STR radiators have been changed respectively from 0.092 m2 and 0.053 m2 for SDR to 0.121 m2 and 0.062 m2 for PDR due to the changes of configurations, temperature limits, and the uncertainty margin.

More heater powers are required to maintain the IRU and STR units within the narrow allowable temperature ranges (20oC ~ 30oC for IRU and 18oC ~ 22oC for STR) in nominal mode, although the heater margin was changed from 10oC to 6oC in the PDR thermal analysis.

Both worst hot and cold predicted temperatures of IRU and STR are all within their maximum and minimum operating/non-operating limits with proper margins by applying radiators and heaters.

Due to the narrow operating temperature ranges, IRU and STR should be precisely controlled by proper radiator and heater sizing in nominal operation.

ROCSAT-2

ISUAL Thermal Issues

ISUAL units are originally designed to be thermally conducting to the PIP. However, the thermal interface constraint of thermal isolation between the ISUAL and the PIP may force the ISUAL to change its interior or interface design. In the ISUAL SDR meeting (6/7 - 6/9 in NSPO), UCB (ISUAL Prime Contractor) considered it would be a great hardship to do any design modification because of tight budget and schedule.

ISUAL detailed thermal analysis can not be started without the knowledge of operating/non-operating temperature limits and thermal properties of critical parts (such as CCD, optical lenses, parts with high voltage and high dissipation, etc.) as well as heat transfer paths inside the units. Currently, only averaged temperature for each ISUAL unit is predicted.

ISUAL thermal verification (by analysis and test) is hard to be defined and planned.

rocsat-2 topic: thermal analysis results - isual scientific payload (with str and iru) jeng-der...

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