the comparison of different thermal analysis … · 5. remote sensing instrument modeling rsi...

Remote Sensing Satellite Technology Workshop 2016 Nov. 28, 2016

THE COMPARISON OF DIFFERENT THERMAL ANALYSIS SOFTWARE

FOR THERMAL SIMULATION OF THE SPACE TELESCOPE

Cheng-En Ho, Meng-Hao Chen, Jeng-Der Huang, Chia-Ray Chen

National Space Organization of National Applied Research Laboratories

ABSTRACT

NX SST and TRASYS & SINDA software can

be applied in the thermal analysis of the space

remote sensing system. There are differences

between these two software in mesh generation,

orbital heat resolution, calculation speed and

post process. Both software were applied to

simulate the space telescope and RSI satellite in

thermal vacuum test and to predict the thermal

balance temperature of the telescope and

electronic unit. After model correlation, the

difference between the software simulation

results and thermal balance test results are less

than 5℃.

KEYWORDS：Thermal simulation software

1. INTRODUCTION

Remote sensing image above the Earth is

valuable for land survey, forest preservation,

marine pollution monitoring and disaster rescue.

A stable and suitable temperature range is

important for the performance of the space

optic-mechanic system. However, when the

remote sensing satellite flight in the earth orbit,

it suffers district environment of the

temperature variation because of facing

sunlight or entering eclipse. The thermal

control design and the flight temperature

prediction are important for the success of the

mission.

We use thermal simulation software to analysis

and predict the temperature distribution and

heat absorption of the remote sensing system in

space. For checking and modifying the

parameter in the simulation model, we make

the thermal balance test of the remote sensing

system in the vacuum chamber before the

satellite lunch. The simulation prediction of the

remote sensing system under the thermal

balance condition was correlated with the

thermal balance test data in order to reduces the

simulation error and precisely predict the flight

temperature.

In AMOS-2 communication satellite (Sherman,

2004), THERMICA software was used for the

calculation of the black and gray form factors

of the different satellite surfaces and the

external heat loads. The information calculated

by the THERMICA was embedded into

SINDA/G software that was used for the

temperature calculation. Most of the calculated

temperatures fell within the 5 ℃ of the

measurements. NASA Langley Research

Center correlated the model of the Mars

Reconnaissance Orbiter with the data obtained

from cruise maneuvers (Amundsen, 2007).

Methods of correlation included comparing the

model to flight temperatures, slopes,

temperature deltas between sensors regards to

thermal mass, conductive connections, and

solar response. The heat fluxes obtained from

Thermal Desktop radiation model were used in

the run of the thermal model in Patran Thermal

producing temperature predictions. An overall

average error of the thermal modeling is as low

as 5℃.

TRASYS (Analytix Corporation, USA) and

SINDA (Network Analysis Inc., USA) software

have been used to simulate the thermal balance

test of Formosat-5 remote sensing instrument

(Ho, 2015). TRASYS software was used to

calculate the view factor and the radiation heat

transfer between the surfaces. SINDA software

was used to calculate the steady and transient

temperatures of the remote sensing instrument

based on the radiation exchange data generated

by the TRASYS model. In this research, NX

Space Systems Thermal (Siemens Product

Lifecycle Management Software Inc., Germany)

software is used to calculate space orbit

environment heat and to simulate cube satellite,

micro satellite, the space telescope, and remote

sensing instrument compared with the

TRASYS & SINDA software. These software

are differences in mesh generation, orbital heat

resolution, calculation speed and post process.


2. CUBE SATELLITE MODELING

TRASYS and SINDA mesh established bases

on nodes. The x y z position of the corner of the

node in the coordinate system must be input

manually into TRASYS. Figure 1(a) shows the

cube satellite mesh of TRASYS. Each node has

its thermal capacity. The thermal conductivity

between each node must be typed into SINDA

software. The thermal capacity value of each

node and the thermal conductivity between

nodes shall be calculated by user before input

into SINDA. The command writing and

subroutine calling in SINDA is based on

FORTRAN language. The goodness of SINDA

is clear for checking what we input. The

shortage is time cost in setting up model. NX

SST calculation is based on elements. The

corner of each element or the center of the

element edge is called node in NX. The

element mesh could be 1~3. The 2D mesh

could be triangular element or quadrilateral

element. The 3D mesh is tetrahedral element.

TRASYS & SINDA model is surface mesh, the

node located on the center of the mesh.

2.1 Earth-pointing Orientation

The wall surface of cube satellite is assumed as

black body. Figure 2 shows orbital thermal

environment heat flux absorbed on the each

wall surface. The orbital heat flux calculation

resolution is 30 position points per orbit in

TRASYS. NX use different resolution 30, 60,

120 position points per orbit to compare with

TRASYS. TRASYS automatically increase the

position point at eclipse entering or exiting.

NX’s position points are distributed uniformly

along the orbit. NX user can specify the

calculation position of the orbit to give more

point during the entering or exiting eclipse area.

The orbital heat flux profile with 60 position

points per orbit from NX simulation is similar

as that with 30 position points per orbit from

TRASYS.

The temperature prediction of cube satellite

with black body surface around earth-pointing

orbit 720km is shown on figure 3. The

temperature result of 30 position points per

orbit in NX is similar as the result in TRASYS

& SINDA. But NX takes 120 sec in running

this case with 30 points per orbit for 30 cycles.

TRASYS & SINDA totally takes 15 sec in

running this simple cube satellite case.

2.2 Multiple-pointing Orientation

Cube satellite with different complicate flight

attitude such as normal mode or safe mode is

shown in figure 4. The comparison of the

calculation results of the orbit environmental

heat flux and temperature prediction from

TRASYS & SINDA or NX is shown in in

figure 5, 6. Basically the heat flux profile from

TRASYS and NX are very similar except the

area in entering or exiting eclipse. NX has

benefit in simulating the orbit transfer of

spacecraft. The final temperature of the

spacecraft in the first type orbit can be input as

an initial condition to the next transfer orbit.

Furthermore, NX can visualize the space craft

orientation and orbit as a dynamic display for

user checking.

3. MICRO SATELLITE MODELING

The model description of the micro satellite is

described as following: The 0.9m*0.9m*0.9m

cube box has two internal components and

solar panel. The first internal component

dissipates 40W on the center of +Z wall panel.

The second internal component dissipates 25W

only at night on the center of –Z wall panel.

The satellite covered with MLI except the

center of the +Z panel covered with radiator.

Flight attitude is 700km with 45o beta angle.

The satellite is –Z sun-pointing at day time and

+Z earth-point at night. The model made by

TRASYS and by NX is shown in figure 7(a) (b).

The view factor calculation of TRASYS is a

hybrid double summation / Nusselt sphere

method. The view factor calculation methods of

NX include Hemicube, Determinstic and

Monte Carlo. The Determinstic method of NX

combines Nusselt sphere method and

shadowing check. The time consuming of the

setting is listed on the table 1. The more

element subdivision of NX let the sum of view

factor more close to the correct value 1.0. But

complicated model with high accuracy will cost

much time in calculation. The temperature

prediction of wall panel and solar panel is

shown in figure 7(c) (d). The temperature

difference between SINDA and NX simulation


results is less than 1℃.

4. TELESCOPE MODELING

Space optic-mechanical system modeling of the

telescope is shown in figure 8. The telescope

was put into thermal vacuum chamber to

process the thermal balance test. The hot/cold

thermal balance test condition of the telescope

is listed in table 2. The chamber shroud is

maintained at 30℃ for hot balance test and at

5℃ for cold balance test. Figure 9 illustrates

the balance temperature distribution from

SINDA or NX simulation for the hot/cold

balance. NX has better post-process function.

NX software integrates geometry drawing,

mesh building, solver and post-process. But the

result output of SINDA is txt file that need

other software to plot the temperature

distribution of the telescope and consumes

much time in transferring data.

Furthermore, NX can set specular reflectivity

of the surface such as mirror, but TRASYS

only set emissivity and absorptivity of the

surface such as diffusion surface. The heat

source type of radiation can be selected as

collimated or diffused in NX. On the other

hand, SINDA can show the heater duty in the

output text file. NX can do that but also shown

in the text file. The user needs to remember the

element number of the thermistor location

which controls the heater in order to see the

heater duty results.

After model correlation, the results from

SINDA simulation or NX simulation are very

close to the experiment results of the thermal

balance test. The results comparison is listed on

the table 3 and shown in the figure 10. The

temperature difference between simulation

prediction and experiment results are less than

3℃.

5. REMOTE SENSING INSTRUMENT

MODELING

RSI (remote sensing instrument) system

includes Telescope, FPA (focal plane assembly)

and two EU (electronic unit). The solar arrays

were removed from the satellite during the

thermal balance test. The RSI satellite model is

shown in figure 11. NX software can read and

load the 3D geometry drawing directly from the

computational aided design software such as

AutoCAD, SolidWorks, Pro/ENGINEER. The

node or element establishing in NX can be

according to the 3D engineering drawing,

therefore the size and angle of the NX model

can be precise as the real geometry size of the

satellite. If geometry needs to be updated

during design phase, the mesh can be

automatically updated with geometry in NX. If

the element density of the component needs to

be modified, the work is easier in NX than in

TRASYS & SINDA because NX is graphical

user interface software and TRASYS & SINDA

is command line interface software. In

TRASYS & SINDA, the coordinate position

and thermal property of nodes need to be

manually updated or type during modification.

The maximum number of nodes in NX is one

hundred million and that is ten million in

SINDA.

The hot/cold thermal balance test condition of

the RSI satellite is listed in table 4. The shroud

of the chamber is maintained at -170℃. The

final stable temperature data of the hot/cold

balance are compared with the simulation

results for model correlation. After model

correlation, the RSI temperature from SINDA,

NX and experiment are shown and compared in

figure 12. The temperature difference between

simulation prediction and experiment results

are less than 5℃.

6. CONCLUSION

NX SST and TRASYS & SINDA software can

be applied in the thermal analysis of the space

remote sensing system. There are differences

between these two software in mesh generation,

orbital heat resolution, calculation speed and

post process. The orbit environment heat flux

of TRASYS has better resolution in the

entering or exiting eclipse area. NX has benefit

in illustrating the temperature distribution,

simulating the spacecraft orbit transfer and

display the space craft orientation. NX software

integrates geometry drawing, mesh building,

solver and post-process. NX with graphical

user interface is easier for user input the case

than TRASYS & SINDA with command line

interface. NX can read and load the 3D


geometry drawing from the computational

aided design software. Furthermore, NX can set

specular reflectivity of the surface as mirror,

but TRASYS only set as a diffusion surface. In

the view factor calculation, the more element

subdivision of NX can get more precise results.

But the shortage of NX is taking longer time in

solving problem. After simulation model

correlation with the thermal balance test, both

the simulation results of SINDA and NX are

close to the experiment results. The

temperature difference between simulation and

experiment data are less than 5℃.

7. REFERENCES

AC/TRASYS (Thermal Radiation Analyzer

System) User’s Manual 1997, ANALYTIX

Corporation.

Amundsen, Ruth M.; Dec, Joha A.; Gasbarre,

Joseph F. 2007. Thermal Model Correlation for

Mars Reconnaissance Orbiter. NASA Langley

Research Center, ICES-17.

Ho, Cheng-En; Huang, Jeng-Der; Chen,

Chia-Ray 2015. Thermal Model Correlation of

FORMOSAT-5 Remote Sensing Instrument.

Remote Sensing Satellite Technology

Workshop. 20 November, Hsinchu

NX Space System Thermal Student Guide 2013,

Siemens Product Lifecycle Management

Software Inc.

Sherman, Zeev 2004. The Thermal Balance

Test of AMOS-2 Spacecraft. Proceedings of the

5th International Symposium on Environmental

Testing for Space Programs. 15-17 June,

Noordwijk, the Netherlands, pp 127-136.

SINDA (System Improved Numerical

Differencing Analyzer) /G user’s guide 1998,

Network Analysis Inc.

Table 1 View factor calculation method comparison

Table 2 Test heater power and shroud temperature in

thermal balance test of the telescope.

Table 3. Temperature results from SINDA, NX and

experiment data in the thermal balance test of telescope

Table 4 Component power and test heater power in

thermal balance test of RSI satellite

NameCurrent

(A)

Resistance

(Ω)

Popwer

(W)

M2 baffle fitting 0.120 125.0 1.80

Strut 1 (+Y M_U to R_D) 0.133 153.2 2.71

Strut 2 (+Y M_U to R_U) 0.132 153.2 2.67

Strut 3 (+Y D) 0.133 153.2 2.71

Strut 4 (-Y D) 0.134 153.2 2.75

Strut 5 (-Y M_U to R_U) 0.135 153.2 2.79

Strut 6 (-Y M_U to R_D) 0.131 153.2 2.63

NameCurrent

(A)

Resistance

(Ω)

Popwer

(W)

Main Plate (+Y+X) 0.090 216.3 1.75

Main Plate (-Y+X) 0.090 216.3 1.75

Main Plate (+Y-X) 0.082 266.0 1.79

Main Plate (-Y-X) 0.081 266.0 1.75

Ring (+X) 0.113 144.2 1.84

Ring (-Y) 0.114 144.2 1.87

Ring (+Y) 0.114 144.2 1.87

Hot Balance

Cold Balance


(a) (b)

Figure 1. Cube satellite model (a)TRASYS (b)NX

Figure 2. Orbit environmental heat flux, TRASYS vs.

NX with different resolution.

Figure 3. The temperature prediction of cube satellite,

SINDA vs. NX with different resolution

Figure 4. Satellite flight attitude on Earth orbit

Figure 5. Orbit environmental heat flux and temperature

prediction, TRASYS & SINDA vs. NX in normal

imaging mode orbit.

Figure 6. Orbit environmental heat flux and temperature

prediction, TRASYS & SINDA vs. NX in safe mode

orbit.

NX: 30p/orbit, output 30p/circleTRASYS:30p/orbit, SINDA output:100p/circle

NX:10p/orbit, output 10p/circleNX:60p/orbit, output 60p/circle

20

0

171410.0 177524.8

(sec)

20

0

171410.0 177524.8

(sec)

20

0

171410.0 177524.8

(sec)

Tem

pe

ratu

re (℃

)Te

mp

era

ture

(℃

)

Tem

pe

ratu

re (℃

)

Normal imaging mode

Sun-pointing

Earth-pointing

Sun-pointing

Earth-pointing

Spin –Y 2 round/orbit

Safe mode

Sun-pointing

Sun-pointing

NX

0

200

400

600

800

1000

1200

1400

1600

0.00 0.55 1.10 1.64

Hea

t Flu

x (W

/m^2

)Time (hr)

-Y

+Y

+Z

-Z

-X

+X

Sun-point Earth-point Sun-point

TRASYS

Earth-point

Eclipse

NX: 44p/orbit1600

0 5917.5(sec)0

TRASYS: 32p/orbit

He

at F

lux

(W/m

^2

)

SINDA NX

NX output: 30p/orbitSINDA output: 100p/orbit50

171607.2 177524.7(sec)

Tem

pe

ratu

re (℃

)

-40

0

200

400

600

800

1000

1200

1400

1600

0.00 0.55 1.10 1.64

Heat F

lux (

W/m

^2)

Time (hr)

-Y

+Y

+Z

-Z

-X

+X

+Z-X

Sun-point Eclipse Sun-point

TRASYS

+Z-X

NX

NX: 30p/orbitTRASYS: 27p/orbit1600

0 5917.5(sec)0

He

at

Flu

x (W

/m^

2)

SINDA NX50

171607.2 177524.7(sec)

Tem

pe

ratu

re (℃

)

-40

NX:30p/orbit

NX: 60p/orbit NX:120p/orbit

(hr)

TRASYS:30p/orbit1600

0

0 5917.5(sec)

1600

0

0 5917.5(sec)

1600

0

0 5917.5(sec)

He

at

Flu

x (W

/m2)

He

at

Flu

x (W

/m2)

He

at

Flu

x (W

/m2)


(a) (b)

Figure 7. Micro satellite model (a)TRASYS (b)NX;

(c)wall panel temperature prediction from SINDA vs.

NX (d)solar panel temperature prediction from SINDA

vs. NX

Figure 8. Telescope model (a)TRASYS (b)NX

Figure 9. Telescope temperature prediction from SINDA

or NX in the thermal balance test (a)hot balance (b)cold

balance.

Figure 10. Telescope temperature results comparison

from SINDA, NX and experiment data in the thermal

balance test (a)hot balance (b)cold balance.

Figure 11. RSI satellite model (a)TRASYS (b)NX

(a)

(b)

Figure 12. RSI temperature results comparison from

SINDA, NX and experiment data in the thermal balance

test (a)hot balance (b)cold balance

MainplateM2 CFRP strut

Top panel BipodM1 FPA pin hole plate

M1 baffleSpider

Top panel

(a) (b)

SINDA NX

SINDA NX

15

20

25

30

35

40

47.680 48.090 48.500 48.910 49.320

Te

mp

era

ture

(C

)

Time (hr)

-Y

+Y

+Z

-Z

-X

+X

37.47

25.56

17.47

25.5728.76

19.44

36.21

25.39

25.4428.29

19.33

SINDA NX40

171590.4 177568.5(sec)

1517.39

Tem

per

atu

re (℃

)

(c)

-60

-40

-20

0

20

40

60

80

100

120

47.680 48.090 48.500 48.910 49.320

Tem

pe

ratu

re (

C)

Time (hr)

T713

T714

T715

104.37

97.50

104.39

98.48

-46.21 -45.34

92.17

99.01

SINDA NX

99.24

93.47

120

171590.4 177568.5(sec)

-60

60

0Tem

per

atu

re (℃

)

(d)

(a)

(b)

26

28

30

32

34

36

38

ISM

+X

ISM

+Y

SHIE

LD +

X

SHIE

LD -

Y

M2

FIT

TIN

G

M2

BA

CK

STR

UT

1

STR

UT

3

STR

UT

5

BIP

OD

-Y

-Z

BIP

OD

-Y

+Z

MP

-Z

MP

-Z

MP

+Z

MP

+Z

RIN

G -

Z

RIN

G -

Z

RIN

G +

Z

RIN

G +

Z

SPID

ER

SPID

ER

TO

P P

AN

EL

TO

P P

AN

EL

TO

P P

AN

EL

Exp. data

NX simulation

SINDA simulation

Te

mp

era

ture

(℃

)

(a)

0

2

4

6

8

10

12

ISM

+X

ISM

+Y

SHIE

LD +

X

SHIE

LD -

Y

M2

FITT

ING

M2

BA

CK

STR

UT1

STR

UT3

STR

UT5

BIP

OD

-Y-

Z

BIP

OD

-Y+

Z

MP

-Z

MP

-Z

MP

+Z

MP

+Z

RIN

G -

Z

RIN

G -

Z

RIN

G +

Z

RIN

G +

Z

SPID

ER

SPID

ER

TOP

PAN

EL

TOP

PAN

EL

TOP

PAN

EL

Exp. data

NX simulation

SINDA simulation

Tem

pera

ture

(℃)

(b)

RSI housing

Bus

EU

FPA

Bipod

Ring

Mainplate

Top panel

(a) (b)

-35

-30

-25

-20

-15

-10

-5

0

5

10

15

20

EU-A

+Y

EU-A

-Y

EU-A

-Y

EU-A

+Z

EU-B

-Y

EU-B

+Y

EU-B

+Y

EU-B

+Z

FPA

+Y

FPA

-Y

FPA

-Z

Mai

np

late

Mai

np

late

Mai

np

late

Rin

g

Rin

g

Stru

t -Y

Stru

t +Y

Bip

od

-Y-

Z

Bip

od

+Y-

Z

Bip

od

-Y+

Z

Bip

od

+Y+

Z

Top

Pan

el

Top

Pan

el

Top

Pan

el

FPA

bra

cket

TTC

NX

SINDA

Tem

per

atu

re (℃

)

10

15

20

25

30

35

EU-A

+Y

EU-A

-Y

EU-A

-Y

EU-A

+Z

EU-B

-Y

EU-B

+Y

EU-B

+Y

EU-B

+Z

FPA

+Y

FPA

-Y

FPA

-Z

Mai

npla

te

Mai

npla

te

Mai

npla

te

Ring

Ring

Stru

t -Y

Stru

t +Y

Bipo

d -Y

-Z

Bipo

d +Y

-Z

Bipo

d -Y

+Z

Bipo

d +Y

+Z

Top

Pane

l

Top

Pane

l

Top

Pane

l

FPA

bra

cket

TTC

NX

SINDA

Tem

pera

ture

(℃)

the comparison of different thermal analysis … · 5. remote sensing instrument modeling rsi...

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