2. Overview
• Introduction to CubeSats
• MTU’s Auris CubeSat
• Mission Overview
• Orbit Selection
• Orbit Characteristics & Environment
• Satellite Overview
• Single-NodeThermal Model
• Further Modeling
• Thermal ManagementTechniques
• Model Progression
• ExperimentalValidation
• Industry Opportunities

3. What is a “CubeSat”?
• A miniaturized satellite for space research
• Composed of multiples of 10x10x11.35cm cubic units
• Increasingly popular with universities and private
companies

4. Space Situational Awareness – The Geostationary RF Domain
As more spacecraft occupy the geostationary belt, the potential for electromagnetic interference and
close physical proximity risk grows. How can operators protect their assets when optical image monitoring
systems can’t attribute radiated emissions to individual satellites?
MichiganTech’s Auris CubeSat

5. MichiganTech’s Auris CubeSat
Auris is a pathfinder mission whose purpose is to demonstrate a low-cost platform capable of determining
the interference potential of geostationary communications satellites. Using low-earth orbit based cubesat
technology, Auris will spatially map the antenna beam pattern of a cooperative partner’s geostationary
communications satellite and determine the satellite’s location.
Source: Analytical Graphics Inc. (AGI) ComSpOC

6. Mission Objective #1
The Auris System shall map the spatial distribution of radiated RF power from a cooperative geostationary
communication satellite’s Ku-band transmission.
MichiganTech’s Auris CubeSat

7. Polar Orbits
• Generally used for Earth observation
• These can be Sun-Synchronous orbits
• Constant beta angle
• Unstable orbits compared to lower inclinations

8. PerturbativeTorque due to Oblation
45°
• Orbits inclined <90° will precess over time
• Nodal regression rates can be as high as 4°/day
orbit nodes

9. BetaAngle & Sun-Synchronous Orbits
Non SSO
SSO

10. The Magic of Gravity

11. Low Beta angle
“Cold Case” scenario
High Beta angle
“Hot Case” scenario
Earth’s Shadow
Earth’s Shadow
The BetaAngle
Minimum angle between Earth-Sun vector and orbital plane

12. Auris’ Orbit & the BetaAngle

13. Thermal Environment in LEO
Direct Solar
Albedo (~35% Direct Solar)
Outgoing Longwave Radiation (OLR or Earth IR)
Free Molecular Heating
Generated Power (Hot)
When running most onboard hardware
Generated Power (Cold)
Generally when in Safe Mode

14. Summary of Orbital Environment
• High inclination ideal for mission success criteria
• Low inclination ideal for thermal management
• More time spent in Earth’s shadow
• Less chance for extreme hot case scenario
• While in hot case:
• Constant direct solar
• Near zero albedo
• Nearly constant OLR (generally averaged over one orbit)
• Some free molecular heating
• Generated internal power
• Can be maximum or minimum depending on requirements or current
temperature
• Some energy sent to heat sink/environment (space), some sent to
other satellite components

15. Summary of Orbital Environment Cont.
• While in cold case:
• Fluctuating direct solar
• Fluctuating albedo
• Nearly constant OLR
• Some free molecular heating
• Generated internal power
• Can be maximum or minimum depending on requirements or current
temperature
• Some energy sent to heat sink/environment (space), some sent to
other satellite components

16. Summary of Orbital Environment Cont.
Satellite in
LEO
Cold Orbit Hot Orbit
Extreme Cold
Satellite
Goldilocks
Zone
Medium Hot
Satellite
Extreme Hot
Satellite
Result of
Active Mgmt.
Satellite
Overheats
Satellite
Freezes
Minimal Mgmt.
Required
Satellite in
Safe Mode
SatelliteActive
Satellite in
Safe Mode
SatelliteActive

17. Auris’ Structure
Horn antenna
COTS components
Polished aluminum
back plateLow-noise block

18. Parameter Value
Input Frequency 12.25 – 12.75 GHz
L.O. Stability (after 60 sec) ±5 kHz to ±2 kHz
Noise Figure 0.7 to 0.9 dB
Conversion Gain 60 dB
Operating Temperature - 40 to 60°C
Norsat HS1000 Low-Noise Block
Parameter Value
Input Frequency 10 – 15 GHz
Waveguide Type WR75
3dB Beam Width (E-Plane) 16.3°
3dB Beam Width (H-Plane) 17.2°
Gain 20dB
20dB Horn Antenna
Auris’ Temperature Sensitive Payload

19. Modeling & Management Plan
Define/Gather
Requirements
Characterize
Environments
CreateThermal
Models
Analyze
Results
Develop
Mgmt. System
Implement &
Test System
What does
this mean?

20. Modeling & Management Plan
CreateThermal
Models
MATLAB
Models
TAITherm
Model
Single Node
6-Node
100(+)-Node
Heat Rates
from STK
Meshed Geom.
FromANSA
Final Model w/
1000’s of Nodes
Require Rad.
View Factors
Trusted
Software
Modeled w/
Explicit Geom.

21. Single-NodeThermal Model
• Created using MATLAB
• Synthetic orbital model using ‘Case’ structure
• Node has total external SA equal to that of the true
geometry
Generated Power ON
Generated
Power OFF
Solar & Albedo
Radiation
r calculated by
means of SA

22. Thermal Model Methodology
𝐸𝑠𝑡𝑜𝑟𝑒𝑑 = 𝐸𝑖𝑛 − 𝐸 𝑜𝑢𝑡
𝐸𝑖𝑛 = 𝐸𝑟𝑎𝑑.𝑖𝑛 + 𝐸𝑠𝑜𝑙𝑎𝑟 + 𝐸 𝑎𝑙𝑏𝑒𝑑𝑜 + 𝐸 𝑂𝐿𝑅 + 𝑄 𝑒𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑎𝑙 ∗ 𝑑𝑡 + 𝐸𝑐𝑜𝑛𝑑.𝑖𝑛
𝐸 𝑜𝑢𝑡 = 𝐸𝑟𝑎𝑑.𝑜𝑢𝑡 + 𝐸𝑒𝑛𝑣.𝑟𝑎𝑑 + 𝐸𝑐𝑜𝑛𝑑.𝑜𝑢𝑡
where
and
𝐸𝑠𝑡𝑜𝑟𝑒𝑑 ∗ 𝑑𝑡 = 𝑇𝑛𝑒𝑤 − 𝑇𝑜𝑙𝑑 ∗ 𝑚 ∗ 𝐶 𝑝
𝑇𝑛𝑒𝑤 = 𝑇𝑜𝑙𝑑 +
𝑑𝑡
𝑚𝐶 𝑝
𝐸𝑠𝑡𝑜𝑟𝑒𝑑

23. Thermal AnalysisVariables
Variable
Power Draw (on)
Power Draw (off)
Node Radius
Node Mass
Total Surface Area
Solar Cell Coverage
Radius of the Earth
Node Altitude
Eclipse Time (hot)
Eclipse Time (cold)
Orbit Period
Spacecraft Specific Heat
Avg/Weighted Absorptivity
Avg/Weighted Emissivity
Boltzmann’s Constant
Solar Constant (hot)
Solar Constant (cold)
Earth IR Emission
Albedo
Value
23
2
0.15878
6
0.3168
84.21
6378
600
0
2411
5880
960
0.6492
0.8533
5.67E-08
1419
1317
237
35
Units
Watts
Watts
Meters
kg
m^2
%
km
km
seconds
seconds
seconds
J/kg K
unitless
unitless
W/m^2 K^4
W/m^2
W/m^2
W/m^2
%
Notes
Beta = 90˚
Beta = 0˚
For solid 7075-T6 Aluminum
Considering 84.21% solar cell coverage with 92% absorptance
Considering 84.21% solar cell coverage with 85% emittance
Hot Case Cold Case
Single-NodeThermal Model

24. Single-NodeThermal Model
• Results:
• Hot case approaches a temperature limit
• Cold case cools in Earth’s shadow on each orbit

25. PassiveThermal Management
• Mission requirement changes
• Lower initial orbit inclination
• Problem:
• High inclination necessary for primary mission
objectives
• Keep LNB powered at all times while in cold case
orbit
• Stabilizes component temperature
Maximize time in Earth’s shadow

26. ActiveThermal Management
• In-orbit measurements and maneuvers
• Battery & LNB heaters triggered by network of
thermistors
• Deliberate sun-pointing while in hot case orbit

27. ActiveThermal Management
• Direct solar is reflected (preventing most battery charging)
• Albedo is absorbed (heating the satellite slightly & charging
the battery slightly)
• Battery drain from hardware use and negative charging effect
of reflected solar must be taken into account

28. Model Progression
• Plans to create 6 and 100 node models by building on
existing model
• Obstacles:
• Single-node model must first be validated
• Radiation view factors must be created manually
• View factors should then be validated
• Further models should then be validated
• Validation in space is hard

29. ExperimentalValidation
Auris
TAITherm
Models
Laboratory
Experiments
MATLAB
Models
Thermal
Management

30. Orbit
Selection
Auris
TAITherm
Models
Thermal
Management
ExperimentalValidation
Done separately in STK

31. TAITherm
Satellite Module
Thermal
Management
ExperimentalValidation

32. Opportunities