1. Picosat Mission Introduction
莊哲男/林信嘉
Date: 96/03/08

2. 大綱
衛星系統介紹
Picosat/Nanosat的發展類型及用途
衛星任務選擇考量因素
衛星系統發展
課堂計畫及作業說明

3. Satellite System Architecture
福爾摩沙衛星二號

4. 衛星大小等級 衛星大小等級的分類, 一般依重量分為: 大衛星 (large satellite, 1000公斤以上),
小衛星 (small satellite, 500~1000公斤),
迷你衛星 (mini-satellite, 100~500公斤),
微衛星(micro-satellite, 10~100公斤)
奈米級衛星 (nano-satellite, 1~10公斤),
皮米級衛星或微微衛星 (pico-satellite, 1公斤以內)

5. Picosat Examples P-POD Launcher CubeSat by radio amateurs NSPO-YamSat
CubeSat by the University of Tokyo

6. Picosat/Nanosat的發展類型及用途

7. Picosat/Nanosat的發展類型及用途
1. 做為衛星系統課程的標的物：
Picosat/Nanosat系統複雜度比大型衛星簡單，發展時程較短(約二年)，所需發展及發射經費皆遠低於大型衛星，學生的構想有實現的可能性。
很多學校的發展經驗多有公布在網路上，大家可以彼此交換技術及心得。

8. Picosat/Nanosat的發展類型及用途(續)
2.元件的太空驗證：
Picosat/Nanosat的發展成本低、要求的操作壽命較短，學生可以大膽使用商業用元件，例如一些微微衛星使用商用無線通訊手機模組，當作衛星通訊元件。如此可對商業元件做太空驗證，使以後衛星的元件成本大幅降低。
學生也可將自製的元件，放到太空去驗證效能，例如天線及太陽能板的展開機構等，以讓日後其他衛星採用。

9. Picosat/Nanosat的發展類型及用途(續)
3. 太空技術的驗證：
Picosat/Nanosat衛星體積、質量及電力非常有限，某些用於大型衛星的元件及技術並不適用。元件需要微小化，例如使用微機電(MEMS)技術的感測器或推進系統。
許多有用的衛星任務(例如遙測影像)需要良好的三軸穩定控制，但三軸穩定需要複雜的設計及電能消耗，是待克服的技術。
例如CalPoly發展的CP2衛星，就是希望提供一個三軸穩定控制的衛星本體平台。

10. Picosat/Nanosat的發展類型及用途(續)
4. 太空科學實驗平台：
Picosat/Nanosat衛星雖小，也可執行有用的特定太空科學實驗。
TU Sat 1衛星量測太空中電漿密度，及研究纜線(Tether)通過電離層所產生的電動力學。
MEROPE衛星以輻射計量測Van Allen Belts區域的輻射劑量等。
QuakeSat衛星以磁力計量測高空的超低頻磁場，研究其和地表地震的關聯性。

11. Picosat/Nanosat的發展類型及用途(續)
5. 通訊用途:
衛星和地面站的通訊能力，可以擴展到民生用途。
TU Sat 1衛星就以提供開發中國家的電子郵件通訊為其衛星任務之一。
nCube衛星就用來接收船隻廣播的AIS訊號，包括船隻的位置、速度及方向的資料，再將此資料轉送到地面，可用來監控船隻的安全狀況。

12. Picosat/Nanosat的發展類型及用途(續)
6. 光學照相:
日本東京大學XI-IV衛星使用CMOS的商業用照相機，已可拍攝到地球及太陽的影像。由此可驗證CMOS感測器的太空應用，及太空用光學照相儀器成本降低的可能性。

13. Picosat/Nanosat的發展類型及用途(續)
7. 星群應用：
Picosat/Nanosat衛星的發展成本低，並且一次可用火箭發射多顆，所以星群的使用，可以發揮「螞蟻雄兵」的加成效果。
ICE計畫擬同時發射二個微微衛星，使二者相距100公尺以上，可同時量測GPS衛星訊號的差異，研究GPS訊號通過大氣層的訊號閃耀(scintillation)現象，這和中華衛星三號的操作原理相似。
KUTESat計畫擬同時發射三個微微衛星，彼此間的無線通訊是其實驗項目之一。
可以預期到，未來微微衛星的星群應用會愈來愈多。

14. 國際 Picosat / Nanosat 發展狀況 (1)

15. 國際 Picosat / Nanosat 發展狀況 (2)

16. 國際 Picosat / Nanosat 發展狀況 (3)

17. 衛星任務選擇考量因素

18. 衛星任務選擇考量因素 (1)
任務類別:元件及太空技術驗證

19. 衛星任務選擇考量因素 (2)
任務類別:通訊應用

20. 衛星任務選擇考量因素 (3)
任務類別:光學照相

21. 衛星任務選擇考量因素 (4)
任務類別:科學實驗

22. 衛星系統發展

23. 衛星設計流程

24. Spacecraft Development Cycles
Spacecraft development is an iterative process.
Major changes in the late stage may cause significant impact to the program.
All changes should be evaluated from SYSTEM point of view.
Mission
Need
Requirement
Development
Design
Baseline
Design
Validation
SDR
Manufacturing
System Spec.
PDR
Integration
& Test
Subsystem Spec.
CDR
Operation
Component Spec.
ITR
Test Procedures
PSR

25. Systems Engineering
A development system capable of meeting mission requirements within imposed constraints including mass, cost and schedule.
Trade studies in the system engineering process on requirement definition, resource allocation, and design integration.
Feasibility study
System Requirements
Specification Breakdown
Budget Control and Interface Control
Considering different phases in the spacecraft design

26. Mission Requirements Mission Objectives: Mission Needs:
Communication: Provide communication link between any two locations on earth
Earth Observation: Provide image data of Taiwan island
Science: Grow vegetable in space
Mission Needs:
Communication: coverage area, data type, time latency, etc.
Earth Observation: resolution, revisit time, availability, etc.
Science: type of vegetable, observation time, etc.

27. Mission Analysis To meet Users’ needs Payload Requirements
Operation Algorithm
Orbit & Launch Selection
Mission Requirements
A key aspect of mission analysis is to identify critical features of the mission which have an impact upon system and subsystem design.

28. Payload Performance Requirements
Communication Payload:
- frequency band
- link margin
- BER (Bit Error Rate)
- Others
Earth Observation Payload:
- spectral characteristics
- ground sampling distance
- swath width
- Others

29. Payload Requirements Resource limit of a Picosat/Nanosat: Example:
Weight: 3 Kg (0.75~1 Kg Payload Weight)
Size: 10cm x 10 cm x 30 cm
Power:
Actual available power will depend on the solar array effective size and selected orbit.
Typically half of the power will be needed for spacecraft bus operation.
Payload Downlink Data Rate: <1Mbps (limit by power requirement)
Pointing Accuracy: 0.3~0.5 degree (3 axis nadir pointing control)

30. Spacecraft System Interfaces
Ground Segment
Space Segment
Launch Segment
Spacecraft Bus
Payload
SMS
TCS
RCS
ADCS
TT&C
C&DH
FSW
All interfaces need to be defined and controlled to assure integrity of the final design.

31. Spacecraft System Key Interfaces
Launch Tracking
Ground Segment
Space Segment
Launch Segment
TT&C Frequency
TT&C Format
Link Budget
Mission Operation
Orbit
Weight
Size
Environmental Loads
Mechanical Interface
Electrical Interface
Attitude Control

32. Requirements Definition
Mission
Requirements
Payload
Requirements
Spacecraft Bus
Requirements
Mission Objectives
Mass/Size
System
Mission Needs
Pointing/Stability
SMS
TCS
Thermal
RCS
Operation Modes
ADCS
Power
EPS
Data Rate
TT&C
Field of View
C&DH
Performance
FSW

33. Orbit Trade Studies Selected Orbit - Altitude - - Inclination -
Weight
Size
Propulsion
Thermal Control
Power
Selected Orbit
- Altitude -
- Inclination - LV
Selection
Thermal
Environment
Revisit Time
- Taiwan -
- Global -
Mission Orbit
Are
Mission Needs
Met? No
Coverage
Area
Radiation
Yes
Final
Mission Orbit
Parts Selection
Shielding
Antenna
Operation Mode

34. Spacecraft Bus Requirements
Design requirements for each of the spacecraft bus subsystem can be expressed by a set of design parameters, e.g. link budget, etc.
Definition of key design parameters for each of the spacecraft subsystem and associated analysis for design verification will be discussed in detail in the subsequent lectures.
Some of the requirements, however, have overall effects across all the subsystems, e.g. weight. These requirements are typically classified as the system requirements.

35. Spacecraft Bus Requirements (cont.)
System level trade studies are needed to define these requirements with proper allocation to subsystems.
Design verification of system requirements may be conducted in the subsystem level. Allocation to subsystems may need to be adjusted based on the subsystem design.
Typical set of system requirements:
- Orbit Mission Life Reliability Mass
- Power Link Budget Pointing
- Memory size/throughput

36. Mass Maximum Lift-off Weight Candidate Launch Vehicle Required
Propellant
Mission Orbit
Dry
Weight
Payload Weight
Allocation
Estimation
Within
allocation?
Baseline
Design
System
Subsystem Weight
Harness Weight
Ballast Weight
YES NO
Margin

37. Power
Power requirement could be market driven, payload driven, and for the case of picosat, size and configuration driven.
Design Drivers:
- Customer/User Target planet, Solar distance
- Spacecraft configuration Lifetime
- Attitude control Orbit parameters
- Payload requirements Mission constraints

38. Power Allocation Orbit Parameters Spacecraft Configuration Attitude
Control
Cell
Type
Body Mounted
Solar Cell
Available
Mounting Area
Cell
Temperature
Available
Power (BOL)
Power
Allocation
Mission
Constraints

39. Design Integration Mission Structure ADCS Trades Thermal Power
Spin vs 3-axis vs passive
On-board vs ground navigation
Sensor selection
Actuator selection
Control law
Mission
Orbit? Orbit change?
Earth pointing? Accuracy/Stability?
Slewing requirement? Autonomy?
Structure
C.G. constraints?
Initial constraints?
Sensor location?
Field of view?
Power
Power requirement?
Solar array pointing?
Communication
Antenna pointing?
Thermal
Special maneuvering?

40. Design Verification
All requirements need to be verified either by analysis, test, or inspection.
Test Philosophy:
Acceptance Test: Maximum flight prediction and duration
Qualification Test: Qualification level and duration, i.e. acceptance plus margin
Proto-flight: Qualification level and acceptance duration
Typical Spacecraft System Level Test:
Electromagnetic Compatibility/Interference Test (EMC/EMI), Comprehensive
Performance Test (CPT), Vibration, Shock, Acoustic, Thermal Vacuum/Thermal
Balance Test, Alignment, Mass Property, Leak Test, Spin Balance, Deployment,
etc.
Component
Level
Subsystem
Level
Spacecraft
Level

41. 課堂計畫及作業說明

42. 研習方案2:Preliminary Design of Picosat System
Design a set of picosats which may contain more than one satellite for early warning of sand storm from Gobi desert in north-west mainland China.
Each satellite shall have weight no more than 3kg and size no more than 10cm x 10cm x 30 cm, and the design shall include payload suitable for the mission, adequate system-subsystem structure and elements, and operating sequence to achieve mission objective.
Need to study the characteristics of the sand storm in order to formulate a set of mission requirements.

43. Outline for Program Report
1. Program Introduction
2. Mission objectives and requirements
3. Payload specification and requirements
4. Orbit specification
5. Power specification
6. Structure configuration and specification
7. Thermal control specification
8. TT&C specification
9. Command and Data Handling specification
10. Attitude specification
11. Verification of system
12. Power and mass distribute
13. Flight operation modes and procedures

44. 衛星命名 為何要命名? 衛星命名範例: 命名來源: 代表此衛星的特色 凝聚向心力 ROCSAT-1,中華衛星一號 YamSat, 蕃薯號衛星
LISA (Lost In Space Algorithm), 麗莎
命名來源:
Mission
Payload
象徵意義

45. 衛星主要特性 任務: 酬載: 衛星發射時間: 發射火箭: 軌道: 高度?公里, 傾角?度 衛星質量: 體積: 形狀: 任務壽命: 設計壽命:
衛星質量: 體積: 形狀:
任務壽命: 設計壽命:
電力: 太陽能晶片類型? 太陽能板類型? 充電電池類型? 工作電壓?
通訊:指令上傳頻率,速度,格式; 資料下傳頻率,速度,格式
衛星電腦: 微處理器? 記憶體容量? 作業系統? I/O型態及數量
姿態判定方式及元件? 姿態控制方式及元件?
溫度控制方式及元件?
結構構造及材料?

46. 衛星發展時程規劃

47. 衛星分析及設計
發展軟體工具
衛星軌道模擬
衛星結構繪製
結構分析
電路圖繪製及分析
電力分析
熱控分析
姿控分析

48. Distribution Regulation unit
Product Tree Example
YamSat System
Structure
Thermal Control
Power
TT&C
ADCS
Payload
C&DH
+X Panel
VHF/UHF Antenna
Battery
Magnetometer
Spectrometer
Electronics
OBMU
Black Paint
Distribution Regulation unit
CW Antenna
Magnetic Coil
Optical Parts
-X Panel
Isolator
Transceiver
+Y Panel
Solar Array
Receiver
-Y Panel
Harness
+Z Panel
-Z Panel

49. Flow Chart for Requirements design
Mission
Objectives
System
Requirement
Payload
Specification
Orbit
TTC
Thermal control
Attitude
Power
Structure
C&DH

50. 作業
1.將團隊人員做任務分配
2.定義衛星任務需求
3.依據任務需求, 訂定衛星酬載儀器主要特性
4.依據酬載特性, 訂定衛星系統需求

51. 作業參考例子 (1) 1. 人員任務分配: 組長, 酬載, 結構, 姿控, 電力, 指令及資料處理, 飛行軟體, 通訊, 熱控等。
2. 定義衛星任務需求:
衛星的任務，是量測太陽光在大氣層的散射量，以做大氣成分分析的實驗。
3. 依據任務需求, 訂定衛星酬載儀器主要特性:
衛星酬載是微光譜儀, 其主要特性為:
(1)使用微機電技術所做的分光儀, 將可見光譜分成256波段
(2)有個光學鏡頭需朝外
(3)需在有陽光的時候才能做實驗
(4)微光譜儀鏡頭需緩慢轉動, 掃過大氣層
(5)使用+5V電源. 使用功率 0.5W. 操作時間長短不拘
(6)使用非同步序列介面傳輸科學資料, 每1.172 sec 產生256bytes科學資料
(7)操作溫度範圍為 -20~+40 degC

52. 作業參考例子 (2) 4.依據酬載特性, 訂定衛星系統需求: (1)結構: 結構需有開孔以讓光譜儀鏡頭朝外
(2)姿態控制: 使用B-dot 磁力控制, 使光譜儀緩慢轉動, 並掃過大氣層
(3)電力: 提供足夠電力給衛星各次系統. 提供5V電源給光譜儀, 並能控制其電源ON/OFF
(4)指令及資料處理: 提供微光譜儀的指令及遙傳資料介面, 及資料儲存空間
(5)通訊: 提供地面站和衛星的通訊連結
(6)熱控: 維持衛星各次系統及酬載在適當的溫度