Satellite Engineering BEST Course. CubeSats at ULg

Transcription

1 Satellite Engineering BEST Course CubeSats at ULg

2 Nanosatellite Projects at ULg Primary goal Hands-on satellite experience for students 2

3 Nanosatellite Projects at ULg Primary goal Hands-on satellite experience for students Short-term goal New radio-communications system (D-STAR) Innovative electrical power system (THALES) High-performance solar cells (AZUR SPACE) 3

4 OUFTI-1? Orbital Utility For Telecommunication Innovation but Oufti /uf.ti/ : interjection (Belgium) Showing surprise, amazement (mainly in the vicinity of Liège) = no me digas! 4

5 Payload: D-STAR Digital Smart Technologies for Amateur Radio Simultaneous voice & data transmission Complete routing capacity, including roaming 3 frequencies and 2 data rates - VHF: 144 MHz (2m) 4.8 kbit/sec - UHF: 435 MHz (70cm) 4.8 kbit/sec - SHF: 1.2 GHz (23cm) 4.8 kbit/sec or 128kbit/sec Open protocol 5

6 Payload: D-STAR vs. FM Demo: D-STAR : The conversation can t always be received, but the signal quality is high (digital). FM : The entire conversation can be heard, but the signal quality is not as high as D-STAR (analog). 6

7 Payload: Digital EPS and Solar Cells Prototype of digital EPS High-performance solar cells (30% GaAs triple junction) 7

8 CubeSat: A Standard for Nanosatellites 1 kg liter W 10 cm Standard proposed by Stanford and Calpoly Easier access to space Short development time Ideal for universities 8

9 CubeSat: Launch Poly Picosat Orbital Deployer (P-POD) (3 CubeSats) Vega maiden flight (Oct. 2010) OUFTI-1 with 8 other CubeSats on the same orbit 9

10 Academic & Industrial Partnership Educational satellite but 10

11 Students Involved in All Activities Unusual MS theses! Team spirit Industrial approach Discussions & decisions Communication 11

12 Students Involved in All Activities VEGA Maiden Flight workshop ESA/ESTEC STK comprehensive training Washington ARISS communication with F. De Winne Euro Space Center, Redu Tests at CSL 12

13 Realizations 13

14 OUFTI-1: Orbit 1447 km x 354 km i=71º 14

15 OUFTI-1: Mission Analysis Because the orbit is imposed, mission analysis reduces to analyze its influence on the OUFTI-1 mission. The 354 km x 1447 km appears to be a very demanding orbit (especially regarding radiations). 15

16 OUFTI-1: Mission Analysis 16

17 OUFTI-1: The Satellite 17

18 OUFTI-1: Exploded View 18

19 OUFTI-1: Exploded View 19

20 OUFTI-1: PCBs 20

21 ADCS: Requirements The three different payloads have no specific pointing requirements (D-STAR: monopole antennas will be used). But the satellite should not rotate too quickly (avoid telecommunications signal modulation) Requirement: max 10º/s. No need for active control; passive control is sufficient. 21

22 ADCS: Perturbations Perturbation torques Values [N.m] Gravity gradients Aerodynamic torques Solar radiation pressure Magnetic torque Magnet torque 10-5 (1cm³ of Alnico-5) 22

23 Permanent Magnets and Hysteretic Rods 23

24 ADCS: Numerical Results 24

25 COM: Architecture Payload: D-STAR. TM/TC: AX-25 telecommunication protocol. Beacon: extreme reliability (Morse code). 25

26 COM: Architecture Payload D-STAR D-STAR Demod D-STAR Décod/Coder D-STAR Mod D-STAR RX TX TC AX.25 Demod TC / TM processing AX.25 Mod TM Beacon 26

27 COM: Requirements All links must be located within the agreed ham band specific space allocations. For simplicity, low-gain antennas must be used. The OUFTI-1 system shall be entirely compliant with the D- STAR network. In particular, the Doppler shift must remain unnoticed to the various users. 27

28 COM: Frames D-STAR AX-25: simple and standard within the ham community 28

29 COM: Modulation D-STAR: GMSK, 4800 bauds. AX-25: FSK, 9600 bauds. 29

30 COM: GMSK Modulation used in your cell phones! Gaussian minimum shift keying is a continuous-phase FSK. The digital data stream is first shaped with a Gaussian filter before being applied to a frequency modulator. High spectral efficiency, but it needs a higher power in order to transmit the same amount of data reliably. FSK 30

31 COM: Frequency Bands Uplink to the satellite will be performed in the 70-cm band (435 MHz, UHF) and downlink will be performed in the 2-m band (145 MHz, VHF). Why? UHF needs 9 db more power on the satellite to be heard by the same mobile. But also 31

32 COM: Low-Gain Antennas Two monopole (quarter-wave) antannas : 17 and 50 cms 32

33 COM: Propagation (Downlink) 33

34 COM: Ground Segment TM / TC channel (AX.25) OUFTI-1 User channel (D-STAR) Mission Control Center Ground Station 12:05:49 TCP / IP Satellite Extension D-Star Repeater Control & operations D-STAR 34

35 COM: Ground Segment UHF Antenna VHF Antenna el az H V H V Rotators controller Phasing line Phasing line Tracking card CI-V FM UHF UHF/VHF Transceiver FM VHF 12:05:49 Pointing data Control AX.25 TCP / IP GS computer Serial Data TNC Mission Control Center Ground Station 35

36 COM: Link Budget 36

37 EPS: Block Diagram 37

38 EPS: Solar Cells 38

39 EPS: AzurSpace Solar Cells GaInP/GaAs/Ge on Ge substrate triple junction solar cells At 28ºC 39

40 EPS: I-V Curves 40

41 EPS: Solar Arrays 41

42 EPS: Two Kokam Batteries 42

43 EPS: Test of the Batteries 43

44 EPS: Power Consumption 44

45 EPS: Conditioning Choice of direct energy transfer and not maximum power point tracking Choice of unregulated bus with three DC/DC converters (3.3 / 5 / 7.2 V) 45

46 EPS: Conditioning Schematics of the 7.2 V converter 46

47 EPS: Engineering Model 47

48 Digital EPS: Engineering Model 48

49 THER: Requirements 49

50 THER: Requirements 50

51 THER: The Orbit Eclipse-free orbits Eclipse-free orbits Eclipse-free orbits 51

52 THER: The Orbit 52

53 THER: Hot and Cold Cases 53

54 THER: Experimental Measurements Determination of the frame contact resistance: face 6 is heated up Face 1 Face 3 54

55 THER: Thermal Analysis (Cold Case) Battery is too cold! 55

56 THER: Thermal Analysis (Hot Case) Hot spot due to dissipation transistor! 56

57 THER: Thermal Control The available surface on the satellite panels is very limited. Difficult to control the overall energy balance between the spacecraft and its environment. 57

58 THER: Conductive Links Thermal control can be achieved by an appropriate study and design of the conductive links within the satellite. Copper angle bracket 58

59 THER: Active Control using Heaters Use of two heaters for the batteries (2 x 250mW) 59

60 OUFTI-2 60

61 OUFTI-2 61

62 QB50 An international network of 50 double CubeSats for multi-point, in-situ, long-duration measurements in the lower thermosphere and for re-entry research 62

63 QB50 ISIS 2U Science Unit: Lower Thermosphere Measurements Sensors to be selected by a Working Group Standard sensors for all CubeSats Functional Unit: Power, CPU, Telecommunication, IMU, GPS Optional Technology or Science Package Universities are free to design the functional unit 63

64 QB50 The payload mass versus the altitude of an orbit inclined 78.9 (above the mean Earth radius R mean =6371 km) 64

65 In Summary Three CubeSats projects at ULg: OUFTI-1, OUFTI-2, QB50. Erasmus students are most welcome to work on these projects. 65

66 Satellite Engineering BEST Course CubeSats at ULg 66