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Project solutions for low cost space missions

Politecnico di Torino Departement of Electronics. Project solutions for low cost space missions. Stefano Speretta Advisor: Prof. Leonardo M. Reyneri . Main Goals. Demonstrate design techniques for reducing satellite development cost

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Project solutions for low cost space missions

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  1. Politecnico di Torino Departement of Electronics Project solutions for low cost space missions Stefano Speretta Advisor: Prof. Leonardo M. Reyneri PhD Final Presentation

  2. Main Goals • Demonstrate design techniques for reducing satellite development cost • Demonstrate feasibility of using non space-born components in space • Apply low-cost techniques to most satellite subsytems PhD Final Presentation

  3. Outline • Introduction • Low cost techniques • Radiation tolerance issues • System level design techniques • Conclusions PhD Final Presentation

  4. Introduction • Satellites are complex systems operating in space • They can be orbiting around any celestial body • The main topic of interest are satellites orbiting around the Earth, with particular attention to Low Earth Orbits (LEO) PhD Final Presentation

  5. Satellite subsystems • Power management • Used to supply power to all other subsystems • On-Board Computer • It is the main satellite control unit • Data communication bus • It is used to issue commands and fetch data to satellite sub-systems • Radio communication • Used to send data / receive commands to / from the Earth PhD Final Presentation

  6. Satellite subsystems II • Payload • Main subsystem in a satellite • Attitude and Orbit control • Used to control satellite position and orientation • Ground segment • It is not part of the satellite itself • Is fundamental to transmit data back to the Earth PhD Final Presentation

  7. LEO space environment • Vacuum • No cooling by convection, only radiation and conduction • Ionizing radiation • Van Allen belts trap part of the incoming particles • External temperature range: -40° C ÷ 120° C • Sunlight can change the temperature quite fast • Internal temperature range: -10° C ÷ 70° C • Thermal capacity helps stabilizing the temperature • High atmosphere effects • Atomic oxygen corrosion, electrostatic charges PhD Final Presentation

  8. The radiation environment Space Radiations and Effects on Electronics: Single Event Effects (SEE) Displacement Damage Total Ionizing Dose (TID) Heavy Ions Protons Protons Electrons Sun Flares Radiation Belts Galactic Sources PhD Final Presentation

  9. Radiation induced effect Total Ionizing Dose (TID) • Integral over time of the absorbed energy due to ionizing interactions • Maily due to trapped protons and electrons • Causes transistor threshold level shifts in ICs, impacting their peformances • Its impact can be reduced by shielding PhD Final Presentation

  10. Radiation induced effect II Displacement damages • Integral over time of the absorbed energy due to non-ionizing interactions • Mailny due to solar protons • Causes lattice displacements which mainly impacts bulk defect density • Its impact can be reduced by shielding PhD Final Presentation

  11. Radiation induced effect III Single Event Effects (SEE) • Charge injection due to high energy particles in ICs • Mainly due to solar protons and heavy ions • Causes transient errors in memories • Can cause permanent device damages(latch-up or gate rupture) • Its impact cannot be reduced by shielding(shield thickness would be too high) PhD Final Presentation

  12. Space components • Electronic components should be radiation tolerant • Special components are needed • High cost • Limited production volume • High reliability is needed • No maintenance • Special components are needed • High cost PhD Final Presentation

  13. Proposed low-cost solutions I • Use of COTS (Commercial off-the-shelf) components • Cheaper • Easier to procure (ITAR free) • Problems induced by the space environment • Evaluation of radiation damage • Proper design techniques to increase tolerance PhD Final Presentation

  14. Proposed low-cost solutions II • Use of proper design techniques to reduce satellite development and production cost • Modularity • Redundancy • Scalability PhD Final Presentation

  15. Radiation Tolerance issues PhD Final Presentation

  16. Typical Design Approaches • Use of Rad-Hard components • High cost • Hardness is achieved at technology level • Use of Rad-Tolerant components • Lower cost • Commercial technology with few changes • Radiation Hardening by design • Lowest cost • Shielding • High mass • Limited effects PhD Final Presentation

  17. Proposed Design Approach • Rad-Hard components • Cost is too high • Procurement too complex (ITAR, etc...) • Rad-Tolerant components • Commercial deviced tested under radiation • Rad-Hard by design • Components procurement is simple • Different design techniques needed • Shielding • High mass • Limited effects PhD Final Presentation

  18. COTS components in Space • Commercial components where not developed for the space environment • They require proper solutions to be successfully employed in space • Two practical cases will be analyzed to give a deeper overview: • Wireless optical data bus • Latch-up protection system PhD Final Presentation

  19. Wireless Optical data bus • No harness mass • To save cost and simplify integration • Low datarate (~ 1Mbps) • Mainly for housekeeping and low-end payloads • Insensitive to VHF or S-band noise • Should not be disturbed by on-board transceivers • Short communication distance • Maximum 2 ÷ 3 m • Low power consumption • Limited power budget PhD Final Presentation

  20. Radiation tolerance evaluation I • Model space environment • Solar protons are the most important threat to optical devices (Displacement damages) PhD Final Presentation

  21. Radiation tolerance evaluation II • Evaluation of proton energy spectrum inside the satellite • Analisys with software tools (MULASSIS) • Montecarlo analisys • High precision • High computation time (~ 24h) • Development of an ad-hoc tool • Based on pre-computed coefficients (SRIM) • High speed (~ 10s) • Reasonable precision PhD Final Presentation

  22. Radiation shielding Mechanical structure • 5 mm epoxy (LED plastic case) • 1.6 mm Epoxy (internal PCB) • 2 mm Thermal Insulator • 1.5 mm Al (external panel) • 0.3 mm Epoxy (solar cells PCB) • 160 um Germanium (solar cells) PhD Final Presentation

  23. Particle transport in matter Ion dE/dx dE/dx Projected Longitudinal Lateral Energy Elec. Nuclear Range Straggling traggling ----------- ---------- ---------- ---------- ---------- ---------- 10,00 keV 2,797E-01 4,085E-03 1277 A 501 A 471 A 11,00 keV 2,924E-01 3,861E-03 1382 A 518 A 493 A 12,00 keV 3,044E-01 3,664E-03 1484 A 534 A 514 A 13,00 keV 3,155E-01 3,489E-03 1583 A 549 A 534 A 14,00 keV 3,260E-01 3,332E-03 1681 A 563 A 552 A 15,00 keV 3,359E-01 3,190E-03 1776 A 575 A 570 A 16,00 keV 3,451E-01 3,062E-03 1869 A 587 A 586 A 17,00 keV 3,537E-01 2,945E-03 1961 A 598 A 602 A 18,00 keV 3,618E-01 2,838E-03 2052 A 608 A 617 A 20,00 keV 3,766E-01 2,648E-03 2229 A 628 A 645 A 22,50 keV 3,925E-01 2,448E-03 2444 A 649 A 678 A 25,00 keV 4,062E-01 2,279E-03 2653 A 668 A 708 A 27,50 keV 4,178E-01 2,135E-03 2858 A 685 A 735 A Plots generated with SRIM PhD Final Presentation

  24. Particle transport in matter Ion dE/dx dE/dx Projected Longitudinal Lateral Energy Elec. Nuclear Range Straggling traggling ----------- ---------- ---------- ---------- ---------- ---------- 10,00 keV 2,797E-01 4,085E-03 1277 A 501 A 471 A 11,00 keV 2,924E-01 3,861E-03 1382 A 518 A 493 A 12,00 keV 3,044E-01 3,664E-03 1484 A 534 A 514 A 13,00 keV 3,155E-01 3,489E-03 1583 A 549 A 534 A 14,00 keV 3,260E-01 3,332E-03 1681 A 563 A 552 A 15,00 keV 3,359E-01 3,190E-03 1776 A 575 A 570 A 16,00 keV 3,451E-01 3,062E-03 1869 A 587 A 586 A 17,00 keV 3,537E-01 2,945E-03 1961 A 598 A 602 A 18,00 keV 3,618E-01 2,838E-03 2052 A 608 A 617 A 20,00 keV 3,766E-01 2,648E-03 2229 A 628 A 645 A 22,50 keV 3,925E-01 2,448E-03 2444 A 649 A 678 A 25,00 keV 4,062E-01 2,279E-03 2653 A 668 A 708 A 27,50 keV 4,178E-01 2,135E-03 2858 A 685 A 735 A Plots generated with SRIM PhD Final Presentation

  25. Particle Penetration Approximated equation (Bortfield96, modified) R particle range in matter x particle position α fitting coefficient 1 p fitting coefficient 2 k fitting coefficient 3 PhD Final Presentation

  26. Particle transport in matter SRIM-based approach (left) 10 s computation • cccccc MULASSIS output (right) 24h computation 1M particles PhD Final Presentation

  27. Equivalent damage computation • In laboratory it’s impossible to test with an energy spectrum as broad as can be found in space • From the energy spectrum, an equivalent mono-energetic fluence can be computed to simplify testing • Equivalent spectrum is computed such that damages created by the two spectra are equal • Equivalent spectrum is computed using the Non Ionizing Energy Loss (NIEL), which is the equivalent of TID for non-ionizing damages PhD Final Presentation

  28. Radiation Testing • Equivalent spectrum: 3x108 protons 2 MeV • Irradiation tests performed at AN2000 Legnaro (PD) PhD Final Presentation

  29. Test results PhD Final Presentation

  30. Latch-Up protection system • Protect latch-up sensitive devices from damages • Cut power supply in case of peak current consumption • Keep protected device off until latch-up extinguished • Can be used as a load switch • Output slew-rate limitation • Over-current protection • Monitor current consumption • System can be parallelized to increase reliability PhD Final Presentation

  31. Latch-Up • Event generated by a charge injection in a parasitic SCR • It is originated by a high energy particle • It causes a sharp current consumption increase that can destroy the device • Can be extinguished only by removing power supply PhD Final Presentation

  32. Latch-up Traditional CMOS process with n substrate and p wells Parasitic SCR equivalent circuit PhD Final Presentation

  33. Latch-Up protection system Sense resistor Power switch Current Monitor Monostable multivibrator Load shorting switch PhD Final Presentation

  34. Latch-Up protection system • Monostable multivibrator • Used to generate an asimmetric delay(fast turn-off time and low turn-on time) • The slow turn-on time is used to ensure latch-up has estinguished in the load before turning on • Load shorting switch • Speeds up latch-up extinguishing by shorting the load PhD Final Presentation

  35. Latch-Up protection system • Precision reference • Used to guarantee stable switch-off threshold over temperatre and radiation • Slew-rate controller • Used to prevent false triggering when turning on capacitive loads (inrush current limitation) • Power switch circuit • Can also control an external power switch PhD Final Presentation

  36. Latch-Up protection system • Fully bipolar ICs • Latch-up free operations • Higher tolerance to total dose • Extended industrial temperature range • ICs in die package • Greatly reduces size (where available) • BGA packge with metal case • All ICs are covered with resin to reduce moisture problems • 0.5 mm balls to improve soldering reliability • High thermal conduction to prevent power switch faults PhD Final Presentation

  37. Latch-Up protection system • Size: 13x13 mm • Hibryd technology • BGA package • Supply: 2.7 – 36 V • Max current: 2A • Operating temperature: [ -40 ÷ 125 ] °C PhD Final Presentation

  38. Latch-Up protection system External switch solution PhD Final Presentation

  39. Latch-Up protection system Redundant switch solution PhD Final Presentation

  40. Latch-Up protection system Turn-off time (top-right) Latch-up event (below) Turn-on time (bottom-right) PhD Final Presentation

  41. System level design techniques PhD Final Presentation

  42. Cost reduction techniques • Modularity • Allows to save development time • Easier system upgrade • Scalability • The same system can fit multiple “size” • Development time reduction • Redundancy • Allows to increase reliability (fault tolerance) PhD Final Presentation

  43. The AraMiS architecture • Modular Architecture for Satellites • Highly scalable & redundant • Composed by small buildingblocks (Tiles) • Telecommunication & control • Power Management &attitude control PhD Final Presentation

  44. The AraMiS architecture • Can fit different size • Highly scalable • Flexible • Allows to save money by re-using every module PhD Final Presentation

  45. Power Management Tile Solar Cells Sun Sensor Magnetic torquer Battery Reaction Wheel PhD Final Presentation

  46. Power Management Tile • Basic unit for a scalable power management sub-system • Power generation by means of solar panels • Energy storage using rechargeable batteries • Scalability • Share energy using power bus • Distributed control strategy • Central management PhD Final Presentation

  47. Power generation • GaAs Solar cells (space rated) • Maximum Power Point Tracker PhD Final Presentation

  48. Power storage • Li-Ion COTS batteries (2500 mAh, 18650 cells) • Expected life: 500 cycles(100% charge / discharge) • Commercial charger:LTC4008 from Linear(used on SSETI Express) PhD Final Presentation

  49. Power Distribution Bus • Key element for power supply system scalability • Power from all illuminated solar panels is distributed to all loads and batteries • Bus voltage depends on available power • Bus voltage should be regulated by a fast control loop (cannot be done via OBC) • Bus voltage is used as a state variable PhD Final Presentation

  50. Devices on the bus MPPT PhD Final Presentation

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