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Mission Analyses

Mission Analyses. Rafael Wisniewski Aalborg University. Contents. Introduction to the Course Short History to Spacecraft Engineering Environment and Orbits Spacecraft Configuration What orientation Elements of control Instrumentation Satellite Architecture Launchers

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Mission Analyses

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  1. Mission Analyses Rafael Wisniewski Aalborg University

  2. Contents Introduction to the Course Short History to Spacecraft Engineering Environment and Orbits Spacecraft Configuration What orientation Elements of control Instrumentation Satellite Architecture Launchers Reduction of Mission Cost Mission Examples: Ørsted and Cubesat Exercises

  3. Introduction • General plan for the course 9-9.30  A short summary of the teamwork 9.30-12.15 New Lectures 13-15.30 Team work on Given Excercises • Lectures • Mission Analysis • Spacecraft Engineering and Data Handling • Space Environment and Orbit Modelling • Power System • Spacecraft Modelling • Communication system • Spacecraft Autonomy • Attitude Estimation and Sensors • Course Evaluation

  4. Short History #1 • Sputnik-1 - USSR - (1957) First artificial satellite. • Explorer III - USA - (1958) Discovered Earth's radiation belt. • Pioneer 0 - USA Lunar Orbiter - (August 17, 1958) First stage exploded. • Pioneer 1 - USA Lunar Orbiter - (October 11, 1958) Failed to reach escape velocity. • Pioneer 3 - USA Lunar Flyby - (December 6, 1958) Failed to reach escape velocity. • Luna 1 - USSR Lunar Flyby - 361 kg - (January 2, 1959) Luna 1 was the first lunar flyby. It discovered the solar wind and is now in a solar orbit. • Pioneer 4 - USA Distant Lunar Flyby - 5.9 kg - (March 3, 1959) Space probe is now in a solar orbit. • Luna 2 - USSR Lunar Hard Lander - 387 kg - (September 12, 1959) Luna 2was the first spacecraft to impact the surface of the moon on September 14, 1959.

  5. Short History #2 • Vostok 1 USSR 1961, At the age of 27, Gagarin left the earth. It was April the 12th, 9.07 Moscow time (launch-site, Baikonur). 108 minutes later, he was back . • Luna 9 - Lunar Soft Lander - 1,580 kg - (January 31, 1966) Luna 9 landed on the lunar surface and retuned the first photographs from the surface. • Suerveyor 1- USA Lunar Soft Lander – 269 kg - (April 30, 1966 to 1967) Surveyor 1 was the first American soft landing on the lunar surface. • Apollo 8 - USA Lunar Manned Orbiter - 28,883 kg - (December 21-27, 1968) Crew: Frank Borman, James A. Lovell, Jr., William Anders. The crew undertook the first manned lunar fly-around and Earth return. The astronauts made 10 orbits of the moon. • Apollo 11 - USA Lunar Manned Lander - 43,811 kg - (July 16-24, 1969) Crew: Neil A. Armstrong, Edwin E. Aldrin, Jr., Michael Collins. Apollo 11 was the first manned lunar landing, which took place on July 20, 1969. The landing site was Mare Tranquillitatis at latitude 0°67' N and longitude 23°49' E. Armstrong and Aldrin collected 21.7 kilograms of soil and rock samples.

  6. The Earth – Our Planet in the Solar System Sun is giant thermo-nuclear fusion. Its atmosphere: chromosphere, corona The geomagnetic field an invisible shield

  7. Solar Activity

  8. Solar Cycle

  9. Overview of the Space Environment External Factors • Residual atmosphere (up to 800 km) - Drag causes orbit decay and reentry • Trapped protons - Degrades materials and electronic components, causes single- event effects in semiconductor components. • Trapped electrons - Degrades materials and electronic components • Solar protons from flares - Degrades materials and electronic components, causes single- event effects in semiconductor components. • Cosmic rays - causes single- event effects in semiconductor components. • Solar radiation: IR, Visible, UV, X- Ray - Degrades materials • Plasma from magnetic substorms - Causes spacecraft charging • Atomic oxygen - Erodes exposed surfaces Local Factors • Outgassing (vaporization of surface atoms) – decomposition of materials.

  10. Effects of South- Atlantic Anomaly Van Alen radiation belts UoSAT- 3 Single- Event Upsets

  11. Orbits – definitions #1 semi-major axis is half the longest distance across the ellipse period is the time to make one orbit mean motion is the frequency (revs per day) apogee - highest altitude perigee - lowest altitide eccentricity - orbit's deviation from a circle (shape)

  12. Orbits definitions #2 Ascending node is the satellite's South to North equatorial crossing Inclination is the orbital plane's tilt Right ascension of node is the angle from the Vernal equinox to the ascending node Argument of perigee is the angle between the acsending node and perigee True anomaly - angle from perigee to the satellite

  13. Orbits definitions #3 • The Earth rotation (0.465 km/s max.) is benificiary for prograde orbits • Launching eastward this velocity contributes not negligibly to the 7.9 km/s required for a LEO

  14. Types of Orbits • Geostationary Earth Orbit (GEO) • Low Earth Orbit (LEO) • Sun Synchronous • Earth Synchronous • Highly Elliptical Orbits (HEO) • Molniya • Nongeocentric Orbits • Lunar • Interplanetary

  15. GEO at altitude of 35,786 km

  16. Orbital Perturbations #1 Nodal regression used for Sun and Earth synchronous orbits

  17. LEO orbit - Ørsted Orbit Perigee/apogee: 620x850 Ascending node: 14:30 LT (drifting towards noon) Inclination: 96.65 degree

  18. Orbital Perturbations #2

  19. Molniya Molniya is russian kommunication orbit Apogee: Ca. 40000 km Perigee: Ca. 500 km Inclination: 63.4° Period: 11 timer 58 min. 02 sek. The disadvantage is large dose of radiation from high energy protons and electrons

  20. Spacecraft Subsystems • Structure and Mechanical System • Onboard Computer • Orbit and Attitude Control System • Power System • Onboard Communication • Command and Data Handling • Thermal Control • Ground Station • Payload

  21. Attitude Control Subsystem Torques Attitude Control actuator On-board computer Attitude sensor Error signal Commands Torques Ground control Controller Actuator Spacecraft Sensors Measured attitude Attitude

  22. Attitude Control Subsystem (ACS) • Sensors • Star tracker • Rate sensors • Magnetometer • Sun sensors • Earth horizon sensors • Actuators • Momentum/Reaction wheels • Magnetorquer coils/rods • Thruster • Libration Damper • Permanent magnet

  23. Attitude Control

  24. Solar efficiency

  25. Solar Efficiency

  26. Operational Phases Deployment of appandages Launch Initial acquisition Attitude stabilization Commissioning Science observation Science calibration Contingency operations

  27. ”Mission analysis is a structured method of ensuring that the mission success criteria's are clear and well understood.” & ”Mission analysis ensures, that the mission fulfils the overall success criteria's and at the same time stays within the project boundary conditions technical, political and financial.” & ”Mission analysis define the on- board subsystems configuration and basic subsystem requirements.” What is Mission Analysis ?

  28. Mission Analysis

  29. Mad Circle

  30. Initial Considerations – Mission Requirements and Constraints During the FIRST steps of the space systems engineering process we define mission requirements and constraints: • State the mission objective – why we do the mission • Identify mission users – who will benefit from or use the information produced by the mission • Create the operations concept – how will all the mission elements fit together • Identify mission constraints (Cost, schedule and performance)

  31. Initial Considerations – System Requirements During the SECOND step of the space systems engineering process we derive the system requirements • Review the constraints on mission architecture (Launch vehicle, orbit, operations, lifetime etc.) • Identify and characterize the mission subject – (eg. ”what” will the spacecraft instrument complex (payload) do ?) • Derive payload requirements • Derive orbital requirements • Determine basic spacecraft size and mass (envelope) • Identify potential launch vehicles • Derive operations network requirements (Groundstations).

  32. Initial Considerations - Subsystem definition During the THIRD step of the space systems engineering process we start defining the subsystems, and after a few iterations of the requirements etc, the design can begin. • Define ACS concepts (based on pointing, positioning and stability requirements) • Define reduncdancy concepts. • Define onboard subsystems (EPS, COM, CDH, Payload computer, On board SW, ACS etc. • Perform data flow analysis • Determine ground coverage and communications concept link budget • Determine needed power and power output analysis • Define thermal requirements and perform initial analysis • Determine structural requirements and perform initial analysis • Analyse radiation environment • RE- ITERATE ALL

  33. Mission Analysis in the Loop

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