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More Satellite Orbits

More Satellite Orbits. Introduction to Space Systems and Spacecraft Design Space Systems Design. More Orbits. Importance of Orbits to Mission. When should you start analyzing orbits to satisfy mission requirements? Can the orbit effect any of the following in the mission design?

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More Satellite Orbits

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  1. More Satellite Orbits Introduction to Space Systems and Spacecraft Design Space Systems Design

  2. More Orbits Importance of Orbits to Mission • When should you start analyzing orbits to satisfy mission requirements? • Can the orbit effect any of the following in the mission design? • Revisit time of satellite to a point on earth? • Amount of data that can be transferred between the satellite and ground? • Space radiation environment? • Power generation for the satellite? • Thermal control on the satellite? • Launch costs? 2 Introduction to Space Systems and Spacecraft Design Space Systems Design

  3. More Orbits Orbit References 3 University of Idaho Introduction to Space Systems and Spacecraft Design Space Systems Design

  4. More Orbits Orbit References N Orbit Types GEO – Geosynchronous Orbit LEO – Low Earth Orbit S Around Equator N HEO – Highly Elliptical Orbit S 4 Introduction to Space Systems and Spacecraft Design Space Systems Design

  5. More Orbits Orbit With Respect to Sun Noon-Midnight (max eclipse) Inclined (partial eclipse) Sun Eclipse Terminator Orbit (no eclipse) - Twilight 5 Introduction to Space Systems and Spacecraft Design Space Systems Design

  6. More Orbits Orbit With Respect to Sun 6 Introduction to Space Systems and Spacecraft Design Space Systems Design

  7. More Orbits Orbit With Respect to Sun Equinox Earth's Axis Summer Winter Sun Equinox 7 Introduction to Space Systems and Spacecraft Design Space Systems Design

  8. More Orbits Spacecraft Orbital Velocity and Orbit Period Spacecraft Velocity Orbit Period 8 Introduction to Space Systems and Spacecraft Design Space Systems Design

  9. More Orbits Spacecraft Orbital Velocity and Orbit Period -2 What is ISS altitude? h = (150) (1.852) = 278 km = 17,142 mi/hour convert km/s mi/hour X (km/s) x 60s/m x 60m/hour x (1/1.6) mi/km = X (km/s) x 2250 mi/hour V = (7.739 km/s) x 2250 mi/hour = 17,142 mi/hour 9 Introduction to Space Systems and Spacecraft Design Space Systems Design

  10. More Orbits Equations to Remember Vcir = 631.3481 r-1/2 km/sec Vesc = 892.8611 r-1/2 km/sec r - is from center of the earth 10 Introduction to Space Systems and Spacecraft Design Space Systems Design

  11. More Orbits Changing Orbits 35,786 km V = 3.0727 km/s LEO – Low Earth Orbit from a shuttle launch – 280 km GEO N 280 km V = 7.738 km/s LEO How? S Want to Change Orbit LEO to GEO 11 Introduction to Space Systems and Spacecraft Design Space Systems Design

  12. More Orbits Changing Orbits How? 35,786 km V = 3.0727 km/s GEO • Change to a GTO (GEO transfer Orbit) • For GTO • Want: • Vp = 10.169 km/s • Va = 1.606 km/s • Circularize orbit • Need • V = 3.0727 km/s for GEO • Change V = 3.0727-1.606 = 1.4667 km/s • Burn at Va to increase V to 3.0727 km/s for circular orbit at GEO Va Vp LEO 12 Introduction to Space Systems and Spacecraft Design Space Systems Design

  13. More Orbits Other Ways to Change Orbits 13 Introduction to Space Systems and Spacecraft Design Space Systems Design

  14. More Orbits Other Ways to Change Orbits 14 Introduction to Space Systems and Spacecraft Design Space Systems Design

  15. More Orbits Orbits Perturbations Now you have an orbit for your satellite. • Will it stay where you put it? • Is there anything that will change the orbit once you have it there? 15 Introduction to Space Systems and Spacecraft Design Space Systems Design

  16. More Orbits Orbits Perturbations Special Effects on Orbits Equinox Winter Summer Sun Equinox What happens to the orbit plane as the earth rotates around the sun? 16 Introduction to Space Systems and Spacecraft Design Space Systems Design

  17. More Orbits Orbits Perturbations What effects the orbit? J2 effect J22/J3 effect Lunar gravity Solar gravity Solar pressure Atmospheric drag 17 Introduction to Space Systems and Spacecraft Design Space Systems Design

  18. More Orbits Orbits Perturbations Solar Pressure/Radiation 18 Introduction to Space Systems and Spacecraft Design Space Systems Design

  19. More Orbits Orbits Perturbations Solar Pressure/Radiation Using solar radiation for propulsion. Solar Sails 19 Introduction to Space Systems and Spacecraft Design Space Systems Design

  20. More Orbits Orbits Perturbations Atmospheric Drag Drag Coefficient 20 Introduction to Space Systems and Spacecraft Design Space Systems Design

  21. More Orbits Orbits Perturbations Atmospheric Drag Ballistic Coefficient Bc = K (Mass/Cross Sectional Area) How do they go through the atmosphere? Which stays in orbit longer – a bowling ball or a soccer ball of the same size? 21 Introduction to Space Systems and Spacecraft Design Space Systems Design

  22. More Orbits Orbits Perturbations Atmospheric Drag 22 Introduction to Space Systems and Spacecraft Design Space Systems Design

  23. More Orbits Orbits Perturbations Atmospheric Drag 23 Introduction to Space Systems and Spacecraft Design Space Systems Design

  24. More Orbits Orbits Perturbations Earth-moon tidal friction mechanism 24 Introduction to Space Systems and Spacecraft Design Space Systems Design

  25. More Orbits Orbits Perturbations Earth non-spherical effect East-West drift occurs because the equator is not perfectly circular, so satellites drift slowly towards one of two longitudinal stable points. 25 Introduction to Space Systems and Spacecraft Design Space Systems Design

  26. More Orbits Orbit References – GEO Station Keeping 26 Introduction to Space Systems and Spacecraft Design Space Systems Design

  27. More Orbits Orbits Perturbations Earth non-spherical effect Due to luni-solar perturbations and the ellipticity of the Earth equator, an object placed in a GEO without any station-keeping would not stay there. It would start building up inclination at an initial rate of about 0.85 degrees per year. After 26.5 years the object would have an inclination of 15 degrees, decreasing back to zero after another 26.5 years 27 Introduction to Space Systems and Spacecraft Design Space Systems Design

  28. More Orbits Orbits Perturbations Earth non-spherical effect N Inclination S What is the effect of this? 28 Introduction to Space Systems and Spacecraft Design Space Systems Design

  29. More Orbits Orbits Perturbations Inclination > 900 Orbit < 900 Orbit N N > 90o < 90o S S 29 University of Idaho Introduction to Space Systems and Spacecraft Design Space Systems Design

  30. More Orbits Orbits Perturbations Earth non-spherical effect Oblatness causes rotation counter clockwise Oblatness causes rotation clockwise N N I > 90o Prograde Orbit I < 90o 30 Introduction to Space Systems and Spacecraft Design Space Systems Design

  31. More Orbits Orbits Perturbations a a a a Earth non-spherical effect Sun Synchronous Orbit Orbit rotates to maintain same angle with sun Equinox Winter Summer Sun Equinox 31 Introduction to Space Systems and Spacecraft Design Space Systems Design

  32. More Orbits Orbits Perturbations Earth non-spherical effect Sun Synchronous Orbit 32 Introduction to Space Systems and Spacecraft Design Space Systems Design

  33. More Orbits Orbits Perturbations Earth non-spherical effect 33 Introduction to Space Systems and Spacecraft Design Space Systems Design

  34. More Orbits Orbits Perturbations Sun Synchronous Inclination 34 Introduction to Space Systems and Spacecraft Design Space Systems Design

  35. More Orbits Orbits Perturbations Earth non-spherical effect Special Molniya orbit has a stable orbit that is used by Russians to have high latitude communications – 2 satellites. 35 Introduction to Space Systems and Spacecraft Design Space Systems Design

  36. More Orbits Orbits Perturbations Earth non-spherical effect 36 Introduction to Space Systems and Spacecraft Design Space Systems Design

  37. More Orbits Orbits Perturbations Earth non-spherical effect 37 Introduction to Space Systems and Spacecraft Design Space Systems Design

  38. More Orbits Orbits Perturbations Earth non-spherical effect Effects are secular and accumulative Which are these? J2 effect J22/J3 effect Lunar gravity Solar pressure Atmospheric drag 38 Introduction to Space Systems and Spacecraft Design Space Systems Design

  39. More Orbits Orbits Perturbations Earth non-spherical effect • GEO satellites have drift due to non-spherical earth • East-west drift • North-south drift 39 Introduction to Space Systems and Spacecraft Design Space Systems Design

  40. More Orbits Orbit References – GEO Station Keeping 40 Introduction to Space Systems and Spacecraft Design Space Systems Design

  41. More Orbits Special Orbits Geostationary Orbit Geosynchronous Orbit N N S S Zero Inclination GEO Orbits Satellite appears stationery to earth observer Inclination GEO Orbits Satellite appears go N-S & EW in a figure 8 to earth observer 41 Introduction to Space Systems and Spacecraft Design Space Systems Design

  42. More Orbits GEO Orbits Characteristics 42 Introduction to Space Systems and Spacecraft Design Space Systems Design

  43. More Orbits GEO Orbits Characteristics N S What is the maximum latitude that a GEO satellite can be viewed? 43 Introduction to Space Systems and Spacecraft Design Space Systems Design

  44. More Orbits GEO Orbits Characteristics 44 Introduction to Space Systems and Spacecraft Design Space Systems Design

  45. More Orbits GEO Orbits Characteristics 45 Introduction to Space Systems and Spacecraft Design Space Systems Design

  46. More Orbits LEO Satellite Orbits 46 Introduction to Space Systems and Spacecraft Design Space Systems Design

  47. More Orbits LEO Orbits Characteristics Footprint 47 Introduction to Space Systems and Spacecraft Design Space Systems Design

  48. More Orbits LEO Orbits Characteristics 48 Introduction to Space Systems and Spacecraft Design Space Systems Design

  49. More Orbits LEO Orbits Characteristics 49 Introduction to Space Systems and Spacecraft Design Space Systems Design

  50. More Orbits LEO Orbits Characteristics What is elevation angle on ground antenna? How do you find Di? Use law of cosines. 50 Introduction to Space Systems and Spacecraft Design Space Systems Design

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