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lecture12

# lecture12 - ECE2984 Lecture12:ORBITALMANEUVERS...

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ECE 2984 Lecture 12: ORBITAL MANEUVERS Joseph Baker (ECE Dept) Lecture 12: Orbital Maneuvers ECE 2984:Exploration of Space

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Exam 1 Results The exam was scored out of 65 points: MAXIMUM SCORE 62 MAXIMUM SCORE: AVERAGE SCORE: 47.8 STANDARD DEVIATION: 8.1 “APPROXIMATE” GRADE SCALE: A: >58 A : 54 58 B+: 52 54 B: 50 52 B : 48 50 C+: 46 48 C: 44 46 C : 42 44 Joseph Baker (ECE Dept) Lecture 12: Orbital Maneuvers ECE 2984:Exploration of Space D: 36 42 F: <36
Last Lecture LAST LECTURE: Newton’s Laws and Orbital Mechanics Orbital Elements THIS LECTURE: Ground Tracks Orbital Maneuvers: (1) Hohmann Transfer (2) Rendezvous (3) Orbit Plane Changes Joseph Baker (ECE Dept) Lecture 12: Orbital Maneuvers ECE 2984:Exploration of Space

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Equatorial Coordinates A spacecraft in Earth orbit is best described in the “Geocentric Equatorial Coordinate” (GEC) system: The Earth’s center is the “origin”. The equatorial plane is the “principal plane” The line from the Earth to the l i i h i i l vernal equinox is the “principal direction”. Joseph Baker (ECE Dept) Lecture 12: Orbital Maneuvers ECE 2984:Exploration of Space
Orbital Elements Kepler orbits can be concisely described by six numbers called the “orbital elements”: Eccentricity (e) Semimajor Axis (a) Inclination ( i) Right Ascension of Ascending Node ( Ω ) Argument of Perigee ( ω ) True Anomaly ( ν ) The first and second quantities define the shape and size of the orbit The third and fourth quantities define the orientation of the orbital plane The fifth quantity describes the orientation of the orbit in the orbital plane Joseph Baker (ECE Dept) Lecture 12: Orbital Maneuvers ECE 2984:Exploration of Space The sixth quantity describe the location of the object in the orbit

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Orbital Ground Tracks Joseph Baker (ECE Dept) Lecture 12: Orbital Maneuvers ECE 2984:Exploration of Space
Orbital Ground Tracks The “Ground Track” of a spacecraft is the projection of the spacecraft orbit onto the surface of the Earth. In other words, the ground track is the collection of points on the Earth where the spacecraft passes directly overhead. The ground track is useful for determining where and when the spacecraft can communicate with ground stations to download data and upload new commands. For an Earth imaging spacecraft the ground track provides information about the data coverage of the imaging system. An analysis of the ground track can also provide quick information about the orbital elements. Joseph Baker (ECE Dept) Lecture 12: Orbital Maneuvers ECE 2984:Exploration of Space

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Zero Inclination Orbit (i=0) For a satellite orbiting with an inclination angle i = 0 the an inclination angle i 0 the ground track is simply a straight line along the t equator.
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