McGraw-Hill & US Space Command 1 IT 284 Unit 8 Seminar

McGraw-Hill & US Space Command 2 Navigation * Stars at fixed locations (celestial sphere) Stars at fixed locations could be used to locate position on the earth The octant and sextant Astrolabe (~400) Octant (1731) Sextant (1759)

McGraw-Hill & US Space Command What Stars Tell Us 3 Every Celestial Body has a Ground Point - GP Sextant Angle GP Nautical Almanac had GP for all times every day

McGraw-Hill & US Space Command Taking a Sight 4 What Time is it? What Angle is it? What Body are we Looking at? Sextant Measures Angles - Nothing More!

McGraw-Hill & US Space Command Sir Isaac Newton , London, England – Laws of Motion – Universal Law of Gravity Johannes Kepler , Regensburg, Germany – Three Laws of Planetary Motion 5 Newton & Kepler’s study of our Universe Laid the Foundation of Orbital Mechanics Johannes Kepler Sir Isaac Newton

McGraw-Hill & US Space Command Laws of Planetary Motion 6

McGraw-Hill & US Space Command Law of Planetary Motion 7

McGraw-Hill & US Space Command Law of Planetary Motion Ratio of the squares of the revolutionary periods for two planets is equal to the ratio of the cubes of their semimajor axes. 8

McGraw-Hill & US Space Command Orbits – The Big Picture 9 Orbits are “racetracks” that satellites “drive” around Earth A satellite’s orbit is fixed in space The Earth rotates under the orbit But the satellite’s orbital plane stays fixed

McGraw-Hill & US Space Command 10 Figure Satellite orbits

McGraw-Hill & US Space Command Space Missions Operating Satellites on Orbit 11 Boeing 702 Expanded View

McGraw-Hill & US Space Command Basic Elements of a Satellite 12 Payload + Vehicle or “Bus” = Satellite

McGraw-Hill & US Space Command Satellite Subsystems 13 Power To Operate in Space Thermal Heating & Cooling Structural To Protect the Satellite Communications To Operate the Satellite Attitude Determination and Control To control positioning Navigation, Guidance and Control To safely maneuver in space

McGraw-Hill & US Space Command Operating Satellite Constellations You need Ground Processing and Communications Links! 14

McGraw-Hill & US Space Command 15 The Space Environment A Tough Place to Operate!

McGraw-Hill & US Space Command Orbital Maneuvers 16 Perturbations alter an Orbit: Atmospheric Drag – “Scraping” the Earth’s atmosphere Earth Oblateness -- Causes north/south wandering of GEO satellites Solar Effects – Radiation, particle discharge, geo-magnetic storms Third Body Affects – Gravitational pull Maneuvers are required to maintain an orbit V Lunar Gravity Earth Gravity Solar Gravity

McGraw-Hill & US Space Command 17 Figure Satellite categories

McGraw-Hill & US Space Command 18 Figure Satellite orbit altitudes

McGraw-Hill & US Space Command 19 Figure Triangulation

McGraw-Hill & US Space Command 20 Figure GPS

McGraw-Hill & US Space Command Global Positioning System 21 GPS CONSTELLATION Precise worldwide position, speed, and time 6 orbital planes 4 satellites in each plane 24 satellite constellation Medium Earth Orbit (12,500 miles from Earth)

McGraw-Hill & US Space Command Geodetic Datum Defines the size and shape of the earth Origin and orientation of the coordinate systems Branch of mathematics dating back to Babylonian times (3500 BC) Types include Horizontal, Vertical and Complete 22

McGraw-Hill & US Space Command 23 Figure Iridium constellation

McGraw-Hill & US Space Command 24 Satellite Constellations Iridium – First LEO Satellite communications system 66 satellite constellation (plus 14 spares) Provides worldwide phone coverage Iridium Low Earth Orbit Constellation

McGraw-Hill & US Space Command What is Handover? Leo Satellites circulate the Earth at a constant speed. Coverage area of a LEO satellite changes continuously. Handover is necessary between end-satellites. 25

McGraw-Hill & US Space Command Iridium Network 26

McGraw-Hill & US Space Command Iridium Network (cont.) 4.8 kbps voice, 2.4 Kbps data TDMA 80 channels /beam 3168 beams globally (2150 active beams) Dual mode user handset User-Satellite Link = L-Band Gateway-Satellite Link = Ka-Band Inter-Satellite Link = Ka-Band 27