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ATOMIC CLOCKS IN GPS SATELLITES

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We live in a world governed by precise time. In a world without greater accuracy many of today’s technological inventions would be impossible. We rely on high-precision clocks to navigate. GPS uses atomic clocks as its time base and all the satellites that are orbiting the world now have atomic clocks built into them. What sets atomic clock apart is that the inner rhythm of atom remains unchanged. Clocks that rely on their oscillation are the most accurate in the world. Specifically, a second was defined as the duration of 9,192,631,770 cycles of microwave light absorbed or emitted by the hyperfine transition of cesium-133 atoms in their ground state undisturbed by external fields.
This presentation details how GPS devices get their time more accurately using cesium atomic clock.

Published in: Engineering
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ATOMIC CLOCKS IN GPS SATELLITES

  1. 1. G.NARAYANAMMA INSTITUTE OF TECHNOLOGY & SCIENCE (FOR WOMEN) TOPIC: ATOMIC CLOCKS IN GPS SATELLITES. (under SATELLITE COMMUNICATIONS) A.V. Sridevi I btech E.T.M ID NO: 13251A1702 GNITS akondisridevi999@gmail.com
  2. 2. CONTENTS i. INTRODUCTION ii. TYPES OF ATOMIC CLOCKS. iii. WORKING PRINCIPLE OF CESIUM ATOMIC CLOCKS. iv. ATOMICS CLOCK’S IMPACT ON GPS SATELLITES. v. ADVANTAGES OF ATOMIC CLOCKS. vi. APPLICATION OF ATOMIC CLOCKS IN GPS SATELLITES. vii. EXAMPLES OF PRECISION TIMING IN GPS. viii. FUTURE SCOPE.
  3. 3. INTRODUCTION THE GLOBAL POSITIONING SYSTEM (GPS)- GPS is a satellite navigation system used to determine ground position and velocity (location, speed, and direction). * Satellite constellation: It consists of 24 satellites, designed to provide a continuous global positioning capability. * Trilateration: The GPS receiver computes the location using a mathematical principle called trilateration.
  4. 4. ATOMIC CLOCKS- * An extremely accurate type of clock which is regulated by the vibrations of an atom or molecule. * It is a clock that uses the resonance frequencies of atoms as its resonator. * The resonator is “regulated by the frequency of the microwave electromagnetic radiation emitted or absorbed by the quantum transition of an atom or molecule.” TIMES SCALE- * The second, is one of the fundamental units in International System of Units (SI) units. * A synchronization error of 1µs in a satellite clock will introduce an error of 300m in the pseudorange with a corresponding error in the estimate position. TYPES OF ATOMIC CLOCKS- i. Cesium atomic clocks ii. Hydrogen atomic clocks iii. Rubidium atomic clocks. CESIUM ATOMIC CLOCK- 1)A standard second was adopted based on the frequency of a transition in the Cs-133 atom. 2)A cesium atom always resonates at the same known frequency, that is what makes atomic clocks so precise.1 second = 9,192, 631,770 cycles of the standard Cs-133 transition . 3)Hence the most accurate atomic clocks available today use the cesium atom .
  5. 5. WORKING PRINCIPLE OF CESIUM ATOMIC CLOCKS WORKING- It consists of Oven -Liquid cesium is heated to a gaseous state. Electromagnets- the field splits the cesium into two beams. U shaped cavity- The lower energy state reacts with microwaves of 3.26cmof wavelength. Detector and quartz oscillator. PRINCIPLE: The frequency of the microwaves is adjusted until the electron multiplier output current is maximized, constituting the measurement of the atoms' resonance frequency.
  6. 6. ATOMIC CLOCK’S IMPACT ON GPS SATELLITES. I. Each GPS satellite contains multiple atomic clocks that contribute very precise time data to the GPS signals. II. GPS receivers decode these signals, effectively synchronizing each receiver to the atomic clocks. III. This enables users to determine the time to within 100 billionths of a second. GPS time synchronization: I. But the accuracy of an atomic clock depends on two factors. The first factor is temperature of the sample atoms. II. The second factor is the frequency and intrinsic width of the electronic transition.
  7. 7. ADVANTAGES OF ATOMIC CLOCKS  Proper synchronization of communication systems and other critical infrastructure.  Improved network management and optimisation. APPLICATIONS OF ATOMIC CLOCKS IN GPS SATELLITES • Banking: To synchronize their network computers. • Large and small scale businesses can track,update and manage multiple transcactions made by customers. • Power companies: use GPS based time synchronization devices in power plants and substations to analyze the exact location of a powerline break.
  8. 8. EXAMPLES OF PRECISION TIMING USING GPS  The U.S Federal Aviation Administration(FAA) uses GPS to synchronize reporting of hazardious weather.  Investment banking firm uses GPS to guarantee their transactions are recorded simultaneously at all offices around the world.  Major Pacific Northwest utility company makes sure their power is distributed at just the right time along their 14,797 miles of transmission lines.
  9. 9. FUTURE SCOPE:  Recent improvements in cesium clock include replacement of the state- selection magnets with laser beams, which can select and detect the required transition with greater efficiency and hence less noise from, the radiating atoms.  JILA ‘s Strontium atomic clock: The world’s most accurate atomic clock which would neither gain nor loose a second in more than 200 million years.It ticks 430 million times per second.  As GPS becomes more modernized, further benefits awaits users.
  10. 10. THE END - Life without God is like driving without GPS making all the wrong turns, in the wrong lane taking double the time to get on the right track.

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