Outline

9

Clocks/ Time in Satellite Navigation

  1. Summary

  1. Use of Clocks in Satellite Positioning

  1. Clock’s Evolution

  1. Future Plans of Clocks/ Time in Satellites

Clocks/ Time in Satellite Navigation

Summary

It has always been important for individuals to determine theirposition from different parts of the world. Early marines relied onangular calculations to extraterrestrial bodies like stars and thesun to measure their location. However, in subsequent yearsscientists discovered time in satellite navigation, which laid thebasis for advanced systems like the GPS. The use of clocks insatellite positioning commenced with the launch of “Sputnik”(Taubes 3). The Soviet Union is responsible for launching the“world’s first artificial space satellite”, which was launchedin 1957 (Parkinson 11).

After the “Sputnik”, the satellite clock has evolved, undergoingsignificant improvements. In 1972, the Navy was in the process ofdeveloping a new satellite clock, referred to the “Timation”. Athird important forebear of GPS was 621B, invented by the AmericanAir Force. By 1972, the 621B had already depicted the function of anew kind of satellite ranging signal founded on pseudorandom noise(PRN). Triumphant aircraft examinations had been conducted by the AirForce at Holloman Base to illustrate the PRN method. In 2014, saw thelaunch of NPL time, which provides a specific time signal that can betraced to Universal Time (UTC). The expectations of GPS are virtuallylimitless. The system avails a new, exceptional and immediatelyaccessible address for each square yard of the planet’s surface.

As advent as well as restored international and regional space basednavigation structure develops, interoperability proves to be a majorGNSS future. Development in satellite clocks promises to reduce theproblems of creating envisaged satellite clock improvements. Inprospect, it would be good to have receivers that are capable ofreceiving many satellites during intricate scenarios.

The likelihood of moving in space encouraged plans on how tonavigate from space. Innovators attempted diverse strategies todetermine the possibility of using radio transmissions from orbitingsatellites in validating locations on Earth. This resulted in thefinding that time from particular satellite clocks, conveyed viaradio signals, made it possible to tell location. This resulted inthe creation of GPS (Global Positioning System). Every GPS satellitecomprises of numerous atomic clocks, which provide specific time datato GPS signals. An atomic clock regards to very precise kind oftimepiece in the globe, formulated to calculate time depending onvibrations in atoms. The clocks are employed in the navigation ofsystems, which need extreme precision. Various atomic clocks situatedin different places all through the globe are employed together todetermine Coordinated Universal Time (UTC).

Use of Clocks in Satellite Positioning

In the 1920s, radio navigation was introduced, which relied on radiosthat made it possible for navigators to establish the position oftransmitters at shore (Pace et al. 237). After, the advancement ofartificial satellites enabled the transmission of accurate,noticeable radio navigation signals. It laid the foundation for adeveloped system, GPS (Global Positioning System) referring to thegeneral phrase for satellite navigation systems, which wouldafterward transform navigation (Pace et al. 237). The satellite clockwas then invented and used in satellite navigation.

The use of clocks in satellite positioning commenced with the launchof “Sputnik” (Taubes 3). The Soviet Union is responsible forlaunching the “world’s first artificial space satellite”, whichwas launched in 1957 (Parkinson 11). The satellite resembles a beachball in size and would orbit the earth in 98 minutes. The inventionof the “Sputnik” starts in 1952 following the decision by the“International Council of Scientific Union” to declare the firstof July 1957 to December the following year the “InternationalGeophysical Year, IGY” (NASA).

In 1955, the White House had made public its goal of launching anorbiting satellite during the IGY (NASA). As a result, theysought proposals from several administrative research groups to takepart in the creation of the orbiting satellite. During the IGY, the“Sputnik” was launched becoming the best proposal (Parkinson109). The satellite was accurate at the time. It had regular featuresapparent through the radio signal it radiated. Most fascinating werethe apparent alterations in Doppler shift that were a result of overflight (Parkinson 11). Another basis for the satellite’s accuracyis that it adhered to Kepler’s laws on astrodynamics. The movementof the earth eliminated any uncertainty in the solution. The outcomeswere reliable and straightforward in principle (Parkinson 11).

Clock’s Evolution

After the “Sputnik”, the satellite clock has evolved, undergoingsignificant improvements. Researchers from the “John HopkinsApplied Physics Laboratory” continued to study the signals from the“Sputnik” (Getting 36). They created a computer program thatmeasured the first satellite clock. It was possible to use thecomputer program in determining the uncertain position of a radioreceiver when using the similar kind of Doppler measurements (Madry7). As a result, it was possible to develop satellites for the solepurpose of determining location leading to the invention of thetransit navigation idea.

In 1972, the Navy was in the process of developing a new satelliteclock, referred to the “Timation” under guidance from RogerEaston, Naval Research Laboratory (Xu et al. 306). The satelliteswere basically employed in informing the specific time and transferamid different Earth points. A third important forebear of GPS was621B, invented by the American Air Force. By 1972, the 621B hadalready depicted the function of a new kind of satellite rangingsignal founded on pseudorandom noise (PRN), a signal that satisfiesthe tests for statistical unpredictability (Wolf and Gerard 4405).The satellite clock made it possible for all satellites to broadcaston the similar nominal frequency as well chosen PRN coding sequenceswere almost uncorrelated.

In 1973, in search of a foolproof technique of satellite navigation,the Department of Defense, following consensus at the Pentagonresulted in the idea of GPS. The GPS comprises of 24 Navstarsatellites constructed by Rockwell International (Taubes 4). In 1978,the initial operational GPS satellite was instigated reachingcomplete 24-satellite capacity in 1993 (Taubes 4). In 1996, realizingthe relevance of GPS to citizen users and the military, then Americanpresident Bill Clinton ordered a policy that declared GPS a dual-usesystem (Han et al. 33). Selective availability was stopped in 2000permitting users, other than the American military to get completequality signal.

NIST “National Institute of Standards and Technology” scientistsdepicted a chip-scale atomic clock in 2004. The scientists supposethat the clock is a hundredth the size of others. Hence, the clockbecame appropriate for battery-driven uses. The inner working of theclock was minute and consumed fewer watts making it possible for theclock to be employed on batteries. In 2011, UK’s basic frequencystandard is declared an accurate timekeeper globally (Margolis 83).In 2014, saw the launch of NPL time, which provides a specific timesignal that can be traced to Universal Time (UTC). NPL time is aproficient time distribution service, which is independent of GPS. Itis derived from UK’s National Timescale, that is founded oncontinuous operative atomic clocks and caesium fountain, which hasled to the insight of SI second. In addition, NPL time is precise toa second in one hundred and fifty eight years. It avails resilient aswell as great ability networking among trading centers that haveatomic clock servers.

Current precision timekeeping technologies depend on various diversekinds of atomic clocks, however, in prospect, other clocks may beemployed, every clock optimized for diverse uses. NIST invests invarious atomic clock technologies since the outcomes of scientificstudy cannot be predicted, and since diverse clocks are positionedfor diverse uses. Previous developments in the performance of atomicclock have made possible the development of technologies like GPS andnavigation making them commonplace. This means that almost everyindividual that carries a cell phone employs GPS (Ost 3). NIST atomicclocks are employed for numerous uses, involving direction of spaceprobes.

The “Financial Industry Regulatory Authority” mandates thestamping of all electronic transaction in time that can be traced toNIST (Ost 3). NIST has an internet time service that makes itpossible for the public as well as different users to harmonize theinternal clocks of their computers with the time of NIST. The recordperformance that is achieved by using atomic clocks has led toscientific study. NIST clocks have led to record measurements ofprobable alteration in nature’s basic constants (Ost 3).

Future Plans of Clocks/ Time in Satellites

The expectations of GPS are virtually limitless. The system avails anew, exceptional and immediately accessible address for each squareyard of the planet’s surface. It is possible that computers willnot only be employed in determining someone’s street address, townor state, but also through latitude and longitude (Taubes 8). Asadvent as well as restored international and regional spacebasednavigation structure develops, interoperability proves to be a majorGNSS future. Global collaboration on satellite navigation matters isa main concern by the American administration. The country progressesto be actively involved in bilateral relations with other worldleaders.

Currently, the “caesium fountain atomic clock” is capable ofmeasuring at a preciseness of more than a hundred years (NationalPhysical Laboratory). The coming generation of atomic clocksemploying laser-cooled atoms or ions that are trapped, ought toattain accuracies close to a hundred times better compared to thecurrent greatest atomic clocks. This is corresponding to attaining orlosing not more than a second. According to Hein et al. (64) it ispossible for revolutionary advancements to happen in the field ofclocks. The atomic clocks are possibly a crucial aspect in attaininghigh performance GNSS. Since the growth cycle in clock technology isclose to seven years, advent technologies may be present on orbit intwenty years (Hein et al. 64). Development in satellite clockspromises to reduce the problems of creating envisaged satellite clockimprovements. In prospect, it would be good to have receivers thatare capable of receiving many satellites during intricate scenarios.

Works Cited

Borregaard, Johannes, and AndersSøndberg Sørensen. Efficient atomic clocks operated with severalatomic ensembles.&nbspPhysicalreview letters&nbsp111.9(2013): 09-82.

Getting, Ivan. Perspective/navigation-the global positioning system. Spectrum,IEEE&nbsp30.12 (1993): 36-38.

Han, S-C., J. H. Kwon, and C.Jekeli. Accurate absolute GPS positioning through satellite clock error estimation.&nbspJournalof Geodesy&nbsp75.1(2001): 33-43.

Hein, Gunter., Rodriguez, Jose., Wallner, Stefan., Pany, Thomas.,Eissfeller, Bernd and Hartl, Philipp. Envisioning a Future GNSSSystem of Systems. Working Papers (2007): 64-72.

Kouba, Jan and Tim, Springer. NewIGS station and satellite clock combination.&nbspGPS Solutions&nbsp4.4(2001): 31-36.

Parkinson, Bradford W. Origins, Evolution and Future of SatelliteNavigation. Journal of Guidance, Control and Dynamics20.1(1997): 11-25.

Madry, Scott. Global NavigationSatellite Systems.&nbspGlobalNavigation Satellite Systems and Their Applications.Springer New York, 2015. 1-8.

Margolis, Helen. Timekeepers of thefuture.&nbspNaturePhysics&nbsp10.2(2014): 82-83.

NASA. Sputnik and the Dawn of the Space Age, 10 Oct. 2007.Web. 30 Nov. 2015.

&lt http://history.nasa.gov/sputnik/&gt

NPL NationalPhysical Laboratory. 60 Yearsof the Atomic Clock. Web. 30 Nov. 2015.

&lthttp://www.npl.co.uk/60-years-of-the-atomic-clock/&gt

NPL NationalPhysical Laboratory. AtomicTimeline. Web. 30 Nov. 2015.

&lthttp://www.npl.co.uk/60-years-of-the-atomic-clock/timeline/&gt

Ost, Laura. A New Era for Atomic Clocks. NIST, (4 Feb. 2014):1-3.

Pace, Scott., Frost, Gerald., Lachow, Irving., Frelinger, David.,Fossum, Donna., Wasse, Donald and Pinto, Monica. The GlobalPositioning System: Assessing National Policies. Critical Technologies Institute (1995): 11-361.

Parkinson, Bradford W., et al. Ahistory of satellite navigation. Navigation42.1 (1995): 109-164.

Taubes, Gary. The Global Positioning System: The Role of AtomicClocks. National Academy of Sciences (1997): 1-8.

Wolf, Peter, and Gerard Petit.Satellite test of special relativity using the global positioning system.&nbspPhysicalReview 56.6 (1997):4405.

Xu, Bo, Ying Wang, and Xuhai Yang.Navigation satellite clock error prediction based on functionalnetwork.&nbspNeuralprocessing letters&nbsp38.2(2013): 305-320.