A First-Order, Worldwide, Ionospheric, *z Time-Delay Algorithm - DTIC

AFCRtL-TR-75-0502 /

AIR FORCE SURVEYS IN GEOPHYSICS, NO. 324

A First-Order, Worldwide, Ionospheric,

*z

Time-Delay Algorithm

JOHN A. KLOBUCHAR

25 September 1975

Approved for public release: distribution unliitalto j

IONOSPHERIC PHYSICS LABORATORY PROJECT 4643

AIR FORCE CAMBRIDGE RESEARCH LABORATORIES

HAkSCOM AFB, MASSACHtojETTS 01731

AIR FORCE SYSTEMS COMMAND, USAF

Qualified requestors may obtain additional copies from the Defense Documentation Center. All others should apply to the National Technical Information Service.

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REPORT DOCUJMENTA TION PAGE

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AFICBL-T13-75-0302______

( ,. A7iRST-OI13DER, WVORLDWIDE, IONOSPHERIC,I

-~TIE-DLAYALGORITHTM

_______ ____AFSG,

No. 324 '

S -I.N HACT -4GRANT NUMBER(.)

9. PER70RMING ORGANIZATION NAME AND ADO 4ESS

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Air Force Cambridge Research Laboratories(LP143 iI

H-anscom AFB30

Massachusetts 017:31

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Air Force Cambridge Resoachabrti

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Approved for public releas~e; distribution unlimited.

17. DISTRIBUTION STATEMENT (.1 the .,.~ nt.,.d I. RAo 6 20. HIdI..~ from, Repo.,,)

16. SUPPL-EIAIENTARY NOTESV

19 KEY WORDS (Continue o roo-o aide it necessary and identfly by block number,)

'"

Total Electron Content Range Error Correction Ionospheric Time Delay

20

T RAC T f(Cont1nu- anry..

ld, 1n1 oo., and Id.nlI:y by bWork ... b.,)

14A firs t-order model algorithm designed to reduce ionospheric time-delay

errors by approximately 501o rins on a world-wide basis for single frequency users of the Global Positioning System/NA VSTAR is described. The algorithm was designed for greatest accuracy during times of day when ionospheric timedelay errors are expected to be largest. The algorithm is available in several options from one which requires only a monthly mean solar-flux value to one

which requires 9 daily or monthly update coefficients. Several approximations

DD I 1473 AN7

EDITIroN cF NOV 65 IS OBSOLETE

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20. Abstract (continued) Lalso are made in the geometry calculatinns to further reduce operational user computer storage and running time reqnirerrents.

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Contents

1. INTRODUCTION

5

2. CHARACTERISTICS OF IONOSPHERIC TIM-%E DELAY

6

3. DESIGN OF THE A LGORITHM%

6

4. MODEL ALGORITHAM

7

5. GEOMIETRY CALCULATION REQUIREXMENTS

9

5.1 Earth Angle

9

5. 2 Ionospheric Geodetic Latitude and Longitude

11

5.3 Conversion from Geodetic to Geomagnetic Latitude

12

5.4 Finding Local Time

12

5. 5 The Cbliquit? Factor

14

6. ALGO~iThMNI LAT :ITUE COEFFICIENTS

15

a. I. rhe DC T-rm

15

The Amplitude Term

18

6.3 The Phase of the Diurnal Period

18

6.4 The Diurnal Period

18

7. OPTION'S FOR MODEL INCORPORATION INTO THE SYSTEM

USER COMPUTER

19

1 Option]

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2 Option 2

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3 Option 3

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7.C4 Option 4

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8. DETERMS NING ALGORITHM LATITUDE COEFFICIENTS

OPERATIONALLY

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9. SUMMARY OF STEPS IN MODEL ALGORITHM

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3

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