Existing satellite radio emissions of the global positioning system were exploited as a resource for cost effective high accuracy geodetic measurements. System applications were directed toward crustal dynamics and earthquake research

Macdoran, P. F.

English

NASA Technical Reports Server

SATELLITE EMISSION RADIO JNTERFEROMETRIC EARTH SURVEYING (SERIES) 
P. F. MacDoran 
Jet Propulsion Laboratory 
California Institute of Technology 
ABSTR4CT 
The satellites of the Global Positioning System (GPS) offer an important new geodetic resource 
making possible a highly accurate portable radio geodetic system. A concept called Satellite Emis- 
sion Interferometric Earth Surveying (SERIES) makes use of GPS radio transmissions without any 
satellite modifications. By employing the techniques of very long baseline interferometry (VLBI) 
and its calibration methods, 0.5 to 3 cm three-dimensional baseline accuracy can be achieved over 
distances of 2 to 200 km respectively, with only a few hours of on-site data acquisition. The use 
of quasar referenced ARIES Mobile VLBI to establish a sparse fundamental control grid will pro- 
vide a basis for making SERIES GPS measurements traceable to the time-invariant quasar directions. 
Using four SERIES stations deployed at previously established ARIES sites, allows the GPS satel- 
lites apparent positions to be determined. These apparent positions then serve as calibrations for 
roving SERIES stations at unknown locations to determine their positions in a manner traceable to 
the quasars. Because this proposed radio interferometric configuration accomplishes its signal de- 
tection by crosscorrelation, there is no dependence upon knowledge of the GPS transmitted wave- 
form which might be encrypted. Since GPS radio signal strengths are lo5 stronger than quasar 
signals, a great reduction in telecommunications sophistication is possible which will result in an 
order-f-magnitude-less cost for a SERIES GPS station compared to a quasar based mobile VLBI 
system. The virtual all-weather capability of SERIES offers cost-effective geodetic monitoring 
with applications to crustal dynamics and earthquake research. 
This paper presents the results of one phase of research carried out at the Jet Propulsion Laboratory, California Institute of Tech- 
nology, under Contract No. NAS 7-100, sponsored by the National Aeronautics and Space Administration. 
403 
https://ntrs.nasa.gov/search.jsp?R=19800020337 2020-03-21T17:49:34+00:00Z
404 RADIO INTERFEROMETRY 
NAVSTAR 
GPS 
CIRCUIT 
Figure 1. SERIES-GPS. 
GOALS:TO EXPLOIT EXISTING SATELLITE RADIO EMISSIONS, ESPECIALLY THOSE OF THE 
GLOBAL POSITIONING SYSTEM (GPS), AS A RESOURCE FOR COST-EFFECTIVE HIGH ACCURACY 
GEODETIC MEASUREMENTS WITH EMPHASIS ON GEODYNAMICS APPLICATIONS. 
0BJECTIVES:TO DEVELOP AND DEMONSTRATE A SYSTEM CAPABLE OF SUB-DECIMETER THREE 
DIMENSIONAL ACCURACY ON BASELINES OF SEVERAL HUNDRED KILOMETERS WITH 
CHARACTERISTICS OF: 
LOW COST PER POINT MEASURED (<$2K) 
LOW COST FIELD EQUIPMENT (5SIOOKI 
SHORT TIME ON-SITE (< 2 HOURS) 
REAL-TIME OPERATIONS OPTION 
ALL-WEATHER OPERATIONS 
UNATTENDED STATION OPERATIONS OPTION 
USE OF GPS EMISSIONS WITHOUT KNOWLEDGE OF CODED WAVEFORMS 
GPS AND GEODETIC POSITIONS TRACEABLE TO TIME-INVARIANT QUASAR 
DIRECTIONS 
Figure 2. Satellite Emission Radio lnterferometric Earth Surveying (SERIES). 
WAVES OF THE FUTURE AND OTHER EMISSIONS 405 
ANTENNA (Z.&m2 PHASED-ARRAY,MICROPROCESSOR STEERED) 
RECEIVER TEMPERATURE 
BANDWIDTH SYNTHESIZED 
SATELLITE RADIO SIGNAL FLUX (eg. IO-,suw, ~~ ch.) 
DIGITAL DATA RECORDING RATE KASSETT RECORDER) 
OBSFRVATION TIME PER SATELLITE (4 ch. SAMPLING) 
27 db GAIN 
100 Kelvin 
1OMHz 
1.7xld Jansky 
10 kblsec 
1 set 
SIGNAL TO NOISE RATIO: 24:l 
TIME DELAY PRECISION: 190 psecf-6cmJ,lOOsec of DATAIPHASE RESOLVER/ 
PHASE DELAY PRECISION: lmm 
BASELINEPRECISIONLIMIT: D.~~~G~VEN~CIII~~~OFDATA 
Figure 3. SER I ES-GPS system configuration. 
l PHASE DELAY PRECISION PER SATELLITE OBSERVATION 
. TIME AND FREQUENCY lAflf = 2 x lo-? T = 4 sec. 1 
. TROPOSPHERE 
l DRY (SURFACE METEOROLOGY) 
l WET (LOW-COST WATER VAPOR RADIOMETER) 
. IONOSPHERE (RESIDUAL FROM DUAL L-BAND CALIBRATION) 
*SATELLITE POSITIONAL UNCERTAINTIES 
(ARIES NET OF 2 cm ACCURACY AT 200 KM SPACING: 
GPS SATELLITE RANGE TO 1 KM ACCURACY) 
BASELINE 
EQUIVALENT 
0.3cm 
0.3cm 
l.Ocm 
1.5cm 
l.Ocm 
l.Ocm 
ROOT SUM SQUARE 
PER 4 SECONDS: 2.4cm 
1 min. AVERAGE: 0.6cm 
Figure 4. Randon error sources for SER IES-GPS system 
(<lo0 km baselines). 
406 RADIO INTERFEROMETRY 
.SATELLlTE POSITIONAL UNCERTAINTIES: 
(ARIES NETOF2cmACCURACYAT2DDKM SPACING: 
GPS SATELLITERANGETOl KMACCURACY) 
-11 *TIME AND FREQUENCY(qf = 6x10 , 7=16sec) 
(INCOHERENTAVERAGING OF@ 16secDATA BLOCKS) 
.TROPOSPHERE 
*DRY (SURFACEMETEOROLOGY) 
.WET(LOW-COSTWATERVAPOR RADIOMETRY) 
.IONOSPHERE(RESIDUALFROMDUALL-BANDCALIB) 
BASELINE 
EQUIVALENT 
l.Ocm 
0.3cm 
l.Ocm 
l.5cm 
l.Ocm 
ROOTSUMSQUARE: 2.3cm 
COMBINED RANDOM AND SYSTEMATICERRORS: 2.4cm 
Figure 5. Systematic error sources for SERIES-GPS system 
(<IO0 km baselines). 
100 
QUASAR 
30 - TRACEABLE 
RELATIVE 
ACCURACY NETWORKS 
(mm) 10 - 
3- 
1 I I I I 
1 3 10 30 100 300 
BASELINELENGTH (Km) 
Figure 6. SERIES-GPS accuracy estimates. 
WAVES OF THE FUTURE AND OTHER EMISSIONS 
PINS II ENDED -4 
Mk 1 4TOR 
Figure 7. SERIES field station conceptual design. 
AXXXAXXXA / 
50km 
x x x x x x x x XT 
xxxxxxxxx’ 
x x xxx x x x x 
A XXXAXXXA 
A ARIES DERIVED FUNDAMEMAL CONTROL GRID 
X UNKNOWN SITES TO BE MEASURED 
OBSERVING STRATEGY 
1. FOUR SERIES STATIONS OCCUPY ARIES (4 SITES AND PROVIDE GPS SATELLITE 
POSITION CALIBRATIONS 
2. FOUR ROVING SERIES STATIONS OCCUPY UNKNOWN IX) SITES 
407 
Figure 8. SERIES network densification with quasar traceability. 
408 RADIO INTERFEROMETRY 
+ SERIES PORTABLE OR CONTINUOUSLY 
Figure 9. SERIES-GPS monitoring strategy for southern California. 
l GEODETIC NETWORK DENSIFICATION (20 to 100 km SPACINGS) 
. RAPID MULTI-STATION DEPLOYMENT INTO ZONES OF EARTHQUAKE PRECURSORS 
. UNATrENDED STATION GEODETIC MONITORING 
l EARTHQUAKE R)RECAST REGIONS 
l KNOWN HAZARDOUS AREAS (i.e., VOLCANOES, NUCLEAR WASTE DISPOSAL SITES) 
l GPS SATELLITE ANGULAR POSITIONS RELATIVE TO QUASAR TRACEABLE ARIES 
GEODETIC POSITIONS 
. MEASUREMENT PRECISION AND TEMPORAL RESOLUTION IN A REGIME BETWEEN 
CONVENTIONAL GEODESY AND SEISMOLOGY 
. OCEANOGRAPHY - OPEN OCEAN TIDES, GEODETIC CONTROL AND TRENCH MOVEMEN 
via BOTTOM SONAR TRANSPONDERS 
Figure IO. Applications SERIES-GPS. 
. RF CYCLE AMBIGUITY RESOLUTION 
l DUAL L-BAND IONOSPHERIC CALIBRATION AND HIGH PRECISION DELAY 
MEASUREMENTS 
. SAWRATION EFFECTS IN DATA SYSTEM DUE TO STRONG GPS SIGNALS 
. ASSUMPTION OF ARIES CONTROL FOR SERIES OPERATIONS - HOW OFTEN MUST 
ARIES REMEASUREMENTS BE DONE TO HOLD 2 cm ACCURACY AT 200 km SPACING? 
Figure 11. Challenges SER I ES-GPS. 


Satellite Emission Radio Interferometric Earth Surveying (SERIES)

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