Starlette Satellite Laser Ranging (SLR) data were used, along with several other satellite data sets, for the solution of a preliminary gravity field model for TOPEX, PTGF1. A further improvement in the earth gravity model was accomplished using data collected by 12 satellites to solve another preliminary gravity model for TOPEX, designated PTGF2. The solution for the Earth Rotation Parameter (ERP) was derived from the analysis of SLR data to Starlette during the MERIT Campaign. Starlette orbits in 1976 and 1983 were analyzed for the mapping of the tidal response of the earth. Publications and conference presentations pertinent to research are listed

Schutz, B. E.

Shum, C. K.

English

NASA Technical Reports Server

tk99 GEOPHYSICAL PARAMETERS FROM THE ANALYSIS 
OF LASER RANGING TO STAFUTE 
NASA GRANT NAG5-757 
Annual Research Technical Report 
for the period 
March 15,1986 -March 14,1987 
Submitted to 
Ms. G. Wiseman 
NASA Goddard Space Flight Center 
Mail Code 200 
Greenbelt, MD 20771 
Center for Space Research 
The University of Texas at Austin 
Austin, Texas 78712 
(512) 471-1356 
principal Investigator: 
Dr. B. E. Schutz 
Co-Inves tigator: 
Dr. C. K. Shum 
May 29, 1987 
(NASA-CB-1805S6) GEOPHYSICAL PARALIBTEEIS 187-2 1964 
FROfl TEE A N A L P S I S  OF LASER R A E G I I G  TO 
SIALBLETTE Annual Besearch lechnical  Report, 
15 War, 1986 - 14 Mar, 1987 ('Ieras Univ , )  Unclas 
12 p Avail: H I S  HC A02/flF A G l  C S C L  22A 63/13 0071469 
-- - 
https://ntrs.nasa.gov/search.jsp?R=19870012551 2020-03-20T11:40:08+00:00Z
GEOPHYSICAL PARAMETERS FROM THE ANALYSIS 
OF LASER RANGING TO !3TARLEZTE 
NASA G m t  NAGS-757 
SUMMARY 
The University of Texas Center for Space Research (UTKSR) research efforts under NASA 
Grant NAGS-757 during the time period from March 15, 1986, through March 14, 1987, have 
concentrated on the following areas: 
0 Refining force, earth orientation and measurement models for precise determination of 
Starlette orbits, 
0 Preparing, cataloging, pre-processing, and processing Starlette laser ranging data (both quick- 
look and full-rate data) from 1976 to the present, 
0 Determining earth rotation parameters ( E m )  using satellite laser ranging (SLR) data to 
Starlette, 
0 Precise orbit determination for a long and continuous three-year orbit spanning from 1983 to 
1985 using quick-look data, 
0 Mapping the tidal response of the earth using Starlette data, 
Determining observed seasonal variations from Starlette node residuals and comparing with 
other independently derived parameters. 
Copies of abstracts for some of the publications and conference presentations are included in the 
appendices. 
STARLETTE MODEL REFINEMENT 
Starlette SLR data were used, along with several other satellite data sets, for the solution of a 
preliminary gravity field model for TOPEX, PTGF1. IJTGFl is a significant improvement over the 
1 
GSFC Starlette-tailored field, PGS-1331, in terms of orbit determination on Starlette. FTGFl is 
fitting 5-day Starlette orbits with a range residual under 25 cm rms, and a 92day long arc for 
Starlette using n G F 1  was computed to fit SLR data at range residuals of 1 m rms, thereby enabling 
identification of signals produced by geophysical phenomena. 
A further improvement in the earth’s gravity model was accomplished using data collected by 12 
satellites to solve for another preliminary gravity model for TOPEX, designated PTGF2. PTGF2 
shows slight improvement over PTGFl in terms of Starlette orbit fits. 
A nominal model for absolute plate motion has been adopted. The Minster and Jordan AM1-2 
model, in which the relative motions are relative to a mantle-fixed frame through the use of 
presumably stationary hot spots, has been implemented to comprise part of the Conventional 
I erresniai System ( C i s  j. An improved and consistent poiar morion modei ana the corresponding 
laser tracking station C O O K ~ ~ M ~ ~ S  (CSR 8604) have been derived incorporating the AM1-2 plate 
motion model. 
- 
The atmospheric drag model used for Starlette orbit computation is the French Density 
Temperature Model (DTM). Preliminary evaluation of the DTM model versus the Jacchia models 
(1971, 1977) indicates that the DTM performs more reasonably over a variety of altitudes and 
meteorological phenomena. 
STARLETTE DATA AND ORBIT ANALYSIS 
Quick-look Starlette data from 1983 to the present have been processed on a regular basis. Full- 
rate data from 1976 through 1977 have been processed and compressed into normal points. The 
quick-look data during and after the MERIT Campaign period were collected by more than 20 laser 
stations worldwide and generally have an average of about 6 1 0  observation passes per day. Full- 
rate data from 1980-83 have been preprocessed. Efforts are underway to process and edit the data 
and to compress into normal points. 
2 
Long, continuous and dynamically consistent Starlette ephemerides have been precisely 
determined. These orbits include a one-year arc during 1976-77 and a three-year long an: during 
1983-85 using FTGF1. Quick-look normal points were used in the computation of the 1983-85 
three-year arc. The range residual rms for the 1976-77 orbit is -1 m and the 1983-85 orbit is -4 m. 
The three-year arc is both computationally expensive and difficult to determine precisely. Efforts are 
underway to investigate the feasibility of extending the h e - y e a r  orbit for the examination of 
interesting geophysical parameters. 
DETERMINATION OF EARTH ROTATION PARAMETERS 
The solution for the ERP has been derived from the analysis of SLR data to Starlette during the 
MERIT Campaign from August 30, 1983, to December 2, 1984. This activity has been pursued as 
an evaluation of the quality of the current force models. A covariance analysis indicates that the 
accuracy of the Starlette ERP solution is limited primarily by emrs  in the earth's gravity field 
model. The previous Starlette ERP solution computed using the PGS-1331 gravity field has a 
weighted rms difference compared with the Lageos ERP solution of about 15 mas for the polar 
motion coordinates, x and y. The impmved ERP solution using the PTGFl gravity field has a 
weighted rms difference compared with the Lageos solution of about 5 mas for x and y, thereby 
providing a measure of the quality of this new gravity field. 
MAPPING OF TIDAL RESPONSE 
Starlette orbits in 1976 and 1983 were analyzed for the mapping of the tidal response of the 
earth. Long period perturbations due to Ocean tide mismodeling on the StarIette orbit were analyzed. 
Ocean tidal constituents were determined using precisely determined Starlette long arcs. The 
uncertainties for most of the estimated tidal coefficients are less than 0.1 cm. The effective k2  values 
of the ocean tide parameters derived from the 1976-77 long-arc analysis differ from Schwiderski 
3 
Ocean tide model by roughly 0.003 for diurnal and semidiurnal tides. Theoretical values for the 
lunar deceleration have been computed using the estimated semidiurnal and diurnal tides. The 
values obtained are in good agreement with those obtained by other investigators. 
Using the 1976-77 one-year arc and the 1983-85 three-year arc, the observed nontidal seasonal 
variations due to the changes in the earth's even zonal harmonics have been computed. Annual and 
semiannual seasonal variations were determined from the four one-year Starlette node residuals. 
These Starlette-observed parameters were tabulated and compared with the values derived using 10- 
year Lageos data as well as values determined by independent investigators using air pressure and 
water mass redistribution data. Although the Starlette-determined seasonal amplitudes are high 
compared to the values determined using the meteorological data, the phases are in general 
dgiCciiiciiL 
PUBLICATIONS/PRESENTATIONS 
The following is a list of publications and conference presentations pertinent to research 
activities under NASA Grant NAGS-757: 
0 Starletre Dura Analysis, C. K. Shum. Presented at the Sixth UT/GSFC TOPEX Gravity Model 
Development Meeting held at The University of Texas at Austin, April 8-10, 1986. 
0 Earth Rotation Solution From Starletre Orbit Analysis, B. E. Schutz, M. K. Cheng, C. K. Shum, 
B. D. Tapley, and R. J. Eanes. To be submitted for publication in the Journal of Geophysical 
Research, May 1987. A copy of the abstract is attached in Appendix A. 
0 Long Period Perturbations in Starletre Orbit and Tide Solution, M. K. Cheng, B. E. Schutz, C. 
K. Shum, B. D. Tapley, and R. J. Eanes. To be submitted for publication in Bulletin 
Geodesique, May 1987. A copy of the abstract is attached in Appendix B. 
Starlette Geodynumics, C .  K. Shun. Presented at the 12th Crustal Dynamics Principal 
Investigators Meeting at the Jet Propulsion Laboratory, March 2626,1987. 
4 
Geophysical Parameters From the Analysis o f h e r  Ranging to Starlette, C.  K .  Shum, B. E. 
Schutz, M. K. Cheng, R. J. Eanes, and B. D. Tapley. EOS Trans. AGU, 68(16), April 21,1987. 
A copy of the abstract is attached in Appendix C. 
5 
APPENDIX A 
EARTH ROTATION SOLUTION FROM 
STARLETTE ORBIT ANALYSIS 
B. E. Schutz, M. K. Cheng, C. K. Shum, 
R. J. Eanes, and B. D. Tapley 
Center for Space Research 
The University of Texas at Austin 
Austin, Texas 787 12 
ABSTRACT 
The solution for the Earth Rotation Parameters (ERP), which include the polar motion 
coordinates, x and y , and the length of the day (UD), have been obtained from the analysis of the 
satellite laser range (SLR) data to Starlette collected during the MERIT Campaign from 30 August 
1983 to 2 December 1984. The Starlette ERP solutions have been compared with the solutions 
derived from SLR to Lageos, and the weighted rms about the mean of the difference between these 
solutions are 17 milliarcseconds (mas), 12 mas and 0.7 milliseconds (ms) for Ax, Ay and ALOD, 
respectively. A covariance analysis indicates that the accuracy of the Starlette ERP solution is 
limited primarily by emrs in the earth’s gravity field model. In particular, the first order 
geopotential coefficients produce a systematic perturbation in the solutions for x and y with a 
maximum value up to 29 mas and a dominant period of 74 days. With the improvement of the 
Starlette force model by simultaneous estimation of selected geopotential coefficients and ocean tide 
parameters, the weighted rms of the Starlette-Lageos differences has been reduced to 9 mas and 6 
mas for Ax and Ay, respectively. Using an improved gravity field recently developed by the 
University of Texas Center for Space Research (UTKSR), the weighted rms differences betwen 
Starlette and Lageos ERP solutions have been further reduced to 6 mas and 4 mas for hx and Ay, 
respectively. These results show that a significant improvement of the ERP solution from Starlette 
can be achieved through further refinements in the earth’s gravity field and tide model and that a 
precision of <5 mas in x and y coordinates of the ERP derived by Starlette is feasible. 
APPENDIX B 
LONG PERIOD PERTURBATION IN STARLE’ITE 
ORBIT AND TIDE SOLUTION 
M. K. Cheng, B. E. Schutz, C. K. Shum, 
R. J. Eanes, and B. D. Tapley 
The University of Texas at Austin 
Center for Space Research 
Austin, Texas 787 12 
ABSTRACT 
Long, continuous and dynamically consistent orbits have been precisely determined using 
satellite laser ranging (SLR) data to Starlette for the one-year periods for 1976-77 and 1983-1984. 
The data have been analyzed to show significant long period perturbations in Starlette orbit due to 
e m r  in the earth’s gravity field and the modeling of its tidal response. The residual rms of laser 
range data have been reduced from 5 m to 2 m over the one-year orbit during 1976-1977 by 
simultaneous estimation of the second degree ocean tide constituents SA, SSA and K1 (degrees 2,3 
and 4) as well as low degree zonal harmonic coefficients (degrees 2 to 7). The approach for 
recovering tide response using analysis of long satellite orbital arcs was investigated. A total of 14 
Ocean tidal constituents (48 parameters) were estimated using long arcs 1 one year during 1976-77 
and 1983-1984 with a least squares process. The uncertainties for the most of the estimated tidal 
coefficients are lower than 0.1 cm, the effective k2 values for the diurnal and semidiurnal tides 
solution are in good agreement with the Schwiderski and Parke Ocean tide model and other satellite- 
derived solutions. Theoretical values for the lunar deceleration have been computed using the 
estimated semidiurnal and diurnal tides. The values obtained are in good agreement with those 
obtained by other investigators. Seasonal variations caused by even and odd zonal perturbations 
were observed in the node, eccentricity and perigee residuals for the Starlette long arcs, indicating 
that Starlette’s orbit is sensitive to long period seasonal changes in the earth’s gravity field. The 
observed seasonal variations have been computed. A preliminary comparison with the seasonal 
variations obtained by other investigators using meteorological data shows the values are in general 
agreement. 
APPENDIX C 
GEOPHYSICAL PARAMETERS FROMTHE ANALYSIS 
OF LASER RANGING TO STARLEITE 
C. K. Shum (Center for Space Research, The University of 
Texas at Austin, Austin, Texas 78712) 
B. E. Schuu, LM. K. Cheng, R. J. Eanes, and B. D. Tapley 
The Starlette satellite, launched in 1975 by the French 
Centre National d’Etudes Spatiales (CNES), has provided 
valuable information in the areas of geodesy and 
Seodynhcs. Using a preliminary gravity model 
developed at the University of Texas Center for Space 
Research (UTKSR), fiveday Starlette orbits w e n  
computed at the level of ‘20 cm laser range residual m. 
Quick-look Starlette data have been processed at UT/CSR 
on a regular basis since 1983. From dynamically consistent 
long arcs of one to three years, geodetic and geodynamic 
parameters of interest have been deduced from laser 
ranging to Starlette. In particular, earth rotation parameters 
have been determined. and other geophysical phenomena 
s w h  2s the seasonal V X ~ X ~ Q ~ S  of &e long period tidai 
constituents have been examined. 
.-\cknowfedqmenr. This research was supported by 
YASA under Grant No. NAGS-757. 
1. 
2. 
3. 
4. 
5. 
6. 
7. 
a. 
9. 
1987 Spring Meeting 
Dr. C. K. Shum 
Center for Space Research 
The University of Texas at Austin 
Austin,TX 78712 
(512) 471-5573 
G 
0 
09b 
Ms. Susie Y. Thorn 
Cenm for Space Research 
The University of Texas at Austin 
Austin.= 78712 
C 


Geophysical parameters from the analysis of laser ranging to starlette

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