Multi Year SLR Solution

Horst Müller, Detlef Angermann,Barbara Meisel

14th International Workshop on Laser Ranging, San Fernando, Spain, June 7 – 11, 2004

Deutsches Geodätisches Forschungsinstitut, MünchenE-Mail: mueller@dgfi.badw.de

Motivation

• SLR TRF realization• Contributions to various IERS

projects• Reference for station coordinates

(operational weekly computations)• J2 series• Geocenter and scale

Satellite Tracking Data Used

• All SLR tracking data• LAGEOS-1: Jan. 1981 – May 2004• LAGEOS-2: Oct. 1992 – May 2004• 2 min. normal points computed at DGFI

from FR-data, till 1988• 2 min. normal points from CDDIS• 2 min. onsite normal points, provided by

EDC, since Dec. 1993

Models used for Weekly Arcs

• Models: IERS 2000 Conventions

• Gravity Field: EGM96(to 20x20)

• Biases: significant biases adjusted

• Weighting: loose constraints (1m)

• EOP IERS C04

• Apriori station coord./vel.: DGFI-solution

• Datum: no net rotation on core stations

Solved Parameters

• 6 Orbital Elements• Once per rev. Along-track: 1/arc• Once per rev. Cross-track: 1/arc• Emp. Alongtrack-Paramter: 3/arc• Solar Radiation Correction: 3/arc

• Daily EOP‘s (X,Y,UT1)• Station Coordinates (epoch center of arc)

DOGS Processing Scheme

Weekly single satellite arcs

Conv.

Weekly single satellite arcs

Conv.

Solution Solution

LAGEOS-1 LAGEOS-2

Normals Normals

Biases,outliersBiases,outliers

NormalsNormals NormalsNormalsNormalsNormals

NormalsNormals

Weekly combination

Weeklycomb.sol.Normals combinationcombination

combinationLAGEOS-1/2

solutionLAGEOS-1

solutionLAGEOS-2

solution

NormalsNormals

Number of Normal Points

0

500

1000

1500

2000

2500

3000

3500

4000

4500

19811984

19871990

19931996

19992002

LAGEOS-2LAGEOS-1Edited Obs.

Weekly Orbital Fit [cm]

0

3

6

9

12

15

18

19821985

19881991

19941997

20002003

LAGEOS-1LAGEOS-2

Number of Biases per Week

0

5

10

15

20

25

30

35

19821985

19881991

19941997

20002003

LAGEOS-1LAGEOS-2

Weekly J2 Values(Relative to 1.0826e-3)

-40

-35

-30

-25

-20

-15

-10

1981

1984

1987

1990

1993

1996

1999

2002

LAGEOS-1

LAGEOS-2

[1e-9]

Recent Solution

• Time span Jan. 1999 – May 2004

• LAGEOS-1 and 2 combined

• Datum: no net rotation conditions

• Comparison with ITRF2000

• Comparison with GPS and DORIS onweekly basis

Comparison DGFI - ITRF2000 (Europe)

Comp. DGFI – ITRF2000 (East Asia)

Time Series of Weekly TranslationParameters

Position Time Series (Yarragadee)

-6-3036

nort

h [cm

]

-6-3036

ea

st

[cm

]

-6-3036

1999 2000 2001 2002 2003 2004

up [cm

]

Station Height Variations

Annual signals in station heights

Future Plans

• 12-Years comb. solution (10/92-06/04)• Combined solution 1981-2004• Seasonal signals in positions, low

degree harmonics• Continuous update of solutions• Provide results at

http://ilrsac.dgfi.badw.de/

Position Time Series (Herstmonceux)

-3

0

3

nort

h [cm

]

-6-3036

ea

st

[cm

]

-3

0

3

1999 2000 2001 2002 2003 2004

up [cm

]

Number of Station per Week

0

5

10

15

20

25

30

35

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

LAGEOS-1LAGEOS-2

Number of Passes

0

50

100

150

200

250

300

350

400

1981198219831981

19821983

19841985

19861987

19881989

19901991

19921993

19941995

19961997

19981999

20002001

20022003

2004

LAGEOS-2LAGEOS-1

Comparison DGFI – ITRF2000(South Africa)