GRACE Technical Note 05 

TITLE: Monthly estimates of C20 from 5 SLR satellites

UPDATE HISTORY: Last Updated May 8, 2006 - last month reported is Feb 2006.

AUTHORS:

	M. Cheng & J. Ries 
	Center for Space Research
	The University of Texas at Austin
	Email: grace@podaac.jpl.nasa.gov

DESCRIPTION:

	It is customary among users of Release-01 gravity field models
	to remove the C20 harmonics from the GSM-2 product files before
	using the remaining harmonics for geophysical analyses.

	Several users also replace the values from GSM-2 product files
	by C20 estimates obtained from other satellite geodetic techniques.

	As a convenience to such users, a monthly C20 estimate time series
	is provided. Each estimate is valid for the month whose STARTING MJD
	is provided in the first column. These estimates are obtained from
	the analysis of Satellite Laser Ranging (SLR) data to five geodetic
	satellites: Lageos-1 and 2, Starlette, Stella and Ajisai.

	The product value for C20 harmonic from GSM-2 file may be replaced by
	the C20 value given in Column-3 below.

	This series may be cited as:

	Cheng, M. and Tapley, B.D., "Variations in the Earth's oblateness during
	the past 28 years", Jour Geophys Res v109, B9, Sep 10, 2004.

	This file will be occasionally updated with estimates for latest months.

FORMAT:

	 Column 1: MJD of BEGINNING of month
	 Column 2: Year and fraction of year of BEGINNING of month
	 Column 3: Replacement C20 ( Use this value instead of value in GSM-2 file)
	 Column 4: Delta C20 = C20 from SLR - C20 from GGM01C (1.0E-10)
	 Column 5: Monthly mean of C20 from non-tidal ocean+atmosphere model (1.0E-10)
	 Column 6: C20 Sigma (1.0E-10)
	 GGM01C C20: -0.4841694237900E-03
	 All values are normalized in the same sense as GSM product conventions
	 The sum of Columns 3 and 5 is the value directly estimated from SLR.

	 FORMAT(F7.1,F10.4,E22.14,3f8.4)

PRODUCT:

52275.0 2002.0000 -0.48416939445999E-03  0.2933  0.0000  0.2438
52306.0 2002.0849 -0.48416946306659E-03 -0.3928  0.0000  0.2402
52334.0 2002.1615 -0.48416942451792E-03 -0.0073  0.0000  0.2189
52365.0 2002.2464 -0.48416936567495E-03  1.0677  0.4865  0.2876
52395.0 2002.3285 -0.48416944036349E-03  0.6559  0.8216  0.2599
52426.0 2002.4134 -0.48416943307706E-03 -0.2992 -0.2063  0.2611
52456.0 2002.4956 -0.48416957782753E-03 -1.8215 -0.2811  0.2636
52487.0 2002.5804 -0.48416959946534E-03 -2.3486 -0.5918  0.2496
52518.0 2002.6653 -0.48416962352630E-03 -2.2237 -0.2263  0.2876
52548.0 2002.7474 -0.48416956810892E-03 -0.5618  0.8814  0.2501
52579.0 2002.8323 -0.48416951672077E-03 -0.7539  0.1754  0.2692
52609.0 2002.9144 -0.48416947388981E-03 -0.2361  0.2649  0.2835
52640.0 2003.0000 -0.48416949204538E-03 -0.0304  0.6522  0.2514
52671.0 2003.0849 -0.48416947101790E-03  0.4245  0.8968  0.2464
52699.0 2003.1615 -0.48416936470575E-03  0.8573  0.2665  0.2287
52730.0 2003.2464 -0.48416940072851E-03  0.1554 -0.0752  0.2604
52760.0 2003.3285 -0.48416943203076E-03 -0.2233 -0.1409  0.2594
52791.0 2003.4134 -0.48416944388860E-03 -0.0786  0.1224  0.2258
52821.0 2003.4956 -0.48416952251556E-03 -1.6567 -0.6694  0.2778
52852.0 2003.5804 -0.48416958900970E-03 -2.3097 -0.6575  0.2381
52883.0 2003.6653 -0.48416962348779E-03 -2.2664 -0.2694  0.2253
52913.0 2003.7474 -0.48416960153715E-03 -1.9953 -0.2178  0.2558
52944.0 2003.8323 -0.48416954818053E-03 -0.9033  0.3406  0.2835
52974.0 2003.9144 -0.48416953292620E-03 -0.5693  0.5221  0.2651
53005.0 2004.0000 -0.48416944631251E-03  0.7979  1.0231  0.2620
53036.0 2004.0849 -0.48416945329704E-03  0.5049  0.8000  0.2400
53065.0 2004.1643 -0.48416945400173E-03 -0.1968  0.1053  0.2573
53096.0 2004.2491 -0.48416943424922E-03 -0.0653  0.0393  0.3011
53126.0 2004.3313 -0.48416945692537E-03 -0.5133 -0.1819  0.2730
53157.0 2004.4162 -0.48416948533770E-03 -1.2622 -0.6467  0.2985
53187.0 2004.4983 -0.48416944001435E-03 -1.1470 -0.9848  0.3750
53218.0 2004.5832 -0.48416954585328E-03 -1.7681 -0.5475  0.2340
53249.0 2004.6680 -0.48416958312786E-03 -2.1782 -0.5848  0.2809
53279.0 2004.7502 -0.48416954457835E-03 -1.5464 -0.3385  0.2796
53310.0 2004.8350 -0.48416951406716E-03 -1.0788 -0.1760  0.2745
53340.0 2004.9172 -0.48416950156153E-03  0.2595  1.0372  0.2921
53371.0 2005.0000 -0.48416936988742E-03  1.6258  1.0868  0.2327
53402.0 2005.0849 -0.48416933700874E-03  1.8153  0.9475  0.2976
53430.0 2005.1615 -0.48416937560137E-03  0.7589  0.2770  0.2848
53461.0 2005.2464 -0.48416938553822E-03  0.3388 -0.0437  0.2557
53491.0 2005.3285 -0.48416940252436E-03  0.5362  0.3235  0.2418
53522.0 2005.4134 -0.48416939769208E-03  0.3898  0.1288  0.2433
53552.0 2005.4956 -0.48416954060363E-03 -1.9334 -0.7653  0.2450
53583.0 2005.5804 -0.48416955283606E-03 -1.9630 -0.6725  0.2270
53614.0 2005.6653 -0.48416959343071E-03 -2.1288 -0.4324  0.2779
53644.0 2005.7474 -0.48416950903921E-03 -1.1817 -0.3292  0.2373
53675.0 2005.8323 -0.48416954682977E-03 -0.8535  0.3769  0.2639
53705.0 2005.9144 -0.48416951883139E-03  0.9655  1.9159  0.2688
53736.0 2006.0000 -0.48416946836862E-03  0.6932  1.1390  0.2554
53767.0 2006.0849 -0.48416943954076E-03  0.5782  0.7357  0.3073