Note date 2016-02-16

1) Monthly GRACE gravity fields are available for the period of December 2015 
   as following:

   GSM-2_2015345-2016003_0024_JPLEM_0001_0005   2015   DEC (see 1.b, 1.c and 1.e)

     REMARKS:
     1.a - For each month, an unconstrained 90x90 field is provided.
     1.b - For each month, an unconstrained 60x60 field is provided.
     1.c - Solution derived including data from adjacent month.
     1.d - The standard deviations of the harmonics included in the GSM-2*
           products represent ONLY formal (NOT calibrated) errors of the
           estimate.
     1.e - These filenames end with the string "_0001_0005", denoting 
           the Release 5.1 Level-2 products.
     1.f - Due to the increasing errors in the monthly fields at higher
           degrees, users are cautioned against using spherical harmonic
           coefficients past approximately degree 70 in the monthly fields.
     1.g - The differences of these products relative to the Release-05
           products are the change of Earth reference system to consistent
           with the IERS 2010 recommendations and the usage of 100x100 
           expansion of S1/S2 air tide (Ray and Ponte, 2003) in process.
           These model upgrades are described in the JPL Level-2 Processing 
           Standards Document - version 5.1.
     1.h - The value of C20 derived from GRACE in RL05.1 (as with many of the 
           Analysis centers) is less well observed. Users should substitute the 
           SLR values for best results.

2) For each month six product files are available. For example, the available
   products for January 2008 are:

     GSM-2_2008001-2008031_0031_JPLEM_0001_0005
     GSM-2_2008001-2008031_0031_JPLEM_0001_0005.README
     GAA-2_2008001-2008031_0031_JPLEM_0001_0005
     GAB-2_2008001-2008031_0031_JPLEM_0001_0005
     GAC-2_2008001-2008031_0031_JPLEM_0001_0005
     GAD-2_2008001-2008031_0031_JPLEM_0001_0005

     REMARKS:
     2.a - The monthly GAA, GAB, GAC, and GAD files are the monthly averaged
           harmonics from AOD (RL05).
     2.b - The zero-th and first degree terms in GAA, GAB, GAC, and GAD 
           products have not been applied in the level-2 gravity recovery 
           process.
     2.c - The averaging of GAA, GAB, GAC, and GAD are carried out over a 
           whole number of days, regardless of whether full or partial day's 
           data were used in creating the GRACE monthly solution.
     2.d - The header information in these files contain slightly different 
           values of GM (Earth gravitational parameter) and Ae (Earth 
           equatorial radius) - when compared to the values in the headers of 
           the geopotential product files GSM*. All analysis has been done with 
           the values using the GM and AE values in the headers of the GSM* 
           files.