Generation of a good gravity field solution requires accumulation of satellite-to-satellite tracking data for about 1 month. The data we give here are labeled by their nominal month (consecutive since 1/1/2002=1). We list the actual data dates (start, end, and missing) over which data were collected corresponding to the nominal month. Within that month, a few days of data may not be used due to instrument issues. The 'Common' missing days are missing in solutions from all 3 centers; the last 3 columns indicate additional days missing from that center's solutions.
Please note there are several missing consecutive weeks due to 'battery management' starting in 2011, occurring approximately every 6 months.
In addition, there are certain months during which the GRACE orbit is in a near-repeat pattern. This phenomenon leads to sub-optimal spatial sampling and thus typically leads to larger errors in the higher spherical harmonic coefficients. Those months are also labeled below.