The Impact of New Accelerometer Transplant Data (ACH) on GRACE Follow‐On Along‐Orbit Inter‐Satellite Laser Ranging Observations and Monthly Time‐Variable Gravity and Mascon Solutions.

GRACE‐D accelerometer data show significant bias jumps since one month after the launch of the GRACE Follow‐On (GRACE‐FO) satellites in May 2018, making them inapplicable for correcting GRACE‐FO products for non‐gravitational accelerations. The GRACE‐FO Science Data System (SDS) compensated this issue by transplanting the GRACE‐C accelerometer data toward that of GRACE‐D. Recently, GRACE‐FO SDS implemented an updated transplant method, used in the latest release of GRACE‐FO data. Here, we examine the impact of updated accelerometer transplant data (ACH) on GRACE‐FO measurements at all levels: (a) Level‐1B inter‐satellite laser ranging residuals measured along satellite orbit, (b) Level‐2 time‐variable gravity solutions from all SDS centers (JPL, CSR, and GFZ), and (c) Level‐3 mascon solutions. We show that inter‐satellite laser ranging residuals are modified at low frequencies below 1 mHz, affecting the along‐orbit analysis of large‐scale time‐variable gravity signals. When mapped into monthly Level‐2 spherical harmonic coefficients of geopotential, the low‐frequency change in inter‐satellite ranging residuals leads to substantial improvement of coefficients associated with resonant orders (i.e., 15, 30, 45, etc.) and C30. We also present an improved SLR‐derived C30 which significantly improves the agreement with updated GRACE‐FO C30 at seasonal and interannual timescales. Moreover, we demonstrate the noise reduction in mass change estimates from new GRACE‐FO Level‐2 data over oceans, Greenland, and Antarctica for all SDS solutions. GRACE‐FO mascon solutions show a moderate change in the updated release. Our comprehensive analyses demonstrate high‐quality estimates of non‐gravitational accelerations by the updated transplant method, resulting in more accurate GRACE‐FO time‐variable gravity and mass change observations. Plain Language Summary: GRACE Follow‐On (GRACE‐FO) consists of two satellites that orbit around the Earth at ∼500 km altitude, following each other at a distance of ∼200 km. The inter‐satellite distance between the two satellites changes because of the gravitational as well as non‐gravitational forces (e.g., air drag), and it is measured by high‐precision sensors. To estimate time‐variable gravity caused by mass change in the Earth system from inter‐satellite ranging data, the effect of non‐gravitational forces is reduced using on‐board accelerometer measurements. The accelerometer on‐board the GRACE‐D satellite started to return erroneous measurements about 1 month after the launch. The GRACE‐FO Science Data System (SDS) compensated this issue by transplanting the GRACE‐C accelerometer data toward that of GRACE‐D. An updated transplant accelerometer data set for GRACE‐D was recently released by the GRACE‐FO SDS and, consequently, new time‐variable gravity and mass change solutions were released. In this paper, we demonstrate the improved accuracy of the new GRACE‐FO time‐variable gravity and mass change solutions caused by high‐quality estimates of non‐gravitational accelerations by the updated transplant method. Key Points: GRACE Follow‐On (GRACE‐FO) laser ranging residuals are modified at low frequencies by ACH, affecting the along‐orbit analysis of large‐scale mass changesGeopotential spherical harmonic coefficients associated with resonant orders (i.e., ∼15, 30, 45, etc.) show the largest improvement by ACHMonthly gravity fields show significantly lower noise for months when the angle between GRACE‐FO orbital plane and Sun‐Earth direction is ∼0 [ABSTRACT FROM AUTHOR]