The GRACE and GRACE Follow-On missions provide monthly time-variable gravity field estimates since 2002 with a 11-month gap between 2017-2018. This gap makes it difficult to retrieve gravity variations signals with pluri-annual and decadal temporal scales. This poster summarizes diverse approaches proposed in the literature and compare them. Some are an extrapolation of the GRACE products, others propose to use Swarm gravity field products to deduce the missing data. The estimation of the accuracy of the Swarm product is an order of magnitude larger than the accuracy of the GRACE product with a truncation at degree 12. Comparison of estimation techniques suggests that a spherical harmonics approach is more precise to reconstruct the GRACE data and that the Swarm product might pollute the reconstruction. The best reconstruction uses a Single Spectrum Analysis on spherical harmonics with only GRACE products. This reconstruction will provide a great addition to the study of long term gravity processes.