A traceable GRACE/GRACE-FO Level-1C scientific dataset (2002-2026) for reproducible mass-change analysis

While monthly Level-2 products of GRACE/-FO are widely used as essential climate variables for mass-transport studies, published processing chains and intermediate outputs are often insufficiently documented for transparent diagnostics, method intercomparison, and fully reproducible re-solving. Building on existing uses of the Level-1C concept, we present Hawk Level-1C, an integrated scientific dataset that links calibrated Level-1B observations with monthly Level-2 gravity fields and supports consistent, transparent, traceable, and reproducible mass-change studies with GRACE/GRACE-FO. Specifically, this Level-1C dataset comprises four subsets: (1) K-band range-rate residuals, (2) line-of-sight gravity differences, (3) normal equations, and (4) calibrated accelerometer data. Each subset provides much complementary information beyond conventional Level-2 gravity fields and opens up new scientific applications, making it possible to (1) recover the submonthly gravity signal, (2) monitor rapidly evolving events such as floods and hurricanes, (3) enable accurate land water assimilation/fusion, and (4) perform neutral density modeling related to space weather. This product is provided on a monthly basis, spanning the available mission months from April 2002 to June 2026, to cover both GRACE and GRACE-FO, which will be openly available through Zenodo soon. In addition, we declare that this Level-1C, as well as the companion Level-2 product, is completely reproducible through our open source software and the configuration files provided. In this work, the entire data processing chain from Level-1B to Level-1C and Level-2 is documented. Long term diagnosis and rigorous validation of our Level-1C against other publicly available resources are carried out, which have demonstrated the satisfactory quality of our product. In the end, we showcase how this product helps to explore and exploit the scientific potential of GRACE/GRACE-FO in a manner different from the standard Level-2 product.