Derivation of an alternative GRACE Follow-On LRI1B data product

Abstract

<p>The Gravity Recovery and Climate Experiment (GRACE) was a space mission from 2002-2017. While the two identical satellites were orbiting the Earth one after the other, the inter-satellite distance variations caused by the Earth's mass distribution were measured. This data can be used to determine the structure of the Earth's gravity field and observe its time-varying component, such as melting ice caps or water storage on land.  In order to continue these useful data streams, a GRACE Follow-On mission was launched in 2018. This successor hosts a novel instrument called the Laser Ranging Interferometer (LRI) for measuring the distance variations with higher precision than the conventional Microwave Instrument (MWI).</p><p>The raw measurements of the LRI need to be converted into an intermediate data product before the gravity field recovery can start. The official LRI1B data product is provided by the Science Data System (SDS) based on multiple processing steps. Here, we present an alternative LRI1B data set, that allows investigating different processing strategies and algorithms which might improve the data quality. For instance, our processing uses a different deglitching algorithm for detecting and removing phase jumps,  which are caused by thruster activation of the satellites. Furthermore, we indicate special events like phase jumps, sun-blindings and momentum-transfer-events likely caused by micrometeorites in the quality flag. Additionally, the light time correction used for conversion of the biased range into an instantaneous range is computed differently for the AEI-LRI1B product. Comparing the versions of SDS and AEI allows us to verify and validate the correctness of the officially provided LRI1B of SDS.</p>