This documents provides a brief explanation of why the L1B and L2A Version 2.0 datasets were created and what was updated from previous Version 1.x's. Overview of Version 2.0 ----------------------- The L1B and L2A version 2.0 collections represent a complete historical re-processing of the L1B and L2A data record, respectively. This was done in part to combine versions 1.1 - 1.3 (which covered three different time ranges) into a single data set. It also updates calibrations from the 1.2 and 1.3 versions. The versions 1.2 and 1.3 were created for time ranges later in the operating period of RapidScat when there was a loss of an amplifier that led to reduced signal to noise ratio. Versions 1.2 and 1.3 revised the preliminary calibrations of the data after the anomaly. Version 2.0 provides a further update on the calibrations for the time periods originally covered by versions 1.2 and 1.3. See below for more details on the reprocessing periods. First reprocessing period ------------------------- Version 1.2 was a replacement and continuation of the Version 1.1 data forward from orbital revolution number 5127, corresponding to 19 August 2015; the overlapping time period starting on 19 August 2015 corresponds to the first time period of the recorded low signal-to-noise ratio (SNR). Version 1.2 differed from 1.1 as follows: 1) L1B sigma-0 was re-calibrated during the periods of low SNR and 2) during low SNR periods the L1B sigma-0 calibration was determined using re-pointed L1B QuikSCAT data (these updated calibrations were then transferred to later versions of the L2A collections). The Version 2.0 data sets are a further update to the Version 1.2 calibration. Second reprocessing period -------------------------- Version 1.3 was a replacement and continuation of the Versions 1.1 and 1.2 data forward from orbital revolution number 7873, corresponding to 11 February 2016; on 11 Feb 2016, RapidScat entered it's 3rd low signal to noise ratio (SNR) state and the initial calibration of low SNR 3 was preliminary during the Version 1.2 release. The fundamental difference between Version 1.3 and the previous Version 1.2 datasets is that the L1B sigma-0 were re-calibrated during the periods of low SNR states 3 and 4 using re-pointed QuikSCAT data (these updated calibrations were then transferred to later versions of the L2A collections). The Version 2.0 data sets are a further update to the Version 1.3 calibration.