## 2 ARD Framework
### User-Defined Configuration  
The proposed ARD framework incorporates a set of configurable parameters to customise the characteristics of the end-product according to the requirements of the user. The selection of Sentinel-1 and Sentinel-2 bands and masks is user-defined, including the ability to select only Sentinel-1 and/or Sentinel-2. The Sentinel-1 mission comprising the Sentinel-1A satellite and its twin Sentinel-1B provides SAR data operating in the C-band of the electromagnetic spectrum. The high revisit frequency of the Sentinel-1 mission (6 days) and its global coverage together with its active sensing and ability to penetrate clouds make it ideal for all-weather Earth observation [42]. The main acquisition mode of Sentinel-1 for land is the Interferometric Wide (IW) swath mode. Sentinel-1 satellites have a single transmitter chain and can provide dual-polarisation (VV+VH or HH+HV) or single-polarisation (HH or VV) radar data in the IW mode depending upon the geographic location. The Sentinel-1 Level-1 Ground Range Detected (GRD) product is generated from the Single Look Complex (SLC) product by multi-looking and projecting the flange range to the ground range. GRD provides the radar backscatter amplitude and intensity information, while the phase information is not retained. The framework offers the possibility to select the VV and/or VH polarisation bands from the Sentinel-1 GRD product depending on the application.  
The Sentinel-2 mission comprising Sentinel-2A and Sentinel-2B satellites has a combined revisit frequency of 5 days and provides MSI imagery with 13 optical spectral bands in the visible and near-infrared spectrum at spatial resolutions of 10 m, 20 m and 60 m for each band [43]. The Sentinel-2 Level-2A products used in the framework are ortho-rectified Bottom of Atmosphere (BoA) reflectance with atmospheric correction already applied. Note that the Level-2A product contains all multi-spectral bands except band 10 as this band does not contain any surface information [44]. The Level-2A product contains water vapour maps, Aerosol Optical Thickness (AOT) maps, cloud masks for opaque clouds, cirrus clouds included in the Level-1C product, scene classification masks for the detection of dark feature shadow, cloud shadow, vegetation, non-vegetation, water, thin cirrus clouds, medium- and high-probability clouds, snow and ice. The proposed ARD framework permits the configuration of bands and masks of interest to reduce the final product size and processing requirements based on user/application requirements.  
The temporal frequency of the time series data can be chosen with consideration of the satellite orbital tracks. For example, the Sentinel-2 satellite mission has a revisit frequency of 5 days, but the overlap between neighbouring tracks can increase further the revisit frequency if the target ROI falls within the overlapped region. Sentinel-1 and Sentinel-2 data are combined with the closest temporal match to completely cover the ROI in the case when multi-mode data are requested by the user. For the Sentinel-2 products, filtering can be executed based on the cloud cover so that only minimally cloud-affected Sentinel-2 products are chosen. Moreover, ML applications commonly ingest satellite data in the form of rectangular image patches; the framework allows cropping into patches of customised sizes with user-defined vertical and horizontal overlap between the patches to accommodate this requirement.  
The parameters of the ARD framework used during configuration and run-time are summarised in Tables 1 and 2, respectively, in Appendix