Generated by the Space-based Imaging Spectroscopy and Thermal pathfindER (SISTER) activity in support of the NASA Earth System Observatory's Surface Biology and Geology (SBG) mission, this dataset utilizes existing airborne and spaceborne sources to generate prototype data products spanning terrestrial ecosystems, inland and coastal aquatic ecosystems, hydrology, and geology. The objective of SISTER is to mature many of the workflows, algorithms, and data products envisioned for SBG, lay the groundwork to develop a robust cal/val network, and build a vigorous and expansive user community ahead of launch. This dataset contains experimental Level 2B fractional cover maps for water, vegetation, snow/ice, and soil at 30 m spatial resolution derived from data measured by the DLR Earth Sens-ing Imag-ing Spec-trom-e-ter (DESIS) instrument (https://www.dlr.de/eoc/desktopdefault.aspx/tabid-13614). For the purposes of SISTER, only a handful of scenes have been selected from this mission, with a temporal range between 2021-08-20 and 2019-02-04 and a spatial coverage that is global in scale. DESIS samples spectra over the visible and near-infrared wavelength range from 400 to 1000 nm with a unique spectral resolution of 2.5 nm. The raw DESIS data is first processed to L1B orthocorrected calibrated radiance by the German Aerospace Center (DLR) and then ingested into the SISTER platform for further downstream analysis. This collection was derived from corrected surface reflectance using a spectral mixture analysis. Spectral unmixing was performed to derive per-pixel fractional cover estimates of soil, vegetation, water and snow/ice using a generic four endmember dataset. The output products are provided in GeoTIFF format with values expressed as percentages in the range 0-1.