The soil moisture plays a crucial role in a multitude of hydrology applications such as water-flow forecasting, soil conservation, soil erosion, infiltration control, flood prediction, and its distribution knowledge is critical even for meteorology, climate change and agriculture. So far, soil moisture retrievals has been attempted mostly from scatterometer/radiometer/SAR data neglecting that even the radar altimeters detect the backscattering coefficient along the overflown track and also provide nadir measurements that allow to minimize the incidence angle effect and are less sensitive to surface roughness. Furthermore, the next generation SAR altimeters are going to provide high along-track spatial resolution, overcoming the previous spatial limit of pulse-limited altimetry. This project is developing of a novel methodology to generate soil moisture estimates in arid and semi-arid regions from multi-mission satellite radar altimetry. Prior to the SMOS mission these areas were extremely hard to measure remotely. Key to this approach is the development of detailed DRy Earth ModelS (DREAMS), which encapsulate the detailed and intricate surface brightness variations over the Earth's land surface, resulting from changes in surface roughness and composition. DREAMS have been created over a number of arid and semi-arid deserts worldwide to produce historical SMALT time series over soil moisture variation. These products are available in two formats - a high resolution track product which utilises the altimeter's high frequency content alongtrack and a multi-looked 6" gridded product at facilitate easy comparison/integration with other remote sensing techniques. Validation has been performed over a number of deserts by comparing SMALT products with other remote sensing techniques, results of the comparison between SMALT and Metop Warp 5.5. Comparisons with other remote sensing techniques have been limited in scope due to differences in the operational aspects of the instruments, the restricted geographical coverage of the DREAMS and the low repeat temporal sampling rate of the altimeter. The potential to expand the SMALT technique into less arid areas has been investigated demonstrated the potential to provide soil moisture estimates over dry areas. SMALT products provide a first order estimation of soil moisture in areas of very dry terrain, where other datasets are limited. Potential to improve and expand the technique has been found, although further work is required to produce products with the same accuracy confidence as more established techniques. The data are made freely available to the scientific community through the website http://tethys.eaprs.cse.dmu.ac.uk