ESA is undertaking an extensive program aimed at the fabrication of high quality superconducting tunnel junctions, based on Nb, to be used for the detection of radiation from infrared to gamma ray wavelengths. To extend our knowledge of current technology, devices have been manufactured using an alternative technology, consisting of epitaxial Nb bottom electrode film, and a variety of materials and layouts for the tunnel layers as well as the top film. A specific mask set has been designed to enable optimized fabrication, diagnostics and testing of these devices which also includes the first 3 by 3 Nb superconducting tunnel junction test array. Preliminary results are presented on the performance of various types of devices where the tunnel barrier characteristics and device size have been systematically varied.