Exploring the origins and the evolution of galaxies is of growing interest in the astrophysics community and requires the deployment of ambitious new far–infrared/submillimeter spectrometers into space. An instrument under study by NASA is the Background-Limited Infrared/Submillimeter Spectrograph (BLISS), which is a grating spectrometer with R=?/??=400-700. BLISS requires detector arrays that are scalable to thousands of pixels, are broadband over 35–435 um, and are very sensitive with a noise equivalent power on the order of 10-20 W/Hz1/2. I will discuss our progress at JPL to build and test arrays of suspended-membrane transition-edge sensors (TESs) that are compatible with BLISS and meet all of the instrument’s requirements. The TES arrays are fabricated in-house at the Microdevices Lab from bare 100-millimeter Si wafers to fully functional arrays using a wide variety of fabrication techniques and tools. The electrical characteristics of the TES arrays are measured at JPL in a sub-kelvin testbed equipped with a SQUID multiplexer. I will discuss many of the unique challenges of measuring these TES arrays with their extraordinary sensitivity.