Made In Space, Inc. (MIS) proposes the construction of large baseline structures, 15 meters or greater, for infrared space interferometry missions by autonomous in-space manufacturing and assembly. This enables the deployment of large primary trusses unconstrained by launch load or volume restrictions that meet science requirements for the high angular resolutions (less than 0.3 arcseconds) necessary to detect planets near bright stars and measure individual objects in star clusters. In this Phase I effort, MIS investigates the mass, performance, and mission planning benefits of in-space manufacturing for structurally-connected interferometers (SCI). MIS is the leading developer of manufacturing technologies in the space environment. Utilizing technologies derived from Archinaut, a NASA Tipping Point 2015 award winner, large infrastructure can be manufactured on orbit and enable a multitude of missions. Optimast is a self-contained, scalable machine for producing microgravity-optimized linear structures on-orbit, developed as a product application of the Archinaut technologies. MIS has developed Optimast to a TRL-6 with successful thermal vacuum testing of extended structure manufacturing in 2017. Adapting the MIS Optimast technology to produce long baseline structures with low thermal expansion materials enables simultaneous structural fabrication and positioning of the optical subsystems to the required absolute (static) and dynamic (thermal deflection and oscillation) tolerances. An Optimast-SCI baseline structure thus provides superior absolute position control over traditional deployable structures at much lower cost, mass, and integration complexity and eliminates the parasitic mass from hinge mechanisms and traverse rails. Potential NASA Applications Long baseline interferometry is necessary to provide the sub-arcsecond angular resolution and high spectral resolution for collecting spectral data on protostellar disks, finding protoplanets hidden in dust fields, and resolving questions about how galaxies merge. The Optimast-SCI technology is also applicable to the development of large deployable antennas, manufactured structures for large backplanes and other spacecraft systems, and structurally-connected interferometry in other wavelengths. Potential Non-NASA Applications MIS has preliminarily identified opportunities for Earth remote sensing and space situational awareness for large optical interferometers in Earth orbit. Depending on the customer requirements for spatial resolution, target resolution, and imaging wavelength, MIS plans to consult with industry partners and further develop concepts for structurally-connected interferometers intended for commercial applications.