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This NASA SBIR Phase I proposal is in response to the need for Ultra-Stable Telescope Structures at 10m to 20m length scales and is designed to scale ultra-stable ALLVAR Alloy struts from cm-length to m-length scales. Additionally, a novel method for tuning a strutrsquo;s CTE without changing the strutrsquo;s length will be validated for their potential use in space-telescope structures critical to NASArsquo;s future missions. Telescopes used for astrophysics, exoplanet, and planetary studies require picometer stability over several minutes to hours. Building large support structures with picometer level stability is a challenge with currently available materials such as carbon fiber composites due to their high cost and moisture expansion. ALLVAR Alloys offer a new material solution for thermally stable structures. They exhibit negative thermal expansion and can compensate for the positive thermal expansion of other materials to stabilize a telescope. Bars with thermal stability approaching Zerodurrsquo;sreg; have previously been made by joining ALLVAR Alloys to commercially available Titanium alloys and struts exhibiting pm-level stability have been fabricated and tested. This Phase I project is designed to leverage this previous development to create the first large scale ultra-stable ALLVAR Alloy structures and develop a brand-new method for tuning its CTE. If successful, this new technology could enable CTE tuning of fully assembled ultra-stable structures in-situ. The Phase I project would fabricate and characterize a ~2m long strut segment in preparation for larger scale manufacturing and testing in a Phase II project.