In 2016, the National Science Foundation (NSF) unveiled a set of “Big Ideas,” 10 bold, long-term research and process ideas that identify areas for future investment at the frontiers of science and engineering (seehttps://www.nsf.gov/news/special_reports/big_ideas/index.jsp). The Big Ideas represent unique opportunities to position our Nation at the cutting edge of global science and engineering leadership by bringing together diverse disciplinary perspectives to support convergence research. As such, when responding to this solicitation, even though proposals must be submitted to the Office of Integrative Activities, once received, the proposals will be managed by a cross-disciplinary team of NSF Program Directors. NSF-supported science and engineering research increasingly relies on cutting-edge infrastructure. With its Major Research Instrumentation (MRI) program and Major Multi-user Facilities (“Major Facilities”) projects, NSF supports infrastructure projects at the lower and higher range of infrastructure project costs, Foundation-wide, across science and engineering research disciplines. The Mid-scale Research Infrastructure Big Idea is intended to provide NSF with an agile, Foundation-wide process to fund experimental research capabilities in the mid-scale range between MRI and Major Facilities. NSF defines Research Infrastructure (RI) as any combination of facilities, equipment, instrumentation, or computational hardware or software, and the necessary human capital in support of the same. Major facilities and mid-scale projects are subsets of research infrastructure. The NSF Mid-scale Research Infrastructure-1 Program (Mid-scale RI-1) supports either the design or implementation of unique and compelling RI projects. Mid-scale implementation projects may include any combination of equipment, instrumentation, cyberinfrastructure, broadly used large scale datasets and the personnel needed to successfully commission the project. Mid-scale RI-1 design projects include the design efforts intended to lead to eventual implementation of a mid-scale class RI project. Mid-scale RI-1 projects should involve the training of a diverse workforce engaged in the design and implementation of STEM research infrastructure. Mid-scale RI-1 emphasizes strong scientific merit, a response to an identified need of the research community and/or fulfillment of a national need to enable U.S. researchers to be competitive in a global research environment. Well-conceived technical and management plans are essential for both design and implementation proposals, as are well-developed plans (e.g., mentoring and professional development) for student training and the involvement of a diverse STEM workforce in all aspects of mid-scale design and/or implementation activities. The inclusion of individual project participants who are women, early-career researchers, persons with disabilities and members of other underrepresented groups are especially encouraged at all levels of the project team. Within Mid-scale RI-1, proposers may submit two types of projects, “Implementation” (e.g., acquisition and/or construction) or “Design”. The “Design” track is intended to facilitate progress toward readiness for a mid-scale range implementation project. Both Implementation and Design projects may involve new or upgraded research infrastructure. Mid-scale RI-1 “Implementation” projects may have a total project cost ranging from $4 million up to but not including $20 million. Mid-scale RI-1 “Design” projects may request less than $4 million, with a minimum request of $400,000 and a maximum request up to but not including $20 million, as appropriate, to prepare for a future mid-scale range implementation project. (Note: Successful award of a Mid-scale RI-1 design project does not imply NSF commitment to the future implementation of the project being designed, nor is a Mid-scale RI-1 design award required for the submission of an implementation project.) The Mid-scale RI-1 Program seeks to broaden the representation of PIs and institutions in its award portfolio, including a geographically diverse set of institutions (especially those in EPSCoR jurisdictions). Proposals submitted by, or involving partnerships between institutions are encouraged. PIs who are women, early-career researchers, persons with disabilities and other underrepresented minorities in STEM are also encouraged. To improve participation in science and engineering research for persons with disabilities, Mid-scale RI-1 encourages PIs to incorporate accessibility as part of a Mid-scale RI-1 design and implementation projects. Please consult NSF's Research Infrastructure Guide, RIG, (available at https://www.nsf.gov/pubs/2021/nsf21107/nsf21107.pdf) for definitions of certain terms used in this solicitation, such as the Project Execution Plan (PEP). Section 5 of the RIG provides guidance specific to Mid-scale Research Infrastructure Projects, including references to other parts of the RIG as needed. Note that PEP should be appropriately scaled for the complexity of the project and may not require all of the elements described in the RIG. Mid-scale research infrastructure projects with total project costs beyond the Mid-scale RI-1 Program limit are separately solicited through the Mid-scale RI-2 Program. Proposals to the Mid-scale RI-1 Program with total project costs beyond this solicitation's budgetary limits, either during initial submission or cost analyses/revisions during subsequent review, are subject to return without further review.