https://spacenews.com/new-report-questions-dods-multi-orbit-plan-for-space-sensors/

In their latest new budget request, the US Space Force (USSF) has sought several billion dollars to procure and deploy a large-scale constellation of satellites for missile indication and warning (I&W). The proposed architecture would include approximately 135 low Earth orbit (LEO) and 16 medium Earth orbit (MEO) space vehicles. Traditional space-based I&W capabilities have resided in geosynchronous Earth orbit (GEO) to provide near-constant tactical and strategic overhead persistent coverage [1]. However, the shift to lower orbital regimes seems to be fully backed by congress, who have cut funding for next-generation GEO systems while nearly doubling the funding for LEO and MEO.

From a policy perspective, this sets up a looming battle between the DoD and congress, and future constellation maintenance and replenishment costs begin to soar. The DoD may find itself in the position of cutting funding to other programs to fully support the lifecycle of these large-scale constellations.

From a security perspective, orbital debris is of concern to space constellations. Debris traveling through an orbital plane has the potential for destroying multiple vehicles, reducing coverage.

[1] Hensley, T. K., Caviness, L. P., Vaughn, S., & Morton, C. (2015). Understanding the Indications and Warning Efforts of US Ballistic Missile Defense. Joint Force Quarterly, 78(3), 91-97.