During the study, GAO reviewed the status of the Patriot system and the army's strategy for carrying out the upgrades.
It also examined the extent to which the upgrades will address the Patriot requirements, and the level of oversight and accountability provided for the enhancements.
The army currently does not have an oversight mechanism in place to track or report the upgrades' progress against initial cost, schedule, or performance estimates.
GAO claimed that oversight mechanisms will provide the army with an opportunity to track progress on the upgrades, and help decision-makers to make investment choices.
The army has spent nearly $1.1bn on the upgrades, with plans to invest $1.8bn over the next five years.
The project will also involve the development of a long-term radar solution, and the integration of Patriot components into a central network, command and control system.
These improvements are intended to improve the system's performance, reliability, and communications, as well as address obsolescence and sustainment issues.
These improvements include major software upgrades called Post Deployment Build-8 (PDB-8) and PDB-8.1, in a bid to improve communications and system capabilities against threats.
Operational testing for PDB-8 and PDB-8.1 will be carried out in fiscal 2016 and 2019, respectively.
Funded by a 13-nation partnership, the PDB-8 upgrades are expected to improve Patriot's ability to destroy threats, make it easier to operate, and allow it to differentiate between friendly and enemy aircraft.
Image: A Patriot Advanced Capability-3 missile blasts out of its launcher to intercept an airborne target. Photo: courtesy of Lockheed Martin Corporation.