Material published on the Serpo site in August 2006 mentions a project GLEAM which would be a project to communicate with the alien “visitors” that the US Government interacts with.
The communication system would consist of a complex, highly classified series of relay stations and satellites that are also used in the “Echelon” project. At least part of the technology would have been provided by the “visitors.” It would first have been tested in 2002.
Note that no other source mentions this project. Instead, all other sources refer to projects Sigma and Plato as the projects that deal with communications with extraterrestrials.
However, as these sources are ‘older,’ there still is a possibility that Gleam would be a new name, or a new subproject.