An intelligence gathering system widely used by the Army in Afghanistan to detect roadside bombs and predict insurgent activity has severe limitations and is "not suitable," according to a memo from the Army's senior equipment tester to the Army's chief of staff, Gen. Raymond Odierno.

The e-mail memo was sent to Odierno on August 1, and comes as the system -- known as the Distributed Common Ground System (DCGS) -- is in the middle of Army and congressional investigations.

The inquiries surrounds a newly developed software system called Palantir, which -- according to U.S troops and commanders who have used it -- is more effective in helping troops in Afghanistan track and predict the location of deadly roadside bombs than the existing DCGS.

The memo to Odierno, written by the head of the Army's test and evaluation command -- Gen. Genaro J. Dellarocco -- hammers the DCGS system for its "poor reliability" and "significant limitations," during operational testing and evaluation earlier this year.

The memo covers an evaluation of the DCGS during May and June of this year, according to the document, which was first reported in the Washington Times.

It is not clear what prompted the evaluation, which came during a time when the DCGS was still being heavily criticized by troops in the field as inferior for discovering roadside bombs and after requests to field the software were denied by Army civilians at the Pentagon.

While the language of the memo was technical in nature, it describes the DGCS software during testing of its overall systems as having limited effectiveness and "poor reliability" as exemplified by "server failures that resulted in reboots/restarts every 5.5 hours of test."

The memo also said that during high usage the system suffers decreased reliability and its software characteristics "negatively impacted operator confidence and increased their frustration."

During tests to see how the system can protect itself during cyberattacks, the evaluation was again poor, saying evaluators were able to, "identify and exploit several vulnerabilities," and recommended that a "tech bulletin" be distributed to troops in Afghanistan using the system to warn them of the hacking vulnerability.

In a response to CNN inquiries about the memo, Army spokesman George Wright said, "The report provides an initial review of DCGS software, which identified specific limitations in its performance. Many of these limitations were already identified by the Army and software updates have been implemented to address the concerns."