The panel investigating the James Webb Space Telescope program, led by John Casani of NASA's Jet Propulsion Laboratory in Pasadena, Calif., prepared the report at the request of Sen. Barbara Mikulski, D-Md., USA Today reported Wednesday.
The $5 billion budget has ballooned to $6.5 billion, the panel said, because the 2008 budget for the project was initially set too low, and NASA headquarters did not catch escalating cost overruns.
Budget aside, the telescope was described by Mikulski as "technically sound."
"I was heartened that the Casani panel found JWST to be technically sound and vital to scientific advancement," Mikulski said in a statement. "But we cannot let its scientific potential blind us to the continual pattern of cost growth. Simply put, we are not in the business of cost overruns."
"The telescope is an outstanding technical achievement," Casani said at a NASA briefing. "Money been spent mainly in technology development and executing the program has been money well spent."
In a letter to NASA, Mikulski said the launch of the JWST will be delayed to 2015.
"The good news is that technically we are in good shape," says Chris Scolese, associate administrator at NASA Headquarters. "We have to make every dollar count."