WASHINGTON: The cost of NASA’s replacement for the Hubble Space Telescope is giving new meaning to the word astronomical’ growing another $1.5 billion’ according to an internal NASA study released Wednesday.

NASA’s explanation: We are better rocket scientists than accountants. Management and others did not notice that major costs for the James Webb Space Telescope were omitted during a major program review in July 2008’ officials said.

The study says in the best case scenario it will now cost about $6.5 billion to launch and run the powerful’ new telescope. And that can happen only if NASA adds an extra $500 million in the next two years over current budget plans. If the agency cannot get the extra money from Congress’ it ultimately will cost even more and take longer to launch the telescope.

Before now’ the cost of the telescope had ballooned from $3.5 billion to $5 billion.

NASA officials said they had not done a good job of figuring out the confirmation cost for the massive telescope. The report said the budget in 2008 ‘‘understated the real requirements’’ and managers did not realize how inadequate it was.

‘‘We were missing a certain fraction of what was going on’’’ NASA associate administrator Chris Scolese said in a late Wednesday afternoon teleconference.

The Webb telescope’ ‘‘we hope is just an aberration’’ Scolese said’ but suggested there may be other budget-busting projects. He said the agency is now reviewing all its projects’ not just to find extra money for Webb but to see if there are similar cases of poor budgeting.

The costs are not because of problems with the technology’ design or construction of the instrument. NASA said’ technically’ it is in good shape. It is designed to look deeper in the universe to the first galaxies. A collaboration with the European Space Agency’ the telescope is being built by Northrop Grumman and will be run out of Baltimore’ Maryland’ like Hubble.

The fault ‘‘lies with us’ no question about it’’’ Scolese said.

The Webb telescope is already late. When first announced more than a dozen years ago’ it was supposed to launch in 2007. That eventually was delayed until 2014. The new report’ issued at the request of the Democratic Sen. Barbara Mikulski’ says the earliest launch date now would be September 2015.

Scolese said technically the telescope was not confirmed as a project until 2008 _ even though many millions of dollars had been spent on it and NASA had been promoting it since 1998. In 2008’ NASA said it would cost $5 billion and that’s the number to use for how overbudget it is’ Scolese said. But previous numbers that NASA provided said it would cost $3.5 billion.

This follows the well-worn path of the Hubble telescope. In current dollars’ it cost NASA $4.7 billion to build and launch Hubble and then another $1.1 billion to fix it in orbit.

Astronomer Garth Illingworth’ a professor at University of California’ Santa Cruz and a member of the internal study team’ said Webb will be worth the money.

He said the Webb ‘‘is hugely more powerful than Hubble’ 100 times more powerful at least.’’ – AP