Under development for two decades, the James Webb Space Telescope isn't quite ready to go into space yet. On Thursday, NASA announced that the next-generation space telescope would not be ready for launch in October 2018 and would have to slip into 2019.

“The change in launch timing is not indicative of hardware or technical performance concerns,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate at Headquarters in Washington. “Rather, the integration of the various spacecraft elements is taking longer than expected.” Engineers have determined that integration activities, such as the installation of more than 100 sunshield membrane release devices, will require more time.

The agency said its existing budget reserves would accommodate the launch delay. Now, NASA is targeting a launch between March and June 2019 from French Guiana aboard an Ariane 5 rocket. In the NASA news release, Zurbuchen said taking a little more time to ensure that the Webb telescope can properly deploy in space is a wise investment. The instrument will still be able to complete a full science program—observing everything from exoplanet atmospheres to the earliest galaxies in the universe.

It is not immediately clear what pushback NASA will get from Congress or the White House over the additional delay. Initial estimates from scientists were that the telescope could launch in 2011 for $1.6 billion. Now the cost has risen to $8.8 billio, and the launch delayed until 2019. The chief congressional champion of the telescope, Maryland Senator Barbara Mikulski, retired in January.