TITUSVILLE, Fla. — The optics and instruments for NASA’s James Webb Space Telescope have arrived at the California factory where they will be integrated later this year with the rest of the spacecraft for launch next year.

The Optical Telescope and Integrated Science instrument module, or OTIS, arrived at a Northrop Grumman facility in Redondo Beach, California, late Feb. 2 after being flown on a U.S. Air Force C-5 cargo plane from Ellington Field, Texas, near the Johnson Space Center.

The OTIS unit, which consists of the telescope’s optics and science instruments, recently completed a 100-day thermal vacuum test in an Apollo-era chamber at the Johnson Space Center. Those tests confirmed the performance of those key parts of the telescope at very low temperatures.

OTIS is now at the same Northrop Grumman facility where the company has been building the mission’s other key components, the spacecraft bus and a deployable sunshield the size of a tennis court, collectively known as the integrated spacecraft element. “It’s exciting to have both halves of the Webb observatory — OTIS and the integrated spacecraft element — here at our campus,” said Scott Willoughby, vice president and program manager for Webb at Northrop Grumman, in a statement. “The team will begin the final stages of integration of the world’s largest space telescope.”

The two halves, though, won’t immediately be combined. In an interview last month during a meeting of the American Astronomical Society in suburban Washington, DC, Willoughby said the bus and sunshield must first complete a series of environmental tests and well as tests of the deployment of the sunshield. He said OTIS would likely be installed on the spacecraft in August or September, after which the combined spacecraft will undergo additional environmental and deployment tests.

The combined spacecraft will be transported by ship from California to French Guiana in early 2019 for launch on an Ariane 5. That launch is planned for between March and June of 2019, although NASA has not yet set a more specific date.

NASA had earlier planned to launch JWST this October, but announced in September 2017 that the launch would be delayed to early 2019 because of issues with the spacecraft development. These problems included delays in deployment tests of the sunshield and a problem with valves in spacecraft thrusters.

Those issues, Willoughby said last month, led to a mutual decision by NASA and Northrop to delay the launch to give the team more time to complete work. “When we looked at all of that, we said that, for the work we have in front of us, we need more time.”