The James Webb Space Telescope — which NASA has long expected to replace the fabled Hubble — was initially meant to go into service this year but has faced multiple hitches.

The Webb telescope will be the most powerful ever built — about 100 times more sensitive than Hubble — and is to be deployed on a mission to give astronomers an unprecedented glimpse at the first galaxies that formed in the early universe.

Its most recent delay was announced in March, when NASA said blast off would likely be in May 2020. The latest snags stemmed from a variety of human errors, technical problems and even “excessive optimism,” said Tom Young, chair of the Independent Review Board.

“The complexity and risk cannot be overstated or overestimated,” he told reporters in a conference call.

NASA administrator Jim Bridenstine said in a video message that the telescope “is going to do amazing things, things we’ve never been able to do before as we hear from other galaxies, and see light from the very dawn of time.”

“In space, we always have to look at the long term. And sometimes, the complexities of our missions dont come together as soon as we wish. But we learn, we move ahead, and ultimately we succeed. We will get there with Webb,” he said.

“I assure you that in the end, the Webb Telescope will be worth it,” he said.

The NASA technical report said that in one case, “an improper solvent was used to clean propulsion system valves that had been stored. The error was a failure to check with the valve vendor to ensure the solvent to be used was recommended and would not damage the valves. The valves had to be removed from the spacecraft, repaired or replaced, and reinstalled.”

“Another human-induced error was improper test wiring that caused excess voltage to be applied to transducers,” it said.

The project, a joint endeavor with the European and Canadian space agencies, has already drawn scrutiny from lawmakers for its ballooning costs, given that its initial budget of $3.5 billion had already soared to a an estimated $8 billion the last time a delay was announced.

The James Webb telescope is named after NASA’s second administrator, in office from 1961 to 1968. It will be launched aboard an Ariane-5 rocket from French Guiana. DM