NASA reveals new details about the successor to James Webb

The Habitable World Observatory: a "mountaintop observatory" in space

Despite the fact that the HWO is still in the concept stage, the name clearly shows where NASA's priorities lie. Over the last few years, the US space agency has increasingly turned its attention toward the search for extraterrestrial life. James Webb just discovered its first exoplanet, but the HWO will likely take things a step further.

Thanks to the discussion at the American Astronomical Society meeting, we do also know that James Webb's planned successor will be designed so that it can be upgraded by robots while in space. This will give it a strong advantage over James Webb, which is orbiting in Lagrange Point 2, far from Earth, and won't be serviced until its science operations end in roughly a decade's time.

"Serviceability will be huge," Aki Roberge of NASA's Goddard Space Flight Center said, as per Science. It will essentially create a "mountaintop observatory at L2," she continued. In other words, the observatory will enable state-of-the-art instruments to be swapped in when needed, and it's really "the instruments that make a difference," Roberge said.

Clampin also confirmed that the HWO would likely be deployed far from Earth to a Lagrange Point, much like James Webb. As a point of reference, Webb is located roughly 1.5 million kilometers (1 million miles) from Earth. Unlike Webb, which works with infrared light, the HWO will capture optical light.

The HWO isn't the next NASA observatory scheduled for launch. That title goes to the dark energy and exoplanet-hunting Nancy Grace Roman Observatory, which is scheduled to launch around 2027.

There have also been a number of different proposals for something resembling HWO to date. These include the 4-meter mirror observatory HabEx and the 15-meter observatory LUVOIR. Much like Webb, LUVOIR (pictured at the top of the page) would utilize a segmented mirror design, meaning it can pack a much larger mirror into a rocket faring. NASA pointed out that much of the technology conceptualized for LUVOIR and HabEx could also be used for the HWO.

Serviceability is key for NASA's next-gen observatory plans

The Hubble Space Telescope was serviceable by astronauts who flew to the orbital observatory aboard NASA's Space Shuttle. The HWO, though, will likely utilize autonomous robots that are currently in development for NASA's Artemis moon missions.

NASA has noted that it wishes to take learnings from the James Webb program over to the HWO, as it aims to avoid the cost overruns and delays suffered by the Webb program. It's worth noting that the serviceability could also make the HWO more palatable to Congress. If anything goes wrong with the $10 billion James Webb observatory, it will essentially render the program obsolete. That wouldn't be the case with the HWO due to its serviceability.

According to the new report, the HWO will likely feature a smaller mirror than LUVOIR but a larger one than HabEx and Webb, which has a 6.5-meter mirror. Crucially, the fact that it will be serviceable in space means that — besides its mirror and main structure — its design at launch won't necessarily be its final iteration.