WASHINGTON — Scientists gathering this week for the country’s largest astronomy meeting will discuss plans for future space telescopes, while raising questions about the status of upcoming missions.

More than 3,000 people are expected to attend the 231st Meeting of the American Astronomical Society (AAS) at National Harbor, Maryland, for a week of scientific presentations as well as mission and policy updates from NASA and the National Science Foundation.

Astronomers come to the meeting as NASA’s next two flagship astrophysics missions, the James Webb Space Telescope and Wide-Field Infrared Survey Telescope (WFIRST), face delays and questions about their budgets and capabilities.

NASA had planned to launch JWST this October on an Ariane 5, but in September announced a delay until the spring of 2019. The agency said at the time that the mission was facing no specific hardware issues, but instead that integration and testing of the $8 billion observatory was taking longer than anticipated.

“This is nothing to worry about,” said Martin Still, executive secretary of the Exoplanet Program Analysis Group (ExoPAG) at NASA Headquarters at a meeting of the group Jan. 7 in advance of the AAS conference. “This is the first time that NASA engineers and Northrop Grumman engineers had put all this together. They’re learning as they go, and they were just a little bit overenthusiastic about their schedule, overenthusiastic about how many things they could do in parallel.”

At a House Science Committee hearing a month ago, Thomas Zurbuchen, NASA associate administrator for science, said that an updated launch date for JWST would be ready for release in January and February, after an independent review of the status of the mission. Others at the hearing, though, cautioned that additional delays may be possible as the spacecraft goes through integration and testing work in the next year.

“More delays are possible given the risks associated with the work ahead and the level of schedule reserves that are now below what is usually recommended,” said Cristina Chaplain of the Government Accountability Office at the Dec. 6 hearing.

NASA’s next flagship astrophysics missions after JWST, WFIRST, is also facing scrutiny. Zurbuchen announced in October that he was asking program officials to make changes to the proposed mission, still in early stages of development, after an independent review concluded its estimated costs were approaching $4 billion. The redesign, Zurbuchen said, should bring the mission’s cost down to $3.2 billion.

That effort is in progress and is scheduled to be completed in February. Zurbuchen, in his October memo calling for the redesign, raised the possibility of revisiting the decision to use a donated 2.4-meter telescope assembly from the National Reconnaissance Office for WFIRST, rather than a smaller telescope originally envisioned for the mission, should the redesign not meet its cost cap.

At the December hearing, Thomas Young, a retired aerospace executive, said he was not particularly concerned about the WFIRST review. “I want to emphasize that there is no cause for panic,” he said. “What is transpiring is a perfectly healthy process to assure that the scope, cost and risk are appropriately defined prior to proceeding past milestone B,” a reference to Key Decision Point B, which NASA has postponed while the WFIRST redesign takes place.

Despite the problems with JWST and WFIRST, another NASA astrophysics missions is making good progress for a launch in the next few months. At the ExoPAG meeting, Still said the Transiting Exoplanet Survey Satellite (TESS) was wrapping up integration and test activities, and should be delivered to the Kennedy Space Center in February.

TESS is scheduled for launch no earlier than March 20 on a SpaceX Falcon 9, a launch date that is dependent on NASA certifying the vehicle in time for carrying science missions like TESS. Zurbuchen said at the December hearing that he expected that certification effort to be complete by early 2018.

“Everybody at Headquarters is excited enough that they’re starting to book flights” to attend the TESS launch, Still said.

TESS is a successor to Kepler, a NASA mission that has allowed astronomers to discover thousands of exoplanets as they cross, or transit, the disks of the stars they orbit, causing brief, periodic dimmings of those stars that can be observed. Kepler is expected to end operations later this year when it runs out of fuel used by its thrusters and is no longer to maintain attitude control.

“It is very much running on fumes,” Still said of Kepler. “Some time over the next 12 months, Kepler will indeed start to inelegantly drift away in pointing and will be unusable.”

At the AAS meeting, scientists will also be looking ahead to missions unlikely to fly for more than a decade. As part of preparations for the next astrophysics decadal survey, scheduled for release in late 2020, studies are underway of four concepts for flagship-class missions for consideration by that report. Updates about those mission concepts — the Habitable Exoplanet Imaging Mission, the Large Ultraviolet/Optical/Infrared Surveyor, the Lynx X-ray observatory and Origins Space Telescope — are scheduled for presentation at the conference, along with an update for the planning of the decadal survey.