WASHINGTON — Forced to find nearly $30 million in cost savings, NASA’s astrophysics program has trimmed budget reserves on one mission approaching launch and delayed the schedule of another.

In an Oct. 18 presentation to the Astrophysics Advisory Committee, Paul Hertz, director of NASA’s astrophysics division, said the changes, enacted in an operating plan for fiscal year 2017 approved with less than a month left in the year, were needed to respond to changes in funding levels for specific programs required by Congress.

NASA’s astrophysics programs, including funding for the James Webb Space Telescope, received $1.4 million overall than requested. However, Hertz noted that Congress required NASA to spend $15 million more than requested on the Wide Field Infrared Survey Telescope (WFIRST) and $1.4 million more on the Stratospheric Observatory for Infrared Astronomy. Science education spending, bookkept in the astrophysics division but shared among the other science divisions, also resulted in a $12 million increase.

“It required us to find $27 million in savings out of our total budget” from other astrophysics programs, Hertz said. Those cuts were incorporated into an operating plan for fiscal year 2017 approved in early September, less than a month before the end of the fiscal year.

The program affected the most is the Transiting Exoplanet Survey Satellite (TESS), a mission to search for exoplanets that is nearing completion for launch next year. A $15 million cut came from deferring a launch payment to fiscal year 2018 and effectively eliminating the remaining budget reserves held at NASA Headquarters.

“There are no further headquarters-held reserves in TESS funding that the project has received to launch in March of 2018,” Hertz said. The progress the mission was making, with the spacecraft currently undergoing a series of tests, made him confident the mission could stick to that schedule.

“Their schedule reserves are tight, but they have schedule reserves and they can make it,” he said. Should TESS run into problems, he said, NASA would have to find cuts in other astrophysics programs to make up the difference, or not launch TESS at all.

Hertz said $3 million in cuts came from a program for flying astrophysics experiments on balloons, while the other $9 million will be spread among “many programs and projects” by rephasing them or reducing funds carried over from one year to the next.

One of those programs is the Imaging X-ray Polarimetry Explorer (IXPE) mission, selected by NASA early this year as its next Explorer-class astrophysics mission. “As part of having to solve our budget problems, we rephased IXPE’s budget to the right a little bit,” he said. “That will result in about a six-month delay in the IXPE project.” The launch, originally planned for late 2020, is now scheduled for April 2021.

Those budget issues have no effect on JWST, whose six-month delay announced last month, in turn, will not have an effect on the astrophysics budget. “It is funded by the Webb reserves,” Hertz said of the delay. “There is no impact on the rest of astrophysics. The James Webb reserves fully cover that delay.”

That caused some confusion to committee members, who wondered how a six-month delay could have no effect on the rest of astrophysics when the program previously reported reserves of just three and a half months. Eric Smith, JWST program manager, said later the same day that the difference came from separate reserves held at the headquarters level.

“This delay is entirely funded by money in headquarters reserves,” Smith said, who declined to disclose the size of those reserves other than that this delay will use up most of it. “It’s likely this change in the launch date will consume much of the headquarters-held reserve.”

Smith also said that the delay had nothing to do with a potential launch schedule conflict with ESA’s BepiColombo mission to Mercury. That mission is planning an October 2018 launch on an Ariane 5, the same date as JWST prior to the delay.

“In the end, it turned out to be completely unrelated,” he said. NASA is required to give ESA one year’s notice of the planned JWST launch, but Smith said that by the time such a notice would have been needed for an October 2018 launch, it was clear that integration issues with JWST would require a delay. “In the end, it didn’t matter that Bepi was there. We needed to move for our own reasons.”

The astrophysics program, like the rest of NASA and the federal government, is currently operating under a continuing resolution (CR) that provides funding at 2017 levels from the start of the 2018 fiscal year Oct. 1 through Dec. 8. Hertz, giving a similar budget presentation to the Space Studies Board’s Committee on Astronomy and Astrophysics Oct. 24 in Irvine, California, said that CR is not having an effect on his programs.

“We are executing our proposed plan right now because our budget number for ’18 was our budget number for ’17,” he said. “We face no changes in our plans because we’re under a continuing resolution.”

Should a continuing resolution be extended, perhaps for all of fiscal year 2018, Hertz added he saw no problems unless Congress made specific changes, or “anomalies,” to the CR related to his programs. “A full-year CR would be fabulous for NASA’s astrophysics point of view because it would allow us to execute our proposed plan, if there were no anomalies,” he said.