NASA's Roman Telescope Was Built With Fuel for 10 Years. Its First Course-Correction Burn Used 40 Pounds Instead of the 441 Budgeted, and the Spacecraft Launched 3,845 Pounds Lighter Than Planned. It Now Has Fuel for at Least 22 Years.

NASA's Nancy Grace Roman Space Telescope, which left Earth on a SpaceX Falcon Heavy on August 30, has already more than doubled the length of the mission it can fly. The observatory was designed with propellant for 10 years, five years of primary science and five years of extended operations. After its first mid-course correction on August 31, and with the accounting from launch now complete, mission engineers at NASA's Goddard Space Flight Center project that Roman has fuel for at least 22 years of potential science operations.

"As a result of exquisite planning by our orbital dynamics team, brilliant execution by the operations team, and a precise launch from SpaceX, Roman has fuel for at least 22 years of potential science operations," Jamie Dunn, center director at Goddard, said in a mission update written by Ashley Balzer and posted September 14.

The extra time comes from three sources, each worth roughly four years. The first is the August 31 burn. Mission planners had budgeted 441 pounds of propellant for that maneuver, which corrects any error left over from the launch and steers the spacecraft toward the second Sun-Earth Lagrange point, L2, about a million miles from Earth. The Falcon Heavy delivered Roman so precisely that the burn was more than 99 percent accurate and consumed about 40 pounds, less than a tenth of the allocation.

The second is mass. Roman left the pad weighing 17,760 pounds against a budgeted maximum of 21,605 pounds. Engineers plan against a conservative upper bound on mass so that the propellant load will never fall short, and when the finished spacecraft came in 3,845 pounds under that bound, they were able to fill the tanks well beyond what a 10-year mission required. "We base the propellant budget on a set maximum value so we won't come up short," propulsion lead Alison Rao explained. A lighter spacecraft also needs less fuel for every maneuver it makes for the rest of its life.

The third source is still ahead. A second mid-course correction is planned for later in September and is expected to be small, given how clean the first one was. Once Roman arrives at L2 about 100 days after launch and settles into its halo orbit, it will need only brief station-keeping burns roughly every 28 days to hold position. Savings on the insertion and on those maintenance burns are expected to add the final four years.

The payoff is scientific rather than merely operational. Roman's Wide Field Instrument, a 300-megapixel infrared camera, can survey the sky roughly 1,000 times faster than Hubble at comparable sharpness, and its core program is a statistical one: mapping the distribution of galaxies and the expansion history of the universe to test dark energy, and cataloging thousands of exoplanets through microlensing. Doubling the years of observing time roughly doubles the size of every one of those catalogs, and it opens the door to long-baseline studies, such as watching the same patches of sky for two decades, that the original mission could never have attempted. NASA reported this week that the telescope's primary instrument has been activated and its coronagraph has passed initial checkout.