Eight months early and under budget, the Roman Telescope is ready to launch

Since the rethink, things have gone incredibly smoothly. At the time of the hardware gift in 2012, estimates suggested that the earliest we could see a launch was earlier this decade. It’s only a bit beyond that highly optimistic estimate, and NASA Administrator Jared Isaacman told the press that the September launch would be “eight months ahead of schedule and under budget.” There was a lot of discussion about how the lessons learned here might inform future NASA projects. The NGRST will carry just two instruments. The first is its Wide Field Instrument, meant to capture a huge portion of the sky at once. NASA compares the size of its field of view to that of a full Moon; it’s roughly 100 times wider than the largest images Hubble can capture. That will be paired with an array of 18 individual detectors, each capable of capturing 4096 x 4096 pixels. Scientifically, it will be used to image exoplanets in distant orbits from their stars. But it also serves an engineering purpose: starting the development of a coronagraph for the planned Habitable Worlds Observatory that will need to be 100 times more effective at blocking out stars. Compared to something like the Webb Telescope, Roman is also delightfully simple. It has relatively few moving parts that need to be deployed once in space, and those that exist, like the solar arrays and high-gain antenna, are simple spring-loaded devices. Once latches are released, they’ll simply open into place, a process that NASA’s Melton said will start as soon as 20 minutes after the NGRST separates from the launch vehicle. Commissioning is planned to take only 90 days, and Melton told Ars that it could be doing science before it completes the final burn to put it into orbit around the L2 Lagrange point. He said the fuel needed to keep it in orbit will be the primary factor limiting the observatory’s life. Using very conservative estimates of its rate of use, NGRST will be sent to space with 10 years of fuel, so barring a major hardware failure, it’s likely to be operational for quite a bit longer. One of the key targets of the NGRST surveys is what are called baryon acoustic oscillations. In the extremely early Universe, matter was dense enough that sound waves could create interference patterns in the material, with areas forming that had higher or lower densities than average. As the Universe expanded, these patterns were frozen into place and ultimately formed regions with a higher or lower density of galaxies. Identifying these patterns at large scales can tell us about the composition of the Universe, including the factors that shape most of its structure: dark matter and dark energy. Tracking how they evolve over time could also help us determine whether dark energy is changing with time rather than being in constant acceleration. There have been hints that some details of our understanding of these factors are wrong, and the NGRST will provide an independent measure of them. In addition to directly imaging exoplanets, the NGRST will conduct a microlensing survey to detect them. This effort will focus on the galactic bulge, where star density is much higher, and will take advantage of the fact that a planet can act as a small gravitational lens, briefly brightening any background stars that pass between it and Earth. These events are very brief, often only a few hours, and NGRST will repeatedly observe the same locations at a 15-minute cadence, providing the opportunity to capture much of the curve of the brightening and dimming. That will often be accompanied by the lensing event produced by the planet’s host star, but we’re also expecting to capture some “rogue planets” that have been ejected from extrasolar systems and are floating freely through space. In any case, the expectation is that we’ll identify tens of thousands of planets in this survey, most of them further from the host star than the ones spotted by Kepler. Those are the planned targets for now. There will also be time set aside for individual research proposals that may find additional uses for the hardware. But there was a clear sense that we were likely to either find something entirely new with the RST or be able to use it to help tackle future problems. McEnery summed everything up by saying, “I very much hope and in fact expect that the most exciting science from Roman is going to be the things that we didn’t expect that we couldn’t predict, but that will set the new, deep questions [for] future missions to address.”