A high-precision reconnaissance satellite developed in response to the 9/11 attacks has turned its telescope toward space. It is the Nancy Grace Roman Space Telescope, which the National Aeronautics and Space Administration (NASA) is launching at 7:26 a.m. on the 30th (8:26 p.m. Korea time) from Kennedy Space Center in Florida. NASA received a reconnaissance satellite that the National Reconnaissance Office (NRO) had been building and converted it into a space telescope.
The results of recycling—choosing science instead of scrapping a canceled military development—have already appeared. NASA, unprecedented for an astronomy research program, moved up the Roman Space Telescope's schedule. The original launch date was May 2027. Director General Jared Isaacman of NASA said at a press conference in April, "We should learn from the magical elements that created success stories like the Roman Space Telescope."
◇ Reconnaissance satellite developed after 9/11 converted
Roman's starting point was the Decadal Survey that the National Academies of Sciences, Engineering, and Medicine (NASEM) released in 2010. It is a report that sets priorities and mission directions for the United States' space and Earth science research over the next 10 years. The report at the time put a space telescope to study dark energy and dark matter at the top of the list.
In 1998, astronomers observing Type Ia supernovae exploding in distant galaxies found they were dimmer than expected. That was because the expansion of the universe had been accelerating. To explain this accelerated expansion, the concept of dark energy that pushes the universe emerged. The research won the 2011 Nobel Prize in physics. Scientists believe that only 5% of the universe is matter we can observe, and 70% is dark energy. The remaining 25% is called dark matter, which does not emit light but pulls objects together.
NASA immediately pursued the Wide-Field Infrared Survey Telescope (WFIRST) project. With a space telescope with a 1-meter-class mirror, it planned to survey the entire sky to track the trend of cosmic expansion. However, as calls mounted to include exoplanet exploration in the mission, the effort hit a snag. Because NASA had already poured a large budget into developing the James Webb Space Telescope (JWST), it was impossible to satisfy both demands.
At that time, the National Reconnaissance Office's Future Imagery Architecture, a next-generation reconnaissance satellite program accelerated after the Sept. 11, 2001, attacks, was proposed as an alternative. Like the Hubble Space Telescope, this satellite was equipped with a 2.4-meter mirror and was expected to spot objects smaller than a coffee cup on the ground, but development was halted in 2005 due to schedule delays and cost overruns.
In 2012, the National Reconnaissance Office donated already developed reconnaissance satellite components to NASA. The primary mirror that collects light on the reconnaissance satellite was twice as large as what NASA had initially planned for dark energy research, enabling it to take on both tasks, including exoplanet tracking. NASA officially began developing the Wide-Field Infrared Survey Telescope in 2016. It has spent $4.3 billion to complete the Roman Space Telescope, which is now set for launch.
◇ Field of view 100 times wider than Hubble, rapid surveying
The Roman Space Telescope measures 12 meters long and 4 meters wide, similar to the Hubble Space Telescope. The primary mirror's diameter is the same as Hubble's. But its observing capability is incomparable. Roman carries a 300-megapixel camera with a field of view at least 100 times wider than Hubble's. Roman's Wide Field Instrument (WFI) arranges 18 large infrared detectors in a mosaic.
Simply put, behind the same size telephoto lens, Roman uses a much larger image sensor than Hubble. Even if the lens is the same, a wider sensor captures a much larger area in a single frame. Roman does not see individual objects 100 times larger or sharper than Hubble; instead, it rapidly obtains Hubble-quality detail over an area 100 times wider. This is why NASA says that a galaxy so vast it would take a century to observe with Hubble can be completed in a month with Roman.
Roman also takes on the task of finding exoplanets outside the solar system. About 6,000 exoplanets have been found so far, and NASA said the Roman Space Telescope could find 40 times more using triple-tracking techniques. Julie McEnery, the project scientist for Roman, said, "Think of it as conducting the largest-ever census of planets beyond the solar system."
Exoplanets are usually found using the transit method. When a planet passes in front of its star, it blocks some of the light. Like a solar eclipse dimming the sun, astronomers detect the brief dimming of a star from Earth to confirm an exoplanet's existence. But this method is easier when a massive planet crosses in front of the star.
To find exoplanets the size of Earth or Mars, Roman will also use microlensing. It detects the effect of a planet's gravity bending and magnifying light from a distant star to infer the planet in reverse. It is also equipped with a coronagraph that blocks a distant star's light so it can observe the planet's faint light. While this method has long been used on ground-based telescopes, this is the first time it will be used on a space telescope.
◇ Bearing Hubble's mother's name, heading where James Webb is
The Roman Space Telescope is named after Nancy Grace Roman (1925–2018), who served as NASA's first chief of astronomy in the 1960s. Roman helped establish the space telescope program to observe the universe from Earth orbit and is called "the mother of the Hubble Space Telescope." On the ground, Chile's Vera Rubin Observatory bears the name of a woman astronomer, but this is the first time a woman scientist's name has been given to a space telescope.
After launch, the Roman Space Telescope will head to the second Lagrange point (L2), about 1.5 million kilometers from Earth on the side opposite the sun. That is about four times farther than the distance between Earth and the moon (385,000 kilometers). L2 is ideal for space observations. There, the gravity of the sun and Earth and the telescope's centrifugal force balance out, causing no distortion of light. In particular, the sun is always hidden behind Earth, so sunlight does not interfere.
The James Webb Space Telescope has already been observing the universe from L2 since 2022. Still, its mission does not overlap with Roman's. If James Webb is a super-telephoto lens that zooms in on a single distant object, Roman is an ultra-wide-angle camera that captures a broad swath of the sky at once.
The Roman Space Telescope will track dark energy and dark matter, whose nature remains unknown, and exoplanets that may exist somewhere beyond the solar system. Although the targets have changed, in continuing to track secrets, it inherits the tradition of a reconnaissance satellite. Perhaps Roman will find a planet where life could exist like on Earth. A reconnaissance satellite that wins in science, not war, is something to look forward to.
References
NASA, https://science.nasa.gov/mission/roman-space-telescope/