We are at a pivotal period in defining NASA’s future. In the current debate about redirecting U.S. civil space activities, it is important to keep this in mind: Both human space exploration and space science are fundamental to that future. The partnership between human spaceflight and space science programs flourishes when their mutual interests are not just simply aligned, but when they find ways together to build on their respective strengths.
The most prominent recent example was the return of seven astronauts to the Hubble Space Telescope to install new scientific instruments and repair failed components, making it more powerful than at any time since its launch nearly two decades ago. This partnership is core to NASA’s mission and is an essential element to achieving the next great leaps in space science.
The proposed “flexible path,” in which NASA would not focus on returning astronauts to the Moon but send humans and robots to a variety of points far from Earth, provides the opportunities to reach the next exciting frontiers in space science. As scientists, we seek to see farther and with greater clarity in order to reveal nature’s unseen phenomena. This will require increasingly large and complex structures well beyond low Earth orbit. Some of these scientific facilities will require assembly in orbit and launch vehicles capable of delivering massive payloads to high Earth orbits, Sun-Earth Lagrange points, and beyond. NASA’s current plan recognizes and enables this by laying out a sequence of realistic and frequent steps to extend our ability to build, deploy and operate advanced spacecraft at ever-increasing distances from Earth.
As successful as NASA has been over its 50-plus years, NASA’s new plan can enable both revolutionary new scientific capabilities from space and, at the same time, propel our human exploration of space forward. Here are two prime examples:
A little over two decades ago, the first planet was found orbiting a distant star. Now, more than 400 such planets are known, and NASA’s Kepler mission will reveal how common are Earth-size planets located in the temperate zones around their host stars where liquid water can exist on a planet’s surface. The James Webb Space Telescope may be able to study the atmospheres of a handful of Earth-like planets, but only if a separate “star shade” spacecraft is flown alongside.
To definitively address the question of whether life exists elsewhere in the universe, however, requires a space telescope that is at least four times larger than the Hubble and at least four times more precise in its imaging capabilities than the Webb telescope. With such an observatory, we will be able to directly search for the faint signatures of life in the atmospheres of more than 100 planets around stars as far away as 60 light years, allowing us, for the first time in history, to systematically address the question: “Are we alone?” A still larger telescope would enable even more—the ability to detect oceans and track changes in weather and seasons on potentially habitable worlds.
One of the other major frontiers of astrophysics is to “see the beginning.” The quest to see back to the time when the very first stars formed will tell us much about how the universe came to be filled with all the chemical elements we see today and which enable life. But detecting these first stars is a terrific challenge. The Webb telescope will detect the first galaxies these massive stars formed, but will not be able to see the X-ray-emitting remnants of each of those first stars—the black holes they leave behind. We can fill that gap with a next-generation large X-ray telescope that is 1,000 times more sensitive than any X-ray observatory ever built.
Both of these remarkable next-generation telescopes are tantalizingly within reach but will require new heavy-lift launchers or assembly in space. They will also likely be designed to be serviceable (either by humans or robotic spacecraft) to allow them to pursue scientific investigations for decades beyond their commissioning. These capabilities are precisely the same ones our human space exploration program will require to make the next major foray into our Solar System. The two pillars of NASA—exploration and science—have made it synonymous with inspiration, vision and discovery. Both are intrinsically outward-looking endeavors. The next steps can be revolutionary, if we think boldly.
Marc Postman is an astronomer at the Space Telescope Science Institute in Baltimore and works on future mission concepts. Kathryn Flanagan is a senior scientist at the institute and heads its mission office for the James Webb Space Telescope.