Discovering the Universe

Paul Hertz is Director of Astrophysics in the Science Mission Directorate at NASA. He is responsible for the Agency's research programs and missions necessary to discover how the universe works, to explore how the universe began and developed into its present form, and to search for Earth-like planets. Hertz previously served as a Senior Scientist and as the Chief Scientist of the NASA Science Mission Directorate. Prior to joining NASA, he was an astrophysicist at the Naval Research Laboratory in Washington DC, where his research concentrated on X-ray emission from galactic neutron stars, black holes, and globular clusters.

Hertz will be a plenary speaker at SPIE Optics + Photonics, where he will summarize NASA's astrophysics program and discuss possible visions for the future of NASA astrophysics.

What are some of your primary responsibilities as Director of Astrophysics in the Science Mission Directorate at NASA?

NASA's strategic goals in astrophysics are to discover how the universe works, to explore how the universe began and developed into its present form, and to search for Earth-like planets. As Director, I am responsible for both the overall strategic direction of NASA, and also the top-level management of the NASA programs and projects, required to address this goal. This means leading an integrated government-academia-industry team (plus international collaboration) in a multi-year joint enterprise.

What are some of the short-term and long-term plans for the future of NASA astrophysics?

The most important near-term milestone for NASA astrophysics is the launch of the James Webb Space Telescope. Under development for over 20 years, Webb will launch this fall. Once deployed in space a million miles from Earth, Webb will use the largest mirror ever launched into space and a suite of sensitive instruments to detect the first stars and galaxies that formed after the Big Bang.

Long term, NASA is studying next-generation missions that can characterize planets around other stars for the presence of biomarkers and directly observe the dawn of supermassive black holes. The eagerly awaited Decadal Survey from the National Academy of Sciences will advise NASA on its strategic direction.

Paul Hertz with the James Webb Space Telescope in 2017. Credit: Paul Hertz

You mentioned NASA's strategic goals in astrophysics — to discover how the universe works, explore how it began and evolved, and search for Earth-like planets — how do you rank these in terms of importance when evaluating potential missions?

All of these goals are important, and I do not rank them. Our strategic vision is to have a portfolio of missions of all sizes so that we can make essential progress in all of these areas. Because a large space telescope is a multipurpose tool, astronomers use our Great Observatories to address all of these important questions.

What aspects are you most excited about in terms of how Lynx, LUVOIR, HabEx, and Origins Space Telescope will showcase the best new advancements in astronomy?

I have said many times that it is not a question of which of these missions we will do, it is only a question of the order in which we will do them. Each of these mission concepts offers capabilities that are essential for taking the next big steps in our understanding of the universe. One of the drivers of the great advances we have made in astrophysics over the past 30 years is the suite of Great Observatories we have had that work across the electromagnetic spectrum. All of these missions will contribute as Great Observatories to our understanding of the universe and our search for habitable exoplanets.

What are some of the programs that support research and technology development for NASA space missions?

We have a suite of research programs that offer funding opportunities for scientists and technologists who are interested in the supporting research and technology that enables and capitalizes our missions. The Astrophysics Research and Analysis (APRA) program supports basic technology inception and suborbital investigations that are relevant to NASA's programs in astronomy and astrophysics. The Astrophysics Data Analysis Program (ADAP) provides support for investigations whose focus is on the analysis of archival data from NASA space astrophysics missions. The Astrophysics Theory Program (ATP) supports efforts to develop the basic theory for NASA's space astrophysics programs. The Strategic Astrophysics Technology (SAT) program supports the maturation of key technologies for potential infusion in space flight missions.

Many of NASA's most ambitious projects begin with a proposal that includes undeveloped technology, how do you balance physics and budgets with innovative ideas and next generation technologies?

Our practice is to develop new and innovative technologies to a relatively mature state before infusing it into a mission. For instance, we spent the first half of the last decade maturing the technology needed for the Roman Space Telescope, and only after it was sufficiently mature did we begin developing the mission.

NASA requires all technologies to be at specified readiness levels before allowing a mission to pass through certain developmental gates. Our program is broad enough that we are simultaneously developing missions whose technology has been matured and maturing new technologies for the next generation of missions.

You've been directly involved with or leading NASA's science and astrophysics for over 20 years, is there one mission that stands out to you as being remarkable or surprising in its success?

That is a slightly unfair question, because all of our astrophysics missions are outstanding. One example is the Kepler Space telescope. When Kepler was first conceived in the 1990s by NASA scientist Bill Borucki, we had only recently discovered the first planets around other stars, and none of them were vaguely Earth-like. Kepler was designed to measure the frequency of Earth-like planets around Sun-like stars. New technology was required to enable a 100 Mpixel space camera that had photometric precision of 1 part in a million.

Kepler was designed to be sensitive because the frequency of exoplanets was expected to be low. Kepler discovered thousands of planets around other stars. Kepler discovered that essentially every star has a system of planets orbiting it. Kepler discovered that around 25% of all Sun-like stars have an Earth-like planet in the habitable zone. That means there are tens of billions of potentially habitable, Earth-like planets in our galaxy alone. I don't think even the most optimistic member of the Kepler science team was expecting that.