Behind the Scenes of the Nancy Grace Roman Space Telescope

Join the Engineering and Technology Directorate as we interview Mark Melton, mission system engineer for the development of the Nancy Grace Roman Space Telescope. In this extended tell-all episode, learn more about the inner workings of the telescope, some interesting stories about its development and the significance of the project.

Transcript

DIVYA SUNDARAM, HOST: 

Hello. You are listening to NASA’s Goddard Space Flight Center Engineering and Technology podcast. My name is Divya Sundaram and I will be your guide in today’s episode. A deep dive into Roman. Roman is an infrared telescope named after Nancy Grace Roman that seeks to explore the mysteries of dark energy and image exoplanets. Roman and the James Webb Space Telescope offer broader ranges of sight when compared to the Hubble Space Telescope and are steps NASA is taking to uncover the secrets of space. Today we are doing a deep dive into the missions and engineering of the Roman space telescope with mission system engineer Mark Melton. 

MARK MELTON, GUEST: 

We know the universe is expanding after The Big Bang, but everyone thought that it would start slowing down. At some point, the expansion started accelerating. The name for that force that caused it to start accelerating is dark energy. So, we have multiple techniques that we’re using to study dark energy. 

SUNDARAM: 

Melton, who is a systems Engineer at Goddard Space Flight Center graduated from University of Maryland. With a Bachelor of Science in aerospace engineering. Melton worked at Swales Aerospace for 15 years before coming to Goddard, where he was first a thermal engineer. Melton also worked on the gamma Ray large Area Space Telescope, also known as GLAST, for six and a half years. Now, Melton’s the mission system engineer for the Roman Space Telescope. Romans two main objectives is discovering the cause of the expansion of the universe and searching for exoplanets. Despite this, Roman is also collecting various general information that hopes to support scientific endeavors of the astrophysics community. Previously, the Kepler mission served as a way to identify exoplanets that resided in a portion of the Milky Way Galaxy. Over its lifetime, Kepler identified over 2,600 planets, some of which have Earth-like qualities. However, the Roman Space Telescope looks to push past the limits of Kepler. 

MELTON: 

Kepler was sensitive to planets from the earth in and we’re mostly sensitive to the Earth out in terms of finding planets, and we use a technique called microlensing which uses gravitational lensing, the bending of light around gravitational sources. We’ll be looking toward the center of our Galaxy, and there are stars kind of moving back and forth in front of each other in terms of just distance. We’re looking toward the galactic bulge, which has a dense population of stars, and then when two stars line up, you’ll get kind of a brightening effect where the light from the background start kind of bends around the foreground star. And so, it looks brighter and so we’ll see lots of those lensing events. And then if there happens to be a planet around the star in the foreground, you could get a kind of a secondary little brightening. So that’s how we’ll detect planets. We won’t actually know like where they are like, “oh, it’s around that star,” but we’ll kind of have a census of the size of planets and through some of the dynamics of that reading that curve. You can kind of gauge the size of the planet and about how far it is from its host star. We also have technology demonstration instrument the chronograph built by JPL, which we’ll be doing imaging and spectroscopy. 

SUNDARAM: 

Spectroscopy is a field of scientific study that measures how matter absorbs and emits light. In this sense, different substances can be identified based on their absorption and emission of light along the electromagnetic spectrum or the rainbow. Roman will be carrying a chronograph that will be doing spectroscopy of exoplanets for the first time in space. 

MELTON: 

So, the other interesting thing about Roman is that we have a Hubble sized primary mirror. Our primary mirror is 2.4 meters in diameter, so about 8 feet in diameter. We had to then build front end optics to feed our two instruments, but we got significant hardware contribution there, so it’s using a Hubble sized telescope. But because of the size and the number of detectors we have in our wide field instrument, our field of view and instantaneous picture of Roman is about 1 to 200 times, depending on which kind of instrument on Hubble you look at. So, when you see, you know, if it takes Hubble 100 pictures to kind of form a picture of a Galaxy, we can get that in one snapshot. 

SUNDARAM: 

When looking at the range of view available to Roman, it is similar to taking a picture of a single blade of grass but having the capability to zoom out and see the entire field. James Webb and Hubble focus in on certain portions of space, but Roman can extend the view of a single snapshot through its new technological developments. Additionally, James Webb and Roman can be complementary to each other, since Webb can see further back in time due to its ability to see deeper into the infrared. Due to this, Roman can potentially take large snapshots of space to find interesting targets while Webb can home in on these specific curiosities. 

MELTON: 

Our Follow-On detector from what was on Hubble Space Telescope and James Webb, the Hubble detectors are they’re infrared detectors, they’re mercury cadmium Telluride detectors. The Hubble detectors were 1000 pixels by 1000 pixels. The James Webb detectors are 2000 pixels by 2000 Pixels, and Roman’s are 4000 pixels by 4000 pixels, and we have eighteen of those in our focal plane. 

SUNDARAM: 

If the engineering and technology directorate at NASA has made multiple contributions to the Roman Space Telescope, these contributions may hold the key towards achieving Roman’s goal of understanding dark energy. 

MELTON: 

ETD is contributing to PRISM and the GRISM. Both of those support our dark energy missions. 

SUNDARAM: 

Both the PRISM and the GRISM are spectroscopic instruments that break up light into the colors of the rainbow. By breaking down this light, both the instruments can measure the red shift of stars and galaxies in order to pinpoint their speed and distance in relation to Earth. Generally, both the PRISM and the GRISM have spectroscopic roots but different specific application. 

MELTON: 

So, the GRISM is used for our broad sky survey for dark energy, and then the prism is used for our looking at supernova, also for the dark energy. I mentioned, we have multiple techniques that we use so dark energy was initially was discovered using supernova, which can be what they call a standard candle. They essentially have the same brightness and so you can use that to measure a distance basically. The GRISM will be using to measure red shifts of large areas of the sky of galaxies and help to figure out how fast they’re moving away, and that will kind of gauge that expansion curve when things moved away. Because of the field of view of Roman and the size of that focal plane, they’re massive. I mean they’re I think they’re like maybe four or five inches in diameter which is really big for optics. Normally, things are much much smaller than that. They’re multiple element instead of just like a wedge of glass. They’re multiple glasses put together, so they had to mount those and co-align those optics and we have some unique glass materials to get all the properties. So, there were some challenges there. And then the last kind of major piece of hardware that we haven’t talked about yet is called our instrument carrier. So, our instrument carrier is a composite Truss kind of structure that supports the telescope. The telescope mounts to it, and the two instruments slide into it. If you know anything about JWST, it’s kind of like the ISIM. 

SUNDARAM 

The integrative science instrument model, also known as ISIM, is the heart of the James Webb Space Telescope. It contains the main science payload. Which detects the light found in distant stars, galaxies and planets. 

MELTON: 

There’s one other, I guess, one other aspect of the spacecraft I didn’t mention. The spacecraft is also providing what we call the outer Barrel assembly. So, you’re used to a telescope that’s got a big tube around it to keep out light. So, Goddard is building that. It provides thermal control for the telescope as well. And then we have a what we call deployable aperture cover. During launch, it’s closed up and it provides it prevents sun from getting in the telescope when we’re when we’re launched, and then on orbit, once it’s deployed, it provides stray light protection from sun getting down into the outer barrel. 

SUNDARAM: 

The deployable aperture cover is known as a soft deployable. The cover folds up, and when extended after launch, materials like Kevlar give this structure some micrometeorite protection. Every detail of this telescope is meticulously planned to ensure the greatest probability of success. Collaborations have played a large role in the creation of Roman. Every member of the team has different qualifications on specialties, and together they have worked to understand each other’s needs and to create the next big telescope, after the James Webb Space Telescope. Their interactions and dedication to the mission have been the key in creating Roman. 

MELTON: 

For our telescope, we have our own team here at Goddard. Even though we’re not building anything, we have a team that does oversight. So, we have, you know, people who have mechanical expertise and thermal expertise in optics. So, they provide oversight, they participate in meetings with them. They review design packages and things like that, so we still have some of our folks who do that for the wide field instrument. We have the team that does then who designs and builds the electronics that assembles the focal plane, designs the GRISM, and then we have lots of interactions with the vendor in terms of defining our interfaces. We have interface control documents and drawings that we that we all sit down and agree to, you know, this is how we’re going to interface these two pieces of hardware. What are the requirements for that? Since we’re building hardware and kind of providing oversight of them, we still have our folks who do cross checks of their analysis and things like that, as well. 

SUNDARAM: 

The Romans based telescope is currently set to be built and launched before the end of the decade. With the help of the talented scientists and engineers at NASA, the Roman Space Telescope may be able to unravel the secrets of dark energy. With that, I am Divya Sundaram with NASA’s Engineering and Technology Directorate signing off. Stay passionate and stay curious. Special thanks to Mark Melton, Joe Hill, George Jackson, Denise Cervantes and the civil servants at NASA. This podcast was produced and recorded by Divya Sundaram and Anthony Cusat.