We continue our conversation with NASA Aerospace and Mechanical Engineer at NASA Goddard Space Flight Center since 2000 and dynamic analysis engineer for the deployable structures and space mechanisms of the James Web Space Telescope since 2013, Alejandro Rivera. If you haven’t read the first part of the interview, you can find it here .
Sarah Romero: At what frequencies can the telescope see?
AR: Unlike Hubble, which observes in the near-ultraviolet, visible, and near-infrared (0.1 to 1.0 μm) spectra, JWST will observe in a lower frequency range, from long-wavelength visible light ( red) to the mid-infrared (0.6 to 28.5 μm). This will allow it to observe high infrared redshift objects that are too old, faint and distant for Hubble.
SR: What is the feature or detail that stands out most about the James Webb?
AR: Without a doubt, the great number of deployable structures and separation mechanisms and the great complexity. Due to its large size, with a 6.5-meter main mirror (2.5 times larger than Hubble’s) and a sunshade the size of a tennis court, the telescope had to be completely folded ‘origami’ style in the upper cone of the Ariane 5 rocket to later unfold in space. This has represented one of the greatest technological challenges of the mission, since nothing on this scale has ever been done in history. During the launch, the deployable structures must be secured with the fastening and separation mechanisms. James Webb has a total of 178 of these mechanisms that I worked on and some of which I helped design, and they all had to work perfectly, otherwise the mission would be over.
SR: The first images of Webb should be available in the summer of 2022, right? What can we hope to discover with James Webb?
AR: Indeed, if all goes as planned, Webb will begin his science mission around the end of June. JWST has four main scientific goals: to search for the first galaxies or luminous objects that formed after the Big Bang; observe the formation of stars from their birth to the formation of their planetary systems; determine how galaxies evolved from their formation to the present; and finally, measure the physical and chemical properties of planetary systems and investigate the potential for life in those systems.
SR: What would you personally like to see Webb surprise us with in its first few years of operation once fully active?
AR: I would like it to surprise us in many ways. Besides the science goals I’ve already mentioned, my favorite is that we have a lot to learn about how galaxies got supermassive black holes at their centers, and we don’t really know if black holes caused galaxies to form or vice versa. I hope that the James Webb Telescope will help us answer this question. My second “astronomical wish” is that at this point we don’t know much about dark matter or dark energy, but with Webb we hope to learn more about where dark matter is now and we hope to learn the history of the acceleration of the universe that we attribute to dark energy.
SR: What does it mean to you, as a member of the project for almost a decade, to have finally been able to witness the launch into space and the successful deployment of the telescope?
AR: It represents the culmination of many years of effort and sacrifice in which we had to overcome many technological challenges. After spending so much time doing the dynamic analysis of the deployments and contingency analysis of all the deployable structures of the optical module and scientific instruments (upper part where the mirrors and scientific instruments are), as well as the analysis of the clamping and separating mechanisms , but then all the tests of the dropdowns that took us a long time, seeing everything work well was a great satisfaction.
These deployments I worked on, as well as the rest, were extremely critical and had they not gone according to plan, the mission would have been over in most cases. JWST had the most deployments and the most complexity of any satellite in history. To put things into perspective, JWST has 344 single points of failure, or points that, if failed, would end the mission. Of these, 275 (80%) belong to the separation mechanisms and deployable structures teams. By comparison, the Galileo probe had around 30 and a Mars landing has an estimated 100. In the deployable structures and separation mechanisms team we feel like we’ve made space history.
SR: Will Webb help us answer some of our big astronomical questions, like “how did the universe develop after the Big Bang?” “are we alone”?
AR : JWST was not designed to look at the beginnings of the universe and the Big Bang, but to look at a period in the history of the universe that we haven’t seen before . Specifically, we want to see the first objects that formed when the universe cooled after the Big Bang. That time period is perhaps hundreds of millions of years later than the COBE, WMAP and Planck satellites were built to see. We think that the small temperature ripples these satellites observed were the seeds that eventually grew into galaxies . We don’t know exactly when the universe created the first stars and galaxies, or how. This is what we hope JWST can help answer and why we built it.
SR: The mission, for now, is being a success and that is also a guarantee that JWST could live for a long time. For how many years is the mission planned in principle?
AR: The minimum duration of the mission is planned at 5 years, but the expectation is 10 years of scientific life. Webb’s separation from the second stage of the Ariane 5 rocket was so precise that the two trajectory correction maneuvers that were made used far less fuel than anticipated . Due to this, it is expected that Webb can be in orbit making astronomical observations for more than 10 years, since now it will have much more fuel for the trajectory and orientation adjustment maneuvers that are periodically necessary to maintain the correct orbit around L2. .
SR: Why is JWST said to be like a “time machine” and how is JWST able to see what the universe was like 13.5 billion years ago?
AR: Sunlight takes 8 minutes and 20 seconds to reach Earth, so when we look at the sun with our eyes we see it as when it was 8 minutes and 20 seconds younger. The light from the galaxy NGC 174 takes an average of 159 million years to reach Earth, so if we look at it through a telescope we see it as it was when the Earth was still inhabited by dinosaurs in the Jurassic . If we extrapolate this and build a telescope capable of capturing light emitted 13.5 billion years ago, we can see what the universe was like in its infancy when the first stars formed, some 300 million years after the ‘Big Bang’.
SR: How do you know where to point the James Webb telescope to see the first galaxies? How do you know the direction in which the universe originated?
AR: The Webb telescope can really look in any direction as long as it’s into deep space. The reason is because the universe does not have a “central point”. The term “Big Bang” is somewhat confusing, since it suggests that there was an explosion in a specific place and from that central point and that instant in time the universe began to expand. The reality is that the universe has no center, is infinite and expands on itself. The “Big Bang” happened everywhere at once and it was a process that happened in time, not a point in time. We know this because we see galaxies moving away from each other, not from a central point, and we can see the heat left over from the “early stage” of the universe, heat that evenly fills the universe.
From MuyInteresante, we wish James Webb a happy stay in L2 🙂
