Dr. Evan Kelly

What is your research focus?

The focus of my research is instrument development and spatial heterodyne Raman spectroscopy (SHRS). The SHRS is a relatively new technique that has recently started to become utilized more in a number of fields. The basic idea behind spatial heterodyne spectroscopy (SHS) is that we combine two separate spectroscopic techniques in order to create a new one which helps overcome the drawbacks of both. The two spectroscopic techniques or instruments which are combined are a dispersive spectrometer and an interferometer. Specifically, the SHS utilizes a modified Michelson interferometer which consists of a beam splitter and two mirrors. The light enters the beam splitter and is directed towards the two mirrors before coming back and recombining to create an interference pattern that is imaged by a detector. This technique requires you to scan through one of the mirrors in order to constrain things like resolution and spectral range. Dispersive spectrometers utilize a grating which separates the light into its individual wavelengths all at once before being imaged on a detector. Dispersive spectrometers utilize narrow entrance slits in order to constrain the resolution. The SHS replaces the mirrors of the Michelson interferometer with gratings from the dispersive spectrometer. This has the effect of removing the need to scan through one of the mirrors, thus removing the need for moving parts, while at the same time removing the need for a small entrance slit to constrain the resolution, allowing more light to enter the spectrometer. In short, the SHS gives you the best of both worlds.

Instead of focusing on specific science questions myself, I seek to answer the question of what kind of instruments or modifications to instruments I can make in order to help others answer as many science questions as possible. Thus, the focus of my work changes depending on the particular topic or mission. Currently, based on the new priorities of NASA under this administration, the question is how we can modify the SHRS to help astronauts and scientists map out mineral distributions on the Moon to aid in resource utilization. To do this, the SHRS is modified to be a monolith which results in the gratings and beamsplitter in the SHRS to be fused into one solid piece made of one material. Making it monolithic makes the SHRS, now the monolithic SHRS (mSHRS), robust by any day-to-day variations in alignment and removing its sensitivity to things like vibrations, making it a suitable instrument for planetary science and space missions. Additionally, we modify it so as to replace one grating with a mirror, creating the one-grating mSHRS (1g-mSHRS). This has the effect of both increasing the spectral range and the signal-to-noise ratio (SNR). This spectral range is inversely related to resolving power, with resolving power increasing as the number of gratings or the density of the grooves on the gratings increase. Thus, removing a grating lowers the resolving power and increases the spectral range. The SNR increases with this modification because the mirror causes more light to be sent to the detector instead of the light being diffracted into other direction on top of being sent to the detector. This is important as Raman spectroscopy, while powerful and able to unambiguously identify molecules and substances, is inherently insensitive, so an increase to the SNR would aid in mapping minerals on the Moon.

Photo Credit: Michelle Friedman.

What is one space mission that you are particularly excited about, and why?

One space mission I am particularly excited about is Dragonfly, which is a robotic rotorcraft which is set to be sent to Titan. There are a number of reasons why this mission excites me. The first is that it is a basically a helicopter which will fly on another world, much like Ingenuity did on Mars. That is pretty cool in and of itself. Moreover, Titan is an extremely interesting moon which has its own dense atmosphere and liquid bodies on its surface, on top of having a liquid ocean underneath the surface. Dragonfly's goal is to basically look at the progression of prebiotic chemistry and search for any evidence of past or present life on Titan. Because it is a rotorcraft, it will be able to move much quicker than any other robotic craft sent to another planet before, allowing scientists to cover more ground than any other surface mission before. I expect it will tell us a lot about how complex chemical reactions occur on another body, as well as help inform us on exactly how its surface came to be in its current form. I would have loved to have a Raman instrument on the craft as well, since once you overcome the insensitivity, it is probably the best technique for identifying compounds of various states of matter compared to its size.

Photo Credit: Evan Kelly.

Did you always know that you wanted to study Planetary Science and instrument development?

The short answer is no. The long answer is that in high school I wanted to be either a lawyer or doctor, because of money. Eventually, I started to focus on becoming a doctor, with specific hopes of becoming an anesthesiologist. However, this changed in 2016 once I saw that SpaceX was making waves, and the idea of going to Mars was potentially on the horizon. During the later years of my time in college, I came to understand that choosing a career solely for the money has a high potential of making you miserable. So, I asked myself: “What do I need to do in order to be a good candidate to get to go to Mars?” This question has led me to where I am now, with a Ph.D. working for NASA. I will continue to keep an eye out for new opportunities, such as being an astronaut or going to space, but my current focus has shifted to designing and building an instrument which will be utilized on a planetary science missions in the future.

Photo Credit: Mario, owner of Unseen Namibia.

Are you involved in any upcoming space missions?

Currently, I am not involved in any upcoming space missions. However, before coming to Goddard, and while I was at the University of Hawaii at Manoa (UHM), I was part of the science team on the Perseverance Rover. I started on that mission around October of 2020, and it landed on Mars in February of 2021. I worked on the mission until December of 2024, which is almost 4 years. While on the mission I worked as a science payload downlink (sPDL) for the SuperCam instrument, which is led by Roger Wiens out of Purdue. As an sPDL, I would be one of the first to look at the data received from SuperCam on the specific day I had a shift, and I would interpret the data before sending it off to the rest of the science team for further analysis and to plan next steps.

Photo Credit: Eleni Ravanis.

If you were to expand your current research focus, what new topic(s) would you explore?

If I were to expand my current research focus, which I plan to eventually do once I am more situated, I would focus on the development of nuclear magnetic resonance (NMR) for planetary science missions. I did work during my Ph.D. on this very topic, and this can be read in Chapter 5 of my dissertation “Next Generation Spectroscopic Techniques and Methods for Planetary Exploration”. The chapter is titled “Evaluation of the Viability of Nuclear Magnetic Resonance spectroscopy as an analytical tool for Planetary Exploration”, and it is currently available on ProQuest. However, if accessing it is difficult, then feel free to reach out to me, and I will send a copy to whoever would like it. It basically boils down to NMR being able to do things no other spectroscopic technique can accomplish. One such ability is determining the connectivity within a molecule, allowing NMR to identify novel molecules, biological markers (such as peptides), and isomers. This is on top of being able to show how molecules interact with one another in an environment utilizing two dimensional (2D) techniques. Furthermore, NMR can be utilized for reaction monitoring, where the changes in the composition can be monitored over time. This can help aid in determining reaction dynamics within a system, which in turn could help with modeling efforts of subterranean oceans in the outer solar system. Together, these capabilities would make NMR incredibly useful in the search for life beyond our planet.

Photo Credit: Eleni Ravanis.

What early career advice do you have for those looking to do what you do?

Ultimately, my advice can be applied to any goal, not just what I do. First, you need to realize that you alone are the one who determines what you are capable of. No one else can truly dictate that. As long as you remember this, barring a few exceptions (such as becoming president), you will ultimately determine how far you go and what you eventually achieve.

With that in mind, you need to set an overarching goal for yourself. Ideally, this should be an extraordinary goal, like my goal of going to Mars. Then ask yourself the question: “What skills and experiences do I need to accomplish this goal or to make myself a good candidate for the position I ultimately want?” Once you answer that, ask: “Where can I gain these skills and/or experiences?” After you identify where these can be acquired, determine the steps you need to take to make yourself a good candidate to get to those places.

Once this is mapped out, you shouldn’t focus constantly on achieving the big, extraordinary goal. Instead, focus on the immediate here and now, and take it one step at a time. Don’t be afraid to use anything and everything at your disposal to achieve each of these small steps. And don’t hesitate to ask others for help. If you follow these general steps, you should do well for yourself.

Even if you ultimately don’t achieve that extraordinary overarching goal, you’ll likely fall just a little short, and honestly, being just shy of extraordinary is still something to be proud of. Either way, if you follow these steps and set your goal far above what you want, you’ll likely reach your real goal. In other words: aim higher than your goal to increase your chances of reaching it.

I feel like I should give a little context about where I’m coming from. I have ADHD and dyslexia, and it was hard for me to even learn how to read and write initially. In kindergarten, I was once told I was stupid and would never amount to anything. That’s why I say that you, and no one else, truly determine what you’re capable of. Stick to that, and you’ll be surprised at what you end up achieving.

Photo Credit: Eleni Ravanis.

What research accomplishment are you most proud of?

So far, the research accomplishment I am most proud of is the work I did for my Ph.D. Specifically, I am proudest of my second paper, which was featured on the cover of the Journal of Applied Spectroscopy for the December 2023 Issue. This was work that technically spanned the entirety of the United States. Some of this work was completed on the East Coast at the University of South Carolina (USC), in their chemistry department, under Mike Angel, while the rest was in the Pacific Ocean in Hawaii in HIGP at UHM, under Shiv Sharma. The study centered on comparing the performance of different types of cameras, specifically an intensified charged coupled device (ICCD), a charged coupled device (CCD), and a complementary metal-oxide semiconductor (CMOS), when utilized in SHRS. The results went against conventional wisdom for camera technology and SNR. Generally, the larger the pixel size, the higher the SNR. This is, basically, because the larger the pixel, the more light each pixel receives, meaning the higher the signal will be. However, we got the opposite results, with the detector with the smallest pixel size (the CMOS) having the highest SNR compared to the ICCD and CCD. If you are interested in knowing more, I encourage you to check out the publication for yourself to get a more complete and in-depth understanding as to why this was the case. The name of the publication was: Single-Grating Monolithic Spatial Heterodyne Raman Spectrometer: An Investigation on the Effects of Detector Selection. The DOI for the publication is: 10.1177/00037028231204894.