Andreas Faisst

Assistant Research Scientist


This profile series introduces current Caltech/IPAC scientists who support various projects at IPAC. They also carry out their own scientific research.

In this profile, we feature Andreas Faisst, an early-career assistant research scientist at IPAC, who works on NASA’s SPHEREx, the NASA/IPAC Infrared Science Archive (IRSA), and his own active research program. 

SPHEREx is an all-sky, visual to mid-infrared spectral mapping Medium Explorer mission. It will map the entire sky four times and will allow scientists to answer big questions about the early universe, the history of galaxies, and the prevalence of life-sustaining molecules in planet-forming regions of space. It is currently expected to be launched no later than April 2025. Andreas leads several components of the data reduction pipeline of SPHEREx, and is part of the SPHEREx science team, focusing on quasars and dust in early galaxies.

Andreas works on the data science team at IRSA, which is one of the NASA Astrophysics mission archives. In particular, he is involved in testing and implementing Fornax (, a cloud-based system that brings together data, software, and computing so that researchers can focus on science. 

Scientifically, Andreas is interested in characterizing galaxy formation and evolution in the early Universe, including the study of star-forming clumps, dust-obscured galaxies, and the emergence of the first quiescent ("dead") galaxies. He also leads three large programs with ALMA and JWST to study the gas and dust properties of star-forming galaxies less than one billion years after the Big Bang.

How and when did you start thinking about becoming an astronomer, and where were you living at that time?

I grew up in Zurich, Switzerland, about 20 minutes from downtown by tram or bus. When I was about 10 years old, I became interested in the night sky. From our balcony facing south, and because we lived a bit outside of the city, I had a great view of the planets and stars. Soon my parents bought me a small refractor telescope (which later got upgraded to a 9.25" Celestron), that I used regularly to photograph the planets and their moons, as well as some deep sky objects. From that point on, I decided to become a physicist. I was not ready to commit to astronomy/astrophysics yet, but I wanted to keep my options open.

During my high school years, I became a member of several amateur astronomy clubs, and I brought my Celestron telescope to the mountains to try astrophotography. At 19, I started giving tours at a small observatory just outside of Zurich. Starting with my physics bachelor’s and master’s studies at ETH Zurich, I started to give regular tours and public talks at the Urania Observatory in Zurich, for many hundreds of people each month. This is when I decided to pursue a career in astrophysics.

I also liked to watch a lot of movies about space, such as Star Wars and Stargate. My favorite books were Science Fiction books, and a lot of my reading at the time was of lighter nature to give my brain some rest!

From that time on, what was the path to your current job and what do you think were your decisive strengths that allowed you to obtain your current job?

I went to graduate school, where I still had some options as to what kind of research I wanted to pursue in physics. One cool thing that we did during my first year in the master’s program was to take an astronomy lab class. We spent a week high in the mountains, observing with real telescopes and doing all the relevant data reduction steps. We measured the speed of the light from observations of Jupiter’s moons, and we determined the age of globular clusters from the measurement of their color. We also had to write real observing proposals (“to get the observing time”). 

After finishing my master’s astronomy and other, mostly physics, classes, I started working on my master’s thesis in astrophysics under the supervision of my future Ph.D. mentor at ETH Zurich. The goal of my master’s thesis was to measure the physical properties of star-forming gas clumps in galaxies. Shortly thereafter, I was hired to pursue a Ph.D. in astrophysics, which I did from 2011 to 2015, with a broad topic of studying the evolution of star-forming and non-star-forming galaxies through cosmic time. At the end of my Ph.D. studies, I obtained a prestigious Swiss fellowship (equivalent to the Hubble Fellowship) that provided funding to pursue a three-year postdoc anywhere in the world. Since I had collaborators at Caltech already, I chose Caltech/IPAC as the place for my postdoc. Finally, at the end of 2018 I became a staff member at Caltech/IPAC.

I think that one of my strengths is my broad knowledge of different topics in astronomy. I am also collaborating with many various people who are experts in different areas of astronomy. This allows me to formulate science use cases for future missions, such as The PRobe far-Infrared Mission for Astrophysics (PRIMA) far-infrared telescope concept. Furthermore, leading several large scientific collaborations has taught me how to work with different personalities.

What are the best things about working at IPAC?

The work at IPAC is very flexible and has many components. These include working on cutting edge space missions, pursuing exciting science, and passing along knowledge and expertise to students and postdocs. I also like that Caltech is a relatively small school, which makes it possible to connect with other departments and pursue interdisciplinary science projects. Specifically, I have worked with Summer Undergraduate Research Fellowship (SURF) undergraduate students with computer science majors at Caltech who were very good with computers and in coding.

Tell us a funny story from your science career or training?

During my studies in the Ph.D. program at ETH, I became famous for eating a banana (or two or three) at 4 pm every day. When I left for California to pursue my postdoctoral research, my colleagues and friends sent me a gigantic box of bananas (I believe it was about 50 lbs). That's when I learned how to make banana smoothies, banana bread, and frozen banana popsicles. I still eat a banana everyday between 4 and 6 pm. I usually eat a banana in the morning as well.

What do you hope to continue learning about, either personally or professionally? What are your current main pursuits in science?

I recently began working on Fornax, a collaboration among the NASA mission archives to leverage cloud resources to build tools that will enable astronomers to analyze the huge quantities of data coming from the current and next generation of telescopes. We want to allow the simultaneous analysis of data from various telescopes. Such a science platform also allows universities and colleges with smaller financial possibilities to use the data from these telescopes and to pursue cutting-edge science. My role is to formulate various science use cases for this science platform.


Andreas Faisst is the US lead of the ALPINE ALMA large program, which aims at understanding the gas and dust properties of galaxies 1 billion years after the Big Bang through the measurement of far-infrared continuum and emission lines. He also leads the JWST NIRSpec/IFU follow-up of some of these galaxies. The image shows a collage of far-infrared [CII] line emission for a subset of ALPINE galaxies. (Image credit: M. Ginolfi – ALPINE collaboration).

I am currently leading several large science programs with JWST and ALMA data, which will lead to breakthroughs in our understanding of the very first galaxies in the Universe. My goal is to study galaxies through a multi-wavelength perspective and learn about their stars, gas and dust, as well as their co-evolution with their nuclear supermassive black holes. Leading many large groups is currently my main priority, and I am still learning every day how to optimize the organization of these projects. 

I am also attending workshops and courses to improve my teaching and mentoring skills. I have found these courses very helpful not only for managing students and postdocs, but also for improving the interaction between team members of large collaborations. And I am also interested in outreach. I am a telescope captain for the Friday night public lectures in the Caltech Astronomy Department, where I get to teach new Caltech graduate students how to use telescopes. I really like the interaction with students, and I have summer students working with me almost every summer. It makes me very happy when I can share knowledge and see them learn computer skills and scientific thinking that we, as professionals, need every day. 

I feel like the students today are missing an important component of learning about the data and the possibly uncertainties of the data, as they are doing mostly just remote observing. They should really get hands-on experience at a telescope, where you are exposed to the various systematic uncertainties that may affect your data.

What is a passion or hobby that brings you joy or fulfillment?

Astronomers do not have 9-to-5 jobs. I find myself regularly working on weekends, and it is not unusual for me to work late on weeknights. Therefore, it is very important to take time off occasionally. 

My main passion outside of work currently is playing volleyball (both at Caltech and currently in a league in Alhambra and even in Irvine once a month) and playing pool billiards with friends (in Alhambra, Burbank and Pasadena; I was playing in national level leagues in Switzerland). 

I also have a background in playing the piano. Although I am not playing concerts anymore, I do like to play for myself and at small gatherings. Other than that, I regularly go on hikes and bike rides (I bike to work every day), and I like skiing and snowboarding in winter.

Another passion of mine is airplanes. As a private pilot, I used to explore Switzerland from 6000 ft and above. Unfortunately, I had to quit this hobby due to the lack of available time. Instead, I now have several remote-controlled airplanes that I fly in nearby parks, such as the Victory Park in Pasadena.

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