About Me

Fellow grad students during a partial solar eclipse
My favorite artwork
Me and the prototype ngVLA antenna

Education: Summer 2025: PhD in Astrophysics - Arizona State University
Graduated Fall 2019: Bachelor of Sciences in Physics - Fresno State, Minors in Astronomy and Mathematics, Magna Cum Laude

Research Interests: Astronomy instrumentation. 21-cm cosmology, specifically in connection to the Epoch of Reionization and Cosmic Dawn.

Publications:
HERA Memo #058: Constant Offset in Cross-Polarized HERA IDR2.1, 2018
Investigating mutual coupling in the MWA Phase II compact array, 2024, In Press
OVRO LWA Memo #17: Cable Reflections in Stage 3 Autocorrelation Delay Spectra

Research

Current Research

Testing the ngVLA prototype antenna
I am a member of the team testing the ngVLA prototype antenna at NRAO. This includes studying RFI contributions, performing holography measurments of the antenna surface, and integrating the prototype antenna into the existing VLA.

Mutual Coupling in low frequency radio interferometers
Mutual coupling and antenna-to-antenna reflections cause excess correlation in observations with low frequency radio interferometers. This is especially concerning for 21 cm cosmology. I have built models in FEKO determine how strong mutual coupling is and how it changes as more antennas are added. These results are compared to semi-analytic models of mutual coupling to determine how accurate these parameterized models are for use in visibility predictions and calibration pipelines.

Past Research

Cable Reflections in the OVRO-LWA
I worked with Dr. Daniel Jacobs during the Phase 3 EoR commissioning of the OVRO-LWA radio telescope. I used observations to study how the upgrade affected the amount of cable reflections present. I wrote code in Python to create 2-D power spectra of the Phase 3 observations and compared to historic observations to determine if the severity of cable reflections had been reduced with the upgrade.

Low reflectivity surface treatments for a spectrograph optical table
I worked with Dr. Nathaniel Butler on the EXoplanet Climate Infrared TElescope (EXCITE). Because the spectrograph is made of reflective metal, there was a concern over scattered light making its way into the detector. To minimize this issue, I researched possible low reflectivity surface treatments to coat the inside of the spectrograph. I modeled the light scattering and thermal emission properties of each treatment in python to compare to the theoretical noise level requirement.

Stress in transition edge sensor-based bolometers
Summer research internship at NASA Goddard Space Flight Center under the supervision of Dr. Edward J. Wollack and Dr. Karwan Rostem
I studied sources of stress in cryogenically cooled transition edge sensor (TES) based bolometers. I built models in COMSOL and simulated the fabrication process of the bolometers to determine what caused the existing bolometers produced by the HIRMES team for an experiment on SOFIA to deform.

Maintenance on a 16-inch optical telescope
Semester research at CSU Fresno under the supervision of Dr. Fredrick Ringwald
I performed maintenance on Fresno State's station at Sierra Remote Observatories. This included updating the computers, mounting a camera on the 16-inch telescope, commissioning replacement hardware, and other routine maintenance required.

Signal leakage in the Hydrogen Epoch of Reionization Array
Summer internship at ASU working with Dr. Daniel Jacobs.
I worked with the HERA radio telescope to study the source of signal leakage in the cross-polarization data. I wrote code in CASA and Python to create 2-D and 3-D power spectra. I then created a mathematical model of the possible sources and compared to the real observations.

Community

Mentoring

Cal-Bridge
I have been a peer mentor with Cal-Bridge since 2020. This has included one-on-one mentoring for undergradute students and volunteering at workshops on applying to graduate school, mental health in college, and research and scientific coding.

LoCo Lab
From the summer of 2021 to the summer of 2025, I acted as a mentor to the undergraduate students working in the LoCo lab. During the school year, I provided advice and answers to research questions for the ASU students who conduct research as part of the lab. During the summers, I acted as a research mentor to the summer interns who are employed in the lab.

Outreach and Science Communication

Low Frequency Cosmology (LoCo) Lab Graduate Student Representative
I epresented the LoCo lab at various outreach events with SESE at ASU, along with other students. This included answering questions about the research in the lab, leading demonstrations, and overseeing the undergraduate student representatives.

Fresno State Downing Planetarium Assistant
I worked with the head of the Planetarium, Dr. White, on the science communication aspects of running the Planetarium. This included leading visiting school groups through crafts about astronomy, leading guided tours of the museum, and giving science demonstrations. During the monthly shows open to the public, I assisted with customer service aspects of the job as well as setting up and operating the telescope.

Teaching

ASU
I taught the Introduction to Astronomy - Laboratory at ASU for two years. As a TA for one semester, I taught three lab sections. As Head TA for three semesters, I taught two lab sections per semester. This involved creating lesson plans, updating existing lab materials, advising other TA's, and leading telescope observing labs.

Fresno State
I was a recitation leader for Calculus II for one semester, and then a recitation leader for Introduction to Thermodynamics and Electromagnetism for three semesters.
I was a Physics tutor for one year.

Contact

Email: kelder[at]nrao.edu