Research Engineer & Post Doctoral Fellow

Icefin Robot

• Description: Icefin is a modular underwater robot designed for under-ice exploration, and capable of being deployed through narrow holes drilled through glaciers. It is a tool for polar research, as well as a NASA funded project advancing technologies for future exploration of ocean worlds such as Europa. - Icefin Homepage, Thwaites ‘Melt’ Project

• Contributions: As an engineer on the Icefin team, I contributed to system testing and development, as well as extensive field operations and logistics. I conducted three field seasons in Antarctica, working on five projects:
  • 2018-19: Ross Ice Shelf & Europa Underwater Probe (RISEUP)
  • 2019-20: International Thwaites Glacier Collaboration (ITGC)
  • 2021-22: HiPSMI - Ocean Supercooling Study, Scott Base Bathymetric Survey, Kamb Ice Stream
• Outcomes: The Icefin team collected ocean data in previously inaccesible regions beneath Antarctic glaciers. Surveys revealed key processes impacting ice melt, providing critical data for modeling sea level rise. Concurrently, deployments beneath ice shelves demonstrated important capabilities for future ocean worlds exploration.
• Co-Authored Publications: Schmidt et al. Nature 2023, Davis et al. Nature 2023, Lawrence et al. Nature Geoscience 2023, Meister et al. IEEE Global OCEANS 2020
• Media: BBC, New York Times, Washington Post, Wall Street Journal, more

Vertical Entry Robot for Navigating Europa (VERNE)

Subsurface Science and Search for Life in Ocean Worlds Fig 1. Conceptual diagram of the SSSLOW payload. (A life detection package concept for future sub-surface missions to “Ocean Worlds” such as Europa and Enceladus.)

Vertical Entry Robot for Navigating Europa (VERNE) Mission and System Design Fig 2. VERNE concept of operations for drilling through Europa’s the ice shell.

• Description: Europa is a moon of Jupiter with a thick ice shell overlying a large liquid ocean. VERNE is a NASA funded mission concept to melt through the ice shell of Europa in order to search for life in its interior.

• Contributions: Co-led a team of 21 scientists and engineers developing a conceptual life detection science payload for the VERNE melt probe. Team surveyed state-of-the-art life detection technologies from ocean, earth, and space science.

• Outcomes: The team developed a conceptual Europa sub-surface life detection package, integrating multiple scientific instruments. Defined critical science objectives, leveraged existing technological capabilities, and identified areas for needing further development. The team also developed a melt probe probe design and sub-surface mission architecture.

• Co-Authored Publications: Lawrence (co-lead), Mullen (co-lead), et al. Planetary Science Journal 2023, Bryson et al. AIAA ASCEND 2020, Bryson et al. Earth and Space Science (accepted)
  
  

Submersible Digital Holographic Microscope (DHM)

DHM Antarctic deployment.

DHM system design.

Euglena motility observations in lab experiment.

• Description: Holography is a computational imaging technique used to record a three dimensional volume. The submersible DHM uses this approach at small scale to observe microbial motility in the ocean. This is a proof of technology for future life detection missions to ocean worlds, and builds on existing DHM work from JPL.

• Contribution: Concieved and led collaboration with Georgia Tech & NASA JPL developing a submersible DHM for the Icefin ROV. Led development of instrument including compact microscopic optics, sumbersible housings, embedded electronics, and image processing software. Deployed system in Antarctica, and analyzed data.

• Outcomes: DHM successfully observed microbial motility in sub-ice Antarctic waters which serve as an analog for future “ocean world” exploration.

• Publication: journal paper in prep, presented at AGU AbSciCon 2022

Oceans Across Space & Time (OAST)

• Description: The OAST project is a NASA Astrobiology funded effort to study extreme salty environments on Earth as an analog for other planets. The Orca Basin cruise conducted underwater robotic investigations of the hypersaline Orca Basin brine pool, which has a salinity of greater than 7x ocean water and is at a depth of over 2,000m in the Gulf of Mexico. - OAST Homepage

• Contributions: Led team which developed a custom physical-chemical instrument package for remotely operated vehicle (ROV). Served as ROV Instrumentation Lead on research cruise.

• Outcomes: Team collected detailed physical-chemical-bio survey of Orca Basin brine pool over the course of 10 ROV dives. ROV and instrument packaged profiled full depth of brine pool.

Pingo Sub Terranean Aquifer Reconnaissance and Reconstruction (PINGO STARR)

• Description: Pingos are ice cored hills which exist on earth and potentially other planetary bodies. This NASA PSTAR (Planetary Science and Technology from Analog Research) project is investigating Pingos with ground penetrating radar, conductivity, and magnetotelluric techniques. - Pingo STARR Homepage

• Contributions: Lead Field Engineer on two field season surveying Pingos in the Arctic.

• Outcomes: Team utilized of geophysical instruments to provide new measurements of Pingo subsurface structure, with data anylsis is still ongoing.

• Presentations: LPI 2021, journal publications in prep
  
  

Graduate School

Benthic Underwater Microscope

Imaging unit internal components.	Control unit internal components.	Underwater operation by a scientific diver.
In situ coral image. Main scale bar 500 μm, inset 50 μm.	Fluorescent coral image taken in lab. Main scale bar 500 μm, inset 50 μm.	In situ coral competition timeseries.

• Description: Diver operated microscope capable of obeserving sea floor organisms such as corals in situ. Microscopic imaging is performed using a focus tunable lens, long working distance objective, and focused illumination. The system inculdes embedded computing and power in a custom housing

• Contributions: Co-led the system development with Dr. Tali Treibitz. Jointly developed and tested optics, led development of imaging unit electronics, and led SCUBA deployments of instrument.

• Outcomes: First system to image seafloor subjects such as corals underwater at micron-scale. Applied system to study coral behavior and bleaching in natural environments.

• Publications: Mullen (co-lead), Treibitz (co-lead), et al. Nature Communications 2016, Mullen et al. OSA Novel Techniques in Microscopy 2017

• Media: New York Times, Washington Post, Physics Today (Cover), Scientific American, Microscopy Today 2017 Innovation Awards

Submersible Micro-Particle Tracking Velocimetry (PTV)

Underwater Micro-PTV system.

Particle tracking, 500 μm scale bar.

Time averaged velocity field, 500 μm scale bar.

• Decription: PTV is a technique used to measure two dimensional fluid dynamics based on images of particle motion. Here the Benthic Underwater Microscope was enhanced to perform PTV at micro-scales in the ocean around individual coral polys.

• Contributions: Concieved and led project. Developed dark-field illumination to observe micro particles, implemented precision pulsed imaging, and developed particle tracking code. Deployed system in ocean and perform Fourier analysis of fluctuating two dimensional velocity fields.

• Outcomes: Measured viscous fluid boundary layer surrounding coral polyps in the ocean for the first time, and observed interactions with surrounding ocean waters.

• Publications: Ph.D. Thesis

Nassau Grouper Egg Tracking

Towed underwater microscope system, year 1.	Towed microscope images, year 1.	Egg tracking density map, year 1.
Towed underwater microscope system, year 2.	Towed microscope images, year 2.	Egg tracking density map, year 2.

• Decription: Processes occuring during egg life stage of fish is critical to population dynamics, however drifting eggs are very difficult to study in the natural environment. Here we developed a towed microscope system and used it to investigate Nassau Grouper egg dispersal following a mass spawning event.

• Contribution: Engineering lead on integration and deployment of the towed microscopic imaging system. Worked with science team to deploy system in two sequential years to investigate the transport and dispersion of eggs following Grouper spawning.

• Outcomes: Successfully tracked egg cloud and mapped egg densities in water column over multiple spawning nights.

• Presentations: Stock, et al. Proceedings of the Royal Society B, 2023, Stock BC, Mullen A, et. al. 69th Annual Gulf and Caribbean Fisheries Institute, 2016, Stock BC, Mullen A, et. al. 70th Annual Gulf and Caribbean Fisheries Institute, 2017, journal publication accepted for publication in Proceedings of the Royal Society B: Biological Sciences
  
  

Undergraduate

Groundwater Hydrology, Benin, West Africa

• Description: International collaboration between the University of Notre Dame and University Abomey Calavi studying salt water intrusion into the coastal aquifers surrounding the capital city of Cotonou. (Advisor: Dr. Stephen Silliman)

• Contributions: Conducted hydrology measurements at remote field sites to study costal saltwater intrusion over two summers. Lead small international team in field work, taught sampling methods, designed low-cost hydraulic field instruments, analyzed groundwater models.

• Publications: SE Silliman et. al. Sustainibility 2010

NOAA Hollings Scholar, University of Alaska Fairbanks

• Description: Summer internship at the University of Alaska Fairbanks studying oceanorgaphy of the Chukchi Sea, supported by the NOAA Hollings Scholarship. (Advisor: Dr. Tom Weingartner)

• Contributions: Prepared and deployed ocean gliders and HF radars collecting data for pollution spill models in Arctic Ocean.