Kristina Davis

Grad Teaching Associate
Graduate Assistant/Associate
TEMPE Campus
Mailcode
6004

Student Information

Graduate Student
Exploration Systems Design (Instrumentation)
Liberal Arts & Sciences

Biography

     I am a current senior graduate student at Arizona State University. My PhD. Program is in Exploration Systems Design (ESD), which is a hybrid course of study to develop instrumentation for astronomical research. The School of Earth and Space Exploration and the Ira A. Fulton School of Engineering jointly oversee the ESD program. My research focus is in the development and characterization of instruments spanning 300 GHz to 5 THz. I have been a team member of several ground-based and atmospheric observing missions, assisting with instrument development, remote site integration, receiver characterization, and data analysis and publication. All of the missions I have been involved with seek to observe the creation, disruption, and feedback mechanisms from interstellar medium (ISM) clouds in the Milky Way as they cool and condense, and possibly collapse into proto-stellar cores. My professional goal is to pursue an academic career in the technology development to make increasingly sensitive and more detailed studies of these regions possible.

     Specifically, the bulk of my dissertation focuses on beam pattern measurements of various instrumentation types and using different analysis techniques in the terahertz frequency regime. I have worked on developing new techniques to employ phase-sensitive beam mapping measurement techniques with incoherent detectors, streamlining designs of previous systems to make them easier and cheaper to implement, and applying both coherent and incoherent beam pattern measurements in the laboratory and in the field to calibrate new receiver components and flight hardware.

     I have developed novel techniques to measure beam patterns for multiple detector systems at different frequencies, system configurations, and detector types. My area of expertise is complex beam pattern measurements, which measure phase of the received signal as well as amplitude (power). Most notably, I am part of the team that developed a technique to measure the phase of direct detectors (MKIDS), which are intrinsically phase-insensitive. This work began as a collaboration with the Netherlands Institute for Space Research (SRON) in 2014  by demonstrating the novel measurement technique on a single pixel. The collaboration has continued into the present by expanding the analysis to the characterization of 784 pixels of the AMKID focal plane array. The basis of the technique is to use a coherent beam pattern measurement set-up, where one coherent source is mounted on a planar scanning device and a second is used as a local oscillator. Phase detection of the MKID detectors is accomplished by referencing the time domain modulated KID signal to a reference signal created at low frequency from the synthesizers used to drive the high frequency sources.

     I have developed Python modules to run the essential lab equipment that is easily adaptable for the specific text commands used to run each device. I have also developed a rigorous plane-wave spectrum Fourier analysis and Gaussian Beam Mode analysis software algorithms to analyze big datasets from large detector arrays. With this technique, end-to-end receiver characterization including direct, detailed comparison to electromagnetic simulations is possible, as well as propagation of the complex field from the near to far field, wave front error analysis, pointing offset characterization, and spatial filtering and masking. 

     I have worked on several missions to design feedhorns for heterodyne Hot Electron Bolometer (HEB) arrays, at multiple frequencies and with multiple feedhorn profiles. Specifically, I have worked on integrating a circular to rectangular waveguide transformer into the feedhorn block, such that the transformer can be machined from within the aperture of the feedhorn. I have worked with the Stratospheric Terahertz Observatory-2 (STO-2, 2013-2017), the Galactic/Ultragalactic Stratospheric Terahertz Observatory (GUSTO, 2015-2017), and Super Heterodyne Array for Space Terahertz Applications (SHASTA, phase A, 2016) missions. I have designed feedhorn blocks to be direct metal micro-machined rather than electroformed, making large arrays quick and relatively inexpensive to manufacture. In this frequency regime, the dimensions and tolerances of these horns require new fabrication techniques. I have worked closely with our in-house machinist to ensure the designs are easily repeatable and can be scaled from engineering models to large arrays with hundreds to thousands of pixels. I do my designs in both Computer Simulation Technology (CST) and High Frequency Electromagnetic Field Simulation (ANSYS-HFSS), and draft all of my designs using Solidworks.  The horn block is designed to be drilled with a 3-axis milling machine, which holds precision well enough to enable horns up to ~2 THz to be machined with this technique. Integrating the transformer into the feedhorn block allows for more precise alignment and quicker manufacturing times where such a transformer is necessary. 

                The research that I have enjoyed the most has been with instrument commissioning of flight hardware at remote field sights. I was a part of the SuperCam commissioning campaign on the Heinrich Hertz telescope on Mt. Grahm in the spring of 2014. I participated on the development of the data reduction pipeline at the end of the observing mission and continuing into 2015. I was also a part of two field campaigns at McMurdo Station, Antarctica with the STO-2 mission. The first campaign was from November 2015-January 2016 but the flight was delayed due to poor launch conditions lasting the entire launch window. I went back for the second season in November 2016-January 2017. STO-2 launched successfully on December 8, 2016 and was in flight for 22 days. On both campaigns, I was in charge of taking incoherent beam scans of the instrument pre-flight. I was also the lead for near-field focusing tests using high-power LO transmitter at 850 Ghz and a corner cube reflector to act as a point source in the field. During the 2016/2017 campaign, I was a science operator of the instrument during the flight. I was in charge of monitoring the instrument subsystems via real-time communication with the payload, and looking at the data packets coming down to ensure high quality data and repeat raster scans if necessary.