<mods:mods xmlns:mods="http://www.loc.gov/mods/v3" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-7.xsd"><mods:titleInfo><mods:title>From Images to Azimuth: A Comprehensive Study of Orientation Calibration Techniques for the EXoplanet Climate Infrared TElescope (EXCITE)</mods:title></mods:titleInfo><mods:typeOfResource authority="primo">dissertations</mods:typeOfResource><mods:name type="personal"><mods:namePart>Deng, Feifan</mods:namePart><mods:role><mods:roleTerm type="text">creator</mods:roleTerm></mods:role></mods:name><mods:name type="personal"><mods:namePart>Tucker, Greg</mods:namePart><mods:role><mods:roleTerm type="text">Advisor</mods:roleTerm></mods:role></mods:name><mods:name type="corporate"><mods:namePart>Brown University. Department of Physics</mods:namePart><mods:role><mods:roleTerm type="text">sponsor</mods:roleTerm></mods:role></mods:name><mods:originInfo><mods:copyrightDate>2025</mods:copyrightDate></mods:originInfo><mods:physicalDescription><mods:extent>, None p.</mods:extent><mods:digitalOrigin>born digital</mods:digitalOrigin></mods:physicalDescription><mods:note type="thesis">Thesis (Sc. M.)--Brown University, 2025</mods:note><mods:genre authority="aat">theses</mods:genre><mods:abstract>During the August 2024 test flight of the EXoplanet Climate Infrared TElescope (EXCITE),&#13;
a balloon-borne observatory designed to characterize exoplanet atmospheres, absolute azimuth&#13;
data from the on-board GPS compass was not available throughout the flight. To supplement the&#13;
pointing information, we developed a method to reconstruct the payload’s azimuth using images&#13;
from a 360° action camera mounted externally on the gondola. The front-facing lens of the camera&#13;
was approximately aligned with the forward (stern-bow) direction of the gondola.&#13;
Through a ground-based calibration test, we determined that the camera follows an equidistant&#13;
projection model, allowing sun positions in the image to be mapped to azimuth angles with a&#13;
resolution of 0.5°. An automated Python pipeline was created to detect and centroid the sun in&#13;
each image and to assign an azimuth relative to the camera’s reference frame. These relative angles&#13;
were then combined with solar ephemeris data to recover the payload’s absolute azimuth.&#13;
The image-derived azimuth was compared with the yaw data calculated from gyroscope in-&#13;
tegration. While the two datasets showed similar trends across the flight, a growing offset was&#13;
observed in the later hours, likely due to integrated bias in the gyroscope solution. An additional&#13;
elevation analysis using both encoder data and image-derived solar elevation helped confirm the&#13;
accuracy of the elevation relative to the Sun. The secondary mirror temperature increase near 11:30&#13;
AM (GDT-6) is consistent with reconstructed pointing that placed the telescope closely aligned&#13;
with the Sun within ±3° elevation and ±5° azimuth relative to the Sun.&#13;
This work demonstrates that 360° imaging, combined with basic calibration and supporting&#13;
flight data, can provide a robust alternative means of azimuth reconstruction. The approach offers&#13;
a valuable tool for future balloon missions where direct azimuth measurements may be limited or&#13;
unavailable.</mods:abstract><mods:subject authority="fast" authorityURI="http://id.worldcat.org/fast" valueURI="http://id.worldcat.org/fast/01063025"><mods:topic>Physics</mods:topic></mods:subject><mods:subject authority="fast" authorityURI="http://id.worldcat.org/fast" valueURI="http://id.worldcat.org/fast/00819797"><mods:topic>Astrophysics</mods:topic></mods:subject><mods:subject authority="fast" authorityURI="http://id.worldcat.org/fast" valueURI="http://id.worldcat.org/fast/01146496"><mods:topic>Telescopes</mods:topic></mods:subject><mods:language><mods:languageTerm authority="iso639-2b">English</mods:languageTerm></mods:language><mods:recordInfo><mods:recordContentSource authority="marcorg">RPB</mods:recordContentSource><mods:recordCreationDate encoding="iso8601">20250707</mods:recordCreationDate></mods:recordInfo></mods:mods>