03/07/2025
By Thaddeus Potter
Time: Thursday, March 27th, 1-3 pm ET
Location: Wannalancit Mills, Room 305
Committee:
Timothy Cook, Ph.D. (Advisor)
Christopher Mendillo, Ph.D.
Supriya Chakrabarti, Ph.D.
Wei Guo, Ph.D.
Daewook Kim, Ph.D.
Abstract:
The Planetary Imaging Concept Testbed Using a Recoverable Experiment-Coronagraph (PICTURE-C) is a high-altitude balloon-borne observatory that uses a vector vortex coronagraph to image debris disks and exo-zodiacal dust around nearby stars. The instrument has thus far flown twice; an engineering flight demonstrating core instrument and control systems took place in September of 2019, and a science flight which achieved a pointing stability of 1 milli-arcseconds and a contrast of 4e-6 at working angles of 0.5-2" took place in September of 2022.
During each flight, the high-altitude environment presented several challenges in thermal and mechanical effects. Low ambient pressure and temperature, approximately 4 Torr and 240 K respectively, combined with significant and varying solar irradiance, led to time-dependent and anisotropic thermal deformation of the supporting structure and optical elements. A constantly swaying observatory in a 1g environment and the mechanical strains of a pointing system keeping the instrument on target lead to both a sag and flexing of the support structure.
In order to characterize how these effects limit the ultimate performance of the mission, I present a structural, thermal and optical performance (STOP) model of the flight instrument, implemented in Thermal Desktop, ANSYS mechanical, and Zemax, which takes into account thermal interactions with the environment, and sets a framework for present and future analysis of the PICTURE mission series.