MS Thesis Defense - Danny Nelson

Tue, 21 Jan 2025 16:20:46 -0500

Hello ME Community,

Are you invited to join the Masters Thesis Defense of Danny Nelson, beginning at 2:00pm on Friday, January 24 in the M.E. Conference Room (ENGR210).

Advisor: Carlos Romero-Talamás

Title:
Thermal Design and Analysis of a Next-Generation Hyper-Angular Rainbow Polarimeter (HARP) Instrument

Abstract:
Hyper-Angular Rainbow Polarimeter (HARP) is an imaging polarimeter concept designed by the UMBC Earth Space Institute. Since 2017, the instrument has had several air- and spaceborne iterations, including HARP2 on board NASA’s PACE satellite, which is currently operating in orbit. MegaHARP is a next-generation HARP instrument that will improve its predecessors’ performance in several key measures. It is planned to fly on NASA’s Atmospheric Observation System (AOS) mission on the polar-orbiting AOS-Sky satellite. MegaHARP’s ambitious performance improvements come with engineering challenges. The design of the thermal system is one such challenge.
The thermal design has two key requirements: (1) to maintain its electronics within healthy temperature ranges in orbit, and (2) to maintain the instruments ultraviolet-visible (UV-VIS) and shortwave infrared (SWIR) focal plane arrays (FPAs) at constant, set temperatures throughout an acquisition to minimize temperature-related noise.
The instrument will be passively cooled to avoid the need for excess resources and complexity. A cold-biased approach is used to maintain the FPAs at a constant temperature (within ±0.5°C) throughout an acquisition, which lasts the entirety of the orbit’s day side. In this approach, the FPA radiators are sized to passively cool the FPAs below their set point, and pulse-width-modulated trim heaters raise their temperatures to the target. The heaters and radiators are first sized using orbital averaged environmental heat loads as a baseline. These baseline sizes are improved upon using heat path information obtained during the ground testing of HARP2. Although the instruments are not identical, MegaHARP inherits key design elements from its predecessor, making HARP2 test data a valid starting point for thermal characterization. Finally, a full orbital model is used to validate the instrument’s thermal design.
Using the thermal model, which takes into account details such as transient orbital heat loads and parasitic heat, the final radiator and heater sizes are obtained to achieve the thermal design requirements. The results indicate that a passive thermal system is viable within the mission’s volume and mass allocations, and that the cold-biased control scheme allows stability of ±0.5°C of both the UV-VIS and SWIR FPAs throughout an entire orbit at a range of desired target temperatures.