Structural, Thermal, and Optical Performance (STOP) analysis of the NASA ARCSTONE instruments

Abstract

Calibration accuracy and long-term precision are key on-orbit performance metrics for Earth observing spaceborne sensors. The accuracy and consistency of environmental measurements across multiple instruments in low Earth and geostationary orbits are directly connected to the scientific understanding of complex systems, such as Earth’s weather and climate. It is common for instruments to carry on-board references for calibration at various wavelengths, but these are subject to degradation with time spent in-orbit, and also increase complexity, mass and power requirements. ARCSTONE is a mission concept that provides a solution to the challenge of achieving and maintaining required instrument calibration accuracy on-orbit in the reflected solar wavelength range. As an orbiting spectrometer flying on a small satellite in low Earth orbit, ARCSTONE will provide lunar spectral reflectance with accuracy sufficient to establish the Moon as an SI-traceable absolute calibration standard for past, current, and future Earth weather, land imaging, and climate sensors in both low and geostationary Earth orbits. The ARCSTONE instruments are required to provide spectral measurements in a thermal environment that varies by 40 °C or more depending on whether the instrument is in direct sunlight or shade. A Structural, Thermal, and Optical Performance (STOP) analysis is conducted to assess the robustness of these instruments in this thermal setting and to highlight areas for possible design improvement. The analysis is performed for transient thermal environments representing a thermal vacuum chamber (TVAC) test. Analysis was performed for both the ultraviolet – visible (UVVNIR) and infrared (SWIR) instruments, however, this paper will focus solely on the UVVNIR instrument. Additional considerations for the future flight units are presented, including modeling effects of preloads and sliding of lenses in their mounts on outcomes of the thermoelastic model. The ARCSTONE instrument design has been optimized based on the results of this analysis.