The Uranus Multi-Experiment Radiometer for Haze and Clouds Characterization

Abstract

The aerosols (clouds and hazes) on Uranus are one of the main elements for understanding the thermal structure and dynamics of its atmosphere. Aerosol particles absorb and scatter the solar radiation, directly affecting the energy balance that drives the atmospheric dynamics of the planet. In this sense, aerosol information such as the vertical distribution or optical properties is essential for characterizing the interactions between sunlight and aerosol particles at each altitude in the atmosphere and for understanding the energy balance of the planet’s atmosphere. Moreover, the distribution of aerosols in the atmosphere provides key information on the global circulation of the planet (e.g., regions of upwelling or subsidence).

To address this challenge, we propose the Uranus Multi-experiment Radiometer (UMR), a lightweight instrument designed to characterize the aerosols in Uranus’ atmosphere as part of the upcoming Uranus Flagship mission’s descending probe payload. The scientific goals of UMR are: (1) to study the variation of the solar radiation in the ultra-violet (UV) with altitude and characterize the energy deposition in the atmosphere; (2) to study the vertical distribution of the hazes and clouds and characterize their scattering and optical properties; (3) to investigate the heating rates of the atmosphere by directly measuring the upward and downward fluxes; and (4) to study the cloud vertical distribution and composition at pressures where sunlight is practically negligible (p > 4-5 bars).

The instrument includes a set of photodetectors, field-of-view masks, a light infrared lamp, and interference filters. It draws on the heritage of previous instruments developed at the Instituto Nacional de Técnica Aeroespacial (INTA) that participated in the exploration of Mars, where similar technology has demonstrated its endurance in extreme environments while utilizing limited resources regarding power consumption, mass and volume footprints, and data budget. The radiometer’s design and characteristics make it a valuable complementary payload for studying Uranus’ atmosphere with a high scientific return.