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Detecting and improving the scientific understanding of global trends in complex Earth systems, such as climate, increasingly depend on assimilating datasets from multiple instruments and platforms over decadal timescales. Calibration accuracy, stability, and inter-consistency among different instruments are key to developing reliable composite data records from sensors in low Earth and geostationary orbits, however, achieving sufficiently low uncertainties for these performance metrics poses a significant challenge. Space-borne instruments commonly carry on-board references for calibration at various wavelengths, but these increase mass and mission complexity and are subject to degradation in the space environment. The Moon can be considered a natural solar diffuser which can be utilized as an on-orbit calibration target by most space-borne Earth-observing instruments. Since the lunar surface reflectance is effectively time-invariant, establishing the Moon as a high-accuracy calibration reference enables broad inter-calibration opportunities even between temporally non-overlapping instruments and provides an exo-atmospheric absolute radiometric standard. This on-orbit radiometric spectral reference helps enable high-accuracy absolute calibrations and inter-calibrations of past, current, and future Earth-observing sensors, meteorological imagers, and long-term climatemonitoring satellite systems. The goal of the ARCSTONE In-Space Validation of Earth Science Technologies (InVEST) project, funded by NASA ESTO, is to demonstrate its novel lunar measurement approach from space and improve the Moon as a radiometric SI-traceable reference for high-accuracy on-orbit calibrations spanning the visible and nearinfrared spectral regions. The ARCSTONE instrument is a compact spectrometer which will be accommodated on a 6U CubeSat intended for low Earth orbit with planned readiness for launch in about 2 years. It will measure the lunar spectral reflectance with combined standard uncertainty of 0.5% (k=1) across the 350 nm to 2300 nm spectral range. The ARCSTONE InVEST team will present the status of the project, the instrument design, calibration approach, concept of operations, and the planned path toward mission implementation.

Increasing atmospheric mixing ratios of CO2 have already lowered surface ocean pH by 0.1 units compared to preindustrial values and pH is expected to decrease an additional 0.3 units by the end of this century. Pronounced physiological changes in some phytoplankton have been observed during previous CO2 perturbation experiments. Marine microorganisms are known to consume and produce climate-relevant organic gases. Concentrations of (CH3)2S (DMS) and CH2ClI were quantified during the Third Pelagic Ecosystem CO2 Enrichment Study. Positive feedbacks were observed between control mesocosms and those simulating future CO2. Dimethyl sulfide was 26% (±10%) greater than the controls in the 2x ambient CO2 treatments, and 18% (±10%) higher in the 3xCO2 mesocosms. For CH2ClI the 2xCO2 treatments were 46% (±4%) greater than the controls and the 3xCO2 mesocosms were 131% (±11%) higher. These processes may help contribute to the homeostasis of the planet.