We present the current development of the Carbon Balance Observatory (CARBO). CARBO is a wide-swath mapping, low Earth orbit (LEO) new generation of instruments that expands on the ground-breaking CO2 and Solar Induced Fluorescence (SIF) measurements pioneered by the Orbiting Carbon Observatory (OCO-2/3) by adding CH4 and CO detection. The instrument's spatial coverage is delivered at 2 km by 2 km resolution with a field-of-view of 10° to 15° from LEO for a ∼200 km wide swath. It achieves roughly 20x better spatial coverage than the OCO-2 instrument, and 3x better Solar Induced Chlorophyll Fluorescence (SIF) detection sensitivity, in a smaller package. CARBO will measure CO2 at <1.5 ppm, CH4 at <7 ppb, CO at <5 ppb and SIF < 20%. The measurement of CO2/CH4/CO/SIF at these concentrations will significantly increase our ability to disentangle carbon fluxes into their constituent components. CARBO utilizes innovative immersion grating technology and enables high resolving power spectroscopy (roughly 20,000) in a smaller and lighter package that is more cost effective than current space-based CO2 remote sensing instruments. CARBO modules cover 4 different spectral ranges (from 740 nm to 2.3μm), where two channels will be built and field tested. CARBO's modular architecture reduces implementation risk, accelerates access to space, and extends opportunities to a more diverse set of platforms and launch vehicles. CARBO significantly improves our understanding of the global carbon cycle. Here we discuss an overview of the design elements and focus on the expected radiometric performance of channels 1 (∼760 nm) and 2 (∼1600 nm).