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).
The High-resolution Imaging Multiple-species Atmospheric Profiler (HiMAP) is an ultraviolet imaging spectro-polarimeter in development at the Jet Propulsion Laboratory for measuring O3 and NO2 concentrations in the troposphere from an airborne platform or satellite. In this paper: (1) the HiMAP design is illustrated and modeled using 3D polarization ray tracing calculus, (2) the dependency between the condition number of the systems polarization measurement matrix and properties of individual optical components is used as a method for tolerancing, and (3) the polarimeter capabilities of manufacturable thin film designs of polarizing and non-polarizing beam splitters is explored using numerical methods. The condition number of an optical system is calculated from a polarization ray tracing (PRT) matrix model of the polarimeter. Deviations of the condition number are calculated for non-ideal polarization elements and coatings to understand component and alignment tolerances.
The Carbon Observatory Instrument Suite, or CARBO, consists of four carbon observing instruments sharing a common instrument bus, yet targeted for a particular wavelength band each with a unique science observation. They are: a) Instrument 1, wavelength centered at 756 nm for oxygen and solar-induced chlorophyll fluorescence (SIF) observations, b) Instrument 2, centered at 1629 nm, for carbon dioxide (CO2) and methane (CH4) observation, c) Instrument 3, centered at 2062 nm for carbon dioxide and d) Instrument 4, centered at 2328 for carbon monoxide (CO) and methane. From low-Earth orbit, these instruments have a field-of-view of 10 to 15 degrees, and a spatial resolution of 2 km square. These instruments have a spectral resolving power ranging from ten to twenty thousand, and can monitor columnaverage dry air mole fraction of carbon dioxide (XCO2) at 1.5 ppm, and methane (XCH4) at 7 ppb. These new instruments will advance the use of immersion grating technology in spectrometer instruments in order to reduce the size of the instrument, while improving performance. These compact, capable instruments are envisioned to be compatible with small satellites, yet modular to be configured to address the particular science questions at hand. Here we report on the current status of the instrument design and fabrication, focusing primarily on Instruments 1 and 2. We will describe the key science and engineering requirements and the instrument performance error budget. We will discuss the optical design with particular emphasis on the immersion grating, and the advantages this new technology affords compared to previous instruments. We will also discuss the status of the focal plane array and the detector electronics and housing. Finally, we report on a new approach – developed during this instrument design process - which enables simultaneous measurement of both orthogonal polarization states (S and P) over the field-of-view and optical bandpass. We believe this polarization sensing capability will enable science observations which were previously limited by instrumental and observational degeneracies. In particular: improved sensitivity to all species, better sensitivity to surface polarization effects, better constraints on aerosol scattering parameters, and superior discrimination of the vertical distribution of gases and aerosols.