We have reÐned the analysis of the data from the FIRAS (Far-InfraRed Absolute Spectrophotometer) on board the COBE (COsmic Background Explorer). The FIRAS measures the di †erence between the cosmic microwave background and a precise blackbody spectrum. We Ðnd new, tighter upper limits on general deviations from a blackbody spectrum. The rms deviations are less than 50 parts per million of the peak of the cosmic microwave background radiation. For the Comptonization and chemical potential, we Ðnd o y o \ 15 ] 10~6 and o k o \ 9 ] 10~5 (95% conÐdence level [CL]). There are also reÐne-ments in the absolute temperature, 2.728^0.004 K (95% CL), the dipole direction, (l, b) \ (264¡ .14 0.30, (95% CL), and the amplitude, 3.372^0.014 mK (95% CL). All of these results 48¡ .26^0.30) agree with our previous publications.

The FIRAS instrument on the COBE satellite has conducted an unbiased survey of the far-infrared emission from our Galaxy. The rst results of this survey were reported by Wright et al. (1991). We report the results of new analyses of this spectral survey, which includes emission lines from 158 m C + , 122 m and 205 m N + , 370 m and 609 m C 0 , and CO J=2-1 through 5-4. We report the morphological distribution along the galactic plane (b = 0 ) of the spectral line emission, and the high galactic latitude intensities of the C + and 205 m N + emission. In the galactic plane the 205 m line of N + generally follows the 158 m C + line distributions, but the intensities scale as I(N + 205 m) / I(C + 158 m) 1:5 towards the inner Galaxy. The high galactic latitude intensity of the 158 m ne structure transition from C + is I(C + 158 m) = (1:43 0:12) 10 6 csc jbj erg cm 2 s 1 sr 1 for jbj > 15 , and it decreases more rapidly than the far infrared intensity with increasing galactic latitude. C + and neutral atomic hydrogen emission are closely correlated with a C + cooling rate of (2:65 0:15) 10 26 erg s 1 H atom 1 . We conclude that this emission arises almost entirely from the Cold Neutral Medium. The high galactic latitude intensity of the 205 m ne structure transition from N + is I(N + 205 m) = (4 1) 10 8 csc jbj erg cm 2 s 1 sr 1 arising entirely from the Warm Ionized Medium. We estimate the total ionizing photon rate in the Galaxy to be = 3:5 10 53 ionizing photons per second, based on the 205 m N + transition.

Abstract. NASA's Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission, scheduled for launch in the timeframe of 2023, will carry a hyperspectral scanning radiometer named the Ocean Color Instrument (OCI) and two multi-angle polarimeters (MAPs): the UMBC Hyper-Angular Rainbow Polarimeter (HARP2) and the SRON Spectro-Polarimeter for Planetary EXploration one (SPEXone). The MAP measurements contain rich information on the microphysical properties of aerosols and hydrosols and therefore can be used to retrieve accurate aerosol properties for complex atmosphere and ocean systems. Most polarimetric aerosol retrieval algorithms utilize vector radiative transfer models iteratively in an optimization approach, which leads to high computational costs that limit their usage in the operational processing of large data volumes acquired by the MAP imagers. In this work, we propose a deep neural network (NN) forward model to represent the radiative transfer simulation of coupled atmosphere and ocean systems for applications to the HARP2 instrument and its predecessors. Through the evaluation of synthetic datasets for AirHARP (airborne version of HARP2), the NN model achieves a numerical accuracy smaller than the instrument uncertainties, with a running time of 0.01 s in a single CPU core or 1 ms in a GPU. Using the NN as a forward model, we built an efficient joint aerosol and ocean color retrieval algorithm called FastMAPOL, evolved from the well-validated Multi-Angular Polarimetric Ocean coLor (MAPOL) algorithm. Retrievals of aerosol properties and water-leaving signals were conducted on both the synthetic data and the AirHARP field measurements from the Aerosol Characterization from Polarimeter and Lidar (ACEPOL) campaign in 2017. From the validation with the synthetic data and the collocated High Spectral Resolution Lidar (HSRL) aerosol products, we demonstrated that the aerosol microphysical properties and water-leaving signals can be retrieved efficiently and within acceptable error. Comparing to the retrieval speed using a conventional radiative transfer forward model, the computational acceleration is 103 times faster with CPU or 104 times with GPU processors. The FastMAPOL algorithm can be used to operationally process the large volume of polarimetric data acquired by PACE and other future Earth-observing satellite missions with similar capabilities.

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