2.3.1 spase://NASA/NumericalData/SES-14/GOLD/L2/ON2/PT8S Gold Level L2 ratio of the column abundance of thermospheric O relative to N2 2020-07-07T21:15:18Z GOLD daytime disk scan (DAY) measurements are used to derive the ratio of the column abundance of thermospheric O relative to N2, conventionally referred to as O/N2 or ΣO/N2, but abbreviated to ON2 for the GOLD data product. ON2 is derived for each valid dayside Level 1C pixel for approximately 68 disk scan measurements performed per day by GOLD in nominal operation. Algorithm heritage The disk ON2 retrieval algorithm was originally developed by Computational Physics, Inc. (CPI) for use with GUVI and SSUSI radiance images (Strickland et al., 1995). The GOLD implementation of this algorithm takes advantage of GOLD’s ability to transmit the full spectrum to maximize the signal-to-noise ratio and eliminate atomic emission lines that contaminate the N2 LBH bands (e.g., N I 149.3 nm). This algorithm has been extensively documented and applied over the past several decades (e.g., Evans et al. [1995]; Christensen et al. [2003]; Strickland et al. [2004]). Algorithm theoretical basis The geophysical parameter retrieved, O/N2, is the ratio of the vertical column density of O relative to N2, defined at a standard reference N2 depth of 1017 cm-2, which is chosen to minimize uncertainty in the derived O/N2. It is retrieved directly from the ratio of the O I 135.6 nm and N2 LBH band intensities measured by GOLD on the dayside disk (DAY measurement mode). The AURIC atmospheric radiance model (Strickland et al. [1999]) is used to derive this relationship as a function of solar zenith angle and to create the look-up table (LUT) used by the algorithm. References Christensen, A. B., et al. (2003), Initial observations with the Global Ultraviolet Imager (GUVI) in the NASA TIMED satellite mission, J. Geophys. Res., vol. 108, NO. A12, 1451, doi:10.1029/2003JA009918. Evans, J. S., D. J. Strickland and R. E. Huffman (1995), Satellite remote sensing of thermospheric O/N2 and solar EUV: 2. Data analysis, J. Geophys. Res., vol. 100, NO. A7, pages 12,227-12,233. Strickland, D. J., R. R. Meier, R. L. Walterscheid, J. D. Craven, A. B. Christensen, L. J. Paxton, D. Morrison, and G. Crowley (2004), Quiet-time seasonal behavior of the thermosphere seen in the far ultraviolet dayglow, J. Geophys. Res., vol. 109, A01302, doi:10.1029/2003JA010220. Strickland, D.J., J. Bishop, J.S. Evans, T. Majeed, P.M. Shen, R.J. Cox, R. Link, and R.E. Huffman (1999), Atmospheric Ultraviolet Radiance Integrated Code (AURIC): theory, software architecture, inputs and selected results, JQSRT, 62, 689-742. Strickland, D. J., J. S. Evans, and L. J. Paxton (1995), Satellite remote sensing of thermospheric O/N2 and solar EUV: 1. Theory, J. Geophys. Res., 110, A7, pages 12,217-12,226. National Aeronautics and Space Administration; Dr. Richard Eastes spase://SMWG/Person/Richard.Eastes PrincipalInvestigator spase://SMWG/Person/James.M.Weygand MetadataContact GOLD Homepage web page https://gold.cs.ucf.edu/ GOLD web page with news and other information. GOLD Missions Space Science Reviews Article https://doi.org/10.1007/s11214-017-0392-2 Eastes, R.W., McClintock, W.E., Burns, A.G. et al. Space Sci. Rev. (2017) vol. 212, pp.383. spase://VSPO/NumericalData/SES-14/GOLD/L2/ON2/PT8S spase://SMWG/Repository/NASA/GSFC/SPDF Online Open FTPS from SPDF (not with most browsers) ftps://spdf.gsfc.nasa.gov/pub/data/gold/level2/ FTPS access to Gold Level L2 data HTTPS from SPDF https://spdf.gsfc.nasa.gov/pub/data/gold/level2/ HTTPS access to Gold Level L2 data NetCDF Space Physics Data Facility of the NASA Goddard Space Flight Center; Robert E McGuire Calibrated GOLD Gold Level L2 Molecular Oxygen Density Profile Level 2 1 spase://SMWG/Instrument/SES-14/GOLD ImageIntensity 2018-10-06T00:00:00 P1D PT8S Earth.NearSurface.Ionosphere O relative to N2 GOLD SES-14 Mask Defining OI 1356 Bandpass mask_oi_1356 Wavelength mask defining OI 1356 bandpass used in retrieval. PT8S 0 1 -2147483647 Other Random Uncertainty in N2 LBH n2_lbh_unc_ran Random uncertainty in N2 LBH brightness. PT8S Rayleighs 0 100000 9.9692e+36 Photon Uncertainty Intensity Lookup Table lookup_table Lookup table filename. PT8S Other Mask Wavelength mask_wavelength Wavelength grid for MASK_N2_LBH and MASK_OI_1356. PT8S nm 130 170 9.9692e+36 Photon Scalar Wavelength OI 1356 brightness radiance_oi_1356 OI 1356 brightness used in retrieval. PT8S nm 0 100000 9.9692e+36 Photon Scalar Intensity GOLD channel channel GOLD channel (‘A’ or ‘B’). PT8S Scalar Other Latitude latitude Pixel latitude. PT8S degrees -90 90 9.9692e+36 Direction Positional Retrieved O/N2 column density ratio on2 Retrieved O/N2 column density ratio used in QEUV retrieval. PT8S 0 5 9.9692e+36 Other Ratio Random Uncertainty in Oxygen 135.6 nm Brightness oi_1356_unc_ran Random uncertainty in oxygen 135.6 nm brightness. PT8S Rayleighs 0 100000 9.9692e+36 Photon Uncertainty Intensity Random Uncertainty in O/N2 Ratio on2_unc_ran Random uncertainty in retrieved O/N2 column density ratio. PT8S 0 100000 9.9692e+36 Uncertainty Other Overall Quality Flag dqi NMAX data quality index (see table below). PT8S 0 2147483647 -2147483647 Scalar Other Scan Start Time scan_start_time UTC start time of scan, e.g., "2017-06-21T23:46:38.015Z". PT8S date/time ' ' Magnitude Temporal Solar Zenith Angle at 225 km solar_zenith_angle Solar zenith angle at 225 km tangent point. PT8S degrees 0 180 9.9692e+36 Direction Positional Longitude longitude Pixel longitude. PT8S degrees -180 180 9.9692e+36 Direction Positional O/N2 Ratio Quality Flag on2_dqi ON2 data quality index per pixel (see table below). PT8S 0 2147483647 -2147483647 Scalar Other Systematic Uncertainty in O/N2 Ratio on2_unc_sys Systematic uncertainty in retrieved O/N2 column density ratio. PT8S 0 5 9.9692e+36 Uncertainty Other Model Uncertainty in O/N2 Ratio on2_unc_mod Model uncertainty in retrieved O/N2 column density ratio. PT8S 0 5 9.9692e+36 Uncertainty Other Systematic Uncertainty in N2 LBH brightness n2_lbh_unc_sys Systematic uncertainty in N2 LBH brightness. PT8S Rayleighs 0 100000 9.9692e+36 Uncertainty Other UTC time time_utc UTC date/time string: "2017-06-21T23:46:38.015Z". PT8S date/time ' ' Magnitude Temporal Mask Defining LBH Bandpass mask_n2_lbh Wavelength mask defining LBH bandpass used in retrieval. PT8S 0 1 -2147483647 Other L1C File Name input_l1c_file L1C file name for each occultation. PT8S ' ' Scalar Other N2 LBH brightness radiance_n2_lbh N2 LBH brightness used in retrieval. PT8S nm 0 100000 9.9692e+36 Photon Scalar Intensity Pixel Emission Angle emission_angle Pixel emission angle (relative to zenith). PT8S degrees 0 90 9.9692e+36 Direction Positional Scan Stop Time scan_stop_time UTC stop time of scan, e.g., "2017-06-21T23:46:38.015Z". PT8S date/time ' ' Magnitude Temporal Systematic Uncertainty in Oxygen 135.6 nm Brightness oi_1356_unc_sys Systematic uncertainty in oxygen 135.6 nm brightness. PT8S Rayleighs 0 100000 9.9692e+36 Photon Uncertainty Intensity Hemisphere Scanned hemisphere Hemisphere scanned (‘N’ or ‘S’). PT8S ' ' Scalar Other