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.
Version:2.6.0
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.
| Role | Person | StartDate | StopDate | Note | |
|---|---|---|---|---|---|
| 1. | PrincipalInvestigator | spase://SMWG/Person/Richard.Eastes | |||
| 2. | MetadataContact | spase://SMWG/Person/James.M.Weygand |
GOLD web page with news and other information
Eastes, R.W., McClintock, W.E., Burns, A.G. et al. Space Sci. Rev. (2017) vol. 212, pp.383.
In CDF via ftps from SPDF
In CDF via https from SPDF
Access to ASCII, CDF, and plots via NASA/GSFC CDAWeb
Web Service to this product using the HAPI interface
Wavelength mask defining OI 1356 bandpass used in retrieval
Random uncertainty in N2 LBH brightness
Lookup table filename
Wavelength grid for MASK_N2_LBH and MASK_OI_1356
OI 1356 brightness used in retrieval
GOLD channel ('A' or 'B')
Pixel latitude
Retrieved O/N2 column density ratio used in QEUV retrieval
Random uncertainty in oxygen 135.6 nm brightness
Random uncertainty in retrieved O/N2 column density ratio
NMAX data quality index (see table below)
UTC start time of scan, e.g., 2017-06-21T23:46:38.015Z
Solar zenith angle at 225 km tangent point
Pixel longitude
ON2 data quality index per pixel (see table below)
Systematic uncertainty in retrieved O/N2 column density ratio
Model uncertainty in retrieved O/N2 column density ratio
Systematic uncertainty in N2 LBH brightness
UTC date/time string: 2017-06-21T23:46:38.015Z
Wavelength mask defining LBH bandpass used in retrieval
L1C file name for each occultation
N2 LBH brightness used in retrieval
Pixel emission angle (relative to zenith)
UTC stop time of scan, e.g., 2017-06-21T23:46:38.015Z
Systematic uncertainty in oxygen 135.6 nm brightness
Hemisphere scanned ('N' or 'S')