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:2.3.1
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 | |
|---|---|---|
| 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.
FTP access to GOLD on2 Level L2 data
HTTP access to GOLD on2 Level L2 data
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’).