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GOLD Level L2 Molecular Oxygen Density Profile
var authors='Eastes, Richard';
document.write(authors);
(2025).
GOLD Level L2 Molecular Oxygen Density Profile.
[Data set].
Space Physics Data Facility.
https://doi.org/10.48322/gj9t-v633. Accessed on document.write(currentDateStr);.
Note: Proper references, including
Copy BibTeX Citation
or other formats, should include the "Accessed on date" to identify the version of the resource being cited in a given publication.
ResourceID
spase://NASA/NumericalData/GOLD/L2/O2DEN/PT20M
Description
O2 is derived from measurements of stellar occultation in the Shumann Runge continuum.
As the star rises or sets relative to the satellite position the stellar spectrum is measured across
the GOLD spectral bandpass, from 132 to 162 nm. Geolocation of the OCC L1B data provides the
line-of-sight tangent altitude vs. time during the occultation. This results in a 2-dimensional
map of the stellar signal, in counts or calibrated geophysical units (irradiance), vs. wavelength
and tangent altitude. A sample of this image is represented in the top left panel of the OCC L1D
image in Figure 3-22.
The measured counts profile is then normalized by the unattenuated, exo-atmospheric spectrum, yielding
the slant path transmission profile vs. wavelength at the native L1C spectral sampling of 0.12 nm.
The defining characteristic of the atmospheric transmission is that it is completely independent of
instrument calibration or absolute accuracy. The full transmission spectrum is binned into a small
number of 2-nm spectral channels for use in the retrievals. These retrieval channels are chosen to
span the spectral dependence of the O2 absorption cross-section in order to maximize the O2 retrieval
altitude range (approximately 120-240 km). In the Version 1 O2DEN data set two spectral channels
are used, centered at 142- and 159-nm.
Since stars rise or set at approximately 3 km/sec, as observed from orbit, the 100-msec occultation
cadence results in a measurement of extremely high (sub-km) vertical resolution. The data are binned
to enhance signal-to-noise, producing an effective vertical resolution of 10 km or less, which is
sufficient to easily resolve the scale height of the O2 thermospheric profile.
The algorithm uses an optimal estimation routine, which provide a complete error analysis and
retrieval diagnostics such as averaging kernels and information content. A data vector constructed
from the multiple spectral channels of slant path transmission is used to derive the atmospheric
state vector – O2 density vs. geometric altitude – via a nonlinear, iterative inversion. The retrieved
O2 density profile is reported on a fixed altitude grid with 5-km spacing. The valid altitude range
varies for each event, but generally ranges from ~120 – 240.
Metadata Rights
CC0-1.0:
Creative Commons Zero v1.0 Universal
Note
CC0 1.0 Universal is the Creative Commons license applicable to all publicly available SPASE metadata descriptions. The actual data/software may be subject to a different license.
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Version:2.7.1
NumericalData
ResourceID
spase://NASA/NumericalData/GOLD/L2/O2DEN/PT20M
NamingAuthority
NASA
ResourceType
NumericalData
ResourceHeader
ResourceName
GOLD Level L2 Molecular Oxygen Density Profile
DOI
https://doi.org/10.48322/gj9t-v633
ReleaseDate
2026-06-26 13:17:02Z
RevisionHistory
RevisionEvent
ReleaseDate
2020-09-14 16:47:17Z
Note
Only known prior ReleaseDate of the metadata
RevisionEvent
ReleaseDate
2025-11-14 16:02:21Z
Note
Added PublicationInfo. Added ResourceType and NamingAuthority. Changed http to https in top-level schemaLocation attribute. Fixed version number separator in top-level schemaLocation attribute. Matched version number in schemaLocation attribute to updated value in Version tag. ZCB
RevisionEvent
ReleaseDate
2025-12-04 13:29:18Z
Note
Added MetadataRightsList and RightsList(s). Updated to 2.7.1. ZCB
RevisionEvent
ReleaseDate
2026-03-05 13:29:18Z
Note
Added ProductKey. JMW
RevisionEvent
ReleaseDate
2026-06-26 13:17:02Z
Note
Add 'Z' to TemporalDescription:TimeSpan:StartDate. ZCB
Description
O2 is derived from measurements of stellar occultation in the Shumann Runge continuum.
As the star rises or sets relative to the satellite position the stellar spectrum is measured across
the GOLD spectral bandpass, from 132 to 162 nm. Geolocation of the OCC L1B data provides the
line-of-sight tangent altitude vs. time during the occultation. This results in a 2-dimensional
map of the stellar signal, in counts or calibrated geophysical units (irradiance), vs. wavelength
and tangent altitude. A sample of this image is represented in the top left panel of the OCC L1D
image in Figure 3-22.
The measured counts profile is then normalized by the unattenuated, exo-atmospheric spectrum, yielding
the slant path transmission profile vs. wavelength at the native L1C spectral sampling of 0.12 nm.
The defining characteristic of the atmospheric transmission is that it is completely independent of
instrument calibration or absolute accuracy. The full transmission spectrum is binned into a small
number of 2-nm spectral channels for use in the retrievals. These retrieval channels are chosen to
span the spectral dependence of the O2 absorption cross-section in order to maximize the O2 retrieval
altitude range (approximately 120-240 km). In the Version 1 O2DEN data set two spectral channels
are used, centered at 142- and 159-nm.
Since stars rise or set at approximately 3 km/sec, as observed from orbit, the 100-msec occultation
cadence results in a measurement of extremely high (sub-km) vertical resolution. The data are binned
to enhance signal-to-noise, producing an effective vertical resolution of 10 km or less, which is
sufficient to easily resolve the scale height of the O2 thermospheric profile.
The algorithm uses an optimal estimation routine, which provide a complete error analysis and
retrieval diagnostics such as averaging kernels and information content. A data vector constructed
from the multiple spectral channels of slant path transmission is used to derive the atmospheric
state vector – O2 density vs. geometric altitude – via a nonlinear, iterative inversion. The retrieved
O2 density profile is reported on a fixed altitude grid with 5-km spacing. The valid altitude range
varies for each event, but generally ranges from ~120 – 240.
Acknowledgement
National Aeronautics and Space Administration; Dr. Richard Eastes
PublicationInfo
Authors
Eastes, Richard
PublicationDate
2025-11-14 16:02:21Z
PublishedBy
Space Physics Data Facility
Contacts
Role
Person
StartDate
StopDate
Note
1.
PrincipalInvestigator
spase://SMWG/Person/Richard.Eastes
2.
MetadataContact
spase://SMWG/Person/James.M.Weygand
InformationURL
Name
GOLD Homepage web page
URL
https://gold.cs.ucf.edu/
Description
GOLD web page with news and other information.
InformationURL
Name
GOLD Missions Space Science Reviews Article
URL
https://doi.org/10.1007/s11214-017-0392-2
Description
Eastes, R.W., McClintock, W.E., Burns, A.G. et al. Space Sci. Rev. (2017) vol. 212, pp.383.
PriorIDs
spase://VSPO/NumericalData/GOLD/L2/O2DEN/PT20M
spase://NASA/NumericalData/SES-14/GOLD/L2/O2DEN/PT20M
AccessInformation
RepositoryID
spase://SMWG/Repository/NASA/GSFC/SPDF
Availability
Online
AccessRights
Open
RightsList
Rights
SchemeURI
https://spdx.org/licenses/
RightsIdentifierScheme
SPDX
RightsIdentifier
CC0-1.0
RightsURI
https://spdx.org/licenses/CC0-1.0.html
RightsName
Creative Commons Zero v1.0 Universal
Note
CC0 1.0 Universal is the Creative Commons license applicable to all publicly available NASA Heliophysics data products
AccessURL
Name
FTPS from SPDF (not with most browsers)
URL
ftps://spdf.gsfc.nasa.gov/pub/data/gold/level2/o2den
Description
FTP access to GOLD o2den Level L2 data
AccessURL
Name
HTTPS from SPDF
URL
https://spdf.gsfc.nasa.gov/pub/data/gold/level2/o2den
Description
HTTP access to GOLD o2den Level L2 data
AccessURL
Name
CDAWeb
URL
https://cdaweb.gsfc.nasa.gov/cgi-bin/eval2.cgi?dataset=GOLD_L2_O2DEN&index=sp_phys
ProductKey
GOLD_L2_O2DEN
Description
Format
NetCDF
AccessDirectoryTemplate
https://cdaweb.gsfc.nasa.gov/pub/data/gold/level2/o2den/$Y
AccessFilenameTemplate
gold_l2_o2den_2018_292_v06_r01_c01.nc
Acknowledgement
Space Physics Data Facility of the NASA Goddard Space Flight Center; Robert E McGuire
AccessInformation
RepositoryID
spase://SMWG/Repository/NASA/GSFC/SPDF
Availability
Online
AccessRights
Open
AccessURL
Name
CDAWeb Programmatic Data Access
URL
https://cdaweb.gsfc.nasa.gov/WS/cdasr/1/dataviews/sp_phys/datasets/GOLD_L2_O2DEN/clientLibraryExample/
Style
WebService
ProductKey
GOLD_L2_O2DEN
Description
Access to this data from common programming environments. Note: this AccessInformation element was added by HDPWS.
Format
Binary
Acknowledgement
Space Physics Data Facility of the NASA Goddard Space Flight Center; Robert E McGuire
ProcessingLevel
Calibrated
ProviderName
GOLD
ProviderResourceName
Gold Level L2 Molecular Oxygen Density Profile
ProviderProcessingLevel
Level 2
ProviderVersion
1
InstrumentIDs
spase://SMWG/Instrument/GOLD
MeasurementType
ImageIntensity
TemporalDescription
TimeSpan
StartDate
2018-10-19 00:00:00Z
RelativeStopDate
P1D
Cadence
PT20M
ObservedRegion
Earth.NearSurface.Ionosphere
Keywords
Day disk data
GOLD
SES-14
Parameter #1
Name
Spectral Width
ParameterKey
spectral_width
Description
Width of each data spectral channel.
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
Units
nm
ValidMin
0
ValidMax
10
FillValue
9.9692e+36
Wave
WaveType
Photon
Qualifier
Scalar
WaveQuantity
Wavelength
Parameter #2
Name
O2 Density Random Uncertainty
ParameterKey
o2den_unc_ran
Description
Random uncertainty of retrieved O2.
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
Units
mol/cm^3
ValidMin
100000
ValidMax
999999986991104
FillValue
9.9692e+36
Support
Qualifier
Uncertainty
SupportQuantity
Other
Parameter #3
Name
Reference Longitude
ParameterKey
lon_ref
Description
Longitude at 225 km tangent point.
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
Units
degrees
ValidMin
-180
ValidMax
180
FillValue
9.9692e+36
Support
Qualifier
Direction
SupportQuantity
Positional
Parameter #4
Name
O2 Density Model Uncertainty
ParameterKey
o2den_unc_mod
Description
Model uncertainty of retrieved O2.
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
Units
mol/cm^3
ValidMin
100000
ValidMax
999999986991104
FillValue
9.9692e+36
Support
Qualifier
Uncertainty
SupportQuantity
Other
Parameter #5
Name
Temperature
ParameterKey
temperature
Description
Assumed temperature profile.
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
Units
K
ValidMin
0
ValidMax
1000
FillValue
9.9692e+36
Particle
ParticleType
Molecule
ParticleQuantity
Temperature
AtomicNumber
16
Parameter #6
Name
Retrieval geometric altitude grid
ParameterKey
zret
Description
Retrieval geometric altitude grid.
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
Units
km
ValidMin
0
ValidMax
1000
FillValue
9.9692e+36
Support
Qualifier
Direction
SupportQuantity
Positional
Parameter #7
Name
O2 Density
ParameterKey
o2den
Description
Retrieved O2 density.
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
Units
mol/cm^3
ValidMin
100000
ValidMax
999999986991104
FillValue
9.9692e+36
Particle
ParticleType
Molecule
ParticleQuantity
NumberDensity
AtomicNumber
16
Parameter #8
Name
Number of Data Points
ParameterKey
nzdat
Description
Number of points in data altitude grid.
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
FillValue
-2147483647
Support
Qualifier
Scalar
SupportQuantity
Other
Parameter #9
Name
UTC time
ParameterKey
TIME_UTC
Description
UTC date/time string: "2017-06-21T23:46:38.015Z".
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
Units
date/time
FillValue
' '
Support
Qualifier
Magnitude
SupportQuantity
Temporal
Parameter #10
Name
Number of Iterations
ParameterKey
n_iter
Description
Number of iterations to converge.
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
Units
number
FillValue
-2147483647
Support
Qualifier
Scalar
SupportQuantity
Other
Parameter #11
Name
Convergence flag
ParameterKey
convergence
Description
Retrieval convergence flag (= 1 if retrieval converged).
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
FillValue
-2147483647
Support
Qualifier
Scalar
SupportQuantity
Other
Parameter #12
Name
Number of Levels in Retrieval Altitude Grid
ParameterKey
nzret
Description
Number of levels in retrieval altitude grid.
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
Units
number
FillValue
-2147483647
Support
Qualifier
Scalar
SupportQuantity
Other
Parameter #13
Name
L1C File Name
ParameterKey
input_l1c_file
Description
L1C file name for each occultation.
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
FillValue
' '
Support
Qualifier
Scalar
SupportQuantity
Other
Parameter #14
Name
O2 Systematic Uncertainty
ParameterKey
o2den_unc_sys
Description
Systematic uncertainty of retrieved O2.
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
ValidMin
100000
ValidMax
999999986991104
FillValue
9.9692e+36
Support
Qualifier
Uncertainty
SupportQuantity
Other
Parameter #15
Name
Reference Latitude
ParameterKey
lat_ref
Description
Latitude at 225 km tangent point.
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
Units
degrees
ValidMin
-90
ValidMax
90
FillValue
9.9692e+36
Support
Qualifier
Direction
SupportQuantity
Positional
Parameter #16
Name
Normalization
ParameterKey
normalization
Description
Transmission normalization factor (unattenuated stellar brightness).
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
Units
counts
ValidMin
0
ValidMax
90
FillValue
NaN
Support
Qualifier
Scalar
SupportQuantity
Other
Parameter #17
Name
O2 Data Quality
ParameterKey
o2den_dqi
Description
O2 data quality indicator per altitude (see table in The GOLD Public Science Data Products Guide).
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
ValidMin
0
ValidMax
2147483647
FillValue
-2147483647
Support
Qualifier
Scalar
SupportQuantity
Other
Parameter #18
Name
Channel
ParameterKey
channel
Description
GOLD channel (‘A’ or ‘B’).
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
Support
Qualifier
Scalar
SupportQuantity
Other
Parameter #19
Name
Central Wavelength
ParameterKey
central_wavelength
Description
Center wavelength of each data channel.
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
Units
nm
ValidMin
0
ValidMax
400
FillValue
9.9692e+36
Wave
WaveType
Photon
Qualifier
Scalar
WaveQuantity
Wavelength
Parameter #20
Name
Signal to Noise
ParameterKey
signal_to_noise
Description
Effective signal to noise (above atmosphere).
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
Support
Qualifier
Scalar
SupportQuantity
Other
Parameter #21
Name
Number of Points in Data Altitude Grid
ParameterKey
zdat
Description
Number of points in data altitude grid.
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
Units
number
Support
Qualifier
Scalar
SupportQuantity
Other
Parameter #22
Name
Overall Quality Flag
ParameterKey
dqi
Description
Overall data quality index per scan (see table below).
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
ValidMin
0
ValidMax
1000
FillValue
9.9692e+36
Support
Qualifier
Scalar
SupportQuantity
Other
Parameter #23
Name
Model Fit Data
ParameterKey
transmission_fit
Description
Forward model fit to data.
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
ValidMin
0
ValidMax
10
FillValue
9.9692e+36
Support
Qualifier
Scalar
SupportQuantity
Other
Parameter #24
Name
Transmission Profile
ParameterKey
transmission
Description
Measured slant path transmission profile.
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
ValidMin
0
ValidMax
10
FillValue
9.9692e+36
Support
Qualifier
Scalar
SupportQuantity
Other
Parameter #25
Name
A Priori O2 Density
ParameterKey
o2_apriori
Description
A priori O2 density used in retrieval.
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
Units
mol/cm^3
ValidMin
100000
ValidMax
999999986991104
FillValue
9.9692e+36
Particle
ParticleType
Molecule
ParticleQuantity
NumberDensity
AtomicNumber
16
Parameter #26
Name
Solar Zenith Angle at 225 km
ParameterKey
sza_ref
Description
Solar zenith angle at 225 km tangent point.
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
Units
degrees
ValidMin
0
ValidMax
180
FillValue
9.9692e+36
Support
Qualifier
Direction
SupportQuantity
Positional
Parameter #27
Name
Transmission Profile Uncertainty
ParameterKey
transmission_unc
Description
Transmission variance.
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
ValidMin
0
ValidMax
10
FillValue
9.9692e+36
Support
Qualifier
Scalar
SupportQuantity
Other
Parameter #28
Name
Name of Target Star
ParameterKey
target_star
Description
Name of target star.
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT20M
ValidMin
0
ValidMax
5
FillValue
9.9692e+36
Support
Qualifier
Scalar
SupportQuantity
Other