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Gold Level L2 exospheric temperature
var authors='Eastes, Richard';
document.write(authors);
(2025).
Gold Level L2 exospheric temperature.
[Data set].
Space Physics Data Facility.
https://doi.org/10.48322/9m3m-tg87. Accessed on document.write(currentDateStr);.
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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/TLIMB/PT8S
Description
GOLD retrieves the exospheric temperature from the integrated N2 LBH radiance profile
obtained from atmospheric limb scans (LIM observation mode). This data product, referred to as TLIMB,
is derived from limb scan data by fitting the shape of the LBH radiance profile between 100 and 300 km.
Algorithm heritage
An approach similar to the GOLD TLIMB retrieval has been used to analyze data from TIMED/GUVI,
Cassini/UVIS and MAVEN/IUVS. The GOLD TLIMB algorithm is most similar to the operational algorithm
used to retrieve exospheric temperature on Mars from MAVEN/IUVS CO2 density retrievals. The GOLD
algorithm follows the procedure outlined in Lo et al. [2015] as originally applied to the atmosphere of
Mars. The operational code is implemented in IDL and has been generalized to be used with any species in
any planetary atmosphere.
Algorithm theoretical basis
Limb profiles of thermospheric airglow emissions depend fundamentally on temperature, particularly
the decay rate with altitude above the peak of the emission. This has been exploited in retrieval
algorithms for analyzing far-ultraviolet limb emissions from low-Earth orbit (e.g., Picone and
Meier [2000]). For GOLD, the low spatial resolution on the limb mandates that, rather than attempting
to fit an entire temperature profile, we only infer a single parameter, the exospheric temperature
(TLIMB), defined as the temperature of the atmosphere when in diffusion equilibrium.
We use daytime, non-auroral N2 LBH emission limb brightness profiles where the only excitation
mechanism is photoelectron impact on N2. LBH emission bands in the 137-160 nm range are integrated
spectrally, excluding the N I 149.3 nm line. The GOLD limb scan measurements are done in one hemisphere
at a time, and the L1C LIMB data covers a latitude range from the equator to ~20 degree.
The specific steps involved in the TLIMB retrieval are as follows:
• Filter data using topside tangent height range (~100-300 km).
• Fit a Chapman function to the emission brightness profile.
• Obtain the N2 scale height H (Zo) from the Chapman fit.
• Obtain T∞ from H (Zo) = kT/Mg, where k is Boltzmann’s constant, M is the molecular mass of
N2, and g is the gravitational acceleration.
Note that this fit is independent of the absolute brightness calibration of the airglow intensity,
it depends only on the shape of the radiance profile. For this reason, it is necessary to detect stars
in the field-of-view, since the emission from stars can produce a profile shape that can be very
different from a profile produced solely by thermospheric airglow.
References
Picone and Meier (2000), Similarity transformations for fitting of geophysical properties: Application
to altitude profiles of upper atmospheric species, J. Geophys. Res., 105, 18599, doi:10.1029/1999JA000385].
Lo, D. Y., et al. (2015), Nonmigrating tides in the Martian atmosphere as observed by MAVEN IUVS, Geophys.
Res. Lett., 42, 9057–9063, doi:10.1002/2015GL066268.
Snowden, D., R. V. Yelle, J. Cui, J.-E. Wahlund, N. J. T. Edberg, and K. Ågren (2013), The thermal
structure of Titan’s upper atmosphere, I: Temperature profiles from Cassini INMS observations,
Icarus, 226, 52–582.
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/TLIMB/PT8S
NamingAuthority
NASA
ResourceType
NumericalData
ResourceHeader
ResourceName
Gold Level L2 exospheric temperature
DOI
https://doi.org/10.48322/9m3m-tg87
ReleaseDate
2026-06-26 13:17:03Z
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
2026-06-26 13:17:03Z
Note
Add 'Z' to TemporalDescription:TimeSpan:StartDate. ZCB
Description
GOLD retrieves the exospheric temperature from the integrated N2 LBH radiance profile
obtained from atmospheric limb scans (LIM observation mode). This data product, referred to as TLIMB,
is derived from limb scan data by fitting the shape of the LBH radiance profile between 100 and 300 km.
Algorithm heritage
An approach similar to the GOLD TLIMB retrieval has been used to analyze data from TIMED/GUVI,
Cassini/UVIS and MAVEN/IUVS. The GOLD TLIMB algorithm is most similar to the operational algorithm
used to retrieve exospheric temperature on Mars from MAVEN/IUVS CO2 density retrievals. The GOLD
algorithm follows the procedure outlined in Lo et al. [2015] as originally applied to the atmosphere of
Mars. The operational code is implemented in IDL and has been generalized to be used with any species in
any planetary atmosphere.
Algorithm theoretical basis
Limb profiles of thermospheric airglow emissions depend fundamentally on temperature, particularly
the decay rate with altitude above the peak of the emission. This has been exploited in retrieval
algorithms for analyzing far-ultraviolet limb emissions from low-Earth orbit (e.g., Picone and
Meier [2000]). For GOLD, the low spatial resolution on the limb mandates that, rather than attempting
to fit an entire temperature profile, we only infer a single parameter, the exospheric temperature
(TLIMB), defined as the temperature of the atmosphere when in diffusion equilibrium.
We use daytime, non-auroral N2 LBH emission limb brightness profiles where the only excitation
mechanism is photoelectron impact on N2. LBH emission bands in the 137-160 nm range are integrated
spectrally, excluding the N I 149.3 nm line. The GOLD limb scan measurements are done in one hemisphere
at a time, and the L1C LIMB data covers a latitude range from the equator to ~20 degree.
The specific steps involved in the TLIMB retrieval are as follows:
• Filter data using topside tangent height range (~100-300 km).
• Fit a Chapman function to the emission brightness profile.
• Obtain the N2 scale height H (Zo) from the Chapman fit.
• Obtain T∞ from H (Zo) = kT/Mg, where k is Boltzmann’s constant, M is the molecular mass of
N2, and g is the gravitational acceleration.
Note that this fit is independent of the absolute brightness calibration of the airglow intensity,
it depends only on the shape of the radiance profile. For this reason, it is necessary to detect stars
in the field-of-view, since the emission from stars can produce a profile shape that can be very
different from a profile produced solely by thermospheric airglow.
References
Picone and Meier (2000), Similarity transformations for fitting of geophysical properties: Application
to altitude profiles of upper atmospheric species, J. Geophys. Res., 105, 18599, doi:10.1029/1999JA000385].
Lo, D. Y., et al. (2015), Nonmigrating tides in the Martian atmosphere as observed by MAVEN IUVS, Geophys.
Res. Lett., 42, 9057–9063, doi:10.1002/2015GL066268.
Snowden, D., R. V. Yelle, J. Cui, J.-E. Wahlund, N. J. T. Edberg, and K. Ågren (2013), The thermal
structure of Titan’s upper atmosphere, I: Temperature profiles from Cassini INMS observations,
Icarus, 226, 52–582.
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/TLIMB/PT8S
spase://NASA/NumericalData/SES-14/GOLD/L2/TLIMB/PT8S
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/
Description
FTPS access to Gold Level L2 data
AccessURL
Name
HTTPS from SPDF
URL
https://spdf.gsfc.nasa.gov/pub/data/gold/level2/
Description
HTTPS access to Gold Level L2 data
Format
NetCDF
Acknowledgement
Space Physics Data Facility of the NASA Goddard Space Flight Center; Robert E McGuire
ProcessingLevel
Calibrated
ProviderName
GOLD
ProviderResourceName
Gold Level L2 Exospheric Temperature
ProviderProcessingLevel
Level 2
ProviderVersion
1
InstrumentIDs
spase://SMWG/Instrument/GOLD
MeasurementType
ImageIntensity
TemporalDescription
TimeSpan
StartDate
2018-10-06 00:00:00Z
RelativeStopDate
P1D
Cadence
PT8S
ObservedRegion
Earth.NearSurface.Ionosphere
Keywords
O relative to N2
GOLD
SES-14
Parameter #1
Name
Model Uncertainty in Exospheric Temperature
ParameterKey
tdisk_unc_mod
Description
Model uncertainty in retrieved exospheric temperature.
Cadence
PT8S
Units
K
ValidMin
0
ValidMax
1000
FillValue
9.9692e+36
Support
Qualifier
Uncertainty
SupportQuantity
Other
Parameter #2
Name
Random Uncertainty in N2 LBH
ParameterKey
n2_lbh_unc_ran
Description
Random uncertainty in LBH slant path radiance.
Cadence
PT8S
Units
Rayleighs
ValidMin
0
ValidMax
100000
FillValue
9.9692e+36
Wave
WaveType
Photon
Qualifier
Uncertainty
WaveQuantity
Intensity
Parameter #3
Name
Random Uncertainty in LBH Scale Height
ParameterKey
n2_scale_height_unc_ran
Description
Random uncertainty in top side LBH scale height.
Cadence
PT8S
Units
km
ValidMin
0
ValidMax
2
FillValue
9.9692e+36
Support
Qualifier
Uncertainty
SupportQuantity
Other
Parameter #4
Name
Exospheric Temperature
ParameterKey
tlimb
Description
Retrieved exospheric temperature.
Cadence
PT8S
Units
K
ValidMin
0
ValidMax
100000
FillValue
9.9692e+36
Particle
ParticleType
Molecule
ParticleQuantity
Temperature
AtomicNumber
14
Parameter #5
Name
Mask Wavelength
ParameterKey
mask_wavelength
Description
Wavelength grid for N2_LBH mask.
Cadence
PT8S
Units
nm
ValidMin
130
ValidMax
170
FillValue
9.9692e+36
Wave
WaveType
Photon
Qualifier
Scalar
WaveQuantity
Wavelength
Parameter #6
Name
Channel
ParameterKey
channel
Description
GOLD channel (‘A’ or ‘B’).
Cadence
PT8S
Support
Qualifier
Scalar
SupportQuantity
Other
Parameter #7
Name
TLimb Quality Flag
ParameterKey
tlimb_dqi
Description
TLimb data quality index per pixel (GOLD Public Science Data Products Guide).
Cadence
PT8S
ValidMin
0
ValidMax
2147483647
FillValue
-2147483647
Support
Qualifier
Scalar
SupportQuantity
Other
Parameter #8
Name
Systematic Uncertainty in LBH Scale Height
ParameterKey
n2_scale_height_unc_ran
Description
Systematic uncertainty in retrieved exospheric temperature.
Cadence
PT8S
Units
km
ValidMin
0
ValidMax
2
FillValue
9.9692e+36
Support
Qualifier
Uncertainty
SupportQuantity
Other
Parameter #9
Name
Tangent Point Latitude
ParameterKey
tangent_point_latitude
Description
Latitude at each tangent point.
Cadence
PT8S
Units
degrees
ValidMin
-90
ValidMax
90
FillValue
9.9692e+36
Support
Qualifier
Direction
SupportQuantity
Positional
Parameter #10
Name
Systematic Uncertainty in Exospheric Temperature
ParameterKey
tlimb_unc_sys
Description
Systematic uncertainty in retrieved exospheric temperature.
Cadence
PT8S
Units
K
ValidMin
0
ValidMax
10000
FillValue
9.9692e+36
Wave
WaveType
Photon
Qualifier
Uncertainty
WaveQuantity
Intensity
Parameter #11
Name
Random Uncertainty in Exospheric Temperature
ParameterKey
tlimb_unc_ran
Description
Random uncertainty in retrieved exospheric temperature.
Cadence
PT8S
Units
K
ValidMin
0
ValidMax
10000
FillValue
9.9692e+36
Wave
WaveType
Photon
Qualifier
Uncertainty
WaveQuantity
Intensity
Parameter #12
Name
Overall Quality Flag
ParameterKey
dqi
Description
TLIMB data quality index (GOLD Public Science Data Products Guide).
Cadence
PT8S
ValidMin
0
ValidMax
2147483647
FillValue
-2147483647
Support
Qualifier
Scalar
SupportQuantity
Other
Parameter #13
Name
Scan Start Time
ParameterKey
scan_start_time
Description
UTC start time of scan, e.g., "2017-06-21T23:46:38.015Z".
Cadence
PT8S
Units
date/time
FillValue
' '
Support
Qualifier
Magnitude
SupportQuantity
Temporal
Parameter #14
Name
TLimb Lookup Table
ParameterKey
tlimb_lookup_table
Description
Retrieval lookup table filename.
Cadence
PT8S
Support
SupportQuantity
Other
Parameter #15
Name
Solar Zenith Angle
ParameterKey
tangent_point_solar_zenith_angle
Description
Solar zenith angle at each tangent point.
Cadence
PT8S
Units
degrees
ValidMin
0
ValidMax
180
FillValue
9.9692e+36
Support
Qualifier
Direction
SupportQuantity
Positional
Parameter #16
Name
Tangent Point Longitude
ParameterKey
tangent_point_longitude
Description
Longitude at each tangent point.
Cadence
PT8S
Units
degrees
ValidMin
-180
ValidMax
180
FillValue
9.9692e+36
Support
Qualifier
Direction
SupportQuantity
Positional
Parameter #17
Name
Systematic Uncertainty in LBH Slant Path Radiance
ParameterKey
n2_lbh_unc_sys
Description
Systematic uncertainty in LBH slant path radiance.
Cadence
PT8S
Units
Rayleighs
ValidMin
0
ValidMax
100000
FillValue
9.9692e+36
Support
Qualifier
Uncertainty
SupportQuantity
Other
Parameter #18
Name
UTC time
ParameterKey
time_utc
Description
UTC date/time string: "2017-06-21T23:46:38.015Z".
Cadence
PT8S
Units
date/time
FillValue
' '
Support
Qualifier
Scalar
SupportQuantity
Temporal
Parameter #19
Name
Top Side Scale Height of LBH Profile
ParameterKey
n2_scale_height
Description
Top side scale height of N2 LBH radiance profile.
Cadence
PT8S
Units
km
ValidMin
15
ValidMax
30
FillValue
9.9692e+36
Support
Qualifier
Scalar
SupportQuantity
Other
Parameter #20
Name
L1C File Name
ParameterKey
input_l1c_file
Description
L1C file name for each occultation.
Cadence
PT8S
FillValue
' '
Support
Qualifier
Scalar
SupportQuantity
Other
Parameter #21
Name
N2 LBH brightness
ParameterKey
radiance_n2_lbh
Description
N2 LBH brightness used in retrieval.
Cadence
PT8S
Units
Rayleighs
ValidMin
0
ValidMax
100000
FillValue
9.9692e+36
Wave
WaveType
Photon
Qualifier
Scalar
WaveQuantity
Intensity
Parameter #22
Name
Tangent Point Altitude
ParameterKey
tangent_point_altitude
Description
Tangent point altitude at each latitude/longitude grid point.
Caveats
The size of the data array varies with the number of stellar occultations.
Cadence
PT8S
Units
km
ValidMin
0
ValidMax
1000
FillValue
9.9692e+36
Support
Qualifier
Direction
SupportQuantity
Positional
Parameter #23
Name
Model Uncertainty in LBH Scale Height
ParameterKey
n2_scale_height_unc_mod
Description
Model uncertainty in top side LBH scale height.
Cadence
PT8S
Units
km
ValidMin
0
ValidMax
2
FillValue
9.9692e+36
Support
Qualifier
Uncertainty
SupportQuantity
Other
Parameter #24
Name
Scan Stop Time
ParameterKey
scan_stop_time
Description
UTC stop time of scan, e.g., "2017-06-21T23:46:38.015Z".
Cadence
PT8S
Units
date/time
FillValue
' '
Support
Qualifier
Magnitude
SupportQuantity
Temporal
Parameter #25
Name
Mask Defining LBH Bandpass
ParameterKey
mask_n2_lbh
Description
Wavelength mask defining LBH bandpass used in retrieval.
Cadence
PT8S
ValidMin
0
ValidMax
1
FillValue
-2147483647
Support
SupportQuantity
Other
Parameter #26
Name
Hemisphere Scanned
ParameterKey
hemisphere
Description
Hemisphere scanned (‘N’ or ‘S’).
Cadence
PT8S
FillValue
' '
Support
Qualifier
Scalar
SupportQuantity
Other