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Data Access
FTPS from SPDF (not with most browsers)
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CDAWeb
WebService:
CDAWeb Programmatic Data Access
HAPI: CDAWeb HAPI Server
TWINS 2 Lyman Alpha Detector (LAD) Geocorona
var authors='McComas, David, J.; Fahr, Hans, J.';
document.write(authors);
(2023).
TWINS 2 Lyman Alpha Detector (LAD) Geocorona.
[Data set].
Space Physics Data Facility.
https://doi.org/10.48322/yvt8-0a64. Accessed on document.write(currentDateStr);.
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ResourceID
spase://NASA/NumericalData/TWINS2/LAD/L1/PT1.333S
Description
TWINS, Two Wide-angle Imaging Neutral-atom Spectrometers, is a Mission of Opportunity under NASA's Small Explorer, SMEX, Program. TWINS-1 and TWINS-2 are the Designations for NASA-Sponsored Instruments flying on Unspecified Non-NASA U.S. Government Spacecraft. The TWINS-1 Instrument High Voltages were turned on in April 2007 and the TWINS-2 High Voltages were turned in May 2008; the Exact Launch Dates are not available. The Data, including both Science Data and Spacecraft Ephemeris and Attitude Information, from the two NASA-Funded Science Instruments are publicly available to the Scientific Research Community. See https://earth.esa.int/web/eoportal/satellite-missions/t/twins/ TWINS is a Stereo Mission whose overall Scientific Objective is to establish the Global Connectivities and Causal Relationships between Processes in Different Regions of the Earth's Magnetosphere. To meet this Goal, TWINS-1 and TWINS-2 provide Stereoscopic Neutral Atom Imaging of the Magnetosphere from Two Widely Spaced, High-Altitude, High-Inclination Spacecraft. TWINS Instrumentation includes an Energetic Neutral Atom, ENA, Imager to capture Charge-Exchange-Produced Neutral Atoms over a Broad Energy Range, approximately from 1 keV ro 100 keV, and a Lyman-alpha Detector to measure the Density of the Neutral Hydrogen Geocorona needed for Extraction of Magnetospheric Ion Fluxes from Neutral Atom Data. The TWINS-1 and TWINS-2 Instruments are identical. Each Spacecraft carrying TWINS Instruments is in a Molniya Orbit, 63.4°, 7.2 Re Apogee, 1000 km Perigee and Period 12 hr. The TWINS Spacecraft are 3-Axis stabilized and with Nadir-Pointing. Each acquires Image Data with Time Resolution of 60 s. The Time required to change Actuator Direction between Scans, an Interval with no Data Collection, was 25 s from June 2008 to July 2009, and 12 s at all other Times. This gives an Effective Cadence of 72 or 85 s. The Nominal Design Lifetime for each Instrument is four Years. TWINS operates only during the Apogee Portion of each Orbit, when the Spacecraft is above the Radiation Belts. The TWINS Lyman-alpha Detector consists of two independent Sensors to measure Lyman-alpha Radiation being emitted by Neutral Hydrogen Atoms. The Sensors oriented at Angles of 40° with respect to the Actuator Spin Axis. Each Sensor has a Full Width, Half Maximum, FWHM, Field-of-View of 4°, defined by Collimation Hole Baffles, uses Lyman-alpha Interference Filters as Narrow Band Transmissions Filters, and applies a KBr or CsI Photodiode for Photon Detection. The Lyman-alpha Detector is located on the rotating Actuator Platform to provide Full 360° Azimuthal Angle Coverage Time resolution is 60 s.
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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Details
Version:2.7.1
NumericalData
ResourceID
spase://NASA/NumericalData/TWINS2/LAD/L1/PT1.333S
NamingAuthority
NASA
ResourceType
NumericalData
ResourceHeader
ResourceName
TWINS 2 Lyman Alpha Detector (LAD) Geocorona
DOI
https://doi.org/10.48322/yvt8-0a64
ReleaseDate
2026-07-21 12:08:14Z
RevisionHistory
RevisionEvent
ReleaseDate
2021-04-27 15:38:11Z
Note
Only known prior ReleaseDate of the metadata
RevisionEvent
ReleaseDate
2023-07-30 12:34:56.789Z
Note
Added DOI and PublicationInfo minted by LFB, metadata versioned up to SPASE 2.6.0, reviewed by LFB 20230727
RevisionEvent
ReleaseDate
2025-10-03 11:24:16Z
Note
Updated PublishedBy name to match ROR Registry. 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 13:32:08Z
Note
Added MetadataRightsList and RightsList(s). Updated to 2.7.1. ZCB
RevisionEvent
ReleaseDate
2026-06-26 13:30:01Z
Note
Add 'Z' to RevisionEvent:ReleaseDate(s), PublicationDate, TemporalDescription:TimeSpan:StartDate, TemporalDescription:TimeSpan:StopDate. ZCB
RevisionEvent
ReleaseDate
2026-07-21 12:08:14Z
Note
Added HelioData InformationURL. JWL
Description
TWINS, Two Wide-angle Imaging Neutral-atom Spectrometers, is a Mission of Opportunity under NASA's Small Explorer, SMEX, Program. TWINS-1 and TWINS-2 are the Designations for NASA-Sponsored Instruments flying on Unspecified Non-NASA U.S. Government Spacecraft. The TWINS-1 Instrument High Voltages were turned on in April 2007 and the TWINS-2 High Voltages were turned in May 2008; the Exact Launch Dates are not available. The Data, including both Science Data and Spacecraft Ephemeris and Attitude Information, from the two NASA-Funded Science Instruments are publicly available to the Scientific Research Community. See https://earth.esa.int/web/eoportal/satellite-missions/t/twins/ TWINS is a Stereo Mission whose overall Scientific Objective is to establish the Global Connectivities and Causal Relationships between Processes in Different Regions of the Earth's Magnetosphere. To meet this Goal, TWINS-1 and TWINS-2 provide Stereoscopic Neutral Atom Imaging of the Magnetosphere from Two Widely Spaced, High-Altitude, High-Inclination Spacecraft. TWINS Instrumentation includes an Energetic Neutral Atom, ENA, Imager to capture Charge-Exchange-Produced Neutral Atoms over a Broad Energy Range, approximately from 1 keV ro 100 keV, and a Lyman-alpha Detector to measure the Density of the Neutral Hydrogen Geocorona needed for Extraction of Magnetospheric Ion Fluxes from Neutral Atom Data. The TWINS-1 and TWINS-2 Instruments are identical. Each Spacecraft carrying TWINS Instruments is in a Molniya Orbit, 63.4°, 7.2 Re Apogee, 1000 km Perigee and Period 12 hr. The TWINS Spacecraft are 3-Axis stabilized and with Nadir-Pointing. Each acquires Image Data with Time Resolution of 60 s. The Time required to change Actuator Direction between Scans, an Interval with no Data Collection, was 25 s from June 2008 to July 2009, and 12 s at all other Times. This gives an Effective Cadence of 72 or 85 s. The Nominal Design Lifetime for each Instrument is four Years. TWINS operates only during the Apogee Portion of each Orbit, when the Spacecraft is above the Radiation Belts. The TWINS Lyman-alpha Detector consists of two independent Sensors to measure Lyman-alpha Radiation being emitted by Neutral Hydrogen Atoms. The Sensors oriented at Angles of 40° with respect to the Actuator Spin Axis. Each Sensor has a Full Width, Half Maximum, FWHM, Field-of-View of 4°, defined by Collimation Hole Baffles, uses Lyman-alpha Interference Filters as Narrow Band Transmissions Filters, and applies a KBr or CsI Photodiode for Photon Detection. The Lyman-alpha Detector is located on the rotating Actuator Platform to provide Full 360° Azimuthal Angle Coverage Time resolution is 60 s.
Acknowledgement
D.J. McComas, H.J. Fahr
PublicationInfo
Authors
McComas, David, J.; Fahr, Hans, J.
PublicationDate
2023-01-01 00:00:00Z
PublishedBy
Space Physics Data Facility
Contacts
Role
Person
StartDate
StopDate
Note
1.
PrincipalInvestigator
spase://SMWG/Person/David.J.McComas
2.
PrincipalInvestigator
spase://SMWG/Person/Hans.J.Fahr
3.
MetadataContact
spase://SMWG/Person/Robert.E.McGuire
4.
MetadataContact
spase://SMWG/Person/Lee.Frost.Bargatze
InformationURL
Name
Initial Inventory CDAWeb TWINS List of Events and Sample Plots
URL
https://cdaweb.gsfc.nasa.gov/TWINS_info.html
Description
Initial Inventory CDAWeb Two Wide-angle Imaging Neutral-atom Spectrometers, TWINS, List of Events and Sample Plots
InformationURL
Name
TWINS Release Notes and other Information, SwRI Web Site
URL
https://earth.esa.int/web/eoportal/satellite-missions/t/twins/
Description
Two Wide-angle Imaging Neutral-atom Spectrometers, TWINS, Release Notes and other Information, Southwest Research Institute, SwRI, Web Site
InformationURL
Name
HelioData
URL
https://helio.data.nasa.gov/dataset/TWINS2_LAD_L1_PT1.333S
Description
The HelioData dataset page provides an overview of the dataset with access links, associated variables, and more.
PriorIDs
spase://VSPO/NumericalData/TWINS2/LAD/L1/PT1.333S
AccessInformation
RepositoryID
spase://SMWG/Repository/NASA/GSFC/SPDF/CDAWeb
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/twins/twins2/lad/
Description
Access to Data in CDF Format via ftp from SPDF
AccessURL
Name
HTTPS from SPDF
URL
https://spdf.gsfc.nasa.gov/pub/data/twins/twins2/lad/
Description
Access to Data in CDF Format via http from SPDF
AccessURL
Name
CDAWeb
URL
https://cdaweb.gsfc.nasa.gov/cgi-bin/eval2.cgi?dataset=TWINS2_L1_LAD&index=sp_phys
ProductKey
TWINS2_L1_LAD
Description
Access to ASCII, CDF, and plots via NASA/GSFC CDAWeb
Format
CDF
Encoding
None
AccessDirectoryTemplate
https://cdaweb.gsfc.nasa.gov/pub/data/twins/twins2/lad/$Y
AccessFilenameTemplate
twins2_l1_lad_$Y$m$d_$v.cdf
Acknowledgement
D.J. McComas, H.J. Fahr. Please acknowledge the data providers and CDAWeb when using these data.
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/TWINS2_L1_LAD/clientLibraryExample/
Style
WebService
ProductKey
TWINS2_L1_LAD
Description
Access to this data from common programming environments. Note: this AccessInformation element was added by HDPWS.
Format
Binary
Acknowledgement
D.J. McComas, H.J. Fahr. Please acknowledge the data providers and CDAWeb when using these data.
AccessInformation
RepositoryID
spase://SMWG/Repository/NASA/GSFC/SPDF/CDAWeb
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
CDAWeb HAPI Server
URL
https://cdaweb.gsfc.nasa.gov/hapi
Style
HAPI
ProductKey
TWINS2_L1_LAD
Description
Web Service to this product using the HAPI interface.
Format
CSV
Acknowledgement
D.J. McComas, H.J. Fahr. Please acknowledge the data providers and CDAWeb when using these data.
ProcessingLevel
Calibrated
InstrumentIDs
spase://SMWG/Instrument/TWINS2/LAD
MeasurementType
ImageIntensity
TemporalDescription
TimeSpan
StartDate
2008-05-02 04:45:26Z
StopDate
2016-10-26 23:59:59.999Z
Cadence
PT1.333S
ObservedRegion
Earth.Magnetosphere
ObservedRegion
Earth.Magnetosphere.Magnetotail
ObservedRegion
Earth.Magnetosphere.Main
ObservedRegion
Earth.Magnetosphere.RadiationBelt
ObservedRegion
Earth.Magnetosheath
Parameter #1
Name
Epoch
ParameterKey
Epoch
Description
Epoch
Cadence
PT1.333S
RenderingHints
DisplayType
TimeSeries
AxisLabel
Epoch
ValueFormat
F12.2
ValidMin
01-Jan-0000 00:00:00.000
ValidMax
01-Jan-9999 00:00:00.000
FillValue
31-Dec-9999 23:59:59.999
Support
SupportQuantity
Temporal
Parameter #2
Name
Timestamps, Modified Julian Date, LAD
Set
Time series defined by using: EPOCH
ParameterKey
time
Description
Timestamps, Modified Julian Date, Lyman-alpha Detector, LAD
Cadence
PT1.333S
RenderingHints
DisplayType
TimeSeries
AxisLabel
Time MJD
ValueFormat
F30.12
ValidMin
51545.0
ValidMax
88070.0
FillValue
-1.0e+31
Support
SupportQuantity
Temporal
Parameter #3
Name
Photon Intensities, Toward LAD Sensor
Set
Time series defined by using: EPOCH
ParameterKey
lad1_data
Description
Photon Intensities, Toward Lyman-alpha Detector, LAD, Sensor
Cadence
PT1.333S
Units
R
UnitsConversion
1e-10>m^-2 s-1
RenderingHints
DisplayType
TimeSeries
AxisLabel
Photon Intensity Toward
ValueFormat
F19.12
ValidMin
0.0
ValidMax
46000.0
FillValue
-1.0e+31
Wave
WaveType
Electromagnetic
Qualifier
Scalar
WaveQuantity
Intensity
Parameter #4
Name
Photon Intensities, Away LAD Sensor
Set
Time series defined by using: EPOCH
ParameterKey
lad2_data
Description
Photon Intensities, Away Lyman-alpha Detector, LAD, Sensor
Cadence
PT1.333S
Units
R
UnitsConversion
1e-10>m^-2 s-1
RenderingHints
DisplayType
TimeSeries
AxisLabel
Photon Intensity Away
ValueFormat
F19.12
ValidMin
0.0
ValidMax
46000.0
FillValue
-1.0e+31
Wave
WaveType
Electromagnetic
Qualifier
Scalar
WaveQuantity
Intensity
Parameter #5
Name
Actuator Position at Sector Start
Set
Time series defined by using: EPOCH
ParameterKey
sector_position
Description
Actuator Position at Sector Start
Caveats
Values run from -90° to +90° during a Scan. Note that Sectors are either 4° Wide for Dynamic Modes, or 1.333 s Long for Static Modes.
Cadence
PT1.333S
Units
°
UnitsConversion
0.0174532925>rad
RenderingHints
DisplayType
TimeSeries
AxisLabel
Actuator Position
ValueFormat
F19.12
ValidMin
-90.0
ValidMax
90.0
FillValue
-1.0e+31
Support
SupportQuantity
Other
Parameter #6
Name
Photon Intensities, Toward LAD Sensor, 0° Offset
Set
Time series defined by using: EPOCH
ParameterKey
lad1_0_data
Description
Photon Intensities, Toward Lyman-alpha Detector, LAD, Sensor, 0° Offset, Diagnostic use only
Caveats
The LAD Counters are read out each 0.67 s, corresponding to 2° at the Nominal TWA Rotation Rate of 3°/s
Cadence
PT1.333S
Units
R
UnitsConversion
1e-10>m^-2 s-1
RenderingHints
DisplayType
TimeSeries
AxisLabel
Photon Intensity Toward 0° Offset
ValueFormat
F19.12
ValidMin
0.0
ValidMax
23000.0
FillValue
-1.0e+31
Wave
WaveType
Electromagnetic
Qualifier
Scalar
WaveQuantity
Intensity
Parameter #7
Name
Photon Intensities, Away LAD Sensor, 0° Offset
Set
Time series defined by using: EPOCH
ParameterKey
lad2_0_data
Description
Photon Intensities, Away Lyman-alpha Detector, LAD, Sensor, 0° Offset, Diagnostic use only
Caveats
The LAD Counters are read out each 0.67 s, corresponding to 2° at the Nominal TWA Rotation Rate of 3°/s
Cadence
PT1.333S
Units
R
UnitsConversion
1e-10>m^-2 s-1
RenderingHints
DisplayType
TimeSeries
AxisLabel
Photon Intensity Away 0° Offset
ValueFormat
F19.12
ValidMin
0.0
ValidMax
23000.0
FillValue
-1.0e+31
Wave
WaveType
Electromagnetic
Qualifier
Scalar
WaveQuantity
Intensity
Parameter #8
Name
Photon Intensities, Toward LAD Sensor, 2° Offset
Set
Time series defined by using: EPOCH
ParameterKey
lad1_2_data
Description
Photon Intensities, Toward Lyman-alpha Detector, LAD, Sensor, 2° Offset, Diagnostic use only
Caveats
The LAD Counters are read out each 0.67 s, corresponding to 2° at the Nominal TWA Rotation Rate of 3°/s
Cadence
PT1.333S
Units
R
UnitsConversion
1e-10>m^-2 s-1
RenderingHints
DisplayType
TimeSeries
AxisLabel
Photon Intensity Toward 2° Offset
ValueFormat
F19.12
ValidMin
0.0
ValidMax
23000.0
FillValue
-1.0e+31
Wave
WaveType
Electromagnetic
Qualifier
Scalar
WaveQuantity
Intensity
Parameter #9
Name
Photon Intensities, Away LAD Sensor, 2° Offset
Set
Time series defined by using: EPOCH
ParameterKey
lad2_2_data
Description
Photon Intensities, Away Lyman-alpha Detector, LAD, Sensor, 2° Offset, Diagnostic use only
Caveats
The LAD Counters are read out each 0.67 s, corresponding to 2° at the Nominal TWA Rotation Rate of 3°/s
Cadence
PT1.333S
Units
R
UnitsConversion
1e-10>m^-2 s-1
RenderingHints
DisplayType
TimeSeries
AxisLabel
Photon Intensity Away 2° Offset
ValueFormat
F19.12
ValidMin
0.0
ValidMax
23000.0
FillValue
-1.0e+31
Wave
WaveType
Electromagnetic
Qualifier
Scalar
WaveQuantity
Intensity