HPDE.io

GOES 12 high resolution magnetometer data

ResourceID
spase://NOAA/NumericalData/GOES/12/MAG/PT0.512S

Description

GOES 12 magnetic field data at 0.512 s time resolution. The vector magnetic field is given in the spacecraft Earth-referenced coordinate system: Hp, He, Hn, and Ht, where Hp is perpendicular to the satellite orbital plane, or parallel to spin axis of the Earth in the case of a 0° inclination orbit, He is perpendicular to Hp and directed earthward, Hn is perpendicular to both Hp and He and directed eastward, and Ht is the total field.

This data product also provides GOES 12 satellite positions and velocities derived from SSCWEB GEI ephemeris, interpolated to 1 min time resolution.

The magnetometer data are downlinked from the spacecraft in real-time to the NOAA Space Weather Prediction Center (SWPC) in Boulder, Colorado. The data from the raw Command and Data Acquisition (CDA) telemetry stream are processed by pre-processors at SWPC and from there 1 min averages are distributed to SWPC Space Weather Operations, as well a archived at the NOAA National Geophysical Data Center (NGDC) and the NASA Coordinated Data Analysis Web (http://cdaweb.gsfc.nasa.gov/). The raw high resolution data are corrected and processed at the NOAA SWPC, and later archived at NGDC.

The major issue for processing the high resolution data is correction for the magnetic signature of spacecraft torquer currents as briefly discussed in the magnetometer instrument descriptions. In normal operation, the magnetometer samples its three axes every 0.512 s, synchronized with the telemetry frames. The magnetometer has an anti-aliasing low-pass filter on each axis. As part of the attitude control on the spacecraft, there are two magnetic torquers. At the magnetometers, these torquers can generate magnetic fields larger than the ambient fields to be measured. Therefore signals from these torquer currents need to be removed. The torquer currents are measured at the same rate as the magnetometer rate, and the currents are used to correct the magnetometer measurements.

However, the torquer currents were not low-pass filtered. As a result, large instantaneous steps in the torquer currents show up in the magnetometer data as a delayed, slowly rising wave with some ringing, just what one would expect from the magnetometer low-pass filters. The so-called "Farthing coefficients" simulate, from a short past history of the torquer measurements, the effects of the magnetometer filters. The torquer current changes are asynchronous with the telemetry frames and the timing between these events must be measured to a eighth of a telemetry frame interval for good performance. The transient responses in changes in torquer currents are reduced, but not eliminated for large changes in torquer currents.

There exists one opportunity at the beginning of each mission to perform a spacecraft rotation maneuver to determine magnetometer offsets. These offsets are used through the duration of the lifetime of each satellite.

Approximate coefficients are:

  • 0.8 mA per torquer current count
  • 4 counts per torquer current command step (3.2 mA per command step)
  • 410 mA full scale current
  • 32 magnetometer counts per nT (approximate)
  • 8 torquer step counts can be up to approximately 0.5 nT (depends on axis, which torquer, which satellite, etc.)

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Details

Version:2.3.1

NumericalData

ResourceID
spase://NOAA/NumericalData/GOES/12/MAG/PT0.512S
ResourceHeader
ResourceName
GOES 12 high resolution magnetometer data
ReleaseDate
2021-04-27 17:52:57Z
Description

GOES 12 magnetic field data at 0.512 s time resolution. The vector magnetic field is given in the spacecraft Earth-referenced coordinate system: Hp, He, Hn, and Ht, where Hp is perpendicular to the satellite orbital plane, or parallel to spin axis of the Earth in the case of a 0° inclination orbit, He is perpendicular to Hp and directed earthward, Hn is perpendicular to both Hp and He and directed eastward, and Ht is the total field.

This data product also provides GOES 12 satellite positions and velocities derived from SSCWEB GEI ephemeris, interpolated to 1 min time resolution.

The magnetometer data are downlinked from the spacecraft in real-time to the NOAA Space Weather Prediction Center (SWPC) in Boulder, Colorado. The data from the raw Command and Data Acquisition (CDA) telemetry stream are processed by pre-processors at SWPC and from there 1 min averages are distributed to SWPC Space Weather Operations, as well a archived at the NOAA National Geophysical Data Center (NGDC) and the NASA Coordinated Data Analysis Web (http://cdaweb.gsfc.nasa.gov/). The raw high resolution data are corrected and processed at the NOAA SWPC, and later archived at NGDC.

The major issue for processing the high resolution data is correction for the magnetic signature of spacecraft torquer currents as briefly discussed in the magnetometer instrument descriptions. In normal operation, the magnetometer samples its three axes every 0.512 s, synchronized with the telemetry frames. The magnetometer has an anti-aliasing low-pass filter on each axis. As part of the attitude control on the spacecraft, there are two magnetic torquers. At the magnetometers, these torquers can generate magnetic fields larger than the ambient fields to be measured. Therefore signals from these torquer currents need to be removed. The torquer currents are measured at the same rate as the magnetometer rate, and the currents are used to correct the magnetometer measurements.

However, the torquer currents were not low-pass filtered. As a result, large instantaneous steps in the torquer currents show up in the magnetometer data as a delayed, slowly rising wave with some ringing, just what one would expect from the magnetometer low-pass filters. The so-called "Farthing coefficients" simulate, from a short past history of the torquer measurements, the effects of the magnetometer filters. The torquer current changes are asynchronous with the telemetry frames and the timing between these events must be measured to a eighth of a telemetry frame interval for good performance. The transient responses in changes in torquer currents are reduced, but not eliminated for large changes in torquer currents.

There exists one opportunity at the beginning of each mission to perform a spacecraft rotation maneuver to determine magnetometer offsets. These offsets are used through the duration of the lifetime of each satellite.

Approximate coefficients are:

  • 0.8 mA per torquer current count
  • 4 counts per torquer current command step (3.2 mA per command step)
  • 410 mA full scale current
  • 32 magnetometer counts per nT (approximate)
  • 8 torquer step counts can be up to approximately 0.5 nT (depends on axis, which torquer, which satellite, etc.)
Acknowledgement
NASA Contract NAS5-02099
Contacts
RolePersonStartDateStopDateNote
1.PrincipalInvestigator
DataProducer
spase://SMWG/Person/Howard.J.Singer
2.DataProducerspase://SMWG/Person/Ann.Newman
3.DataProducerspase://SMWG/Person/Lorne.Matheson
4.MetadataContactspase://SMWG/Person/Jan.Merka
PriorIDs
spase://VMO/NumericalData/GOES12/MAG/PT0.512S
spase://VMO/NumericalData/GOES/12/MAG/PT0.512S
spase://VSPO/NumericalData/GOES/12/MAG/PT0.512S
AccessInformation
RepositoryID
Availability
Online
AccessRights
Open
AccessURL
Name
FTPS from SPDF (not with most browsers)
URL
AccessURL
Name
HTTPS from SPDF
URL
Description

In CDF via HTTP from CDAWeb

AccessURL
Name
CDAWeb
URL
ProductKey
G12_L2_MAG
Description

For CDAWeb subset, plot and list capabilities

Format
CDF
Encoding
None
AccessInformation
RepositoryID
Availability
Online
AccessRights
Open
AccessURL
Name
CDAWeb HAPI Server
URL
Style
HAPI
ProductKey
G12_L2_MAG@0
ProductKey
G12_L2_MAG@1
ProductKey
G12_L2_MAG@2
Description

Web Service to this product using the HAPI interface.

Format
CSV
InstrumentIDs
MeasurementType
MagneticField
MeasurementType
Ephemeris
TemporalDescription
TimeSpan
StartDate
2007-09-15 23:59:58
StopDate
2008-06-30 23:59:58
Cadence
PT0.512S
ObservedRegion
Earth.Magnetosphere.Main
Caveats
Note that magnetic field values have been replaced with missing data values during calibration periods. Also, note that there can be small jumps in the data (typically <1 nT) when the torquer counts go through zero. The magnitude of the effect can be different for different spacecraft. The GOES 8 to GOES 12 spacecraft are 3-axis stabilized and there is only one opportunity for a spin maneuver at the beginning of the mission to determine on-orbit offsets. There are additional complications that result from needing to know the changing offsets introduced by torquer coils on the satellites. Though comparisons of data to model fields during quiet times, we are doing rather well with the offsets, but it is not possible to give an exact number for the accuracy. We continue to look at comparisons of data and models, and data to other nearby spacecraft encounters. We are interested in anything learned by the user, or working with the user to help interpret the data, or to answer questions. While we have put in a significant effort to remove the effects of torquer coil interference, in the 0.512 s data there can be small, typically less than 1 nT spikes in the data at the time of torquer current changes. More information on this topic is included the more extensive "readme file". This file is a living document that will be updated periodically.
Parameter #1
Name
g12_longitude_time
ParameterKey
g12_longitude_time
Description

GEOS 12 longitude time, UTC, in seconds since 1970-01-01T00:00:00

Caveats
Unleaped seconds
Cadence
P1D
Units
s
ValidMin
0.0
ValidMax
5.0E9
FillValue
NaN
Support
SupportQuantity
Temporal
Parameter #2
Name
g12_longitude_epoch
ParameterKey
g12_longitude_epoch
Description

GEOS 12 longitude epoch

Cadence
P1D
ValidMin
2001-01-01T00:00:00
ValidMax
2100-12-31T23:59:59
FillValue
9999-12-31T23:59:59
Support
SupportQuantity
Temporal
Parameter #3
Name
g12_longitude
ParameterKey
g12_longitude
Description

Satellite geographic west longitude at noon UTC

Cadence
P1D
Units
°
CoordinateSystem
CoordinateRepresentation
Spherical
CoordinateSystemName
GEO
ValidMin
-180.0
ValidMax
180.0
FillValue
NaN
Support
Qualifier
DirectionAngle.AzimuthAngle
SupportQuantity
Positional
Parameter #4
Name
g12_mlt
ParameterKey
g12_mlt
Description

Magnetic local time at satellite position

Cadence
PT1M
Units
h
UnitsConversion
(g12_mlt-12)*15>°
CoordinateSystem
CoordinateRepresentation
Spherical
CoordinateSystemName
SM
ValidMin
0.0
ValidMax
24.0
FillValue
NaN
Support
Qualifier
DirectionAngle.AzimuthAngle
SupportQuantity
Positional
Parameter #5
Name
g12_pos_gei
ParameterKey
g12_pos_gei
Description

Satellite position vector in GEI coordinates

Cadence
PT1M
Units
km
CoordinateSystem
CoordinateRepresentation
Cartesian
CoordinateSystemName
GEI
Structure
Size
3
Element
Name
X, GEI
Qualifier
Component.I
Index
1
Element
Name
Y, GEI
Qualifier
Component.J
Index
2
Element
Name
Z, GEI
Qualifier
Component.K
Index
3
ValidMin
-1.0e6
ValidMax
1.0e6
FillValue
NaN
Support
Qualifier
Vector
SupportQuantity
Positional
Parameter #6
Name
g12_pos_gsm
ParameterKey
g12_pos_gsm
Description

Satellite position vector in GSM coordinates

Cadence
PT1M
Units
km
CoordinateSystem
CoordinateRepresentation
Cartesian
CoordinateSystemName
GSM
Structure
Size
3
Element
Name
X, GSM
Qualifier
Component.I
Index
1
Element
Name
Y, GSM
Qualifier
Component.J
Index
2
Element
Name
Z, GSM
Qualifier
Component.K
Index
3
ValidMin
-1.0e6
ValidMax
1.0e6
FillValue
NaN
Support
Qualifier
Vector
SupportQuantity
Positional
Parameter #7
Name
g12_vel_gei
ParameterKey
g12_vel_gei
Description

Satellite velocity vector in GEI coordinates

Cadence
PT1M
Units
km/s
CoordinateSystem
CoordinateRepresentation
Cartesian
CoordinateSystemName
GEI
Structure
Size
3
Element
Name
Vx, GEI
Qualifier
Component.I
Index
1
Element
Name
Vy, GEI
Qualifier
Component.J
Index
2
Element
Name
Vz, GEI
Qualifier
Component.K
Index
3
ValidMin
-1000.0
ValidMax
1000.0
FillValue
NaN
Support
Qualifier
Vector
SupportQuantity
Velocity
Parameter #8
Name
g12_vel_gsm
ParameterKey
g12_vel_gsm
Description

Satellite velocity vector in GSM coordinates

Cadence
PT1M
Units
km/s
CoordinateSystem
CoordinateRepresentation
Cartesian
CoordinateSystemName
GSM
Structure
Size
3
Element
Name
Vx, GSM
Qualifier
Component.I
Index
1
Element
Name
Vy, GSM
Qualifier
Component.J
Index
2
Element
Name
Vz, GSM
Qualifier
Component.K
Index
3
ValidMin
-1000.0
ValidMax
1000.0
FillValue
NaN
Support
Qualifier
Vector
SupportQuantity
Velocity
Parameter #9
Name
g12_perp
ParameterKey
g12_perp
Description

g12_perpendicular

Cadence
PT1M
CoordinateSystem
CoordinateRepresentation
Cartesian
CoordinateSystemName
GEI
Structure
Size
3
Element
Name
Px, GEI
Qualifier
Component.I
Index
1
Element
Name
Py, GEI
Qualifier
Component.J
Index
2
Element
Name
Pz, GEI
Qualifier
Component.K
Index
3
ValidMin
-1.0
ValidMax
1.0
FillValue
NaN
Support
Qualifier
Vector
SupportQuantity
Other
Parameter #10
Name
range_epoch
ParameterKey
range_epoch
Description

Data epoch range, UTC

Units
ms
UnitsConversion
1.0e-3>s
ValidMin
1990-01-01T00:00:00
ValidMax
2029-12-31T23:59:59
FillValue
9999-12-31T23:59:59
Support
SupportQuantity
Temporal
Parameter #11
Name
g12_ephem_time
ParameterKey
g12_ephem_time
Description

GEOS 12 ephemeris time, UTC, in seconds since 1970-01-01T00:00:00

Caveats
Unleaped seconds
Cadence
PT1M
Units
s
ValidMin
0.0
ValidMax
5.0E9
FillValue
NaN
Support
SupportQuantity
Temporal
Parameter #12
Name
g12_ephem_epoch
ParameterKey
g12_ephem_epoch
Description

GEOS 12 ephemeris epoch, UTC

Cadence
PT1M
ValidMin
2001-01-01T00:00:00
ValidMax
2100-12-31T23:59:59
FillValue
9999-12-31T23:59:59
Support
SupportQuantity
Temporal
Parameter #13
Name
g12_sample_time
ParameterKey
g12_sample_time
Description

GEOS 12 sample time, UTC, in seconds since 1970-01-01T00:00:00

Caveats
Unleaped seconds
Cadence
PT0.512S
Units
s
ValidMin
0.0
ValidMax
5.0E9
FillValue
NaN
Support
SupportQuantity
Temporal
Parameter #14
Name
g12_sample_epoch
ParameterKey
GEOS 12 sample epoch, UTC
Description

g12_sample_epoch

Cadence
PT0.512S
ValidMin
2001-01-01T00:00:00
ValidMax
2100-12-31T23:59:59
FillValue
9999-12-31T23:59:59
Support
SupportQuantity
Temporal
Parameter #15
Name
g12_b_enp
ParameterKey
g12_b_enp
Description

Magnetic field vector samples in ENP coordinates.

Coordinate description for historically used PEN system:

  • Hp magnetic field vector component, points northward, perpendicular to orbit plane which for a 0° inclination orbit is parallel to spin axis of the Earth
  • He magnetic field vector component, perpendicular to Hp and Hn and points earthward
  • Hn magnetic field vector component, perpendicular to Hp and He and points eastward
  • Ht total field
Cadence
PT0.512S
Units
nT
UnitsConversion
1.0e-9>T
CoordinateSystem
CoordinateRepresentation
Cartesian
CoordinateSystemName
ENP
Structure
Size
3
Element
Name
He, LH-ENP (satellite to Earth)
Qualifier
Component.I
Index
1
Element
Name
Hn, LH-ENP (east, in plane)
Qualifier
Component.J
Index
2
Element
Name
Hp, LH-ENP (perpendicular to plane)
Qualifier
Component.K
Index
3
ValidMin
-1.0e6
ValidMax
1.0e6
FillValue
NaN
Field
Qualifier
Vector
FieldQuantity
Magnetic
Parameter #16
Name
g12_b_gei
ParameterKey
g12_b_gei
Description

Magnetic field vector samples in GEI coordinates

Cadence
PT0.512S
Units
nT
UnitsConversion
1.0e-9>T
CoordinateSystem
CoordinateRepresentation
Cartesian
CoordinateSystemName
GEI
Structure
Size
3
Element
Name
Bx, GEI
Qualifier
Component.I
Index
1
Element
Name
By, GEI
Qualifier
Component.J
Index
2
Element
Name
Bz, GEI
Qualifier
Component.K
Index
3
ValidMin
-1.0e6
ValidMax
1.0e6
FillValue
NaN
Field
Qualifier
Vector
FieldQuantity
Magnetic
Parameter #17
Name
g12_b_gsm
ParameterKey
g12_b_gsm
Description

Magnetic field vector samples in GSM coordinates

Cadence
PT0.512S
Units
nT
UnitsConversion
1.0e-9>T
CoordinateSystem
CoordinateRepresentation
Cartesian
CoordinateSystemName
GSM
Structure
Size
3
Element
Name
Bx, GSM
Qualifier
Component.I
Index
1
Element
Name
By, GSM
Qualifier
Component.J
Index
2
Element
Name
Bz, GSM
Qualifier
Component.K
Index
3
ValidMin
-1.0e6
ValidMax
1.0e6
FillValue
NaN
Field
Qualifier
Vector
FieldQuantity
Magnetic
Parameter #18
Name
g12_b_tot
ParameterKey
g12_b_tot
Description

Total magnetic field strength

Cadence
PT0.512S
Units
nT
UnitsConversion
1.0e-9>T
ValidMin
-1.0e6
ValidMax
1.0e6
FillValue
NaN
Field
Qualifier
Magnitude
FieldQuantity
Magnetic
Parameter #19
Name
g12_t1_counts
ParameterKey
g12_t1_counts
Description

Magnetotorquer T1 filtered counts. Signed counts smoothed by 3-point average, delayed, or smoothed by Farthing coefficients.

Cadence
PT0.512S
ValidMin
-1.0e6
ValidMax
1.0e6
FillValue
NaN
Support
SupportQuantity
Other
Parameter #20
Name
g12_t2_counts
ParameterKey
g12_t2_counts
Description

Magnetotorquer T2 filtered counts. Signed counts smoothed by 3-point average, delayed, or smoothed by Farthing coefficients.

Cadence
PT0.512S
ValidMin
-1.0e6
ValidMax
1.0e6
FillValue
NaN
Support
SupportQuantity
Other
Parameter #21
Name
g12_dataqual
ParameterKey
g12_dataqual
Description

Data Quality Flag: An integer with a value from 1 through 7 indicating data quality, with 1 and 2 being no data, and 7 being the best data.

Possible data quality values:

  • 0 no satellite data
  • 1 no Magnetometer data
  • 2 satellite is in storage (spinning) mode or non-standard attitude
  • 3 satellite is in calibration mode
  • 4 3-point averaging failed
  • 5 torquer value not adjusted for commands
  • 6 smoothed with commands but not with Farthing coefficients
  • 7 best quality, smoothed with commands and Farthing coefficients

Commands are not always available in the telemetry, in which case, a 3-point average is done.

Cadence
PT0.512S
ValidMin
0
ValidMax
7
FillValue
4294967295
Support
SupportQuantity
Other