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Comet Wild 2 Ephemeris, Heliocentric Trajectories, Heliographic, Heliographic Inertial, and Solar Ecliptic Coordinates, HelioWeb, Daily Data

ResourceID
spase://NASA/NumericalData/Comet/Wild2/HelioWeb/Ephemeris/P1D

Description

Heliocentric trajectories for Comet Wild 2 in Heliographic, HG, Heliographic Inertial, HGI, and Solar Ecliptic, SE, Coordinates

The original trajectory data are taken from http://ssd.jpl.nasa.gov/horizons.cgi where users can find many more objects. In the case of orbit data for planets, the orbit data can be used as a proxy for spacecraft ephemeris that are in orbit about the planets. On a heliospheric scale, differences between the planet orbital tarjectory and that of the spacecraft are very small. For instance, the heliocentric longitudes differ by only 0.25° for a spacecraft stationed near the L1 Lagrange point at approximately 100 Earth radii upstream of the Earth.

The production of the HG, HGI, and SE trajectory data requires a values for the "Equinox Epoch", which is defined as the epoch time when the direction from the Earth to the sun at the time of the vernal equinox when the sun seems to cross equatorial plane of the Earth from below. This direction is called the First Point of Aries, FPA and it is not a fixed direction but drifts by about 1.4° per century or 50.26" per year. In addition, there are tiny irregularities in FPA drift that are on the order of 1" per year or less. The Equinox Epoch can be determined by using a variety of methods for calculating the instantaneous FPA longitudinal direction and whether the tiny irregularities have been smoothed or averaged out. Four methods for determining the Equinox Epoch are in common usage:

+---------------------------------------------------------------------+
| Method Name | FPA Longitude Definition |
|---------------------------------------------------------------------|
| B1950.0 | the actual FPA at 22:09 UT on December 31, 1949 |
| J2000.0 | the smoothed FPA at 12:00 UT on January 1, 2000 |
| True of Date | the actual FPA at 00:00 UT on the date of interest |
| Mean of Date | the smoothed FPA at 00:00 UT on the date of interest |
+---------------------------------------------------------------------+

The heliocentric trajectory data included in this data product have been calculated by using the Equinox Epoch: defined via the "Mean of Date" method.

More precise coordinates, and some planet-centered coordinates, are found in the "traj" subdirectories of spacecraft specific directories at https://spdf.gsfc.nasa.gov/pub/data/ and http://ssd.jpl.nasa.gov/horizons.cgi.

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Details

Version:2.3.0

NumericalData

ResourceID
spase://NASA/NumericalData/Comet/Wild2/HelioWeb/Ephemeris/P1D
ResourceHeader
ResourceName
Comet Wild 2 Ephemeris, Heliocentric Trajectories, Heliographic, Heliographic Inertial, and Solar Ecliptic Coordinates, HelioWeb, Daily Data
ReleaseDate
2020-07-07 21:14:30Z
Description

Heliocentric trajectories for Comet Wild 2 in Heliographic, HG, Heliographic Inertial, HGI, and Solar Ecliptic, SE, Coordinates

The original trajectory data are taken from http://ssd.jpl.nasa.gov/horizons.cgi where users can find many more objects. In the case of orbit data for planets, the orbit data can be used as a proxy for spacecraft ephemeris that are in orbit about the planets. On a heliospheric scale, differences between the planet orbital tarjectory and that of the spacecraft are very small. For instance, the heliocentric longitudes differ by only 0.25° for a spacecraft stationed near the L1 Lagrange point at approximately 100 Earth radii upstream of the Earth.

The production of the HG, HGI, and SE trajectory data requires a values for the "Equinox Epoch", which is defined as the epoch time when the direction from the Earth to the sun at the time of the vernal equinox when the sun seems to cross equatorial plane of the Earth from below. This direction is called the First Point of Aries, FPA and it is not a fixed direction but drifts by about 1.4° per century or 50.26" per year. In addition, there are tiny irregularities in FPA drift that are on the order of 1" per year or less. The Equinox Epoch can be determined by using a variety of methods for calculating the instantaneous FPA longitudinal direction and whether the tiny irregularities have been smoothed or averaged out. Four methods for determining the Equinox Epoch are in common usage:

+---------------------------------------------------------------------+
| Method Name | FPA Longitude Definition |
|---------------------------------------------------------------------|
| B1950.0 | the actual FPA at 22:09 UT on December 31, 1949 |
| J2000.0 | the smoothed FPA at 12:00 UT on January 1, 2000 |
| True of Date | the actual FPA at 00:00 UT on the date of interest |
| Mean of Date | the smoothed FPA at 00:00 UT on the date of interest |
+---------------------------------------------------------------------+

The heliocentric trajectory data included in this data product have been calculated by using the Equinox Epoch: defined via the "Mean of Date" method.

More precise coordinates, and some planet-centered coordinates, are found in the "traj" subdirectories of spacecraft specific directories at https://spdf.gsfc.nasa.gov/pub/data/ and http://ssd.jpl.nasa.gov/horizons.cgi.

Acknowledgement
Please acknowledge N.E. Papitashvili for use of the Data
Contacts
RolePerson
1.GeneralContactspase://SMWG/Person/Natalia.E.Papitashvili
2.MetadataContactspase://SMWG/Person/Robert.M.Candey
3.MetadataContactspase://SMWG/Person/Lee.Frost.Bargatze
InformationURL
Name
Heliocentric Trajectories HelioWeb Data Service, NASA GSFC
URL
https://omniweb.sci.gsfc.nasa.gov/coho/helios/heli.html
Description

Heliocentric trajectories for selected spacecraft, planets, and comets, HelioWeb data service, hosted by NASA GSFC

InformationURL
Name
Heliocentric Trajectories HelioWeb Data Service Usage Instructions, NASA GSFC
URL
https://omniweb.sci.gsfc.nasa.gov/coho/helios/about_helioweb.html
Description

Instructions for using the Heliocentric Trajectories HelioWeb data service, hosted by NASA GSFC

InformationURL
Name
Heliocentric Trajectories HelioWeb Data Service Usage via CURL or WGET Commands, NASA GSFC
URL
https://omniweb.sci.gsfc.nasa.gov/coho/helios/helioweb_command_line_sample.txt
Description

Instructions for using the Heliocentric Trajectories HelioWeb data service via CURL or WGET commands, hosted by NASA GSFC

InformationURL
Name
HG, HGI, and SE Coordinate System Definitions, NASA GSFC
URL
https://omniweb.sci.gsfc.nasa.gov/coho/helios/coor_des.html
Description

Definitions for the Heliographic, HG, Heliographic Inertial, HGI, and Solar Ecliptic, SE, Coordinate Systems, hosted by NASA GSFC

InformationURL
Name
Satellite Situation Center (SSCWeb) System and Services, NASA GSFC
URL
https://sscweb.gsfc.nasa.gov
Description

Satellite Situation Center (SSCWeb) web page offering a variety of services that provide access to orbit trajectory graphics and listings, hosted by NASA GSFC

InformationURL
Name
HORIZONS Web Interface, NASA JPL
URL
https://ssd.jpl.nasa.gov/horizons.cgi
Description

HORIZONS Web Interface, a web page that provides limited access to the JPL HORIZONS system which can be used to generate ephemerides for solar system bodies

PriorIDs
spase://VSPO/NumericalData/Comet/Wild2/HelioWeb/Ephemeris/P1D
AccessInformation
RepositoryID
spase://SMWG/Repository/NASA/GSFC/SPDF
Availability
Online
AccessRights
Open
AccessURL
Name
FTPS from SPDF (not with most browsers)
URL
ftps://spdf.gsfc.nasa.gov/pub/data/planet_and_comet_positions/helio1day/
Description

Access to Data in CDF Format via ftp from SPDF

AccessURL
Name
HTTPS from SPDF
URL
https://spdf.gsfc.nasa.gov/pub/data/planet_and_comet_positions/helio1day/
Description

Access to Data in CDF Format via http from SPDF

AccessURL
Name
CDAWeb
URL
https://cdaweb.sci.gsfc.nasa.gov/cgi-bin/eval2.cgi?dataset=WILD2_HELIO1DAY_POSITION&index=sp_phys
ProductKey
WILD2_HELIO1DAY_POSITION
Description

Access to ASCII, CDF, and Plots via NASA/GSFC CDAWeb

Format
CDF
Encoding
None
Acknowledgement
Please acknowledge N.E. Papitashvili. Please acknowledge the Data Providers and CDAWeb when using these Data.
ProcessingLevel
Calibrated
MeasurementType
Ephemeris
TemporalDescription
TimeSpan
StartDate
1995-01-01 00:00:00.000
StopDate
2020-12-31 00:00:00.000
Cadence
P1D
Parameter #1
Name
Epoch Time
ParameterKey
Epoch
Description

Epoch Time, beginning of interval

Caveats
This Parameter exhibits an increasing Monotonic Progression
Cadence
P1D
Units
ms
UnitsConversion
1.0e-3>s
RenderingHints
AxisLabel
Epoch
ValueFormat
E14.8
ScaleMin
6.2987652219904e+13
ScaleMax
6.3745034619904e+13
ScaleType
LinearScale
ValidMin
01-Jan-1996 00:00:00.000
ValidMax
01-Jan-2020 00:00:00.000
FillValue
31-Dec-9999 23:59:59.999
Support
SupportQuantity
Temporal
Parameter #2
Name
Comet Wild 2 Position, Heliocentric Radial Distance
Set
Time Series defined by using: EPOCH
ParameterKey
RAD_AU
Description

Comet Wild 2 Position, Heliocentric Radial Distance

Cadence
P1D
Units
ua
UnitsConversion
1.495978706961e11>m
RenderingHints
DisplayType
TimeSeries
AxisLabel
RAD_AU
ValueFormat
F8.2
ValidMin
0.0
ValidMax
1000.0
FillValue
-1.0e+31
Support
SupportQuantity
Temporal
Parameter #3
Name
Comet Wild 2 Position, Latitude, Solar Ecliptic Coordinates
Set
Time Series defined by using: EPOCH
ParameterKey
SE_LAT
Description

Comet Wild 2 Position, Latitude, Solar Ecliptic, SE, Spherical Coordinates

Cadence
P1D
Units
°
UnitsConversion
0.0174532925>rad
CoordinateSystem
CoordinateRepresentation
Spherical
CoordinateSystemName
SE
RenderingHints
DisplayType
TimeSeries
AxisLabel
SE_LAT
ValueFormat
F8.1
ValidMin
-90.0
ValidMax
90.0
FillValue
-1.0e+31
Support
Qualifier
DirectionAngle.ElevationAngle
Qualifier
Scalar
SupportQuantity
Positional
Parameter #4
Name
Comet Wild 2 Position, Longitude, Solar Ecliptic Coordinates
Set
Time Series defined by using: EPOCH
ParameterKey
SE_LON
Description

Comet Wild 2 Position, Longitude, Solar Ecliptic, SE, Spherical Coordinates

Cadence
P1D
Units
°
UnitsConversion
0.0174532925>rad
CoordinateSystem
CoordinateRepresentation
Spherical
CoordinateSystemName
SE
RenderingHints
DisplayType
TimeSeries
AxisLabel
SE_LON
ValueFormat
F8.1
ValidMin
0.0
ValidMax
360.0
FillValue
-1.0e+31
Support
Qualifier
DirectionAngle.AzimuthAngle
Qualifier
Scalar
SupportQuantity
Positional
Parameter #5
Name
Comet Wild 2 Position, Latitude, Heliographic Coordinates
Set
Time Series defined by using: EPOCH
ParameterKey
HG_LAT
Description

Comet Wild 2 Position, Latitude, Heliographic, HG, Spherical Coordinates

Cadence
P1D
Units
°
UnitsConversion
0.0174532925>rad
CoordinateSystem
CoordinateRepresentation
Spherical
CoordinateSystemName
HG
RenderingHints
DisplayType
TimeSeries
AxisLabel
HG_LAT
ValueFormat
F8.1
ValidMin
-90.0
ValidMax
90.0
FillValue
-1.0e+31
Support
Qualifier
DirectionAngle.ElevationAngle
Qualifier
Scalar
SupportQuantity
Positional
Parameter #6
Name
Comet Wild 2 Position, Longitude, Heliographic Coordinates
Set
Time Series defined by using: EPOCH
ParameterKey
HG_LON
Description

Comet Wild 2 Position, Longitude, Heliographic, HG, Spherical Coordinates

Cadence
P1D
Units
°
UnitsConversion
0.0174532925>rad
CoordinateSystem
CoordinateRepresentation
Spherical
CoordinateSystemName
HG
RenderingHints
DisplayType
TimeSeries
AxisLabel
HG_LON
ValueFormat
F8.1
ValidMin
0.0
ValidMax
360.0
FillValue
-1.0e+31
Support
Qualifier
DirectionAngle.AzimuthAngle
Qualifier
Scalar
SupportQuantity
Positional
Parameter #7
Name
Comet Wild 2 Position, Latitude, Heliographic Inertial Coordinates
Set
Time Series defined by using: EPOCH
ParameterKey
HGI_LAT
Description

Comet Wild 2 Position, Latitude, Heliographic Inertial, HGI, Spherical Coordinates

Cadence
P1D
Units
°
UnitsConversion
0.0174532925>rad
CoordinateSystem
CoordinateRepresentation
Spherical
CoordinateSystemName
HGI
RenderingHints
DisplayType
TimeSeries
AxisLabel
HGI_LAT
ValueFormat
F8.1
ValidMin
-90.0
ValidMax
90.0
FillValue
-1.0e+31
Support
Qualifier
DirectionAngle.ElevationAngle
Qualifier
Scalar
SupportQuantity
Positional
Parameter #8
Name
Comet Wild 2 Position, Longitude, Heliographic Inertial Coordinates
Set
Time Series defined by using: EPOCH
ParameterKey
HGI_LON
Description

Comet Wild 2 Position, Longitude, Heliographic Inertial, HGI, Spherical Coordinates

Cadence
P1D
Units
°
UnitsConversion
0.0174532925>rad
CoordinateSystem
CoordinateRepresentation
Spherical
CoordinateSystemName
HGI
RenderingHints
DisplayType
TimeSeries
AxisLabel
HGI_LON
ValueFormat
F8.1
ValidMin
0.0
ValidMax
360.0
FillValue
-1.0e+31
Support
Qualifier
DirectionAngle.AzimuthAngle
Qualifier
Scalar
SupportQuantity
Positional