PDS3_DATA_SET_ID = VG1-J-POS-6-SUMM-HGCOORDS-V1.0
DATA_SET_NAME = VG1 JUP EPHEMERIS HELIOGRAPHIC COORDS
BROWSE V1.0
START_TIME = 1979-02-26T00:00:35.897
STOP_TIME = 1979-03-24T22:49:32.304
ORIGINAL_DATA_SET_RELEASE_DATE = 1998-05-01
PRODUCER_FULL_NAME = Ness, N. F.; Acuna, M. H.; Lepping, R. P.;
Connerney, J. E. P.; Behannon, K. W.;
Burlaga, L. F.; Joy, S. P.
DATA-SET_SOURCE = NATIONAL SPACE SCIENCE DATA CENTER
REFERENCE:
Acton, C.H., Ancillary Data Services of NASA's Navigation and Ancillary
Information Facility, Planet. Space Sci., Vol. 44, No. 1, pp. 65-70, 1996.
DATA_SET_DESCRIPTION
Data Set Overview
=================
This data set consists of Voyager 1 Jupiter encounter ephemeris
data in Heliographic coordinates covering the period 1979-02-26
to 1979-03-24. Two versions, both covering the same time
period, but containing slightly different data, are provided.
One version was generated by the Voyager MAG team from Voyager
1 SEDR, the other by the PDS/PPI node using the VG1_JUP.BSP and
PCK00003.TPC SPICE kernels. (Note: These SPICE kernels are not currently
archived in PDS, but they are available from NASA's Navigation and
Ancillary Information Facility (NAIF),
https://naif.jpl.nasa.gov/naif/index.html)
Two versions of the spacecraft ephemeris data are provided as
an attempt to correct some of the problems in the Voyager SEDR
while preserving the ability to reproduce early results. The
original SEDR data has a variety of problems which may affect
the knowledge of the spacecraft position, or conversely, the
timing associated with certain events such as ring plane
crossings. The SPICE SPK kernel provided on this disk includes
corrections to some, but not all, of the problems associated
with the Voyager SEDR. The Navigation and Ancillary
Information Facility (NAIF) at JPL may issue a new Voyager SPK
kernel in the future that will further improve the knowledge of
the spacecraft location in inertial space.
There are other differences in the in the two versions of
ephemeris data that are the result of improvements in the
knowledge of some of the physical constants associated with
Jupiter and its moons. Since the Voyager era, there have been
updates to the orientation of the jovian spin axis right
ascension and declination, the radius of Jupiter, as well as
the orbital characteristic and other physical parameters of
many of the moons of Jupiter. These changes affect the stated
position of the spacecraft in jovigraphic coordinate systems
like System III without changing the position of the spacecraft
in inertial space. The spin rate of Jupiter is not changed
from the System III (1965) rate of 9h 55m 29.71sec (870.536
deg/day). The SPICE planetary constants kernel (PCK) contains
both the current IAU definitions of the physical constants for
the bodies within in the jovian system (as data) as well as the
older IAU definitions (as comments). This is an ASCII text
file (PCK00003.TCP) and users of the ephemeris data are
encouraged to review it.
SEDR generated ephemeris
------------------------
Data Supplier : Ness, N. F.; Acuna, M. H.; Lepping, R. P.;
Connerney, J. E. P.; Behannon, K. W.; Burlaga,
L. F.; Joy, S. P.
Data sampling rate : 96 seconds
Data Set Start Time : 1979-02-26T00:00:35.897Z
Data Set Stop Time : 1979-03-24T22:47:56.304Z
SPICE generated ephemeris
-------------------------
Data Supplier : S. Joy
Data sampling rate : 48 seconds
Data Set Start Time : 1979-02-26T00:00:35.897Z
Data Set Stop Time : 1979-03-24T22:49:32.304Z
Parameters
==========
SEDR generated ephemeris
------------------------
PARAMETER RESOLUTION/ DESCRIPTION
NAME UNITS
time 96.0 Sec. time of the sample (UT) in the format
yyyy-mm-ddThh:mm:ss.sssZ
m65536 counts spacecraft clock counts
mod60
fds_line
sc_x AU heliographic cartesian coordinates
sc_y position vectors: X, Y, and Z
sc_z
vel_x km/s heliocentric X, Y, and Z spacecraft
vel_y velocity components
vel_z
sc_r AU heliographic spherical coordinates
sc_lat degrees position vectors: range, latitude, and
sc_lon degrees longitude
SolEquatorial_to_HG solar equatorial to heliographic
coordinates rotation matrix containing
9 1pe15.8 elements
HG_to_EarthOrbTrue heliographic to earth orbit true
coordinates rotation matrix containing
9 1pe15.8 elements
Spacecraft_to_HG payload (spacecraft) to heliographic
coordinates rotation matrix containing
9 1pe15.8 elements
SPICE generated ephemeris
-------------------------
PARAMETER RESOLUTION/ DESCRIPTION
NAME UNITS
time 48.0 Sec time of the sample (UT) in the
format yyyy-mm-ddThh:mm:ss.sssZ
R AU heliographic spherical coordinates
LAT degrees position vectors: range, latitude, and
LON degrees and longitude
LocTime hours angular separation between the
meridian containing the sun and the
one containing the spacecraft
converted to a time. The sun meridian
is defined to be noon (12.000), with
midnight (0.000) opposite it. Dawn
(6.000) and dusk (18.000) are where
the sun rises and sets according to
the planet's rotation
Coordinate System
=================
The Heliographic coordinate system is a heliocentric system
defined in the reference epoch of 1950. The unit vectors which
define the coordinate system are as follows:
Heliographic cartesian coordinates
X points towards the the first point of Aries
in the solar equatorial plane on the vernal
equinox of the reference epoch 1950 (positive
away from the Sun)
Y completes the right handed set (X x Z)
Z points along the Sun's spin axis (positive
above the equatorial plane)
Heliographic spherical coordinates
R (Range) the distance from the Sun's position at the
reference epoch to the spacecraft in AU
LAT (Latitude) the angle between the solar equatorial plane
of the reference epoch measured in the plane
containing the solar spin axis of that epoch
(positive above the equatorial plane)
LON (Longitude) longitude is zero in the direction of the
ascending node at the reference epoch (X
direction) and increasing in the direction of
planetary orbital motion (note that LON does
not rotate with the Sun)
For the SPICE data, the definition used for astronomical units
is 1 AU = 149674000 km. The longitude of the ascending node
was calculated using the equation:
LON = 74 [degrees] 22' + 0.84' * ( year - 1900 ).
The inclination of the Sun's North pole measured relative to
the ecliptic was defined as being 7 [degrees] 15' in 1950.
Data Coverage
=============
Filename Records Start Stop
-------------------------------------------------------------------
SEDR057 6046 1979-02-26T00:00:35.897Z 1979-03-04T23:58:11.925Z
SEDR064 6071 1979-03-05T00:00:35.925Z 1979-03-11T23:59:08.059Z
SEDR071 6065 1979-03-12T00:00:44.059Z 1979-03-18T23:58:20.235Z
SEDR078 5303 1979-03-19T00:00:44.236Z 1979-03-24T22:47:56.304Z
SPICE057 12093 1979-02-26T00:00:35.897Z 1979-03-04T23:59:47.925Z
SPICE064 12142 1979-03-05T00:00:35.925Z 1979-03-11T23:59:56.059Z
SPICE071 12131 1979-03-12T00:00:44.059Z 1979-03-18T23:59:56.236Z
SPICE078 10607 1979-03-19T00:00:44.236Z 1979-03-24T22:49:32.304Z
CONFIDENCE_LEVEL_NOTE
Confidence Level Overview
=========================
SPICE generated ephemeris
-------------------------
The SPICE generated data were derived from SPICE using
software that has been extensively tested. They should give
as accurate representation of spacecraft ephemeris as
possible using these kernels.
Missing Data Flag
=================
Any SEDR generated ephemeris data column whose value is
-9.99999999e+10 is a missing data value.
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