Cassini/Saturn Ephemeris Generator 1.2 Help
This form enables you to generate a table listing useful information
about Cassini's viewing geometry for Saturn and/or any of its moons as a
function of time. You are free to specify which of a variety of useful
quantities to tabulate. The file returned will contain a single header
line describing each column, followed by one row of numbers for each
time step.
Change History
1.0 (January 2, 2002):
Original Cassini/Saturn Ephemeris Generator on line.
1.1 (January 9, 2003):
Phoebe added as a satellite choice. An option added for second accuracy
in time tags.
1.2 (August 30, 2007):
Added Cassini-discovered moons and the latest ephemeris options. Also added
the tour for the Cassini extended mission.
The start and stop times (UTC) of the table can be entered in a variety
of formats. For example, the following all parse to 0:01:02 UTC on July
4, 1976:
- 1976-JUL-04 00:01:02.00
- 1976-186 00:01:02.00
- July 4, 1976 12:01:02 am
- 12:01:02 am July 4, 1976
- 1976-07-04T00:01:02Z (PDS format)
- MJD 42963.00071759259
- JD 2442963.50071759259
If you want the gory details of how times are interpreted, click
here.
Enter the time interval to be used for the tabulation as a number in the box,
and select the time unit from the choices provided.
Select the ephemeris you wish to use from among the choices provided.
For most purposes, the latest choice is best, but outdated ephemerides
are included to provide backward compatibility.
Click on the box to the left of each quantity or set of quantities that
you wish to tabulate. The order of the columns in the table will match
the order listed on the form. Possible selections are as follows:
-
Year, DOY, Hour, Minute
Adds four columns containing the UTC date (year, day-of-year) and time
(hours, minutes) as integers.
-
Adds five columns containing the UTC date (year, day-of-year) and time
(hours, minutes, seconds) as integers.
-
Year, Month, Day, Hour, Minute
Adds five columns containing the UTC date (year, month, day) and time
(hours, minutes) as integers.
-
Year, Month, Day, Hour, Minute, Second
Adds six columns containing the UTC date (year, month, day) and time
(hours, minutes, seconds) as integers.
-
Modified Julian Date
Adds a column containing the Modified Julian Date, a common method
of designating dates and times in astronomy. MJD is equal to the number
of (possibly fractional) days elapsed since 0:00 UTC on 17 November
1858.
-
Cassini-Saturn distance
Adds a column containing the Cassini-Saturn distance, in km.
-
Saturn phase angle
Adds a column containing the phase angle of Saturn as seen from
Cassini, in degrees.
-
Ring opening angle to Cassini
Adds a column containing the ring plane opening angle to the Cassini,
in degrees.
-
Ring opening angle to Sun
Adds a column containing the ring plane opening angle to the Sun, in
degrees.
-
Sub-spacecraft inertial longitude
Adds a column containing the sub-spacecraft longitude at Saturn, in
degrees. This is measured from the J2000 ascending node of the planet's
equatorial plane. Note that it is an inertial longitude, not measured
in a frame rotating with the planet.
-
Sub-solar inertial longitude
Adds a column containing the sub-solar longitude at Saturn, in
degrees. This is measured from the J2000 ascending node of the planet's
equatorial plane. Note that it is an inertial longitude, not measured
in a frame rotating with the planet.
-
Sub-spacecraft planetocentric latitude and rotating longitude
Adds a pair of columns containing the sub-spacecraft latitude and
longitude at Saturn, in degrees. These are measured in a frame rotating
with the planet.
-
Sub-solar planetocentric latitude and rotating longitude
Adds a pair of columns containing the sub-solar latitude and
longitude at Saturn, in degrees. These are measured in a frame rotating
with the planet.
-
Sun-Saturn distance
Adds a column containing the Sun-Saturn distance, in km.
-
Saturn RA and Dec
Adds two columns containing the J2000 right ascension and
declination of Saturn. RA is tabulated in units of hours; declinations
is in units of degrees.
You may also include information about the viewing geometry on any set
of inner Saturnian moons in the table. Up to six sets of quantities
can be tabulated for each selected moon:
-
Cassini-Satellite distance
Adds a column containing the Cassini-Satellite distance, in km.
-
Satellite phase angle
Adds a column containing the phase angle of the satellite as seen from
Cassini, in degrees.
-
Sub-spacecraft latitude and rotating longitude
Adds a pair of columns containing the sub-spacecraft latitude and
longitude on the selected moon, in degrees. These are measured in a frame
rotating with the body.
-
Sub-solar planetocentric latitude and rotating longitude
Adds a pair of columns containing the sub-solar latitude and
longitude on the selected moon, in degrees. These are measured in a frame
rotating with the body.
-
RA and dec
Adds a pair of columns containing the J2000 right ascension and
declination for each selected moon. RA values are given in units of
hours; dec values are given in degrees.
-
Offset RA and dec
Adds a pair of columns containing the positional offset of each moon
from the center of the planet. Values are given in units of degrees,
where the first value is the offset in the direction of increasing J2000
RA and the second is in the direction of increasing dec.
Finally, click on the box to the left of each moon that you wish to
include in the table. Note that it is not necessary to include any
moon columns at all.
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Last updated 30 August 2007
Mark Showalter