Mars Ephemeris Generator 2.0 Help
This form enables you to generate a table listing useful information
about the viewing geometry for Mars and/or 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
2.0 (9 November 1999):
Original Mars Ephemeris Generator on line.
(The version number was chosen for consistency with other tools.)
2.1 (10 January 2003):
Added a new column option providing second accuracy in time tags.
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
- 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.
Currently, the Mars Ephemeris Generator can use one of two different
ephemerides. Under most circumstances the last option is to be preferred
because it is most recent and therefore most accurate.
-
MAR022: Slightly outdated JPL ephemeris, valid for the period
1990-Jan-01 to 1999-Dec-31.
-
MAR033: Latest JPL ephemeris, valid for the period
1976-Jun-01 to 2025-Jan-11.
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:
-
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.
-
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.
-
Mars RA and Dec
Adds two columns containing the J2000 right ascension and
declination of Mars. RA is tabulated in units of hours; declination
is in units of degrees.
-
Mars phase angle
Adds a column containing the phase angle of Mars as seen from
Earth, in degrees. This is equal to the Sun-Mars-Earth angle.
-
Ring opening angle to Sun
Adds a column containing the ring plane opening angle to the Sun
(assuming a hypothetical equatorial ring), in degrees. This is
equivalent to the sub-solar latitude as seen from Mars; it equals zero
during a solar ring plane crossing.
-
Ring opening angle to Earth
Adds a column containing the ring plane opening angle to the Earth
(assuming a hypothetical equatorial ring), in degrees. This is
equivalent to the sub-Earth latitude as seen from Mars; it equals zero
during a ring plane crossing.
-
Sub-solar inertial longitude
Adds a column containing the sub-solar longitude at Mars, 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-Earth inertial longitude
Adds a column containing the sub-Earth longitude at Mars, 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 latitude and rotating longitude
Adds a pair of columns containing the sub-solar latitude and
longitude at Mars, in degrees. This is measured in a frame rotating
with the planet.
-
Sub-Earth latitude and rotating longitude
Adds a pair of columns containing the sub-Earth latitude and
longitude at Mars, in degrees. This is measured in a frame rotating
with the planet.
-
Mars' projected equatorial radius
Adds a column containing the projected equatorial radius of Mars
as seen from Earth, in units of arcseconds.
-
Sun-Mars distance
Adds a column containing the Sun-Mars distance, in km.
-
Earth-Mars distance
Adds a column containing the Earth-Mars distance, in km.
-
Lunar phase angle
Adds a column containing the phase angle of the Moon at the
specified time, in degrees. A value near zero corresponds to a full
moon; a value near 180 corresponds to a new moon.
-
Sun-Mars sky separation angle
Adds a column containing the angular separation on the sky from
Mars to the Sun, in degrees. A Sun-Mars value near zero
corresponds to solar conjunction; a value near 180 corresponds to
opposition.
-
Moon-Mars sky separation angle
Adds a column containing the angular separation on the sky
from Mars to the Moon, in degrees.
You may also include the positions of either of the Martian moons in the
table. Up to four pairs of quantities can be tabulated for each
selected moon:
-
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 arcseconds,
where the first value is the offset in the direction of increasing J2000
RA and the second is in the direction of increasing dec.
-
Sub-solar 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.
-
Sub-Earth latitude and rotating longitude
Adds a pair of columns containing the sub-Earth latitude and
longitude on the selected moon, in degrees. These are measured in a frame
rotating with the body.
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 28 February 2005
Mark Showalter