Mars Viewer Help
This form enables you to generate a diagram showing the appearance of the Mars system at a specified time. All bodies are rendered with terminators and shadows as appropriate. Selected background stars can also be included.
In the diagram, Mars and the moons are modeled as triaxial ellipsoids, and are drawn with latitude and longitude contours at 15 degree intervals. Illuminated regions are indicated with black lines; unilluminated regions and terminators are shown as light gray. Penumbral shadows are not indicated. Optionally, the 0 and 180 degree meridians can be shown with a heavier line.
Optionally, the hypothetical rings of Mars are also shown. Their appearances are based on the model ofIn this model, each of Mars' moons generates a cloud of dust. The Phobos ring is modeled as equatorial but 350 km thick and shifted toward the Sun by one Martian radius. The Deimos ring is 5300 km thick and shifted away from the Sun by two Martian radii. It is also tilted out of the equatorial plane toward the ecliptic by 15 degrees. See the above reference for the explanations of these surprising properties.
Each ring is shown by a pair of curves, one indicating each of its vertical limits. The rings are shown in black if illuminated and in gray if not or if the opposite side is illuminated. The Phobos ring is shown by solid lines; the Deimos ring by dashed lines.
The diagram is oriented with J2000 declination increasing upward and with right ascension increasing to the left. The frame has uniformly-spaced tick marks along each axis. The declination axis is labeled in degrees, minutes and seconds; the right ascension axis is labeled in hours, minutes and seconds.
Each diagram includes a caption that summarizes the key parameters used to generate it.
Change History
-
2.0 (November 9, 1999):
Original Mars viewer on line.
(The version number was chosen for consistency with other tools.)
- 2.1 (December 1, 2009): Updated the default ephemerides. To reduce confusion, we have removed the choice about what ephemeris to use.
- 2.8 (January 23, 2013): Renumbered for consistency among all Planet Viewer tools. Ephemeris updates.
- 2.9 (January 4, 2016): Ported to new server. Ephemeris updates.
- 2.10 (October 14, 2020): Ephemeris updates.
- the returned web page now lists the sub-observer and sub-solar longitudes and latitudes for each the planet and each moon.
- the diagram page identifies the sub-observer longitude and latitude, as well as the phase angle, of the planet or selected moon.
- there is now an option to highlight the prime meridian on the planet and moons.
- Viewer requests can now be bookmarked.
- the new Output option lets you jump directly to a PDF or JPEG diagram, bypassing the web page.
- ephemerides have been updated.
- the form now uses a clean, new style sheet.
- bug fix: if selected, the anti-solar direction is now more accurate.
- the JWST and HST viewpoints have been added.
- ephemeris updates.
Observation Time
The observation time (UTC) 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 (ISO format)
- MJD 42963.00071759259
- JD 2442963.50071759259
Field of View
Enter the field of view of the drawing to be generated and select the appropriate units. Units can be seconds of arc (the default), milliradians, microradians, Mars radii, kilometers (projected at the distance to Mars) or the fields of view of certain spacecraft cameras.Diagram Center
Four different methods of specifying the diagram center are supported. Click on the box to the left of the option you wish to use.
Body: The diagram will be centered on the location of the selected body.
Ring or orbit ansa: The diagram will be centered on the ansa of the selected ring or orbit. Specify the east or west ansa using the second box. Note that east is toward the left in the diagram.
J2000 RA and dec: The diagram will be centered on the specified pair of right ascension and declination coordinates. The first box is for the RA and the second box is for the dec. You may also specify whether the RA is in units of hours or degrees. Enter up to three values in each box, separated by spaces; these values are interpreted as degrees/hours, minutes and seconds, respectively. Any or all values can have fractional parts.
Star name: Enter the name of a star as it appears in the current list. The name must match exactly.
Viewpoint
You may specify the point of view of the diagram. By default, the point of view is the center of the Earth.
Observatory: You may select from any viewpoint on the list.
- Earth's center
- JWST: Valid for 2021-Dec-25 to approximately two years after the present day.
- HST: Valid for 1990-Apr-25 to approximately two months after the present day.
- Named observatories: After each observatory's name, you will see listed its latitude and east longitude in degrees, followed by its altitude in meters. Note that only very rarely will a diagram change significantly based on the particular location of an Earth-based observatory.
Latitude & Longitude: If your desired observatory or location is not on the observatory list, you can enter its latitude, longitude and altitude in the three boxes provided. Latitudes and longitudes can each be specified by up to three values, interpreted as degrees, minutes and seconds. Longitudes can be specified either east or west.
If you wish to have an observatory added to the standard list, or to refine the coordinates of a listed observatory, email the necessary information to pds-admin@seti.org.
Ring Selection
You can decide whether to include the hypothetical Martian rings in the diagram. Click on the box to the left to select your option. If selected, both rings are indicated by pairs of dashed lines above and below the ring plane to indicate these rings' physical thickness. The Phobos ring is shown with a solid line and the Deimos ring is shown with a dashed line.
See above for a discussion of the models used for each ring.
Background Objects
You have several independent options for including background objects in the diagrams. These options make it possible to render diagrams around the times of stellar or spacecraft occultations. Objects are marked by pluses and are labeled by name if the Moon & Star Labels option is activated.
Standard stars: Check the box to include any of a standard list of stars that happen to fall inside the field of view of the diagram. The Neptune Viewer does not access a star catalog; instead, it only plots stars from a finite list. To view the current star list, click here. This list is updated periodically at the request of the users; if you would like to have a star added to the list, email the necessary information to pds-admin@seti.org.
Additional star: In addition to or instead of the standard stars, you can specify one additional star to be included in the diagram. Check the box to the left and enter the star's RA, dec, and name in the three boxes. You may also specify whether the RA is in units of hours or degrees. Enter up to three values in the RA and dec boxes, separated by spaces; the values are interpreted as hours/degrees, minutes and seconds, respectively. Any or all values can have fractional parts.
Other bodies:
Check each box to mark the location of the specified body or spacecraft in the diagram.