Help
Limitations
The position of the small body is computed using so-called two-body equations: only the gravitational force of the Sun is considered in the viewer. If the small body makes a close approach to the Earth or a planet, its position as shown in this viewer may become inaccurate. You are especially cautioned against using this viewer to make predictions of the small body's position a long time in the future or past.
Accurate positions of small bodies can be obtained from our Horizons ephemeris system which uses a numerically integrated high fidelity model which includes gravitational perturbations by the Sun, all the planets, and some of the largest asteroids.
The orbit viewer is limited to dates between 1600-01-01 and 2200-01-01.
Orbit Paths
Orbit paths are rendered such that the portion of the orbit above the ecliptic plane is shown with a heavy line weight and the portion below is shown with a light line weight.
When zoomed in extremely close to a planet or moon, it may appear slightly off its orbit path. This is due to the fact that the orbit path is approximated using a series of straight line segments.
Hyperbolic and parabolic orbit paths are only rendered out to about 80 au from the sun.
View Selection
The default view is an oblique perspective of the ecliptic plane. You can select a pre-defined view from the "Look from:" menu.
- Default - oblique perspective of the ecliptic plane
- Above - view from directly above the ecliptic plane
- Ecliptic - view from the edge of the ecliptic plane
- Earth - view from Earth
In all cases above, the views remain centered on the currently selected "Look at" object: the solar-system barycenter (SSB) by default. To change the "Look at" object, you can either select it from the "Look At" pulldown menu or by clicking on the object in the viewer.
Zoom
To zoom in or out, use the mouse wheel or the appropriate zoom "gesture" on your trackpad or mobile device.
Rotation
To rotate the view around the axis normal to the ecliptic plane, drag the mouse left or right within the window, or use the keyboard's left/right arrows. To rotate around the screen's horizontal axis, drag the mouse up or down within the window, or use the keyboard's up/down arrows.
Customizing the Display
There are several controls within the "Settings" menu that allow you to customize the display. The top few controls are general (not specific to any particular object).
- Planet Labels - display the orbits of all objects
- Date Label - display the selected date in the upper right corner
- Ecliptic Grid - display the ecliptic plane grid lines
- Ecliptic Axes - display the ecliptic plane axes
- Distance Display - display the nominal distance between the selected small-body and Earth (and Sun)
- Viewer Controls - show the primary animation controls in the upper right corner
The next group of controls are for customizing the display of specific objects. There is a top-level checkbox for each object which controls all content related to that object. Then there are the following sub-level controls:
- Orbit - display the object's orbit
- Label - display the object's name
- Moon(s) - display the object's moon(s) and their orbits, if the object has any moons
- Drop Lines - display lines which connect the small-body's orbit to the ecliptic plane, perpendicular to the ecliptic plane (only for the small body)
Full Screen
To enter full-screen mode, click on the expansion icon . To exit full-screen, press the ESC key.
Viewer Controls
The viewer controls are presented in four rows: "motion controls", "step size", "date selector", and "extra controls".
motion controls 
- run animation backward in time
- single-step animation backward in time
- stop the running animation
- single-step the animation forward in time
- run the animation forward in time
step size 
Select from various time-step intervals from 1-hour to 1-year.
date selector 
Select the button to display a calendar-date picker. Or, use the date/time input box to manually enter a specific date/time.
extra controls 
- full-screen selector (use ESC-key to exit)
- capture a snapshot of the screen, without menus or controls
Coordinate System
The coordinate system uses the J2000 ecliptic as the reference plane and places the origin at the solar system barycenter. The horizontal axis is directed toward the J2000 vernal equinox, while the vertical axis is normal to the J2000 ecliptic plane. The positive direction of each axis is indicated by a brighter line.
