Current Settings

Specify Observer Location:

Set observer location (the "coordinate origin") using one of the three optional sections below.

Specify a topocentric observer location by choosing from a list of predefined astronomical observatories, major cities on Earth, major sites on other solar system bodies, or by giving the latitude, longitude, altitude, and solar system body.

Body-centered (non-topocentric) sites throughout the solar system (such as the Sun, planet, satellite, or spacecraft centers) can also be specified using body names or codes as described below.

• Specify using a named body or observatory site as origin
• Choose from a list of predefined locations
• Specify coordinate origin using topocentric coordinates and body
• Specify geocentric spacecraft using TLEs

Use unique observatory code numbers (if you know them) or names (which may result in a list to choose from if the name is not unique). For example,

      "675" select the Palomar Mountain main site
  "Palomar" list of matching names to select from

You may also enter pre-defined, non-topocentric observation points and locations for all major bodies in the solar system here. Some examples:

            "500" Earth's center (same as "geocentric")
           "@sun" center of the Sun
             "@0" solar system barycenter (same as "@ssb")
   "Viking 1@499" Viking 1 landing site on Mars (body 499)
           "@hst" Hubble Space Telescope (same as "@-48")
           "@-32" Voyager 2 spacecraft
           "@301" center of the Moon
  "Apollo 11@301" Apollo 11 landing site on the Moon's surface
        "@phobos" center of Phobos, the Martian moon (same as "@401")

To see all sites available for a specific body, use "*@body" where body is body ID. For example, "*@499" will show all pre-defined sites on Mars. See the Horizons documentation for more details on center/observer location codes.

Longitude and Latitude can be entered as either "degrees minutes seconds" or decimal degrees. In either case, they should always be positive and use the appropriate East/West and North/South selections. If entering "degrees minutes seconds" use spaces or commas between elements. If Altitude is unknown, zero can be used for optical sites without much loss of accuracy.

Provide up to 1-750 sets of SGP4/SDP4 TLEs (Two-Line Elements) in standard format to define a geocentric spacecraft not already available in Horizons.