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HORIZONS web-interface Tutorial

This page provides a brief description of how to use the web-interface to the HORIZONS system and gives an illustrative example of generating a topocentric ephemeris. If you are using the telnet or E-mail interface to HORIZONS, you should consult the HORIZONS documentation instead.

How to Generate an Ephemeris

The top-level form displays the current settings to be used in generating an ephemeris. The first time the form is displayed, default values are shown. To change a particular setting, simply follow the "[change]" link near that setting's label. After selecting a "[change]" link, you will see a form below the current settings allowing you to modify that particular setting. The sections below describe each setting. Once you have specified the desired settings, simply press the "Generate Ephemeris" button.

If after examining your ephemeris you would like to change any settings, simply follow the appropriate setting's "[change]" link, select new settings, then generate a new ephemeris. Once you have the desired ephemeris, you can save and/or print the output using your web-browser.

Selecting the Ephemeris Type

There are three possible types of ephemerides available from the HORIZONS system. Most users will be interested in the "OBSERVER" ephemeris which provides quantities (such as right ascension and declination) useful in observing solar system bodies. Tables of Cartesian vectors (e.g. xyz coordinates in a specific reference frame) are available using the "VECTORS" type. The third option is a table of osculating orbital elements via the "ELEMENTS" type.

Selecting a Target Body

To select a different body, follow the "[change]" link next to the current "Target Body" setting. The form shown allows you the option of either looking up a specified body using its name (case is ignored) or designation or selecting major bodies (i.e. anything other than comets and asteroids) from a list. Name and designation lookups support a single wild-card '*' at the beginning or end only of the search string (e.g. "*eros" or "1989 M*"). Here are a few examples.

  • To select the moon, simply enter "moon" and press the "Search" button. You will see a list of matching bodies one of which is the moon and the other is the Earth-moon barycenter. Select "Moon [Luna]" then press the "Select Indicated Body" button. Alternatively, you can use the JPL body number for the moon, "301", and limit the search to "major bodies only".
  • To select a planet, for example saturn, either enter its name or the JPL code "699". Select the appropriate matching body from the resulting list. Alternatively, select the "Sun and Planets" from the menu then press the "Display List" button. Then select "Saturn" from the list.
  • To select a numbered asteroid, for example "433 Eros", enter its IAU number ("433" in this case), optionally limit the search to "small-bodies only", then press the "Search" button. You should get a unique match. If you don't know the asteroid's IAU number, you can search using its name, for example "eros".
  • To select an unnumbered asteroid, for example "1989 ML" (note: this is now a numbered 10302, but the example is still valid), enter the designation "1989 ML". Case is important, so a search for "1989 ml" will fail.
  • To select a comet, for example "9P/Tempel 1", enter the designation ("9P" in this example) or name ("Tempel 1" in this example).
  • To select a point on the surface of a target body (limited to those with an IAU rotational model), use this form (units are degrees and km):
       {g: E.Long, latitude, h@}BODY  [geodetic/planetographic coords]
       {c: E.Long,     DXY, DZ@}BODY  [cylindrical coordinates]
    
    For example: "g: 348.8, -43.3, 0 @ 301" specifies the crater Tycho on the Moon (body 301), at geodetic (planetographic) coordinates 348.8 degrees east longitude, -43.3 degrees latitude (south), and zero km altitude with respect to the IAU reference triaxial ellipsoid.

Specifying a Location

To select a different observing location (or coordinate center), follow the "[change]" link next to the current "Observer Location" setting. You should see a form with sections for looking up a named observatory or city, choosing from a list of known observatories and cities, and specifying geographic coordinates. You can use any one of these sections to select the desired location.

  • To lookup a named location, enter the name (case is ignored), for example "palomar", and press the "Search" button. If more than one locations matches, you can select from the resulting list. If you know the numeric code for the desired observatory (e.g. 568="Mauna Kea"), you can enter the code instead of a name.
  • To choose from a list of locations, choose the desired list ("Observatories", "All Cities", "U.S. Cities", or "non-U.S. Cities") from the popup menu and press "Display List". Or, you can select a U.S. state/possession from the given list and press "Display Cities" to get only cities in that state/possession. From the resulting list, select the desired location and press the "Use Selected Location" button.
  • To enter a geographic location, enter the latitude and check the "North" or "South" buttons as appropriate, enter the longitude and check the "East" or "West" buttons as appropriate, and then enter the altitude above MSL (mean sea level) as kilometers, meters, or feet. Then, press the "Use Specified Location" button.

Setting the Time Span and Output Interval

To change the time span and/or output interval, follow the "[change]" link next to the current "Time Span" setting. For convenience, there are three "preset" buttons available which when pressed will set the start time to the current day (UT) and the stop time 10, 30, or 60 days later. Otherwise, simply specify the desired start and stop times. For example, to set the start time to January 1, 2000 at 0h UT, enter "2000-01-01" or "2000-Jan-01". For ancient times, append "BC" to the year if appropriate (e.g. "300BC-11-07"). If a specific time is requested, simply append it to the date (e.g. "2005-Oct-10 08:21"). You can also use Julian day numbers, in which case, simply prepend "JD" to the desired Julian date (e.g. "JD 2451544.5"). See the HORIZONS documentation for a full description of acceptable date/time formats.

Select the desired output interval value and units/type. For example, to select a 2 hour interval, enter "2" next to "Step Size" then select "hours" from the adjacent menu. See the HORIZONS documentation for a description of the "unitless" and "time-varying" intervals. For "OBSERVER" ephemerides requesting only Rise/Transit/Set times for output (see RTS Mode below), the interval must be less than 10 minutes.

Selecting Desired Output Quantities and Format Options

To select desired ephemeris output quantities and/or format options, follow the "[change]" link next to the current "Table Settings" label. For an "OBSERVER" ephemeris, the resulting form provides inputs for selecting desired ephemeris output quantities (such as "apparent azimuth and elevation" or "airmass") and a separate section for setting output formats and other options.

Output quantities are selected by pressing the check-box next to the desired quantity. For convenience, reasonable defaults can be selected for various body types by pressing the corresponding button at the top of the form. For example, to select default output quantities for comets, press the "small-bodies" button and continue as described below. "OBSERVER" table output quantities are described in the HORIZONS documentation.

Optional table settings vary depending on the selected ephemeris type. For an "OBSERVER" table from a location on the surface of the Earth, you may want to select the "skip daylight" option and possibly set a value for the "elevation cutoff" (for example, a value of "15" would suppress output whenever the object was lower than 15 degrees with respect to the local horizon). There are many more options which are described in detail in the HORIZONS documentation.

After selecting the desired settings, press any one of the buttons labeled "Use Settings Below", "Use Selected Settings", or "Use Settings Above". If you want default output quantities, simply press the "defaults" button above the selection form. Similarly, if you want to reset all optional settings to their defaults, press the "Default Optional Settings" button.

Selecting Display/Output Format

There are three possible display/output formats for the resulting ephemeris. Ephemeris data (or any error messages) will be output using the selected format.

  • Web-style (HTML) - formated to appear like all other pages. This is the default format.
  • Plain text - no special formatting. This format is suitable for subsequent printing or downloading of the resulting ephemeris.
  • Download (save) as plain text file - will save the resulting ephemeris (or error message) as a plain text file.

Special Options

There are currently three special options available below the "Generate Ephemeris" button on the main page. The first allows the user to reset all settings to their defaults except the selected target body. The second allows one to reset all settings to their defaults. Since settings are preserved from one session to another for a given browser, this may be useful in clearing a previous user's settings. The last setting is design to aid potential users of the E-mail interface by displaying the current settings in the format required for that interface.

Display the Ephemeris

After specifying all desired settings, press the "Generate Ephemeris" button to display the requested ephemeris. If there was a problem with any of your inputs or settings, you should get an error message instead of an ephemeris. Most error messages are self explanatory. However, if you are unable to figure out what caused the error, contact the webmaster and please provide as much detail as possible.


An Illustrative Example

Suppose you want to generate a topocentric observer ephemeris for comet 76P/West-Kohoutek-Ikemura for use at Kitt Peak from 1998 July 28 00:00 to 1998 July 30 00:00 (UT) at 1 hour intervals only when the comet is above the horizon and the sun is down. Here is what you should do.

  1. From the main Horizons web-interface form, reset all setting to their defaults by following the link labeled "reset all settings to their defaults" under the "Special Options:" heading below the "Generate Ephemeris" button.

  2. Select the desired target body by following the "[change]" link next to the "Target Body" label. Enter either "76P" or "West-Kohoutek-Ikemura" in the "Lookup the specified body:" field then press the "Search" button.
  3. TIP: If you did not remember how to spell the full name of the comet but only new that it started with "West-", you could enter "West-*" which would result in a list of matching objects from which you could then select "76P/West-Kohoutek-Ikemura".
  4. Follow the "[change]" link next to the "Observer Location" label to select the desired location. Next, follow the "choose from a list of locations" link to the "Choose from a List" section of the displayed "Specify Observer Location" form (or simply scroll down the page to that section). Then, press the "Display List" button under the "Observatories" popup menu. From the resulting alphabetically sorted list, select "[695] Kitt Peak" and press the "Use Selected Location" button.
  5. TIP: If you know the code for your observatory (not all have codes), in this case 695, simply enter that number in the "Lookup Named Location" field and press the "Search" button.
  6. Follow the "[change]" link next to the "Time Span" label to set the desired time span and output interval. Enter the start time as "1998-07-28" and the stop time as "1998-07-30". Then, enter "1" for the step size (output interval) and choose "(hours)" from the adjacent menu. Press the "Use Specified Times" button.

  7. Follow the "[change]" link next to the "Table Settings" label to select desired output quantities and format options. Next, press the "small-bodies" preset button above the observer quantities table (you should notice more check-boxes have been selected). Scroll down the page to the "Optional observer-table settings:" section and select the "skip daylight" checkbox. Also under this section, enter "0" in the "elevation cutoff" field to suppress ephemeris output whenever the comet is below the horizon. Then, press the "Use Settings Above" button at the bottom of the form.

  8. Finally, press the "Generate Ephemeris" button.
If you followed the above example, you should get an ephemeris that looks something like this:

 

Object Data Page

JPL/HORIZONS              76P/West-Kohoutek-Ikemura        2006-Jan-05 11:52:19
Rec #:900453 (+COV)   Soln.date: 2005-Jul-29_17:32:03    # obs: 213 (1980-2001)
 
FK5/J2000.0 helio. ecliptic osc. elements (AU, DAYS, DEG, period=Julian yrs):  
 
  EPOCH=  2452040.5 != 2001-May-11.0000000 (CT)   Residual RMS= .91595         
    EC= .539745065289056   QR= 1.596283292501184  TP= 2451696.772010561        
    OM= 84.1239814645492   W= .10251414059415     IN= 30.49885380709092        
    A= 3.468258941109898   MA= 52.45074966428     ADIST= 5.340234589718612     
    PER= 6.4591515448113   N= .15259377           ANGMOM= .026968751           
    DAN= 1.59628           DDN= 5.34022           L= 84.2123117                
    B= .0520281                                   TP= 2000-Jun-01.2720106      
 
Physical & non-grav parameters (KM, SEC; A1,A2,A3=AU/d^2; DT=days):
    GM= n.a.               RAD= .330              A1= -4.682198E-9             
    A2= -2.748074D-10      A3= n.a.               DT= n.a.                     
    M1= 8.                 M2= 15.5               k1= 30.                      
    k2= 5.                 PHCOF= .030                                         
 
COMET comments 
1: soln ref.= JPL#K004/2, data arc: 1980-Nov-12 to 2001-Apr-12
2: k1=30.0, k2=5.0, phase coef.=0.03;
*******************************************************************************

Results

*******************************************************************************
Ephemeris / WWW_USER Thu Jan  5 11:52:20 2006  Pasadena, USA     / Horizons    
*******************************************************************************
Target body name: 76P/West-Kohoutek-Ikemura       {source: JPL#K004/2}
Center body name: Earth (399)                     {source: DE405}
Center-site name: Kitt Peak
*******************************************************************************
Start time      : A.D. 1998-Jul-28 00:00:00.0000 UT      
Stop  time      : A.D. 1998-Jul-30 00:00:00.0000 UT      
Step-size       : 60 minutes
*******************************************************************************
Center geodetic : 248.405300,    31.9585,     2.06{E-lon(deg),Lat(deg),Alt(km)}
Center cylindric: 248.405300,  5418.2554,  3357.61{E-lon(deg),Dxy(km),Dz(km)}
Center pole/equ : High-precision EOP model        {East-longitude +}
Center radii    : 6378.1 x 6378.1 x 6356.8 km     {Equator, meridian, pole}    
Target pole/equ : No model available
Target radii    : 0.3 km                                                       
Target primary  : Sun                             {source: DE405}
Interfering body: MOON (Req= 1737.400) km         {source: DE405}
Deflecting body : Sun, EARTH                      {source: DE405}
Deflecting GMs  : 1.3271E+11, 3.9860E+05 km^3/s^2                              
Small perturbers: Ceres, Pallas, Vesta            {source: SB405-CPV-2}
Small body GMs  : 6.32E+01, 1.43E+01, 1.78E+01 km^3/s^2                        
Atmos refraction: NO (AIRLESS)
RA format       : HMS
Time format     : CAL 
EOP file        : eop.060104.p060328                                           
EOP coverage    : DATA-BASED 1962-JAN-20 TO 2006-JAN-04. PREDICTS-> 2006-MAR-27
Units conversion: 1 AU= 149597870.691 km, c= 299792.458 km/s, 1 day= 86400.0 s 
Table cut-offs 1: Elevation (  0.0deg=YES),Airmass (>38.000=NO), Daylight (YES)
Table cut-offs 2: Solar Elongation (  0.0,180.0=NO )                           
*******************************************************************************
Initial FK5/J2000.0 heliocentric ecliptic osculating elements (AU, DAYS, DEG):
  EPOCH=  2452040.5 != 2001-May-11.0000000 (CT)   Residual RMS= .91595         
    EC= .539745065289056   QR= 1.596283292501184  TP= 2451696.772010561        
    OM= 84.1239814645492   W= .10251414059415     IN= 30.49885380709092        
Comet physical & dynamic parameters (KM, SEC; A1,A2,A3=AU/d^2; DT=days):
    GM= n.a.               RAD= .330              A1= -4.682198E-9             
    A2= -2.748074D-10      A3= n.a.               DT= n.a.                     
    M1= 8.                 M2= 15.5               k1= 30.                      
    k2= 5.                 PHCOF= .030                                         
**********************************************************************************************************************************************************************************************************************************************
 Date__(UT)__HR:MN     R.A._(ICRF/J2000.0)_DEC R.A.__(a-apparent)__DEC dRA*cosD d(DEC)/dt Azi_(a-appr)_Elev a-mass  T-mag  N-mag   Illu%               r        rdot            delta      deldot    S-O-T /r    S-T-O PsAng PsAMV Cnst GlxLat
**********************************************************************************************************************************************************************************************************************************************
$$SOE
>..... Elevation Cut-off Requested .....<

 1998-Jul-28 03:00 Nm  19 24 55.01 -40 56 28.9 19 24 50.03 -40 56 31.4   -25.62     -7.11 143.2970   2.6223 15.612   n.a.  21.80  99.769  4.604683402501  -5.1492532 3.66927984825326   3.1522824 154.1873 /T   5.5079  36.8 292.2  Sgr -23.37
 1998-Jul-28 04:00 Am  19 24 52.74 -40 56 36.0 19 24 47.77 -40 56 38.5   -25.71     -7.03 152.4426   9.4271  5.846   n.a.  21.80  99.769  4.604559492119  -5.1497239 3.66935663363846   3.2280163 154.1543 /T   5.5146  36.8 292.2  Sgr -23.37
 1998-Jul-28 05:00  m  19 24 50.47 -40 56 42.9 19 24 45.50 -40 56 45.6   -25.77     -6.94 162.9317  14.2878  3.976   n.a.  21.80  99.768  4.604435570445  -5.1501946 3.66943539915212   3.3161170 154.1212 /T   5.5214  36.9 292.2  Sgr -23.36
 1998-Jul-28 06:00     19 24 48.20 -40 56 49.8 19 24 43.23 -40 56 52.5   -25.80     -6.84 174.4266  16.8017  3.413   n.a.  21.80  99.767  4.604311637483  -5.1506653 3.66951638758197   3.4119200 154.0881 /T   5.5281  37.0 292.2  Sgr -23.36
 1998-Jul-28 07:00     19 24 45.92 -40 56 56.6 19 24 40.95 -40 56 59.3   -25.79     -6.73 186.2853  16.7201  3.429   n.a.  21.80  99.767  4.604187693233  -5.1511360 3.66959972240507   3.5102320 154.0550 /T   5.5349  37.1 292.2  Sgr -23.35
 1998-Jul-28 08:00     19 24 43.64 -40 57 03.3 19 24 38.68 -40 57 06.1   -25.74     -6.63 197.7333  14.0518  4.039   n.a.  21.81  99.766  4.604063737696  -5.1516068 3.66968539931004   3.6056871 154.0218 /T   5.5416  37.2 292.2  Sgr -23.34
 1998-Jul-28 09:00     19 24 41.38 -40 57 09.9 19 24 36.40 -40 57 12.7   -25.66     -6.54 208.1444   9.0587  6.060   n.a.  21.81  99.766  4.603939770869  -5.1520775 3.66977328648751   3.6931155 153.9887 /T   5.5483  37.3 292.2  Sgr -23.34
 1998-Jul-28 10:00     19 24 39.11 -40 57 16.4 19 24 34.14 -40 57 19.2   -25.56     -6.46 217.2009   2.1489 17.395   n.a.  21.81  99.765  4.603815792748  -5.1525483 3.66986313366742   3.7678976 153.9557 /T   5.5550  37.3 292.2  Sgr -23.33

>..... Elevation Cut-off Requested .....<

 1998-Jul-29 03:00 Nm  19 24 01.62 -40 59 09.3 19 23 56.64 -40 59 11.9   -25.43     -6.80 144.0081   3.1966 13.832   n.a.  21.81  99.755  4.601706431012  -5.1605529 3.67137643572246   3.6371287 153.3936 /T   5.6686  38.7 292.4  Sgr -23.23
 1998-Jul-29 04:00  m  19 23 59.37 -40 59 16.0 19 23 54.40 -40 59 18.7   -25.52     -6.72 153.2602   9.8566  5.613   n.a.  21.81  99.755  4.601582248919  -5.1610239 3.67146489992373   3.7137775 153.3597 /T   5.6755  38.8 292.4  Sgr -23.22
 1998-Jul-29 05:00  m  19 23 57.12 -40 59 22.7 19 23 52.14 -40 59 25.4   -25.58     -6.63 163.8382  14.5388  3.911   n.a.  21.81  99.754  4.601458055527  -5.1614949 3.67155536211771   3.8024378 153.3257 /T   5.6824  38.8 292.4  Sgr -23.21
 1998-Jul-29 06:00     19 23 54.86 -40 59 29.3 19 23 49.88 -40 59 32.0   -25.60     -6.52 175.3793  16.8486  3.404   n.a.  21.81  99.754  4.601333850840  -5.1619658 3.67164805586546   3.8983934 153.2917 /T   5.6893  38.9 292.4  Sgr -23.21
 1998-Jul-29 07:00     19 23 52.60 -40 59 35.8 19 23 47.62 -40 59 38.5   -25.59     -6.42 187.2227  16.5558  3.461   n.a.  21.81  99.753  4.601209634861  -5.1624368 3.67174309450675   3.9964272 153.2577 /T   5.6962  39.0 292.4  Sgr -23.20
 1998-Jul-29 08:00     19 23 50.34 -40 59 42.1 19 23 45.36 -40 59 45.0   -25.54     -6.32 198.5971  13.6910  4.139   n.a.  21.81  99.753  4.601085407588  -5.1629078 3.67184046337725   4.0911793 153.2237 /T   5.7030  39.1 292.4  Sgr -23.19
 1998-Jul-29 09:00     19 23 48.09 -40 59 48.4 19 23 43.10 -40 59 51.3   -25.46     -6.23 208.8991   8.5322  6.395   n.a.  21.81  99.752  4.600961169019  -5.1633788 3.67194002080809   4.1775148 153.1897 /T   5.7099  39.2 292.4  Sgr -23.19
 1998-Jul-29 10:00     19 23 45.84 -40 59 54.6 19 23 40.86 -40 59 57.5   -25.35     -6.15 217.8359   1.4929 20.482   n.a.  21.81  99.751  4.600836919149  -5.1638499 3.67204150783869   4.2508757 153.1557 /T   5.7167  39.2 292.5  Sgr -23.18

>..... Elevation Cut-off Requested .....<

$$EOE
**********************************************************************************************************************************************************************************************************************************************
Column meaning:
 
TIME

  Prior to 1962, times are UT1. Dates thereafter are UTC. Any 'b' symbol in
the 1st-column denotes a B.C. date. First-column blank (" ") denotes an A.D.
date. Calendar dates prior to 1582-Oct-15 are in the Julian calendar system.
Later calendar dates are in the Gregorian system.

  The uniform Coordinate Time scale is used internally. Conversion between
CT and the selected non-uniform UT output scale has not been determined for
UTC times after the next July or January 1st.  The last known leap-second
is used over any future interval.

  NOTE: "n.a." in output means quantity "not available" at the print-time.
 
SOLAR PRESENCE
  Time tag is followed by a blank, then a solar-presence symbol:

        '*'  Daylight (refracted solar upper-limb on or above apparent horizon)
        'C'  Civil twilight/dawn
        'N'  Nautical twilight/dawn
        'A'  Astronomical twilight/dawn
        ' '  Night OR geocentric ephemeris

LUNAR PRESENCE
  The solar-presence symbol is immediately followed by a lunar-presence symbol:

        'm'  Refracted upper-limb of Moon on or above apparent horizon
        ' '  Refracted upper-limb of Moon below apparent horizon OR geocentric
             ephemeris
 
 R.A._(ICRF/J2000.0)_DEC =
   J2000.0 astrometric right ascension and declination of target. Corrected
for light-time. Units: HMS (HH MM SS.ff) and DMS (DD MM SS.f)
 
 R.A._(a-apparent)__DEC. =
   Airless apparent right ascension and declination of the target with respect
to the Earth true-equator and the meridian containing the Earth true equinox of
date.   Corrected for light-time, gravitational deflection of light, stellar
aberration, precession & nutation. Units:HMS (HH MM SS.ff) and DMS (DD MM SS.f)
 
 dRA*cosD d(DEC)/dt =
    The rate of change of target apparent RA and DEC (airless). d(RA)/dt is
multiplied by the cosine of the declination. Units: ARCSECONDS PER HOUR
 
 Azi_(a-appr)_Elev =
   Airless apparent azimuth and elevation of target. Corrected for light-time,
the gravitational deflection of light, stellar aberration, precession and
nutation. Azimuth measured North(0) -> East(90) -> South(180) -> West(270),
elevation with respect to plane perpendicular to local zenith direction.
TOPOCENTRIC ONLY. Units: DEGREES
 
 a-mass =
   Relative optical airmass. Topocentric EARTH sites, ABOVE HORIZON ONLY.
Unitless.
 
 T-mag N-mag =
   Comet's approximate apparent visual total magnitude ("T-mag") and nuclear
magnitude ("N-mag") by following definitions:
   T-mag =  M1 + 5*log10(delta) + k1*log10(r)
   N-mag =  M2 + 5*log10(delta) + k2*log10(r) + phcof*beta
Units: none
 
 Illu% =
   Fraction of target circular disk illuminated by Sun (phase), as seen by
observer.  Units: PERCENT
 
 r       rdot =
   Target apparent heliocentric range ("r") and range-rate ("rdot") as seen
by observer. Units: AU and KM/S
 
 delta  deldot =
   Target apparent range ("delta") and range-rate ("delta-dot") relative to
observer at print-time. "deldot" is a projection along the line-of-sight from
the coordinate center and indicates direction of motion. A positive deldot
means the target is moving away from the observer/coordinate-center. A negative
deldot means the target is moving towards the observer.  Units: AU and KM/S
 
 S-O-T /r =
    Sun-Observer-Target angle; target's apparent solar elongation seen from
observer location at print-time. If negative, the target center is behind
the Sun. Angular units: DEGREES.

    The '/r' column is a Sun-relative code, output for observing sites
with defined rotation models only.

         /T indicates target trails Sun (evening sky)
         /L indicates target leads Sun  (morning sky)

    NOTE: The S-O-T solar elongation angle is the total separation in any
direction. It does not indicate the angle of Sun leading or trailing.
 
 S-T-O =
   Sun-Target-Observer angle; target's apparent PHASE ANGLE as seen at
observer's location at print time.  Units: DEGREES
 
 PsAng PsAMV =
   The position angles of the extended Sun->target radius vector ("PsAng")
and the negative of the target's heliocentric velocity vector ("PsAMV"),
as seen in the observer's plane-of-sky, measured CCW (east) from reference
frame North Celestial Pole. Small-bodies only. Units: DEGREES.
 
 Cnst =
   Constellation ID; the 3-letter abbreviation for the constellation name of
target's astrometric position, as defined by IAU (1930) boundary delineation.
See documentation for list of abbreviations.
 
 GlxLat =
   Observer-centered Galactic System II (post WW II) latitude of the target's
apparent position. Corrected for light-time, the gravitational deflection of
light and stellar aberration. Units: DEGREES
 Computations by ...
     Solar System Dynamics Group, Horizons On-Line Ephemeris System
     4800 Oak Grove Drive, Jet Propulsion Laboratory
     Pasadena, CA  91109   USA
     Information: http://ssd.jpl.nasa.gov/
     Connect    : telnet://ssd.jpl.nasa.gov:6775  (via browser)
                  telnet ssd.jpl.nasa.gov 6775    (via command-line)
     Author     : Jon.Giorgini@jpl.nasa.gov

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