horizons
Horizons API
Version: 1.3 (2025 June) change log
This API provides access to JPL's Horizons system by specifying Horizons settings as parameters in the URL. An alternate file-based Horizons API is available if you would prefer to submit a Horizons batch input file via HTTP POST.
Additional information about available query parameters is available in the Horizons batch example/instructions document.
[]{#request}
HTTP Request
[GET]{.label} https://ssd.jpl.nasa.gov/api/horizons.api
Example Ephemeris Query
Request an observer ephemeris of Mars in plain-text format:
https://ssd.jpl.nasa.gov/api/horizons.api?format=text&COMMAND='499'&OBJ_DATA='YES'&MAKE_EPHEM='YES'&EPHEM_TYPE='OBSERVER'&CENTER='500@399'&START_TIME='2006-01-01'&STOP_TIME='2006-01-20'&STEP_SIZE='1%20d'&QUANTITIES='1,9,20,23,24,29'`Query Parameters
Special/reserved characters require URL encoding.
The following tables show available query parameters for the Horizons
API. The first table "Common Parameters" lists query
parameters that are independent of the selected
EPHEM_TYPE. The next table
"Ephemeris-Specific Parameters" lists remaining parameters
that are specific to OBSERVER,
VECTORS, and
ELEMENTS ephemeris types and
indicates the EPHEM_TYPE for
which they are available. The last two tables, "SPK File Parameters" and "Close-Approach Table Parameters", list
parameters specific to those special ephemeris types.
Details on parameters can be found in the Horizons documentation and also the Horizons batch example text file. In the tables below, direct links to the appropriate section of the Horizons documentation for specific parameters is given in the "Manual" column when available.
[]{#common}Common Parameters
Parameter Default Allowable Values/Format Description Manual
------------ ---------------------------------------------------- -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ------------------------------------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------------
format `json` `json`, `text` specify output format: `json` for JSON or `text` for plain-text
COMMAND *none* see [details below](#command) target search, selection, or enter user-input object mode [link](https://ssd.jpl.nasa.gov/horizons/manual.html#select)
OBJ_DATA `YES` `NO`, `YES` toggles return of object summary data
MAKE_EPHEM `YES` `NO`, `YES` toggles generation of ephemeris, if possible
EPHEM_TYPE `OBSERVER` `OBSERVER`, `VECTORS`, `ELEMENTS`, `SPK`, `APPROACH` selects type of ephemeris to generate (see [details below](#ephem_type))
EMAIL_ADDR *none* any valid email address optional; used only in the event of highly unlikely problems needing follow-up Note: No output will be generated unless
MAKE_EPHEM='YES'and/orOBJ_DATA='YES', unless a database-search only.
[]{#specific}Ephemeris-Specific Parameters
In the following table, the column heading O (OBSERVER), V (VECTORS), and E (ELEMENTS)
indicate the ephemeris type for which the parameter is available.
Symbol x means the parameter is fully supported for the indicated ephemeris type.
Symbol- means the parameter is partially supported and no symbol (blank) means the parameter is not supported.
Parameter O V E Default Allowable Values/Format Description Manual
--------------------- --- --- --- ------------------------------------------------------------------ ------------------------------------------------------------------------------------------------------------------------------------------------------------- ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- -----------------------------------------------------------------------------------------------------------------------------
CENTER x x x `Geocentric` see [details below](#center) selects coordinate origin (observing site) [link](https://ssd.jpl.nasa.gov/horizons/manual.html#center)
REF_PLANE x x `ECLIPTIC` `ECLIPTIC`, `FRAME`, `BODY EQUATOR` Ephemeris reference plane (can be abbreviated `E`, `F`, `B`, respectively) )
COORD_TYPE x x x `GEODETIC` `GEODETIC`, `CYLINDRICAL` selects type of user coordinates [link](https://ssd.jpl.nasa.gov/horizons/manual.html#center)
SITE_COORD x x x `'0,0,0'` set coordinate triplets for `COORD_TYPE` [link](https://ssd.jpl.nasa.gov/horizons/manual.html#center)
START_TIME x x x *none* specifies ephemeris start time [link](https://ssd.jpl.nasa.gov/horizons/manual.html#time)
STOP_TIME x x x *none* specifies ephemeris stop time [link](https://ssd.jpl.nasa.gov/horizons/manual.html#time)
STEP_SIZE x x x `'60 min'` see [details below](#stepping) ephemeris output print step. Can be fixed time, uniform interval (unitless), calendar steps, or plane-of-sky angular change steps. See also `TLIST` alternative. [link](https://ssd.jpl.nasa.gov/horizons/manual.html#time)
TIME_DIGITS x x x `MINUTES` `MINUTES`, `SECONDS`, `FRACSEC` controls output time precision
TIME_TYPE x x x varies with `EPHEM_TYPE` `UT`, `TT`, `TDB` override default to specify input & output timescale. observer tables: `UT` or TT; vector tables: `TDB` or UT; element tables: `TDB` only
TIME_ZONE x `'+00:00'` specifies local civil time offset relative to UT
TLIST x x x *none* see [details below](#tlist) list of up to 10,000 of discrete output times. Either Julian Day numbers (JD), Modified JD (MJD), or calendar dates
TLIST_TYPE x x x *none* `JD`, `MJD`, `CAL` overrride default assumptions, specify type of time in TLIST. Be sure to include if using JD or MJD for ancient dates.
QUANTITIES x `'A'` list of desired output quantity option codes [link](https://ssd.jpl.nasa.gov/horizons/manual.html#output), [link](https://ssd.jpl.nasa.gov/horizons/manual.html#obsquan)
REF_SYSTEM x x x `ICRF` `ICRF`, `B1950` specifies reference frame for any geometric and astrometric quantities [link](https://ssd.jpl.nasa.gov/horizons/manual.html#frames)
OUT_UNITS x x `KM-S` `KM-S`, `AU-D`, `KM-D` selects output units for distance and time; for example, `AU-D` selects astronomical units (au) and days (d)
VEC_TABLE x `3` see [details below](#vec_table) selects vector table format [link](https://ssd.jpl.nasa.gov/horizons/manual.html#output)
VEC_CORR x `NONE` `NONE`, `LT`, `LT+S` selects level of correction to output vectors; `NONE` (geometric states), `LT` (astrometric light-time corrected states) or `LT+S` (astrometric states corrected for stellar aberration)
CAL_FORMAT x `CAL` `CAL`, `JD`, `BOTH` selects type of date output; `CAL` for calendar date/time, `JD` for Julian Day numbers, or `BOTH` for both CAL and JD
CAL_TYPE x x x `MIXED` `MIXED`, `GREGORIAN` Selects Gregorian-only calendar input/output, or mixed Julian/Gregorian, switching on 1582-Oct-5. Recognized for close-approach tables also.
ANG_FORMAT x `HMS` `HMS`, `DEG` selects RA/DEC output format
APPARENT x `AIRLESS` `AIRLESS`, `REFRACTED` toggles refraction correction of apparent coordinates (Earth topocentric only)
RANGE_UNITS x `AU` `AU`, `KM` sets the units on range quantities output
SUPPRESS_RANGE_RATE x `NO` `NO`, `YES` turns off output of delta-dot and rdot (range-rate)
ELEV_CUT x `'-90'` integer \[-90:90\] skip output when object elevation is less than specified
SKIP_DAYLT x `NO` `NO`, `YES` toggles skipping of print-out when daylight at `CENTER`
SOLAR_ELONG x `'0,180'` sets bounds on output based on solar elongation angle
AIRMASS x `38.0` select airmass cutoff; output is skipped if relative optical airmass is greater than the single decimal value specified. Note than `1.0`=zenith, `38.0` \~= local-horizon. If value is set \>= `38.0`, this turns OFF the filtering effect.
LHA_CUTOFF x `0.0` skip output when local hour angle exceeds a specified value in the domain `0.0` \< X \< `12.0`. To restore output (turn OFF the cut-off behavior), set X to `0.0` or `12.0`. For example, a cut-off value of `1.5` will output table data only when the LHA is within +/- 1.5 angular hours of zenith meridian.
ANG_RATE_CUTOFF x `0.0` skip output when the total plane-of-sky angular rate exceeds a specified value
EXTRA_PREC x `NO` `NO`, `YES` toggles additional output digits on some angles such as RA/DEC
CSV_FORMAT x x x `NO` `NO`, `YES` toggles output of table in comma-separated value format
VEC_LABELS x `YES` `NO`, `YES` toggles labeling of each vector component
VEC_DELTA_T x `NO` `NO`, `YES` toggles output of the time-varying delta-T difference TDB-UT
ELM_LABELS x `YES` `NO`, `YES` toggles labeling of each osculating element
TP_TYPE x `ABSOLUTE` `ABSOLUTE`, `RELATIVE` determines what type of periapsis time (Tp) is returned
R_T_S_ONLY x `NO` `NO`, `YES` toggles output only at target rise/transit/set []{#spk}SPK File Parameters (EPHEM_TYPE=SPK)
The following parameters are available when EPHEM_TYPE is
SPK. Binary SPK file
generation is restricted to small-bodies only (asteroids and comets).
See the Horizons
documentation for
details. See also the section below for details on SPK file
output format.
Parameter Default Description Manual
------------ --------- -------------------------------- ------------------------------------------------------------
START_TIME *none* specifies ephemeris start time [link](https://ssd.jpl.nasa.gov/horizons/manual.html#time)
STOP_TIME *none* specifies ephemeris stop time [link](https://ssd.jpl.nasa.gov/horizons/manual.html#time)[]{#ca}Close-Approach Table Parameters (EPHEM_TYPE=APPROACH)
The following parameters are available when EPHEM_TYPE is
APPROACH. See the Horizons
documentation on
close-approach tables for details.
Parameter Default Units Allowable Values/Format Description
--------------- ---------------------------------------------------------------------------------------- --------- -------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
CA_TABLE_TYPE `STANDARD` `STANDARD`, `EXTENDED` Extended close-approach tables include Julian Day numbers. B-plane information is also output if there is a covariance for the object stored in the system database or specified with user-input elements.
TCA3SG_LIMIT `14400` minutes maximum computed 3-sigma uncertainty in time of Earth close-approach
CALIM_SB `0.05` au sets the spherical radius within which the nominal target must pass one of the perturbing asteroids (Ceres, Pallas, Vesta, etc.) to activate close-approach flagging
CALIM_PL `.1, .1, .1, .1, 1.0, 1.0, 1.0, 1.0, .1, .003` au sets the spherical radius within which the nominal target must pass one of the planets (or the Moon) to activate close-approach flagging, in the order: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto, and Moon[]{#sb}User-specified Heliocentric Ecliptic Osculating Elements
The following parameters are used to define an arbitrary small-body target for numerical integration. See the Horizons documentation for a complete description of these parameters.
Heliocentric ecliptic osculating elements may be specified with
[TP, QR{.language-plaintext
.highlighter-rouge}], [MA,
A], or
[MA, N{.language-plaintext
.highlighter-rouge}]. If elements are not specified with
[TP, QR{.language-plaintext
.highlighter-rouge}], they will be computed from the other possible
input pairs because Horizons always internally uses
[TP, QR{.language-plaintext
.highlighter-rouge}].
Note that other obliquities might be implicit in ecliptic elements from non-JPL sources. For accurate propagation, users should verify which obliquity is relevant, and may have to convert elements obtained from a different source before input here.
Parameter Units Description
----------- ------- -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
OBJECT Name of user input object
EPOCH Julian Day number (JDTDB) of osculating elements
ECLIP Reference ecliptic frame of elements: `J2000` or `B1950`. `J2000` assumes the IAU76/80 J2000 obliquity of 84381.448 arcsec relative to the ICRF reference frame. `B1950` assumes FK4/B1950 obliquity of 84404.8362512 arcsec.
EC Eccentricity
QR au Perihelion distance (see note above)
TP Perihelion Julian Day number (see note above)
OM deg Longitude of ascending node wrt ecliptic
W deg Argument of perihelion wrt ecliptic
IN deg Inclination wrt ecliptic
MA deg Mean anomaly (see note above)
A au Semi-major axis (see note above)
N deg/d Mean motion (see note above)Optional Small-body Parameters
Parameter Object Type Default Units Description
----------- ------------- -------------- --------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
RAD km Object radius
H asteroid Absolute magnitude parameter
G asteroid Magnitude slope parameter; can be \< 0
M1 comet Total absolute magnitude
M2 comet Nuclear absolute magnitude
K1 comet Total magnitude scaling factor
K2 comet Nuclear magnitude scaling factor
PHCOF comet Phase coefficient for `K2`=5
A1 au/d\^2 Radial non-gravitational acceleration
A2 au/d\^2 Transverse non-gravitational acceleration
A3 au/d\^2 Normal non-gravitational acceleration
R0 2.808 au Non-grav. model constant, normalizing distance
ALN 0.1112620426 Non-grav. model constant, normalizing factor
NM 2.15 Non-grav. model constant, exponent m
NN 5.093 Non-grav. model constant, exponent n
NK 4.6142 Non-grav. model constant, exponent k
DT d Non-grav. lag/delay parameter (comets)
AMRAT m\^2/kg Solar pressure model, area/mass ratio
SRC Square-root covariance from JPL (upper-triangular, vector-stored)
EST Estimated non-grav parameter names `A1`, `A2`, `A3`, `DT` in order matching SRC. If no estimated non-gravs in the solution's SRC, `EST=' '` or unspecified.Description of Selected Parameters
[]{#ephem_type}EPHEM_TYPE Parameter
There are five ephemeris types available. These are selected using the
EPHEM_TYPE parameter. The
table below shows the EPHEM_TYPE{.language-plaintext
.highlighter-rouge} values and corresponding ephemeris type.
EPHEM_TYPE Description Typical Usage
------------ --------------------------------------------------------------------- ---------------------------------------------------------------------------------------
OBSERVER Observables (RA/DEC, Az/El, physical aspect, angles, uncertainties) telescope observations
ELEMENTS Osculating orbital elements instantaneous geometry over time, celestial mechanics
VECTORS Cartesian state vectors and uncertainties dynamical studies, propagation, programming
APPROACH Close approaches to planets (and 16 largest asteroids) encounter planning & hazards
SPK SPK binary trajectory files (asteroids and comets only) time-continuous states, navigation, mission-planning, plug-in for visualization toolsCOMMAND Parameter
The COMMAND parameter looks up
the target body, selecting it if a unique match is found, or returning a
list of matches if there are multiple matches. It is also used to enter
user-defined objects. The assigned value for
COMMAND should be delimited
with single quotes (') and
some symbols within the quotes may need to be encoded to be successfully
passed as a URL, as described below.
To specify a major-body (a planet, natural-satellite, spacecraft, or
special pre-computed cases), specify the unique Horizons ID associated
with that body. For example, COMMAND='499'{.language-plaintext
.highlighter-rouge} selects the planet Mars while
COMMAND='5' selects the
Jupiter system barycenter. COMMAND='MB'{.language-plaintext
.highlighter-rouge} will return a list of current major-bodies and their
ID codes.
For small-bodies (asteroids and comets), a search syntax with numerous parameter keywords separated by semi-colons can be used to find objects with certain combinations of properties. For discussion of small-body look-up searching, see Horizons documentation.
When you already know what you are looking for, numbered asteroids can
be selected with the IAU number followed by a semicolon
(;). For example,
COMMAND='1;' selects the
small-body "1 Ceres". If the semicolon is not specified,
COMMAND='1', this will instead
select the Mercury barycenter. The semicolon syntax resolves numbering
ambiguities between major bodies and small-bodies.
Small-body designations, such as '1999 AN10' can be specified using the
DES keyword COMMAND='DES=1999 AN10;'{.language-plaintext
.highlighter-rouge}.
SPK IDs, if known, are considered a type of designation. For example,
COMMAND='99942;' (IAU number)
and COMMAND='DES=2099942;'
(SPK ID), or COMMAND='Apophis;'{.language-plaintext
.highlighter-rouge} (name) all select the object Apophis, though the
numeric forms are guaranteed to be unique matches, while a name search
may not be.
To input an arbitrary target for numerical integration, heliocentric
ecliptic small-body osculating elements can be specified by users
when COMMAND=';'. TLEs
(two-line elements) may be input for Earth-orbiting objects by setting
COMMAND='TLE'.
IMPORTANT: API calls must encode semicolons as %3B{.language-plaintext
.highlighter-rouge} in the URL since the symbol usually cannot be
directly sent without premature interpretation by the local operating
system or software. Implementation of the above examples in a URL would
be COMMAND='1%3B',
COMMAND='DES=1999%20AN10%3B',
COMMAND='Apophis%3B' and
COMMAND='%3B', for example.
Please see the Horizons documentation for more details and examples of object selection, including specification of surface targets.
CENTER Parameter
This setting can be the observing site name, its unique IAU site code,
the string 'coord' (which tells the system to use coordinate information
stored in parameters SITE_COORD{.language-plaintext
.highlighter-rouge} and COORD_TYPE{.language-plaintext
.highlighter-rouge}) or the string 'geo' (meaning geocenter or body
center).
Please see the Horizons documentation for more details and examples.
STEP_SIZE Parameter
This setting specifies table output print times using the form 'integer {units} {mode}'.
{units} Minimum Abbreviation Description Example
--------- ---------------------- -------------------------- --------------------------------------------------------------------------------------------------------------
days d fixed interval `STEP_SIZE='1d'`
hours h fixed interval `STEP_SIZE='3%20h'` (w/URL-encoded space)
minutes m fixed interval `STEP_SIZE='10m'`
years y calendar stepping `STEP_SIZE='1 year'`
months mo calendar stepping `STEP_SIZE='1 mo'`
unitless fixed intervals `STEP_SIZE='86400'` (1 second output given 1 day between start/stop)Calendar stepping
If calendar-stepping units of years or months are specified, output steps will follow the calendar based on the starting date. For example, if the start is 2008-Feb-29, and output is requested at "1 year" steps, output will be returned only for Feb 29 calendar days in those leap years having 29 days in February.
If output is requested at "1 month" intervals, output will occur for every successive month on the 29th of that month. If a start date on the 31st is requested, output will only occur for months having 31 days.
Unitless output stepping
If only the integer component is given in
STEP_SIZE, the interval
between specified START_TIME
and STOP_TIME is divided into
that many evenly spaced output steps. For example, if start and stop
times are 1 hour (3600 seconds) apart, requesting a unitless output step
of '3600' will produce output every second; '240' will output every 15
seconds (3600/15 = 240 intervals).
Unitless STEP_SIZE is the only
way to obtain output with less than 1 minute spacing, while Horizons
output steps must be greater than 0.5 seconds.
For example, given a two-minute span between start/stop (120 seconds), specifying a unitless step-size of 240 would produce output at 0.5 second intervals, the smallest output resolution. Only short periods of time can be covered in a single ephemeris when such fine output resolution is specified.
Rise-Transit-Set event stepping
When EPHEM_TYPE= 'OBS' and
CENTER is a topocentric
location, the optional {mode} setting can be used to toggle output at
rise-transit-set events only (within integer <= 9 min resolution),
where rise and set are relative to one of three reference planes while
considering ELEV_CUT angle
setting:
{mode} Rise-Transit-Set aberrations relative to reference plane Example
-------- ---------------------------------------------------------- -------------------------------------------------------------------------------------------------
TVH True visual horizon (include horizon dip and refraction) `STEP_SIZE='1m TVH'` (RTS with +/- 1 minute resolution)
GEO Geometric horizon (include refraction) `STEP_SIZE='5m GEO'` (RTS with +/- 5 minute resolution)
RAD Radar horizon (geometric horizon, NO refraction) `STEP_SIZE='1m RAD'` (RTS with +/-1 minute resolution)'Geometric horizon' refers to the horizon defined by the plane
perpendicular to the local zenith (modified by
ELEV_CUT).
Time-varying output (angular stepping)
This mode turns on time-varying output, requesting approximate angular motion criteria for output instead of time-based stepping. Angular range can be 60 to 3600 (arcsec).
{mode} Description Example
-------- ---------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------
VAR Output after specified angular change in plane-of-sky position `STEP_SIZE='VAR 600'` (output after moving 600 arcseconds in plane-of-sky)There is no {units} specification for angle-stepping (time-varying) mode, it is implicitly arcseconds.
[]{#tlist}TLIST Parameter
The Horizons TLIST parameter
allows specification of up to 10,000 discrete output times, though URL
length limits may impose smaller limits depending on local software.
When using TLIST, do not use any of the other time-span parameters:
START_TIME,
STOP_TIME, or
STEP_SIZE, but do consider
using TLIST_TYPE and
TIME_TYPE to ensure your input
is interpreted as intended.
TLIST values may be specified
as individually quote-wrapped Julian Day numbers (JD), Modified Julian
Day numbers (MJD, where MJD = JD - 2400000.5, the number of days since
1858-Nov-17), or any calendar date form that Horizons recognizes, such
as '2035-Jul-12 10:17:19.373'. See system documentation for more
examples of supported calendar date forms.
For numeric TLIST values (JD or MJD input), the default behavior is to
determine if the chronologically earliest value is JD or MJD based on
its magnitude. A small value less than
abs(625360.5) will be
interpreted as toggling MJD input for the rest of the TLIST. If they are
in fact ancient Julian Day Numbers (prior to around 3001 BC), set
TLIST_TYPE= 'JD' to force interpretation of small numeric TLIST values
as JD instead of MJD.
TLIST can contain a mix of JD and calendar dates, but MJD values cannot be included in the mix without resulting in all other dates being assumed to be MJD.
When more than one TLIST value needs to be specified, the list of
individually quoted values is further delimited using either comma
(,) or space ` ` characters.
An example specification for Horizons is
TLIST= '2455339.95748' '2455354.92142' '2033-Jan-17 12:10:25.1'
However, to successfully transmit such a list via URL to the API, the
spaces (or commas) and single quotes in the TLIST setting should be
URL-encoded using %20 for
spaces, %2C for commas, and
%27 for single-quotes. The
resulting URL for successful API handling of the example would look like
this:
TLIST=%272455339.95748%27%20%272455354.92142%27%20%272033-Jan-17%2012:10:25.1%27
If URL-length limits are encountered when specifying long TLISTS, the file-based Horizons API provides an alternate input method that supports long lists without the need for URL character-encoding.
[]{#vec_table}VEC_TABLE Parameter
The VEC_TABLE parameter is used to set table format details when
EPHEM_TYPE=VECTOR. Values
assigned can be a single integer from 1 to 6, with optionally present
modifier symbols allowed for numerically integrated small-bodies
Quantities Output:
Value Quantities Output
------- ----------------------------------------------------------------------------
1 Position components {x,y,z} only (with optional statistical request codes)
2 State vector {x,y,z,Vx,Vy,Vz} (with optional statistical request codes)
3 State vector, 1-way light-time, range, and range-rate
4 Position, 1-way light-time, range, and range-rate
5 Velocity components {vx, vy, vz} only
6 1-way light-time, range, and range-rateModifier codes are accepted for values 1{.language-plaintext
.highlighter-rouge} and 2 to
trigger output of formal statistical uncertainties when available (for
asteroids and comets only).
Available modifier codes for values 1{.language-plaintext
.highlighter-rouge} and 2 as
shown in the following table.
Code Description
------ ------------------------------------------------------------------
x XYZ uncertainties (ICRF or FK4/B1950)
a ACN uncertainties (along-track, cross-track, normal)
r RTN uncertainties (radial, transverse, normal)
p POS uncertainties (plane-of-sky; radial, RA, and DEC components)Examples:
VEC_TABLE='1xa'returns position components along with their uncertainties, and with uncertainties in the ACN system also.VEC_TABLE='2xarp'returns position and velocity, with uncertainties in all four coordinate systems.
[]{#tle}TLEs (Two-Line Elements)
Two-Line Elements (TLEs) may be input to define an artificial
Earth-orbiting satellite. They are used only when
COMMAND='TLE' (input object is
the target), or if CENTER='@TLE'{.language-plaintext
.highlighter-rouge} also (meaning the input object is the coordinate
center).
TLEs must be supplied in standard format with starting and ending quote marks enclosing the entire block. Name specification line(s) are optional. Up to 600 pairs (1200 data lines) can be specified, but this limit is subject to change.
Example assignment for object 'SC-1':
TLE = '
SC-1
1 87820U 11053A 11273.79990913 .00099611 00000-0 64461-3 0 9991
2 87820 042.7843 189.7738 0014383 039.8647 002.5266 15.74868665 196
1 87820U 11053A 11273.86983630 -.00085102 +00000-0 -55758-3 0 9998
2 87820 042.7804 189.3478 0014258 040.7498 038.5752 15.74826749000204'IMPORTANT: You must URI-encode such content because a new-line character cannot be directly input via URL. The above example would use
%0Afor the new-line (LF) character as shown below.
TLE='SC-1%0A1 87820U 11053A 11273.79990913 .00099611 00000-0 64461-3 0 9991%0A2 87820 042.7843 189.7738 0014383 039.8647 002.5266 15.74868665 196%0A1 87820U 11053A 11273.86983630 -.00085102 +00000-0 -55758-3 0 9998%0A2 87820 042.7804 189.3478 0014258 040.7498 038.5752 15.74826749000204'Although the above form may work on some systems with space characters
contained within the quote characters ('{.language-plaintext
.highlighter-rouge}), it is best practice to encode all space characters
using %20. The corresponding
content with space-encoding would look like the following.
TLE='SC-1%0A1%2087820U%2011053A%20%20%2011273.79990913%20%20.00099611%20%2000000-0%20%2064461-3%200%20%209991%0A2%2087820%20042.7843%20189.7738%200014383%20039.8647%20002.5266%2015.74868665%20%20%20196%0A1%2087820U%2011053A%20%20%2011273.86983630%20-.00085102%20+00000-0%20-55758-3%200%20%209998%0A2%2087820%20042.7804%20189.3478%200014258%20040.7498%20038.5752%2015.74826749000204'See the Horizons documentation for more details about TLEs.
Data Output
Please always check the JSON payload "signature" object for the API "version". If the version does not match the version in this document (at the top), there is no guarantee that the format has not changed.
Example "signature" object with "version" value "1.0":
"signature":{"version":"1.0","source":"NASA/JPL ... API"}
Successful query requests result in a data payload. The format of such a
data payload is controlled by the format{.language-plaintext
.highlighter-rouge} parameter.
Example text-format Output
The first two lines are added by the API. It is important to note the
API VERSION value when
programmatically processing results to ensure the API version is what
you expect. The number of blank lines following
API SOURCE may vary but will
be at least one. If you request the body information page
(OBJ_DATA='YES'), there will
be an additional block of text output after the blank lines following
API SOURCE. The remainder of
the output is formatted as provided by the Horizons system.
API VERSION: 1.0
API SOURCE: NASA/JPL Horizons API
*******************************************************************************
Ephemeris / WWW_USER Tue Sep 6 22:51:14 2022 Pasadena, USA / Horizons
*******************************************************************************
Target body name: Mars (499) {source: mar097}
Center body name: Earth (399) {source: mar097}
Center-site name: GEOCENTRIC
*******************************************************************************
Start time : A.D. 1998-Jan-01 10:00:00.0000 UT
Stop time : A.D. 1998-Jan-02 00:00:00.0000 UT
Step-size : 60 minutes
*******************************************************************************
Target pole/equ : IAU_MARS {West-longitude positive}
Target radii : 3396.19, 3396.19, 3376.2 km {Equator_a, b, pole_c}
Center geodetic : 0.0, 0.0, -6378.137 {E-lon(deg),Lat(deg),Alt(km)}
Center cylindric: 0.0, 0.0, 0.0 {E-lon(deg),Dxy(km),Dz(km)}
Center pole/equ : ITRF93 {East-longitude positive}
Center radii : 6378.137, 6378.137, 6356.752 km {Equator_a, b, pole_c}
Target primary : Sun
Vis. interferer : MOON (R_eq= 1737.400) km {source: mar097}
Rel. light bend : Sun, EARTH {source: mar097}
Rel. lght bnd GM: 1.3271E+11, 3.9860E+05 km^3/s^2
Atmos refraction: NO (AIRLESS)
RA format : HMS
Time format : CAL
Calendar mode : Mixed Julian/Gregorian
EOP file : eop.220904.p221128
EOP coverage : DATA-BASED 1962-JAN-20 TO 2022-SEP-04. PREDICTS-> 2022-NOV-27
Units conversion: 1 au= 149597870.700 km, c= 299792.458 km/s, 1 day= 86400.0 s
Table cut-offs 1: Elevation (-90.0deg=NO ),Airmass (>38.000=NO), Daylight (NO )
Table cut-offs 2: Solar elongation ( 0.0,180.0=NO ),Local Hour Angle( 0.0=NO )
Table cut-offs 3: RA/DEC angular rate ( 0.0=NO )
*********************************************************************************************
Date__(UT)__HR:MN R.A._____(ICRF)_____DEC APmag S-brt delta deldot
*********************************************************************************************
$$SOE
1998-Jan-01 10:00 20 55 41.20 -18 33 23.0 1.199 4.107 2.13799045474771 5.6049390
1998-Jan-01 11:00 20 55 49.17 -18 32 49.7 1.205 4.112 2.13812533287512 5.6044117
1998-Jan-01 12:00 20 55 57.13 -18 32 16.5 1.221 4.128 2.13826019831403 5.6038846
1998-Jan-01 13:00 20 56 05.09 -18 31 43.1 1.234 4.141 2.13839505107206 5.6033579
1998-Jan-01 14:00 20 56 13.05 -18 31 09.8 1.249 4.156 2.13852989115697 5.6028315
1998-Jan-01 15:00 20 56 21.01 -18 30 36.5 1.229 4.136 2.13866471857652 5.6023055
1998-Jan-01 16:00 20 56 28.97 -18 30 03.1 1.242 4.149 2.13879953333835 5.6017797
1998-Jan-01 17:00 20 56 36.93 -18 29 29.7 1.236 4.143 2.13893433545018 5.6012543
1998-Jan-01 18:00 20 56 44.89 -18 28 56.3 1.225 4.132 2.13906912492008 5.6007292
1998-Jan-01 19:00 20 56 52.85 -18 28 22.9 1.233 4.139 2.13920390175678 5.6002045
1998-Jan-01 20:00 20 57 00.81 -18 27 49.4 1.239 4.146 2.13933866596968 5.5996802
1998-Jan-01 21:00 20 57 08.76 -18 27 15.9 1.246 4.153 2.13947341756857 5.5991564
1998-Jan-01 22:00 20 57 16.72 -18 26 42.5 1.226 4.133 2.13960815656331 5.5986329
1998-Jan-01 23:00 20 57 24.67 -18 26 08.9 1.216 4.123 2.13974288296371 5.5981098
1998-Jan-02 00:00 20 57 32.63 -18 25 35.4 1.205 4.111 2.13987759677950 5.5975872
$$EOE
*********************************************************************************************
Column meaning:
... [some content excluded here for brevity] ...
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 : [email protected]
*****************************************************************************************If there are any errors in your input file (such as requesting ephemeris output times outside the range available), they will be shown at the end of the normal output. Thus, such error detection is the responsibility of the user.
In some cases, error messages will provide suggestions that are only
applicable to the command-line interface. For example, when specifying
an observatory code that does not exist, the message suggests typing
..., ?! for help. In such
cases, if the error is not obvious, please check the Horizons system
documentation.
For automated systems, or when you are satisfied you don't need to confirm output, UNIX/Linux/MacOS command-line users can pipe the API command output through the local 'sed' command to strip out headers and footnotes, leaving only the table data:
| sed -e '1,/$$SOE/d' -e '/$$EOE/,$d'{.language-plaintext
.highlighter-rouge}
Example json-format Output
When json-format is requested,
the API attempts to detect any Horizons error message(s), capture them,
and report them in the error
field. Thus, if the error
field is present in the output, an appropriate programmatic response can
be issued.
In the following successful request, the content of interest will be in
the JSON result field.
{
"signature" : {
"source" : "NASA/JPL Horizons API",
"version" : "1.0"
},
"result" : " \n \n*******************************************************************************\nEphemeris / WWW_USER Tue Sep 6 22:51:14 2022 Pasadena, USA / Horizons \n*******************************************************************************\nTarget body name: Mars (499) {source: mar097}\nCenter body name: Earth (399) {source: mar097}\nCenter-site name: GEOCENTRIC\n*******************************************************************************\nStart time : A.D. 1998-Jan-01 10:00:00.0000 UT \nStop time : A.D. 1998-Jan-02 00:00:00.0000 UT \nStep-size : 60 minutes\n*******************************************************************************\nTarget pole/equ : IAU_MARS {West-longitude positive}\nTarget radii : 3396.19, 3396.19, 3376.2 km {Equator_a, b, pole_c}\nCenter geodetic : 0.0, 0.0, -6378.137 {E-lon(deg),Lat(deg),Alt(km)}\nCenter cylindric: 0.0, 0.0, 0.0 {E-lon(deg),Dxy(km),Dz(km)}\nCenter pole/equ : High-precision EOP model {East-longitude positive}\nCenter radii : 6378.137, 6378.137, 6356.752 km {Equator_a, b, pole_c}\nTarget primary : Sun\nVis. interferer : MOON (R_eq= 1737.400) km {source: mar097}\nRel. light bend : Sun, EARTH {source: mar097}\nRel. lght bnd GM: 1.3271E+11, 3.9860E+05 km^3/s^2 \nAtmos refraction: NO (AIRLESS)\nRA format : HMS\nTime format : CAL \nCalendar mode : Mixed Julian/Gregorian\nEOP file : eop.200513.p200804 \nEOP coverage : DATA-BASED 1962-JAN-20 TO 2020-MAY-13. PREDICTS-> 2020-AUG-03\nUnits conversion: 1 au= 149597870.700 km, c= 299792.458 km/s, 1 day= 86400.0 s \nTable cut-offs 1: Elevation (-90.0deg=NO ),Airmass (>38.000=NO), Daylight (NO )\nTable cut-offs 2: Solar elongation ( 0.0,180.0=NO ),Local Hour Angle( 0.0=NO )\nTable cut-offs 3: RA/DEC angular rate ( 0.0=NO ) \n*****************************************************************************************\n Date__(UT)__HR:MN R.A._____(ICRF)_____DEC APmag S-brt delta deldot deldot\n*****************************************************************************************\n$$SOE\n 1998-Jan-01 10:00 20 55 41.20 -18 33 23.0 1.199 4.107 2.13799045474771 5.6049390\n 1998-Jan-01 11:00 20 55 49.17 -18 32 49.7 1.205 4.112 2.13812533287512 5.6044117\n 1998-Jan-01 12:00 20 55 57.13 -18 32 16.5 1.221 4.128 2.13826019831403 5.6038846\n 1998-Jan-01 13:00 20 56 05.09 -18 31 43.1 1.234 4.141 2.13839505107206 5.6033579\n 1998-Jan-01 14:00 20 56 13.05 -18 31 09.8 1.249 4.156 2.13852989115697 5.6028315\n 1998-Jan-01 15:00 20 56 21.01 -18 30 36.5 1.229 4.136 2.13866471857652 5.6023055\n 1998-Jan-01 16:00 20 56 28.97 -18 30 03.1 1.242 4.149 2.13879953333835 5.6017797\n 1998-Jan-01 17:00 20 56 36.93 -18 29 29.7 1.236 4.143 2.13893433545018 5.6012543\n 1998-Jan-01 18:00 20 56 44.89 -18 28 56.3 1.225 4.132 2.13906912492008 5.6007292\n 1998-Jan-01 19:00 20 56 52.85 -18 28 22.9 1.233 4.139 2.13920390175678 5.6002045\n 1998-Jan-01 20:00 20 57 00.81 -18 27 49.4 1.239 4.146 2.13933866596968 5.5996802\n 1998-Jan-01 21:00 20 57 08.76 -18 27 15.9 1.246 4.153 2.13947341756857 5.5991564\n 1998-Jan-01 22:00 20 57 16.72 -18 26 42.5 1.226 4.133 2.13960815656331 5.5986329\n 1998-Jan-01 23:00 20 57 24.67 -18 26 08.9 1.216 4.123 2.13974288296371 5.5981098\n 1998-Jan-02 00:00 20 57 32.63 -18 25 35.4 1.205 4.111 2.13987759677950 5.5975872\n$$EOE\n*****************************************************************************************\nColumn meaning:\n \nTIME\n\n Times PRIOR to 1962 are UT1, a mean-solar time closely related to the\nprior but now-deprecated GMT. Times AFTER 1962 are in UTC, the current\ncivil or \"wall-clock\" time-scale. UTC is kept within 0.9 seconds of UT1\nusing integer leap-seconds for 1972 and later years.\n\n Conversion from the internal Barycentric Dynamical Time (TDB) of solar\nsystem dynamics to the non-uniform civil UT time-scale requested for output\nhas not been determined for UTC times after the next July or January 1st.\nTherefore, the last known leap-second is used as a constant over future\nintervals.\n\n Time tags refer to the UT time-scale conversion from TDB on Earth\nregardless of observer location within the solar system, although clock\nrates may differ due to the local gravity field and no analog to \"UT\"\nmay be defined for that location.\n\n Any 'b' symbol in the 1st-column denotes a B.C. date. First-column blank\n(\" \") denotes an A.D. date. Calendar dates prior to 1582-Oct-15 are in the\nJulian calendar system. Later calendar dates are in the Gregorian system.\n\n NOTE: \"n.a.\" in output means quantity \"not available\" at the print-time.\n \n R.A._____(ICRF)_____DEC =\n Astrometric right ascension and declination of the target center with\nrespect to the observing site (coordinate origin) in the reference frame of\nthe planetary ephemeris (ICRF). Compensated for down-leg light-time delay\naberration.\n\n Units: RA in hours-minutes-seconds of time (HH MM SS.ff)\n DEC in degrees-minutes-seconds of arc (sDD MN SC.f)\n \n APmag S-brt =\n Target's approximate apparent visual magnitude & surface brightness. For\nplanets and satellites, values are available only for solar phase angles in the\nrange generally visible from Earth. This is to avoid extrapolation of models\nbeyond their valid (data-based) limits.\n Units: MAGNITUDE & VISUAL MAGNITUDES PER SQUARE ARCSECOND\n \n delta deldot =\n Range (\"delta\") and range-rate (\"delta-dot\") of target center with respect\nto the observer at the instant light seen by the observer at print-time would\nhave left the target center (print-time minus down-leg light-time); the\ndistance traveled by a light ray emanating from the center of the target and\nrecorded by the observer at print-time. \"deldot\" is a projection of the\nvelocity vector along this ray, the light-time-corrected line-of-sight from\nthe coordinate center, and indicates relative motion. A positive \"deldot\"\nmeans the target center is moving away from the observer (coordinate center).\nA negative \"deldot\" means the target center is moving toward the observer.\nUnits: AU and KM/S\n\n\n Computations by ...\n Solar System Dynamics Group, Horizons On-Line Ephemeris System\n 4800 Oak Grove Drive, Jet Propulsion Laboratory\n Pasadena, CA 91109 USA\n Information: http://ssd.jpl.nasa.gov/\n Connect : telnet://ssd.jpl.nasa.gov:6775 (via browser)\n telnet ssd.jpl.nasa.gov 6775 (via command-line)\n Author : [email protected]\n\n*****************************************************************************************\n"
}Non-unique Object Specification
If the object specified via the COMMAND{.language-plaintext
.highlighter-rouge} query parameter is not unique within the Horizons
system, you will get a list of matching objects. Below is an example
(text-format) output where
COMMAND='DES=141P;'.
API VERSION: 1.0
API SOURCE: NASA/JPL Horizons API
*******************************************************************************
JPL/DASTCOM Small-body Index Search Results 2021-May-11 07:53:26
Comet AND asteroid index search:
DES = 141P;
Matching small-bodies:
Record # Epoch-yr >MATCH DESIG< Primary Desig Name
-------- -------- ------------- ------------- -------------------------
90001032 2011 141P 141P Machholz 2
90001033 2019 141P 141P Machholz 2
90001034 1994 141P-A 141P-A Machholz 2
90001035 1997 141P-A 141P-A Machholz 2
90001036 1999 141P-A 141P-A Machholz 2
90001037 1994 141P-D 141P-D Machholz 2
90001038 1999 141P-D 141P-D Machholz 2
(7 matches. To SELECT, enter record # (integer), followed by semi-colon.)
*******************************************************************************In the above example, there are three bodies represented: the parent
comet 141P, fragment A
(141P-A), and fragment D
(141P-D). There are also
multiple orbits for each of these comets represented by the
Epoch-yr field in the results
table. This is typically because the orbit may change between
apparitions due to changed outgassing accelerations. Maintaining
different solutions supports the different historical acceleration
models appropriate to the time.
To select the object and orbit of interest, you must specify the
Horizons record number listed in the Record #{.language-plaintext
.highlighter-rouge} column. For example, to select the orbit for the
parent comet with epoch 2019, specify
COMMAND='90001033;'. However,
be warned that for small bodies (comets and asteroids) these record
numbers are subject to change without notice.
For unique comet selection without using Horizons record numbers, there
are additional flags that can be used in the
COMMAND specification. For
example, if you know there are fragments for comet 141P and you want the
parent comet, you can add the NOFRAG{.language-plaintext
.highlighter-rouge} flag to the COMMAND{.language-plaintext
.highlighter-rouge} specification such as
COMMAND='DES=141P;NOFRAG'.
Similarly, if you know you always want the orbit with the most recent
epoch, you can add the CAP
flag (closest-apparition) to the COMMAND{.language-plaintext
.highlighter-rouge} specification such as
COMMAND='DES=141P;CAP'. In
this example, combining CAP
and NOFRAG will result in a
unique match for the parent comet 141P as in
COMMAND='DES=141P;CAP;NOFRAG'.
For fragments, the designation is already unique so you'd only need the
CAP flag as in
COMMAND='DES=141P-A;CAP'.
See the Horizons documentation for more details.
[]{#spk_file}Small-Body SPK File Generation
The binary SPK file is base-64 encoded on return and, for
text-format output, begins
after the API header text with the base-64 string
REFGL1NQ... in the following
example for asteroid 1 Ceres (SPK-ID 2000001).
API VERSION: 1.0
API SOURCE: NASA/JPL Horizons API
ID= '2000001'
SPK Binary Data Follows -- base64 encoded:
REFGL1NQSyACAAAABgAAAFNNQl9TUEtfRklMRSAgICAgICAgICAgICAgICAgICAgICAgICAgICAg
ICAgICAgICAgICAgICAgICAgID4AAAA+AAAAMLcAAExUTC1JRUVFAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
...
AAAAAAAAAAAAAAAAAAAAAAAAAA==To convert the base-64 encoded content to a usable binary SPK file,
extract the encoded portion to a file and use a base-64 decoder. On most
Linux systems this is done with the command
base64 --decode {extracted_file_content}{.language-plaintext
.highlighter-rouge}, where {extacted_file_content}{.language-plaintext
.highlighter-rouge} is the name of the file containing the encoded
content from the API.
[]{#script}Example SPK Horizons Request
For Small-Body in the JPL Database
The following example requests an SPK file spanning 2020-01-01 through 2030-12-31 (TDB) for asteroids 1 Ceres.
https://ssd.jpl.nasa.gov/api/horizons.api?COMMAND='1%3B'&EPHEM_TYPE=SPK&START_TIME='2020-01-01'&STOP_TIME='2030-12-31'&OBJ_DATA=NOFor Small-Body not in the JPL Database
The following example requests an SPK file covering 2030-01-01 through 2031-01-01 (TDB) for the small-body specified with user-supplied osculating elements and non-gravitational parameters.
https://ssd.jpl.nasa.gov/api/horizons.api?COMMAND='%3B'&MAKE_EPHEM=YES&EPHEM_TYPE=SPK&OBJ_DATA=NO&START_TIME='2030-Jan-1'&STOP_TIME='2031-Jan-1'&OBJECT='User%20Apophis'&EPOCH=2459311.5&ECLIP=J2000&EC=0.1915350975906659&QR=0.7458351838564465&TP=2459424.5839352785&OM=203.9782743995174&W=126.6377455281965&IN=3.33973556589891&A1='3.869431020576E-13'&A2='-2.898628963521E-14'&R0=1.&ALN=1.&NM=2.&NN=5.093&NK=0.Command-line Examples
An example Linux command-line to extract the binary SPK file content
from a successful text-format
output is shown below. However, be advised that such usage will not
easily catch errors returned from the API.
curl -s "https://ssd.jpl.nasa.gov/api/horizons.api?format=text&COMMAND='1%3B'&EPHEM_TYPE=SPK&START_TIME='2020-01-01'&STOP_TIME='2030-12-31'&OBJ_DATA=NO" | awk '/REFGL1NQ/,0' | base64 --decode > 2000001.bspSimilarly, for the json-format
output, the SPK encoded content is contained in the
spk: object as in the
following example:
{
"signature" : {
"source" : "NASA/JPL Horizons API",
"version" : "0.2"
},
"result" : "\nID= '2000001'\n\n",
"spk_file_id" : "2000001",
"spk" : "REFGL1NQSyACAAAABgAAAFNNQl9TUEtfRklMRSAgICAgICAgICAgICAgICAgICAgICAgICAgICAg\nICAgICAgICAgICAgICAgICAgID4AAAA+AAA ... AAAA\nAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA\nAAAAAAAAAAAAAAAAAAAAAAAAAA==\n"
}Extract the content from the JSON spk{.language-plaintext
.highlighter-rouge} object excluding the surrounding quotes and then
decode to produce the corresponding binary SPK file. The JSON
spk_file_id value suggests an
appropriate filename (excluding the .bsp{.language-plaintext
.highlighter-rouge} extension) for output: 2000001{.language-plaintext
.highlighter-rouge} in this example from which the filename
2000001.bsp could be formed.
Sample Scripts
The following scripts generate SPK files spanning
2030-01-01 to
2031-01-01 for the small-body
specified on the command-line. In this example, the desired small-body
is specified using its SPK-ID (e.g., 2000001{.language-plaintext
.highlighter-rouge} for asteroid 1 Ceres).
IMPORTANT: You must take care to encode special characters in the URL within your scripts for proper interpretation of your query parameters. In the scripts below, the Horizons
COMMANDparameter contains special characters=and;which must be converted to%3Dand%3B, respectively. For example,COMMAND='DES=2000001;'{.language-plaintext .highlighter-rouge} must be encoded asCOMMAND='DES%3D2000001%3B'.
Perl
Assuming the following Perl script is saved to a file
horizons_spk.pl, it could be
invoked from the command-line to generate an SPK file for asteroid
1 Ceres (SPKID 2000001) as
perl horizons_spk.pl 2000001.
use strict;
use LWP::UserAgent;
use JSON;
use MIME::Base64;
# Define API URL and SPK filename:
my $url = "https://ssd.jpl.nasa.gov/api/horizons.api";
my $spk_filename = 'spk_file.bsp';
# Define the time span:
my $start_time = '2030-01-01';
my $stop_time = '2031-01-01';
# Get the requested SPK-ID from the command-line:
my $spkid = shift;
unless ( defined $spkid ) { die "please specify SPK-ID on the command-line"; }
# Build the appropriate URL for this API request:
# IMPORTANT: You must encode the "=" as "%3D" and the ";" as "%3B" in the
# Horizons COMMAND parameter specification.
$url .= "?format=json&EPHEM_TYPE=SPK&OBJ_DATA=NO";
$url .= "&COMMAND='DES%3D$spkid%3B'&START_TIME='$start_time'&STOP_TIME='$stop_time'";
# Build and submit the API request and decode the JSON-response:
my $ua = LWP::UserAgent->new;
my $response = $ua->get($url);
my $data = decode_json($response->content);
# If the request was valid...
if ( $response->code eq '200' ) {
#
# If the SPK file was generated, decode it and write it to the output file:
if ( defined $data->{spk} ) {
#
# If a suggested SPK file basename was provided, use it:
if ( defined $data->{spk_file_id} ) { $spk_filename = "$data->{spk_file_id}.bsp"; }
open (my $fh, ">", $spk_filename) or die "unable to open $spk_filename: $!\n";
#
# Decode and write the binary SPK file content:
print $fh decode_base64($data->{spk});
close $fh;
print "wrote SPK content to $spk_filename\n";
exit;
}
#
# Otherwise, the SPK file was not generated so output an error:
print "ERROR: SPK file not generated\n";
if ( defined $data->{result} ) { print $data->{result}; }
else { print $response->content; }
exit 1;
}
# If the request was invalid, extract error content and display it:
if ( $response->code eq '400' ) {
print "ERROR in API call: HTTPS response: ", $response->status_line, "\n";
if ( defined $data->{message} ) { print $data->{message}, "\n"; }
else { print $response->content; }
exit 1;
}
# Otherwise, some other error occurred:
print "ERROR in API call: HTTPS response: ", $response->status_line, "\n";
exit 1;Python
Assuming the following Python script is saved to a file
horizons_spk.py, it could be
invoked from the command-line to generate an SPK file for asteroid
1 Ceres (SPKID 2000001) as
python horizons_spk.py 2000001{.language-plaintext
.highlighter-rouge}.
import sys
import json
import base64
import requests
# Define API URL and SPK filename:
url = 'https://ssd.jpl.nasa.gov/api/horizons.api'
spk_filename = 'spk_file.bsp'
# Define the time span:
start_time = '2030-01-01'
stop_time = '2031-01-01'
# Get the requested SPK-ID from the command-line:
if (len(sys.argv)) == 1:
print("please specify SPK-ID on the command-line");
sys.exit(2)
spkid = sys.argv[1]
# Build the appropriate URL for this API request:
# IMPORTANT: You must encode the "=" as "%3D" and the ";" as "%3B" in the
# Horizons COMMAND parameter specification.
url += "?format=json&EPHEM_TYPE=SPK&OBJ_DATA=NO"
url += "&COMMAND='DES%3D{}%3B'&START_TIME='{}'&STOP_TIME='{}'".format(spkid, start_time, stop_time)
# Submit the API request and decode the JSON-response:
response = requests.get(url)
try:
data = json.loads(response.text)
except ValueError:
print("Unable to decode JSON results")
# If the request was valid...
if (response.status_code == 200):
#
# If the SPK file was generated, decode it and write it to the output file:
if "spk" in data:
#
# If a suggested SPK file basename was provided, use it:
if "spk_file_id" in data:
spk_filename = data["spk_file_id"] + ".bsp"
try:
f = open(spk_filename, "wb")
except OSError as err:
print("Unable to open SPK file '{0}': {1}".format(spk_filename, err))
#
# Decode and write the binary SPK file content:
f.write(base64.b64decode(data["spk"]))
f.close()
print("wrote SPK content to {0}".format(spk_filename))
sys.exit()
#
# Otherwise, the SPK file was not generated so output an error:
print("ERROR: SPK file not generated")
if "result" in data:
print(data["result"])
else:
print(response.text)
sys.exit(1)
# If the request was invalid, extract error content and display it:
if (response.status_code == 400):
data = json.loads(response.text)
if "message" in data:
print("MESSAGE: {}".format(data["message"]))
else:
print(json.dumps(data, indent=2))
# Otherwise, some other error occurred:
print("response code: {0}".format(response.status_code))
sys.exit(2)[]{#encode}URL Encoding
If a query parameter value contains any of the following characters,
those characters should be URI-encoded before submitting your request.
The following table shows these reserved characters and their
corresponding encoding. For example, a query string value "My Value"
should be encoded as My%20Value{.language-plaintext
.highlighter-rouge} where the space character is replaced with
%20.
Char. Encoding Name LF %0A line feed (new-line)
\` \` %20 space# %23 hash tag
$ %24 dollar sign
& %26 ampersand
+ %2B plus sign
, %2C comma
/ %2F slash
: %3A colon
; %3B semicolon
= %3D equals sign
? %3F question mark
@ %40 at symbol
[ %5B left square bracket
] %5D right square bracket
More information is available in section 2.3 of RFC3975.
HTTP Response Codes
Most errors are returned via appropriate HTTP response codes. However,
it is possible to submit Horizons input data (e.g., a bad
START_TIME value) resulting in
Horizons-generated errors. In such cases, a non-error code of 200 is
returned so the user is responsible for checking the payload if they
wish to detect such errors.
HTTP Code Description Typical Usage
200 OK normal successful result
400 Bad Request the request contained invalid keywords and/or content or used a request-method other than GET or POST (details returned in the JSON or text payload)
405 Method Not Allowed the request used an incorrect method (see the [HTTP Request](#request) section)
500 Internal Server Error the database is not available at the time of the request
503 Service Unavailable the server is currently unable to handle the request due to a temporary overloading or maintenance of the server, which will likely be alleviated after some delay