HORIZONS.jl
An interface to NASA-JPL HORIZONS system in Julia.
Author
- Jorge A. Pérez-Hernández, Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México (UNAM)
Comments, suggestions, and improvements are welcome and appreciated.
Installation
HORIZONS.jl
is a registered Julia package and may be installed
from the Julia REPL doing import Pkg; Pkg.add("HORIZONS")
. Current stable
release is v0.3.0
, which is compatible with Julia 1.0, 1.3 and 1.4.
External dependencies
Connection to the HORIZONS machine is done via the telnet
command line
utility, which should be locally installed and enabled. File downloading is done via ftp
.
Usage examples
The horizons()
function is a shortcut to the HORIZONS telnet
interface
prompt from the Julia REPL:
julia> using HORIZONS
julia> horizons() # get Horizons prompt from the Julia REPL
JPL Horizons, version 4.70
Type '?' for brief help, '?!' for details,
'-' for previous prompt, 'x' to exit
System news updated June 08, 2020
Horizons>
HORIZONS.jl
also has Julia functions which for some of the scripts authored by
Jon D. Giorgini for automated generation of small-body binary SPK files and tables.
These scripts were originally written in expect
, and can be found at the
JPL's Solar System Dynamics group ftp server ftp://ssd.jpl.nasa.gov/pub/ssd/SCRIPTS/
.
Below, we describe the functions smb_spk
, smb_spk_ele
and vec_tbl
.
smb_spk
The smb_spk
function automates generation and downloading of Solar System
small-bodies binary SPK files from HORIZONS:
using HORIZONS, Dates
# generate a binary SPK file for asteroid 99942 Apophis covering from 2021 to 2029
ftp_name, local_file = smb_spk("b", "DES= 2099942;", DateTime(2021,Jan,1), DateTime(2029,Apr,13))
isfile(local_file) # check that the binary SPK file `local_file` exists
Binary SPK files (i.e., extension .bsp
) can be read using e.g.
SPICE.jl
:
# import Pkg; Pkg.add("SPICE") # uncomment this line to add `SPICE.jl` to current environment
using SPICE, Dates
furnsh(local_file)
et = 86400*(datetime2julian(DateTime(2024,3,1)) - 2.451545e6)
pv = spkgeo(2099942, et, "J2000", 0)
smb_spk_ele
HORIZONS.jl
function smb_spk_ele
generates .bsp
binary SPK files for
small-bodies from a set of osculating orbital elements at a given epoch:
using HORIZONS, Dates
epoch = 2449526.5 # Osculating elements epoch, in Barycentric Dynamical Time (TDB)
ec = 0.6570220840219289 # Orbital eccentricity
qr = 0.5559654280797371 # Perihelion distance
tp = 2449448.890787227 # Julian date of perihelion passage
om = 78.10766874391773 # Longitude of ascending node
w = 77.40198125423228 # Argument of perihelion
inc = 24.4225258251465 # Inclination
start_time = DateTime(2021,Jan,1)
stop_time = DateTime(2022,Jan,1)
# generate a binary SPK file for asteroid 1990 MU at `epoch`
ftp_name, local_file = smb_spk_ele("b", "1990 MU", start_time, stop_time, epoch, ec, qr, tp, om, w, inc)
isfile(local_file) # check that the binary SPK was downloaded
vec_tbl
HORIZONS.jl
function vec_tbl
allows the user to generate vector tables for
designated objects and save the output into a file:
# date variables for start and stop times
t_start = DateTime(2029,4,13)
t_stop = Date(2029,4,14)
# step size (allowed types: Period, Int, String)
δt = Hour(1) # 1 hour step size
# generate tables and save output to Apophis.txt in current directory:
vec_tbl("Apophis", "Apophis.txt", t_start, t_stop, δt; CENTER="@ssb", REF_PLANE="FRAME", OUT_UNITS=2, CSV_FORMAT=true, VEC_TABLE=2)
Note that CENTER
, REF_PLANE
, etc., are keyword arguments. If they are omitted
from the vec_tbl
call, then they will take default values:
δt = 1 #return only one step
# generate tables with default values and save output to Apophis.txt in current directory:
vec_tbl("Apophis", "Apophis.txt", t_start, t_stop, δt)
More details about default values of keyword arguments are available in the
vec_tbl
docstrings.
If the output file is not specified, then vec_tbl
returns the output as a
string, which may be then used for further processing within Julia:
δt = "2 hours" # 2 hour step size
# save into `apophisvt::String` the output from HORIZONS
apophisvt = vec_tbl("Apophis", t_start, t_stop, δt)
# do stuff with `apophisvt` inside julia...
Julia's broadcasting allows the user to get many vector tables at once:
julia> using HORIZONS
julia> IDs = string.([99942, 90000033])
2-element Array{String,1}:
"99942"
"90000033"
julia> local_files = string.(IDs,".txt")
2-element Array{String,1}:
"99942.txt"
"90000033.txt"
julia> vec_tbl.(IDs, local_files, t_start, t_stop, δt) #save output to local files 99942.txt and 90000033.txt in current folder
2-element Array{Void,1}:
nothing
nothing
julia>
Additionally, the vec_tbl_csv
function returns HORIZONS output both as an
Array{Any,2}
and a CSV-formatted String
, which
can in turn be used to construct a DataFrame
(requires
DataFrames.jl to be installed):
using HORIZONS, DataFrames
dt0 = Date(2000)
dtmax = Date(2015)
δt = Year(1)
#tbl is an Array{Any,2}; str is a String with CSV format
tbl, str = vec_tbl_csv("1950 DA", dt0, dtmax, δt;
VEC_TABLE = "2", REF_PLANE="F", CENTER="coord", COORD_TYPE="C", SITE_COORD="1,45,45");
mydataframe = readtable(IOBuffer(str))
Then, mydataframe
is a 16×8 DataFrame
:
# mydataframe:
# 16×8 DataFrames.DataFrame
│ Row │ JDTDB │ Calendar_Date_TDB │ X │ Y │ Z │ VX │ VY │ VZ │
├─────┼───────────┼──────────────────────────────────┼────────────┼────────────┼────────────┼─────────┼──────────┼──────────┤
│ 1 │ 2.45154e6 │ "A.D. 2000-Jan-01 00:00:00.0000" │ 3.49475e8 │ 2.10629e7 │ 5.71688e7 │ 25.2192 │ 15.1321 │ 9.42222 │
│ 2 │ 2.45191e6 │ "A.D. 2001-Jan-01 00:00:00.0000" │ -6.98285e7 │ 2.58022e7 │ 5.45238e7 │ 14.9524 │ -12.6021 │ -10.6881 │
│ 3 │ 2.45228e6 │ "A.D. 2002-Jan-01 00:00:00.0000" │ 3.61348e8 │ -5.69666e7 │ 1.54172e6 │ 31.3711 │ 17.5209 │ 11.1536 │
│ 4 │ 2.45264e6 │ "A.D. 2003-Jan-01 00:00:00.0000" │ 4.38864e7 │ 1.05596e8 │ 1.13413e8 │ 12.2543 │ -1.86915 │ -2.97705 │
│ 5 │ 2.45301e6 │ "A.D. 2004-Jan-01 00:00:00.0000" │ 3.22054e8 │ -1.46042e8 │ -6.27119e7 │ 39.9381 │ 18.0432 │ 11.7154 │
│ 6 │ 2.45337e6 │ "A.D. 2005-Jan-01 00:00:00.0000" │ 1.58117e8 │ 1.26817e8 │ 1.30187e8 │ 14.1172 │ 5.18222 │ 2.03615 │
│ 7 │ 2.45374e6 │ "A.D. 2006-Jan-01 00:00:00.0000" │ 2.16183e8 │ -2.27991e8 │ -1.22995e8 │ 52.494 │ 15.0644 │ 9.69931 │
│ 8 │ 2.4541e6 │ "A.D. 2007-Jan-01 00:00:00.0000" │ 2.52251e8 │ 1.08971e8 │ 1.18844e8 │ 17.5583 │ 9.77493 │ 5.43963 │
│ 9 │ 2.45447e6 │ "A.D. 2008-Jan-01 00:00:00.0000" │ 7.88944e6 │ -2.43067e8 │ -1.36722e8 │ 65.0567 │ -6.41305 │ -5.42335 │
│ 10 │ 2.45483e6 │ "A.D. 2009-Jan-01 00:00:00.0000" │ 3.21987e8 │ 6.3783e7 │ 8.74408e7 │ 21.7692 │ 13.586 │ 8.1631 │
│ 11 │ 2.4552e6 │ "A.D. 2010-Jan-01 00:00:00.0000" │ -1.15663e8 │ -7.63649e7 │ -1.92427e7 │ 27.1975 │ -22.6347 │ -17.6561 │
│ 12 │ 2.45556e6 │ "A.D. 2011-Jan-01 00:00:00.0000" │ 3.57936e8 │ -3.91115e6 │ 3.95854e7 │ 27.1418 │ 16.0684 │ 10.0908 │
│ 13 │ 2.45593e6 │ "A.D. 2012-Jan-01 00:00:00.0000" │ -3.42864e7 │ 6.17015e7 │ 8.08374e7 │ 13.0119 │ -8.54587 │ -7.70992 │
│ 14 │ 2.45629e6 │ "A.D. 2013-Jan-01 00:00:00.0000" │ 3.55506e8 │ -8.52031e7 │ -1.86717e7 │ 33.8279 │ 18.0591 │ 11.5473 │
│ 15 │ 2.45666e6 │ "A.D. 2014-Jan-01 00:00:00.0000" │ 8.32588e7 │ 1.17897e8 │ 1.22693e8 │ 12.6344 │ 0.803698 │ -1.08723 │
│ 16 │ 2.45702e6 │ "A.D. 2015-Jan-01 00:00:00.0000" │ 2.96116e8 │ -1.75053e8 │ -8.37231e7 │ 43.4907 │ 17.7757 │ 11.5517 │
License
HORIZONS.jl
is licensed under the MIT "Expat" license.
Acknowledgments
The HORIZONS system itself is the work of several people at JPL:
- Design/implementation :
- Jon Giorgini
- Don Yeomans
- Cognizant Eng.:
- Jon Giorgini
- Major body ephemerides:
- William Folkner (Planetary ephemerides)
- Bob Jacobson (Satellites)
- Marina Brozovic (Satellites)
- Contributors:
- Alan Chamberlin (web interface, database)
- Paul Chodas (some subroutines)
- The NAIF group (SPICELIB) (esp. Chuck Acton, Bill Taber, Nat Bachman)
Translation from the original expect
scripts to Julia was done using the
Expect.jl package.
References
- HORIZONS documentation (HTML)
- Giorgini, J.D., Yeomans, D.K., Chamberlin, A.B., Chodas, P.W., Jacobson, R.A., Keesey, M.S., Lieske, J.H., Ostro, S.J., Standish, E.M., Wimberly, R.N., "JPL's On-Line Solar System Data Service", Bulletin of the American Astronomical Society, Vol 28, No. 3, p. 1158, 1996.