spktype01

A supporting module for jplephem to handle data type 1 (Version 1.0.0)

This module computes positions and velocities of a celestial small body, from a NASA SPICE SPK ephemeris kernel file of data type 1 (Modified Difference Arrays). See http://naif.jpl.nasa.gov/pub/naif/toolkit_docs/FORTRAN/req/spk.html

You can get SPK files for many solar system small bodies from HORIZONS system of NASA/JPL. See https://ssd.jpl.nasa.gov/?horizons

This module reads SPK files of data type 1, one of the types of binary SPK file. At the point of Oct. 2018, HORIZONS system provides files of type 21 as binary SPK files by default. You can get type 1 binary SPK file for celestial small bodies through TELNET interface by answering back '1' for 'SPK file format'.

Modules required

• jplephem (version 2.6 or later)
• numpy

Usage

from spktype01 import SPKType01
kernel = SPKType01.open('path')
position, velocity = kernel.compute_type01(center, target, jd)
print(kernel)     ---- this line prints information of all segments
kernel.close()

where:
    center - SPKID of central body (0 for SSB, 10 for Sun, etc.)
    target - SPKID of target body
    jd - time for computation (Julian date)
    position - a numpy array (x, y, z)
    velocity - a numpy array (xd, yd, zd)

Modification Log

1.0.0 October 9, 2018

• close function is added
• stable release

0.1.0 October 10, 2016

• beta release