greyskyy/orekit-factory

Factory methods useful when building orekit-based python astrodynamics applications

Orekit-factory

A collection of utilities to bootstrap an orekit-based python application.

Installation

$ pip install orekit-factory

Usage

The utilities provided by the orekitfactory module can be broken out into the categories below. See the python docs for complete details.

Application initialization

The orekitfactory.init_orekit() method reduces the boilerplate for starting python-based orekit applications. It performs the following steps, then returns a handle to the orekit VM:

1. Downloads the default orekit data zip to a data directory. Note the option to re-download the file, if it exists, or simply use the cached version.
2. Setup the data context using that default data zip.

A basic example:

import orekit
import orekitfactory

vm = orekit.initVM()
orekitfactory.init_orekit()

Enumeration utilties

orekitfactory.to_iers_conventions() - Convert a string to the IERSConventions orekit enumeration.

import orekitfactory

iers_conventions = orekitfactory.to_iers_conventions("iers_2010")

Date utilities

Multiple date utilities improve application's abilities to use AbsoluteDate.

orekitfactory.to_absolute_date() - Converts an ISO-8601 string or a datetime instance into an AbsoluteDate instance based on UTC. The data context and time scale can be provided via optional parameters. This method is a no-op if an AbsoluteDate instance is provided.

orekitfactory.DateInterval - This class provides an interval of AbsoluteDate and provides the standard interval operations like duration, comparison, overlap, and intersection.

orekitfactory.DateIntervalList - A list of non-overlapping DateInterval instances. Provides set operations like union, intersection, and subtraction.

orekitfactory.DateIntervalListBuilder - A utility class useful when incrementally building up a DateIntervalList.

import orekitfactory

date1 = orekitfactory.to_absolute_date("2022-08-28T13:15:00Z")
date2 = orekitfactory.to_absolute_date("2022-08-28T13:16:00Z")
date3 = orekitfactory.to_absolute_date("2022-08-28T13:17:00Z")
date4 = orekitfactory.to_absolute_date("2022-08-28T13:18:00Z")

ivl1 = orekitfactory.DateInterval(date1, date3)
ivl2 = orekitfactory.DateInterval(date2, date4)
ivl3 = orekitfactory.DateInterval(date1, date2)

dlist = orekitfactory.DateInteralList(intervals=[ivl1, ivl2, ivl3])

assert 2 == len(dlist)
print(dlist)

dlist2 = orekitfactory.DateIntervalList(interval=DateInterval(date1, date5)).subtract(dlist)

print(dlist2)

Frames and reference ellipsoids

orekitfactory.get_reference_ellipsoid() - A utility function for loading ReferenceEllipsoid instances from summary strings.

orekitfactory.get_frame() - A utility function for loading Frame instances based on shortened summary names, or predefined builtins.

import orekitfactory

itrf = orekitfactory.get_frame("itrf")
wgs84 = orekitfactory.get_reference_ellipsoid("wgs84", frame=itrf)

# an alternate calls
wgs84 = orekitfactory.get_reference_ellipsoid("wgs84", frame="itrf")
wgs84 = orekitfactory.get_reference_ellipsoid("wgs84", frameName="itrf")

Orbit definitions and propagators

orekitfactory.check_tle() - Checks the two lines of a TLE for valid format.

orekitfactory.to_tle() - Constructs an orekit TLE instance using the provided UTC time scale, or loading one from the default data context.

orekitfactory.to_orbit() - Constructs a KeplerianOrbit instance from the provided parameters.

orekitfactory.to_propgator() - Construct a propagator (SGP4 or SDP4 as appropriate for a TLE, or a NumericalPropagator for keplerian orbits) from the provided orbit.

import orekitfactory

assert orekitfactory.check_tle(
    "1 49260U 21088A   22166.94778099  .00000339  00000+0  85254-4 0  9992",
    "2 49260  98.2276 237.1831 0001142  78.2478 281.8849 14.57099002 38060"
)

tle = orekitfactory.to_tle(
    "1 49260U 21088A   22166.94778099  .00000339  00000+0  85254-4 0  9992",
    "2 49260  98.2276 237.1831 0001142  78.2478 281.8849 14.57099002 38060"
)

orbit = orekitfactory.to_orbit(
    a="7080 km",
    e=0.0008685,
    i=85,
    omega=u.Quantity("261.9642 deg"),
    w="257.7333 deg",
    epoch="2022-06-16T17:54:00Z",
    v=1.2,
)

sgp4 = to_propagator(tle)
prop = to_propagator(orbit)

Vectors and Rotations

orekitfactory.to_vector() - Simplifies the creation of Vector3D instances, avoiding the InvalidArgument errors caused by passing int instead of float to the Vector3D constructor.

orekitfactory.to_rotation() - Creates a Rotation using the provided axis defintions.

import orekitfactory

new_x = orekitfactory.to_vector(1, 2, 3).normalize()
new_y = new_x.crossProduct(Vector3D.PLUS_K)

tx = orekitfactory.to_rotation(x=new_x, y=new_y)

orekit-factory's Issues

DateInterval creates naive `datetime` instances

Using DateInterval.start_dt and .stop_dt returns naive instance of datetime.

Expected behavior: these datetime objects are aware, and set in the UTC timezone.