`orbitpy.util` — Util Module

Description

This module is a collection of utility classes and functions used by the orbitpy package.

`StateType`

This is an enumeration class listing the allowed state types for representing the spacecrafts position and velocity. The allowed types are the: KEPLERIAN_EARTH_CENTERED_INERTIAL, CARTESIAN_EARTH_CENTERED_INERTIAL, CARTESIAN_EARTH_FIXED. The Cartesian representations use the equatorial plane (not the ecliptic plane) as the XY plane.

`DateType`

This is an enumeration class listing the allowed date types. GREGORIAN_UT1 refers to the date taken from the Gregorian calender and the time scale as the Universal Coordinate Time (UT1). JULIAN_DATE_UT1 refers to the number of days elapsed on the Julian calender (with the fractional part included) and the time scale as Universal TIme (UT1).

`OrbitState`

This class is used to store and handle the orbit state (i.e. the date, position and velocity of satellite). The from_dict(.) and to_dict(.) functions can be used to convert from/to python dictionary representations. The propcov.AbsoluteDate and propcov.OrbitState objects are used to maintain the date and state respectively. Note that propcov.OrbitState and orbitpy.util.OrbitState classes are different. The class also provides several staticmethods to convert date, orbit-state propcov-class representations to/from inbuilt python datatypes.

Examples

from orbitpy.util import OrbitState
import propcov

# initialize orbit-state using Julian Date UT1 and Cartesian state coordinates
x = OrbitState.from_dict({"date":{"@type":"JULIAN_DATE_UT1", "jd":2459270.75},
                        "state":{"@type": "CARTESIAN_EARTH_CENTERED_INERTIAL", "x": 6878.137, "y": 0, "z": 0, "vx": 0, "vy": 7.6126, "vz": 0},
                        "@id": 123})

# Convert the OrbitState object to a python dict representation. Specify the state as Keplerian.
print(x.to_dict(state_type=StateType.KEPLERIAN_EARTH_CENTERED_INERTIAL))
>> {'date': {'@type': 'JULIAN_DATE_UT1', 'jd': 2459270.75},
    'state': {'@type': 'KEPLERIAN_EARTH_CENTERED_INERTIAL', 'sma': 6878.122235888328, 'ecc': 2.1465323187573002e-06,
              'inc': 0.0, 'raan': 0.0, 'aop': 180.0, 'ta': 180.0}, '@id': 123}


# initialize orbit-state using Gregorian UT1 and Keplerian state coordinates
x = OrbitState.from_dict({"date":{"@type":"GREGORIAN_UT1", "year":2021, "month":2, "day":25, "hour":6, "minute":0, "second":0},
                        "state":{"@type": "KEPLERIAN_EARTH_CENTERED_INERTIAL", "sma": 6878.137, "ecc": 0.001, "inc": 45, "raan": 35, "aop": 145, "ta": -25},
                        })

# Get the propcov object representation of date from a python dictionary
x = OrbitState.date_from_dict({"@type":"JULIAN_DATE_UT1", "jd":2459270.75})
print(x)
>> AbsoluteDate.fromJulianDate(2459270.750000)

# convert the propcov orbit-state object to a python dict
x = OrbitState.state_to_dict(propcov.OrbitState.fromCartesianState(propcov.Rvector6([-5219.8,1473.95,4201.35,-3.86085,-5.99712,-2.69806])))
>> {'@type': 'CARTESIAN_EARTH_CENTERED_INERTIAL', 'x': -5219.8, 'y': 1473.95, 'z': 4201.35, 'vx': -3.86085, 'vy': -5.99712, 'vz': -2.69806}

`Orientation`

This class is used to specify the orientation of an entity in an reference frame. It is imported from the InstruPy package. Please refer to the documentation of the class instrupy.util.Orientation.

`SpacecraftBus`

This class is used to model the spacecraft-bus. An important attribute is the orientation of the bus, i.e. SpacecraftBus.orientation which specifies the bus orientation with respect to a reference frame. By default the orientation is alignment to the nadir-pointing frame (see instrupy.util.ReferenceFrame).

Example

from orbitpy.util import SpacecraftBus

# initialize spacecraft bus at 10 deg rotation about x-axis, followed by 20 degree rotation about y-axis, of the Earth centered inertial frame.
sb = SpacecraftBus.from_json('{"name": "BlueCanyon", "mass": 20, "volume": 0.5,
                               "orientation":{"referenceFrame": "EARTH_CENTERED_INERTIAL", \
                                              "convention": "XYZ","xRotation":10,"yRotation":20,"zRotation":0}, "@id":123}')

`Spacecraft`

This class is used to model a spacecraft. The attributes of this class are the: name of the spacecraft, unique identifier, spacecraft-bus (orbitpy.util.SpacecraftBus), orbit-state (orbitpy.util.OrbitState) and a list of instruments (instrupy.base.Instrument).

An unique identifier is assigned to the ``Spacecraft`` object if the user doe not provide one.

Example

from orbitpy.util import Spacecraft

# Initialize spacecraft with 1 instrument. By default without a SpacecraftBus specification, a bus aligned to the nadir-pointing frame is assigned.
spc1 = Spacecraft.from_json('{"@id": "sp1", "name": "Mars", \
                              "instrument": {"name": "Alpha", "mass":10, "volume":12.45, "dataRate": 40, "bitsPerPixel": 8, "power": 12, \
                                    "fieldOfViewGeometry": {"shape": "CIRCULAR", "diameter":5 }, \
                                    "pointingOption": [{"referenceFrame": "NADIR_POINTING", "convention": "XYZ", "xRotation":0, "yRotation":2.5, "zRotation":0}, \
                                                       {"referenceFrame": "NADIR_POINTING", "convention": "XYZ", "xRotation":0, "yRotation":-2.5, "zRotation":0}  \
                                                      ], \
                                    "@id":"bs1", "@type":"Basic Sensor"}, \
                              "orbitState": {"date":{"@type":"GREGORIAN_UT1", "year":2021, "month":2, "day":25, "hour":6, "minute":0, "second":0}, \
                                             "state":{"@type": "KEPLERIAN_EARTH_CENTERED_INERTIAL", "sma": 6878.137, "ecc": 0.001, "inc": 45, "raan": 35, "aop": 145, "ta": -25} \
                                             } \
                                 }')
# initialize spacecraft with multiple, heterogenous instruments
spc2 = Spacecraft.from_dict({ "name": "Saturn",
                        "instrument": [
                           {   "name": "Alpha", "mass":10, "volume":12.45, "dataRate": 40, "bitsPerPixel": 8, "power": 12,
                              "orientation": {"referenceFrame": "SC_BODY_FIXED", "convention": "REF_FRAME_ALIGNED"},
                              "fieldOfViewGeometry": {"shape": "CIRCULAR", "diameter":5 },
                              "maneuver":{"maneuverType": "CIRCULAR", "diameter":10},
                              "numberDetectorRows":5, "numberDetectorCols":10, "@id":"bs1", "@type":"Basic Sensor"
                           },
                           {"@type": "Passive Optical Scanner", "name": "FireSat", "mass": 28, "volume": 0.12,"power": 32,
                           "fieldOfViewGeometry": {"shape": "RECTanGULAR", "angleHeight": 0.628, "angleWidth": 115.8 },
                           "scanTechnique": "WhiskBROOM", "orientation": { "referenceFrame": "SC_BODY_FIXED", "convention": "SIDE_loOK", "sideLookAngle": 0},
                           "dataRate": 85, "numberDetectorRows": 256, "numberDetectorCols": 1, "detectorWidth": 30e-6, "focalLength": 0.7,
                           "operatingWavelength": 4.2e-6, "bandwidth": 1.9e-6, "quantumEff": 0.5, "targetBlackBodyTemp": 290,
                           "bitsPerPixel": 8, "opticsSysEff": 0.75, "numOfReadOutE": 25, "apertureDia": 0.26, "Fnum": 2.7, "atmosLossModel": "LOWTRAN7"
                           }],
                        "orbitState": {"date":{"@type":"GREGORIAN_UT1", "year":2021, "month":2, "day":25, "hour":6, "minute":0, "second":0},
                                    "state":{"@type": "KEPLERIAN_EARTH_CENTERED_INERTIAL", "sma": 6878.137, "ecc": 0.001, "inc": 45, "raan": 35, "aop": 145, "ta": -25}
                                    }
                        }
                     )

`GroundStation`

This class is used to store and handle ground-station attributes: name, unique-identifier, position (geocentric lat/lon coords and altitude) and minimum elevation angle at which communication from satellite can take place.

An unique identifier is assigned to the ``GroundStation`` object if the user does not provide one.

Example

from orbitpy.util import GroundStation

gs = GroundStation.from_dict({"name": "Atl", "latitude": -88, "longitude": 25, "minimumElevation":12 })
print(gs)

# note a unique random identifier is assigned
>> GroundStation.from_dict({'name': 'Atl', 'latitude': -88.0, 'longitude': 25.0, 'altitude': 0.0, 'minimumElevation': 12.0,
                            '@id': UUID('bd96e327-36e5-4ffb-8da6-864322621e21')})

API

Classes

Functions

orbitpy.util — Util Module

Description

StateType

DateType

OrbitState

Examples

Orientation

SpacecraftBus

Example

Spacecraft

Example

GroundStation

Example

API

`orbitpy.util` — Util Module

`StateType`

`DateType`

`OrbitState`

`Orientation`

`SpacecraftBus`

`Spacecraft`

`GroundStation`