`instrupy.base` — Base

Description

This module provides the Instrument class which serves as a base class (and an alternate means) to work with the InstruPy package. Instrument models can be initialized using the from_dict / from_json functions, where the expected key/value pairs depend on the specific instrument-model (see here).

A Instrument object can be added to a orbitpy.util.Spacecraft object and coverage calculations can be performed. Refer to the OrbitPy coverage calculator module (orbitpy.coveragecalculator) to know how to use the Instrument object for coverage calculations.

The calc_data_metrics function can be used to calculate the data-metrics given the details of the access-event (commonly the spacecraft-state and observed-location (target)). For synthetic-aperture-radars the access-event specification could alternatively involve specifying the incidence angle at the target. Please refer to the description of the respective instrument-model for additional details.

The Instrument class also provides the functionality to specify modes. Please refer to mode JSON object format for details. Each mode corresponds to effectively a different model with the respective mode-parameters.

Example

A Instrument object based on the Basic Sensor model. There is no mode specification, which implies that the instrument has one mode with the instrument model parameterized according to the input specifications. mode_id is entered as None.

from instrupy.base import Instrument

instru1 = Instrument.from_json('{"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":2.5 }, \
                           "sceneFieldOfViewGeometry": {"shape": "CIRCULAR", "diameter":5 }, \
                           "maneuver":{"maneuverType": "CIRCULAR", "diameter":10}, \
                           "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}  \
                                                ], \
                           "numberDetectorRows":5, "numberDetectorCols":10, "@id":"bs1", "@type":"Basic Sensor" \
                           }')

# define access-event
epoch_JDUT1 =  2458543.06088 # 2019 Feb 28 13:27:40 is time at which the ECEF and ECI frames approximately align, hence ECEF to ECI rotation is identity. See <https://www.celnav.de/longterm.htm> online calculator of GMST.
SpacecraftOrbitState = {'time [JDUT1]':epoch_JDUT1, 'x [km]': 6878.137, 'y [km]': 0, 'z [km]': 0, 'vx [km/s]': 0, 'vy [km/s]': 7.6126, 'vz [km/s]': 0} # altitude 500 km
TargetCoords = {'lat [deg]': 0, 'lon [deg]': 0}

obsv_metrics = instru1.calc_data_metrics(mode_id=None, sc_orbit_state=SpacecraftOrbitState, target_coords=TargetCoords)

print(obsv_metrics)

>> {'observation range [km]': 500.0, 'look angle [deg]': 0.03, 'incidence angle [deg]': 0.03, 'solar zenith [deg]': 20.33}

Instrument with multiple modes

Consider a Synthetic Aperture Radar instrument which can operate with either Stripmap or ScanSAR scanning techniques. Such an instrument is considered to be made up of two modes and the scan specifications are included in a list under the mode key. Such an instrument specification effectively makes two synthetic aperture radar models with common parameters specified by the key/value pairs other then the mode key/value. One model shall use Stripmap scan and the other model uses ScanSAR scan.

from instrupy.base import Instrument

specs = {   "@type": "Synthetic Aperture Radar",
            "pulseWidth": 12e-6,
            "antenna":{"shape": "RECTANGULAR", "height": 4.9, "width": 1, "apertureEfficiency": 0.6, "apertureExcitationProfile": "UNIFORM"},
            "operatingFrequency": 9.65e9,
            "peakTransmitPower": 1000,
            "chirpBandwidth": 75e6,
            "minimumPRF": 1,
            "maximumPRF": 20000,
            "radarLoss": 3.5,
            "systemNoiseFigure": 4.5,
            "polarization": {
               "@type": "dual",
               "pulseConfig": {
                  "@type": "SMAP",
                  "pulseSeparation": 2e-6
            }
            },
            "atmosLoss": 1,
            "mode":[{
               "@id": "stripmap-mode",
               "scanTechnique": "Stripmap"
            },
            {
               "@id": "scansar-mode",
               "scanTechnique": "ScanSAR",
               "numSubSwaths": 2
            }
            ]

            }

# obtain the instrument model instance from the python dict
instru = Instrument.from_dict(specs)

# define the access event (time of observation, position, velocity of observer and position of target)
inc_deg = 30
RE = 6378
h = 600
orb_speed = 7.559
data_metrics = instru.calc_data_metrics(mode_id="stripmap-mode", alt_km=h, sc_speed_kmps=orb_speed, sc_gnd_speed_kmps=orb_speed*(RE/(RE+h)), inc_angle_deg=inc_deg,
                                          instru_look_angle_from_target_inc_angle=True)
print(data_metrics)
>> {'ground pixel along-track resolution [m]': 2.24, 'ground pixel cross-track resolution [m]': 4.8, 'NESZ [dB]': -16.23,
   'incidence angle [deg]': 30.0, 'swath-width [km]': 24.5, 'PRF [Hz]': 6269}


data_metrics = instru.calc_data_metrics(mode_id="scansar-mode", alt_km=h, sc_speed_kmps=orb_speed, sc_gnd_speed_kmps=orb_speed*(RE/(RE+h)), inc_angle_deg=inc_deg,
                                          instru_look_angle_from_target_inc_angle=True)
print(data_metrics)
>> {'ground pixel along-track resolution [m]': 4.48, 'ground pixel cross-track resolution [m]': 4.8, 'NESZ [dB]': -16.03,
    'incidence angle [deg]': 30.0, 'swath-width [km]': 49.1, 'PRF [Hz]': 5996}

API

Classes

instrupy.base — Base

Description

Example

API

`instrupy.base` — Base