Target Tracking (With Yaw Compensation)

This tutorial demonstrates how to generate a target tracking profile, aligning with the target velocity direction

Setup

!pip install cesiumpy@git+https://github.com/open-space-collective/cesiumpy

Collecting cesiumpy@ git+https://github.com/open-space-collective/cesiumpy
  Cloning https://github.com/open-space-collective/cesiumpy to /tmp/pip-install-ixu6tl0k/cesiumpy_9ada6a2397f843cf93a2cce86479e06b
  Running command git clone --filter=blob:none --quiet https://github.com/open-space-collective/cesiumpy /tmp/pip-install-ixu6tl0k/cesiumpy_9ada6a2397f843cf93a2cce86479e06b

  Resolved https://github.com/open-space-collective/cesiumpy to commit 7b01ce8826db0a694c3f9b271832e77dcf171923
  Running command git submodule update --init --recursive -q

  Preparing metadata (setup.py) ... ?25l-

 done
?25hRequirement already satisfied: traitlets in /usr/local/lib/python3.11/dist-packages (from cesiumpy@ git+https://github.com/open-space-collective/cesiumpy) (5.14.3)
Requirement already satisfied: geopy>=1.11.0 in /usr/local/lib/python3.11/dist-packages (from cesiumpy@ git+https://github.com/open-space-collective/cesiumpy) (2.4.1)
Requirement already satisfied: geographiclib<3,>=1.52 in /usr/local/lib/python3.11/dist-packages (from geopy>=1.11.0->cesiumpy@ git+https://github.com/open-space-collective/cesiumpy) (2.1)

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[notice] A new release of pip is available: 25.0.1 -> 25.3
[notice] To update, run: python3.11 -m pip install --upgrade pip

import os
import cesiumpy

from ostk.mathematics.object import RealInterval

from ostk.physics import Environment
from ostk.physics.unit import Length
from ostk.physics.unit import Angle
from ostk.physics.time import Scale
from ostk.physics.time import Instant
from ostk.physics.time import Duration
from ostk.physics.time import Interval
from ostk.physics.time import DateTime
from ostk.physics.time import Time
from ostk.physics.coordinate import Position
from ostk.physics.coordinate.spherical import LLA

from ostk.astrodynamics import Trajectory
from ostk.astrodynamics.trajectory import Orbit
from ostk.astrodynamics.flight import Profile
from ostk.astrodynamics.access import Generator as AccessGenerator
from ostk.astrodynamics.access import AccessTarget
from ostk.astrodynamics.access import VisibilityCriterion
from ostk.astrodynamics.viewer import Viewer
from ostk.astrodynamics.viewer import ConicSensor

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Computation

Initialize an environment:

environment = Environment.default(True)
earth = environment.access_celestial_object_with_name("Earth")

Construct an orbit:

orbit = Orbit.sun_synchronous(
    epoch=Instant.date_time(DateTime(2024, 1, 1, 0, 0, 0), Scale.UTC),
    altitude=Length.kilometers(550.0),
    local_time_at_descending_node=Time(14, 30, 0),
    celestial_object=earth,
)

Define an interval of interest:

interval = Interval.closed(
    start_instant=Instant.date_time(DateTime(2024, 2, 9, 0, 0, 0), Scale.UTC),
    end_instant=Instant.date_time(DateTime(2024, 2, 10, 0, 0, 0), Scale.UTC),
)

Define the coordinates of the target to track:

start_lla = LLA(
    latitude=Angle.degrees(0.0),
    longitude=Angle.degrees(0.0),
    altitude=Length.meters(0.0),
)
end_lla = LLA(
    latitude=Angle.degrees(0.5),
    longitude=Angle.degrees(0.1),
    altitude=Length.meters(0.0),
)
mid_lla = start_lla.calculate_intermediate_to(end_lla, 0.5)

Find one access during which the satellite is over the target:

visibility_criterion = VisibilityCriterion.from_aer_interval(
    azimuth_interval=RealInterval.closed(0.0, 360.0),
    elevation_interval=RealInterval.closed(60.0, 90.0),
    range_interval=RealInterval.closed(0.0, 10000e3),
)
access_target = AccessTarget.from_lla(
    visibility_criterion=visibility_criterion,
    lla=mid_lla,
    celestial=earth,
)
access_generator = AccessGenerator(
    environment=environment,
)

accesses = access_generator.compute_accesses(
    interval=interval,
    access_target=access_target,
    to_trajectory=orbit,
)

access = accesses[0]

instants = access.get_interval().generate_grid(Duration.seconds(1.0))

Construct a Vehicle Velocity, Local Horizontal (VVLH) frame from the orbit:

vvlh_frame = orbit.get_orbital_frame(Orbit.FrameType.VVLH)

Generate a flight profile:

line_scan_trajectory = Trajectory.ground_strip(
    start_lla=start_lla,
    end_lla=end_lla,
    instants=instants,
)

/tmp/ipykernel_2824/2653645553.py:1: DeprecationWarning: Use Trajectory(model=TargetScan(...)) instead.
  line_scan_trajectory = Trajectory.ground_strip(

uncompensated_profile = Profile.custom_pointing(
    orbit=orbit,
    alignment_target=Profile.TrajectoryTarget.target_position(
        trajectory=line_scan_trajectory,
        axis=Profile.Axis.Z,
    ),
    clocking_target=Profile.Target(
        type=Profile.TargetType.VelocityECI,
        axis=Profile.Axis.X,
    ),
)

yaw_compensated_profile = Profile.custom_pointing(
    orbit=orbit,
    alignment_target=Profile.TrajectoryTarget.target_position(
        trajectory=line_scan_trajectory,
        axis=Profile.Axis.Z,
    ),
    clocking_target=Profile.TrajectoryTarget.target_velocity(
        trajectory=line_scan_trajectory,
        axis=Profile.Axis.X,
    ),
)

Visualize the scene in 3D:

# Get a token from https://cesium.com/learn/ion/cesium-ion-access-tokens/
viewer = Viewer(
    interval=access.get_interval(),
    cesium_token=os.environ.get("CESIUM_TOKEN"),
)

viewer.add_profile(
    profile=yaw_compensated_profile,
    step=Duration.seconds(10.0),
    show_orbital_track=True,
    cesium_asset_id=669199,
    sensors=[
        ConicSensor(
            "Boresight",
            [0.0, 0.0, 1.0],
            cesiumpy.color.RED.with_alpha(0.5),
            Angle.degrees(0.5),
            Length.meters(6913000.0),
        )
    ],
)

viewer.add_line(
    positions=[Position.from_lla(lla) for lla in LLA.linspace(start_lla, end_lla, 100)]
)

with open("render.html", "w") as f:
    f.write(viewer.render())

---