# Ground Station Visibility

Last revised by Z. Ellis on 2026 APR 6

Objectives

This tutorial will demonstrate

See Celestial Bodies

Imports and Set Up

Here we’ll import the necessary libraries and load in the tutorials data folder. Then we define units and frames and load a metakernel for SPICE functionalities.

import scarabaeus as scb
from tutorial_data import tutorial_data

import os
import numpy as np
import matplotlib.pyplot as plt

# load tutorial data
data = tutorial_data.load()

## units, frames, kernels
km, kg, sec, hr = scb.Units.get_units(['km', 'kg', 'sec', 'hr'])
J2000 = scb.Frame('J2000')

# load tutorial meta kernel
scb.SpiceManager.clear_kernels()    # ensure clean kernel pool
scb.SpiceManager.load_kernel_from_mkfile(data.mk)

SCB tutorial data up to date.

Configure Bodies and Propagate Trajectory

Now we’ll have to create an orbiter spacecraft as well as the Earth for it to orbit around.

First we create the Earth using Scarabaeus’ built in constants and attach DSN stations to it using IDs from the NAIF Integer ID Code list:

## configure primary body
# create an empty Earth
earth = scb.CelestialBody.from_constants('EARTH')

# define a few ground stations and attach them to Earth
DSS_14 = scb.GroundStation('DSS-14', 399014)
DSS_15 = scb.GroundStation('DSS-15', 399015)
DSS_24 = scb.GroundStation('DSS-24', 399024)
DSS_34 = scb.GroundStation('DSS-34', 399034)
DSS_54 = scb.GroundStation('DSS-54', 399054)

all_gs = [DSS_14, DSS_15, DSS_24, DSS_34, DSS_54]
earth.add_ground_station(all_gs)

Now we’ll create a simple point mass spacecraft. Since we’re only using Keplerian dynamics, we won’t need to configure anything else for it:

## configure the orbiter spacecraft
# create Spacecraft object
orbiter = scb.Spacecraft(name     = 'ORCCA_ORBITER',
                         spice_id = -1000,
                         tot_mass = scb.ArrayWUnits(2e3, kg))

With both bodies created, we’re ready to set up the propagation. First define the interval we’d like to examine, for this tutorial we’ll look at a week’s worth of passes. Then we’ll create the initial state, placing the Orcca Orbiter in a circular LEO orbit

# define propagation interval
t0 = scb.EpochArray(scb.SpiceManager.cal2et('2026 JAN 01 00:00:00.000'), 'TDB')
tf = scb.EpochArray(scb.SpiceManager.cal2et('2026 JAN 07 00:00:00.000'), 'TDB')
dt = scb.ArrayWUnits(1, hr)

epochs = scb.EpochArray.interval(t0, tf, dt)

# define initial state
R = scb.ArrayWUnits(8e6, km)     #
# v_circ = scb.ArrayWUnits.sqrt(earth.mu, R)
# print(v_circ)
# scb.ArrayWUnits(np.sqrt((earth.grav_param / R).values), km/sec)
earth.grav_param / R

# pos0 = scb.ArrayWFrame(scb.ArrayWUnits([10e6, 0, 0], km    ), J2000)
# vel0 = scb.ArrayWFrame(scb.ArrayWUnits([0   , 7, 0], km/sec), J2000)
# x0   = scb.StateArray(epoch  = t0,
#                       origin = earth,
#                       state  = scb.StateDefinition()
#                                   .position(orbiter, pos0)
#                                   .velocity(orbiter, vel0))

# ## propagate the orbiter
# # define keplerian dynamics, propagator, and propagate
# kep_dyn = scb.ForceModelTranslation(orbiter)
# prop    = scb.Propagator(primary_body = orbiter,
#                          state_vector = x0,
#                          tspan        = epochs,
#                          force_models = kep_dyn)
# prop.propagate()

# ## write trajectory file
# # create directory in tutorial results folder if it doesn't exist yet
# orbit_traj_path = os.path.join(tutorial_data.RESULTS_PATH, 'GS_vis_tut/')
# if not os.path.exists(orbit_traj_path): os.mkdir(orbit_traj_path)

# # write trajectory
# orbit_traj = scb.Trajectory(os.path.join(orbit_traj_path, 'ORCCA_ORBITER_TRAJ'), state_array = prop.propagated_state_array)

0.049825054429511996 km^2/sec^2

Examine Visibility

blah blah

# compute visibility windows for each ground station
# vis_windows, vis_window_nums = {}, {}
# for gs in earth.gs_list:
#     num_windows, windows = scb.SpiceManager.get_observer_target_visibility_windows(
#                                             obsvr_bdy   = gs,
#                                             trgt_bdy    = orbiter,
#                                             epoch_start = epochs[0],
#                                             epoch_end   = epochs[-1],
#                                             step_size   = 60)
#     # save amount of windows and the windows themselves
#     vis_window_nums[gs] = num_windows
#     vis_windows[gs]     = windows

more blah blah

# Plot GSS visiblity
# scb.Plotting.plot_gs_visibility(vis_windows, epochs[0].times.values)
# plt.show()

Conclusion

FILL OUT