# ISC License
#
# Copyright (c) 2016, Autonomous Vehicle Systems Lab, University of Colorado at Boulder
#
# Permission to use, copy, modify, and/or distribute this software for any
# purpose with or without fee is hereby granted, provided that the above
# copyright notice and this permission notice appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
# OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
import os # Don't worry about this, standard stuff plus file discovery
import numpy
from Basilisk.topLevelModules import pyswice
from Basilisk.utilities import RigidBodyKinematics, macros
[docs]
def ckWrite(handle, time, mrp_array, av_array, start_seg, spacecraft_id=-62, reference_frame="J2000"):
"""
Purpose: Creates a CK kernel from a time_array, mrp_array, and an av_array. Assumes that the SCLK is furnshed
.. warning::
time stamps for the time_array, mrp_array, and av_array must line up exactly!!
:param handle: What you would like the CK file to be named. Note, it must be in double quotes and end in .bc, ex: "moikernel.bc"
:param time: numpy array of time stamps in nanoseconds
:param mrp_array: array of modified Rodriguez parameters in column order x, y, z
:param av_array: array of angular velocities about 3 axis in column order x, y, z
:param start_seg: the SCLK time that the file begins at in UTC Gregorian ex: 'FEB 01,2021 12:00:55.9999 (UTC)'
:param spacecraft_id: spacecraft ID ex:-62
:param reference_frame: reference frame ex:"J2000"
:return:
"""
try:
os.remove(handle)
except OSError:
pass
# Open the CK file
file_handle = pyswice.new_spiceIntArray(1)
pyswice.ckopn_c(handle, "my-ckernel", 0, file_handle)
# Create empty containers for time, attitude and angular velocity
num_data_points = len(time)
time_array = pyswice.new_doubleArray(num_data_points)
vel_array = pyswice.new_doubleArray(num_data_points * 3)
quat_array = pyswice.new_doubleArray(num_data_points * 4)
# Find the elapsed seconds between initial time and reference ephemeris
ephemeris_time_container = pyswice.new_doubleArray(1)
pyswice.str2et_c(start_seg, ephemeris_time_container)
ephemeris_time = pyswice.doubleArray_getitem(ephemeris_time_container, 0)
# Convert the initial time to number of spacecraft clock ticks
start_ticks = pyswice.new_doubleArray(1)
pyswice.sce2c_c(spacecraft_id, ephemeris_time, start_ticks)
# Process data for each timestep
for i in range(num_data_points):
# Process the attitude
quat = RigidBodyKinematics.MRP2EP(mrp_array[i, -3:]) # Grab the last 3 elements in case the first column is time
quat[1:4] = - quat[1:4] # Convert to JPL-style quaternions
for j in range(4):
pyswice.doubleArray_setitem(quat_array, (4 * i) + j, quat[j])
# Process the angular velocity
omega = av_array[i, -3:] # Grab the last 3 elements in case the first column is time
for j in range(3):
pyswice.doubleArray_setitem(vel_array, (3 * i) + j, omega[j])
# Process time
current_time = ephemeris_time + time[i] * macros.NANO2SEC # Compute the current time in elapsed seconds from ephemeris
current_ticks = pyswice.new_doubleArray(1)
pyswice.sce2c_c(spacecraft_id, current_time, current_ticks) # Convert from ephemeris seconds to spacecraft clock ticks
pyswice.doubleArray_setitem(time_array, i, pyswice.doubleArray_getitem(current_ticks, 0))
# Get time into usable format
encoded_start_time = pyswice.doubleArray_getitem(time_array, 0) - 1.0e-3 # Pad the beginning for roundoff
encoded_end_time = pyswice.doubleArray_getitem(time_array, num_data_points - 1) + 1.0e-3 # Pad the end for roundoff
# Save the date into a CK file
pyswice.ckw03_c(pyswice.spiceIntArray_getitem(file_handle, 0), encoded_start_time, encoded_end_time, spacecraft_id,
reference_frame, 1, "InertialData", num_data_points, time_array, quat_array, vel_array, 1,
start_ticks)
# Close the CK file
pyswice.ckcls_c(pyswice.spiceIntArray_getitem(file_handle, 0))
[docs]
def ckRead(time, spacecraft_id=-62, reference_frame="J2000"):
"""
Purpose: Read information out of a CK Kernel for a single instance and returns a quaternion array
and an angular velocity array
.. warning::
Assumes that SCLK and CK kernels are already loaded using furnsh because pyswice gets mad when loading the same files over and over again.
:param time: Should be in UTC Gregorian, and passed in as a string, ex: 'FEB 01,2021 14:00:55.9999 (UTC)'
:param spacecraft_id: Spacecraft ID -- Default: -62
:param reference_frame: is a character string which specifies the, reference frame of the segment. Reference Frame, ex: "J2000"
:return: None
"""
# Find the elapsed seconds between initial time and reference ephemeris
ephemeris_time_container = pyswice.new_doubleArray(1)
pyswice.str2et_c(time, ephemeris_time_container)
ephemeris_time = pyswice.doubleArray_getitem(ephemeris_time_container, 0)
# Convert initial time to spacecraft clock tick
tick = pyswice.new_doubleArray(1)
pyswice.sce2c_c(spacecraft_id, ephemeris_time, tick)
# Get attitude and angular velocity for a specified spacecraft clock time
dcm_container = pyswice.new_doubleArray(9)
av_container = pyswice.new_doubleArray(3)
tick_container = pyswice.new_doubleArray(1)
requested_pointing_flag = pyswice.new_spiceBoolArray(1)
pyswice.ckgpav_c(spacecraft_id, pyswice.doubleArray_getitem(tick, 0), 0, reference_frame, dcm_container,
av_container, tick_container, requested_pointing_flag)
# Grab angular velocity
omega = numpy.zeros(3)
for i in range(3):
omega[i] = pyswice.doubleArray_getitem(av_container, i)
# Grab attitude as a DCM
dcm = numpy.zeros((3, 3))
for i in range(9):
dcm[i // 3, i % 3] = pyswice.doubleArray_getitem(dcm_container, i) # Map 9D array into 3x3 matrix
# Convert attitude to quaternions
quat = RigidBodyKinematics.C2EP(dcm)
quat[1:4] = - quat[1:4] # Convert to JPL-style quaternions
return ephemeris_time, quat, omega
def ckInitialize(ck_file_in):
pyswice.furnsh_c(ck_file_in)
def ckClose(ck_file_in):
pyswice.unload_c(ck_file_in)