`chandra_maneuver`¶

class chandra_maneuver.maneuver.ManeuverProfile(duration: float, max_ang_accel: float, max_ang_vel: float, time_max_ang_vel: float, quat: ndarray, angle: float)¶

Parameters for a spacecraft maneuver.

Attributes¶

durationfloat: Duration of maneuver in seconds
max_ang_accelfloat: Maximum angular acceleration in rad/sec**3 (MAYBE)
max_ang_velfloat: Maximum angular velocity in rad/sec (MAYBE)
time_max_ang_velfloat: Time at which maximum angular velocity occurs in seconds (MAYBE)
quatnp.ndarray: 4-element ndarray representing q_final / q_init which defines the maneuver quaternion
anglefloat: Maneuver angle in degrees

angle: float¶: Alias for field number 5

duration: float¶: Alias for field number 0

max_ang_accel: float¶: Alias for field number 1

max_ang_vel: float¶: Alias for field number 2

quat: ndarray¶: Alias for field number 4

time_max_ang_vel: float¶: Alias for field number 3

chandra_maneuver.maneuver.NSM_attitude(att, time) → Quat¶

Calculate the closest NSM attitude for 90 deg pitch from starting attitude.

This function is DEPRECATED. Use ska_sun.get_nsm_attitude() instead.

Parameters¶

attQuat: Attitude that can initialize a Quat().
timeCxoTimeLike: Time in a valid Chandra.Time format.

Returns¶

Quat: NSM attitude quaternion.

chandra_maneuver.maneuver.attitudes(att1, att2, step=300, tstart=0, exact_steps=False)¶

Determine attitudes in a maneuver from att1 to att2.

This calculate the maneuver profile of the spacecraft and returns time, attitude quaternions, and sun pitch.

By default the time steps are calculated to be the closest possible to the specified step while maintaining an even spacing between the start and end of the maneuver. If exact_steps is True then the time steps are exactly as specified and there will be one uneven step at the end.

Parameters¶

att1QuatLike: Initial attitude (Quat, 3 element RA,Dec,Roll, or 4 element quaternion)
att2QuatLike: Final attitude (Quat, 3 element RA,Dec,Roll, or 4 element quaternion)
stepfloat, optional: Time separation of returned attitudes (seconds), by default 300
tstartCxoTimeLike, optional: Maneuver start time (CxoTime compatible), by default 0
exact_stepsbool, optional: Use the exact time step, by default False

Returns¶

numpy.recarray: Record array with fields: time, q1, q2, q3, q4, pitch, off_nom_roll

Examples¶

>>> import chandra_maneuver
>>> atts = chandra_maneuver.attitudes((0,0,0), (10,20,30))
>>> atts.pitch
array([ 79.64483   ,  81.90894478,  89.10262574,  95.10617367,  96.57590726])
>>> atts.q1
array([ 0.        ,  0.03083816,  0.13619809,  0.23923962,  0.26853582])

chandra_maneuver.maneuver.duration(att1, att2)¶

Calculate the duration of a maneuver.

This is a thin wrapper around the get_maneuver_profile function which is preferred for application code. This function is provided for backward compatibility.

Parameters¶

att1QuatLike: Initial attitude (Quat, 3 element RA,Dec,Roll, or 4 element quaternion)
att2QuatLike: Final attitude (Quat, 3 element RA,Dec,Roll, or 4 element quaternion)

Returns¶

float: Duration of maneuver in seconds

Examples¶

>>> import chandra_maneuver
>>> chandra_maneuver.duration((0,0,0), (20,20,20))
1141.4469982300088

chandra_maneuver.maneuver.get_aberration_correction(q1, q2, time, use_cheta_ephem=False, definitive_ephem=False, include_chandra=False)¶

Calculate the aberration correction of the maneuver from q1 to q2 starting at time.

In the FOT matlab tools, this is called aberration error. The matlab code to calculate these values uses only the Sun/Earth ephemeris (equivalent to include_chandra=False) and the calculated values from the FOT matlab tools are included in the products ManErr file in the columns aber-X, aber-Y, and aber-Z.

This method includes an option to use either the DE432 ephemeris or cheta ephemeris data (the use_cheta_ephem kwarg). Use of the cheta ephemeris data also allows the user to include Chandra’s velocity (via the include_chandra kwarg). Calculating the aberration correction without including Chandra’s velocity is less accurate at a level of around 25%.

With regard to signs, the Ska centroid_report code applies a “correction” for aberration to the one shot values by subtracting the pitch and yaw aber values from the kadi maneuver event one shot pitch and yaw values - that is:

one_shot_pitch_aberr_corrected = manvr_event.one_shot_pitch - aber.pitch
one_shot_yaw_aberr_corrected = manvr_event.one_shot_yaw - aber.yaw

Parameters¶

q1array or Quat: Quaternion representing the initial attitude.
q2array or Quat: Quaternion representing the final attitude.
timeCxoTimeLike: Start time of the maneuver.
use_cheta_ephembool: If True, use the Cheta ephemeris data. If False, use the chandra_aca copy of the DE432 ephemeris. Default is False.
definitive_ephembool: If True, use the definitive cheta ephemeris data. If False, use the predictive cheta ephemeris data. Default is False.
include_chandra: bool: If True, include Chandra velocity in the aberration calculation. Default is False. Note that this may only be set to True if use_cheta_ephem is also True. And note that the calculation without including Chandra’s velocity is less accurate at a level of around 25%.

Returns¶

aberration_correctionNamedTuple: Aberration correction with fields roll, pitch, and yaw in arcseconds.

chandra_maneuver.maneuver.get_eigenaxis(A)¶

Calculate the rotation eigenaxis from first three components of quaternion A.

Parameters¶

Anumpy.ndarray: Quaternion as a 4 element numpy array.

Returns¶

numpy.ndarray: 3 element numpy array.

Calculate maneuver parameters/profile for initial and final attitude quaternions.

Parameters¶

att1QuatLike: Initial attitude (Quat, 3 element RA,Dec,Roll, or 4 element quaternion)
att2QuatLike: Final attitude (Quat, 3 element RA,Dec,Roll, or 4 element quaternion)

Returns¶

ManeuverProfile: Named tuple containing maneuver parameters: - duration: Duration of maneuver in seconds - max_ang_accel: Maximum angular acceleration in rad/sec**3 - max_ang_vel: Maximum angular velocity in rad/sec - time_max_ang_vel: Time at which maximum angular velocity occurs in seconds - quat: 4-element ndarray representing q_final / q_init - angle: Maneuver angle in degrees

chandra_maneuver.maneuver.get_quaternions(atts)¶

Get a list of quaternions from the specified atts attitudes.

Parameters¶

attsnumpy.recarray: Recarray of the attitudes, times and pitches

Returns¶

list: List of corresponding Quat objects

chandra_maneuver.maneuver.inject_errors(atts, att_err, bias_err)¶

Inject errors into atts.

Inject errors into atts corresponding to an initial attitude error att_err and bias error bias_err.

The bias_err input can have shape (3, len(atts)) to allow for a time varying bias error.

Parameters¶

attsnumpy.recarray: Recarray of the attitudes, times and pitches
att_errarray_like: Initial attitude error (roll, pitch, yaw in arcsec)
bias_errarray_like: Bias error (roll, pitch, yaw in arcsec/sec)

Returns¶

numpy.recarray: Recarray array of the attitudes, times and pitches

chandra_maneuver.maneuver.make_phi_dphi(delta, J, eps, tau, s)¶

Calculate the maneuver phi and dphi and the segments of a maneuver.

Given a time array, the maneuver parameters, and a unit vector, calculate the maneuver phi and dphi in the different segments of the maneuver

Parameters¶

deltafloat: Maneuver parameter delta
Jfloat: Maneuver parameter J
epsfloat: Maneuver parameter eps
taufloat: Maneuver parameter tau
snumpy.ndarray: Time array

Returns¶

tuple: Tuple containing (phi, dphi, d2phi)

chandra_maneuver.maneuver.profile(q_init, q_final)¶

Calculate maneuver parameters/profile for initial and final attitude quaternions.

This is for internal use only. Application code should use the get_maneuver_profile function instead.

Parameters¶

q_initQuat, 3 element RA,Dec,Roll, or 4 element quaternion: Initial quaternion
q_finalQuat, 3 element RA,Dec,Roll, or 4 element quaternion: Final quaternion

Returns¶

Tmfloat: Duration of maneuver in seconds
Jfloat: Maximum angular acceleration in rad/sec**3 (MAYBE)
epsfloat: Maximum angular velocity in rad/sec (MAYBE)
taufloat: Time at which maximum angular velocity occurs in seconds (MAYBE)
manvr_quat4-element ndarray: q_final / q_init which defines the maneuver quaternion

chandra_maneuver.maneuver.velocity_earth_wrt_sun(time)¶

Get the velocity of the Earth with respect to the Sun at a given time.

The velocity is returned in km/s.

Parameters¶

time: CxoTimeLike: Time in a valid Cxotime format

Returns¶

vel_km_snp.array: Vector velocity of the Earth with respect to the Sun in km/s.

chandra_maneuver.maneuver.velocity_wrt_sun_cheta(time, definitive=False, include_chandra=True)¶

Get the velocity with respect to the Sun at a given time.

This uses the Cheta ephemeris data.

Parameters¶

timeCxoTimeLike: Time in a valid CxoTime format.
definitivebool: If True, use the definitive ephemeris data. If False, use the predictive ephemeris data. Default is False.
include_chandrabool: If True, include the Chandra orbit ephemeris data. If False, do not include the Chandra orbit ephemeris. Default is True.

Returns¶

vel_km_snp.array: x, y, z velocity with respect to the Sun in km/s. If include_chandra is True, this includes the Chandra orbit velocity otherwise it is just the Earth velocity with respect to the Sun.

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`chandra_maneuver`¶