chandra_maneuver

chandra_maneuver.maneuver.NSM_attitude(att, time)

Calculate the closest normal sun mode attitude for the specified starting attitude att and time.

Parameters:

• att – attitude that can initialize a Quat()

• time – time in a valid Chandra.Time format

Returns:

NSM attitude quaternion

Return type:

Quat

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

Calculate the maneuver profile of the spacecraft and return 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.

Example usage:

>>> 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])

Parameters:

• att1 – initial attitude (Quat, 3 element RA,Dec,Roll, or 4 element quaternion)

• att2 – final attitude (Quat, 3 element RA,Dec,Roll, or 4 element quaternion)

• step – time separation of returned attitudes (seconds)

• tstart – maneuver start time (CxoTime compatible)

• exact_steps – use the exact time step

Return type:

numpy.recarray [ time, q1, q2, q3, q4, pitch]

chandra_maneuver.maneuver.duration(att1, att2)

Calculate the duration of a maneuver.

Example usage:

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

Parameters:

• att1 – initial attitude (Quat, 3 element RA,Dec,Roll, or 4 element quaternion)

• att2 – final attitude (Quat, 3 element RA,Dec,Roll, or 4 element quaternion)

Return type:

float seconds

chandra_maneuver.maneuver.get_eigenaxis(A)

Calculate the rotation eigenaxis from first three components of quaternion A

Parameters:

A – quaternion as a 4 element numpy

Return type:

3 element numpy

chandra_maneuver.maneuver.get_quaternions(atts)

Get a list of quaternions from the specified atts attitudes.

Parameters:

atts – recarray of the attitudes, times and pitches

Returns:

list of corresponding Quat objects

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

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:

• atts – recarray of the attitudes, times and pitches

• att_err – initial attitude error (roll, pitch, yaw in arcsec)

• bias_err – bias error (roll, pitch, yaw in arcsec/sec)

Returns:

recarray array of the attitudes, times and pitches

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

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

Parameters:

• delta –

• J –

• eps –

• tau –

• s – time array

Return type:

tuple (phi, dphi, d2phi)

chandra_maneuver.maneuver.profile(q_init, q_final)

Calculate the parameters/profile of a maneuver, given initial and final attitude quaternions

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