Actuator (pyoof.actuator)

Introduction

This is a developer sub-package. The purpose of actuator is to provide tools for telescopes that have included in their structure an active surface control system. An active system has a model to correct for gravitational deformations, what we propose here is to use the results from fit_zpoly (out-of-focus holography) to compute such model and return the required corrections to apply to every actuator in the active surface, and hence improve the telescope’s sensitivity.

The current sub-package only contains corrections for the Effelsberg telescope in the class EffelsbergActuator, future versions will expand this to other types of active surface.

Active surface at the Effelsberg telescope

To use the actuator is simple, first let’s take a look at the active surface control system and its look-up table at the Effelsberg telescope.

import matplotlib.pyplot as plt
from astropy import units as u
from pyoof.actuator import EffelsbergActuator

ae = EffelsbergActuator(
    frequency=34.75 * u.GHz,  # obs frequency
    nrot=1,                   # convention parameter
    sign=-1,                  # convention parameter
    order=5,                  # Polynomial order
    sr=3.25 * u.m,            # Sub-reflector radius
    pr=50 * u.m,              # Primary reflector radius
    resolution=1000           # Phase-error map resolution
    )

fig = ae.plot()
plt.show()

(Source code, png, hires.png, pdf)

The following table is the transformation from the actuator space (in micrometer displacement) to the phase-error space. Notice that nrot and sign are important parameters to be defined. Several tests at the Effelsberg telescope lead us to find those values.

Reference/API

pyoof.actuator Package

This sub-package contains tools to transform the telescope phase (as an optical system) to an equivalent phase in terms of an active surface control system that can correct such deformations using actuator displacement.

Classes

EffelsbergActuator([frequency, nrot, sign, …])

Several tasks for the Effelsberg telescope and the active surface control system located in the 6.5 m sub-reflector.