Commit 0ca51fa7 by Gregory Ashton

### Adds method to calculate frequency range of signal

parent 286b576c
 ... ... @@ -3,4 +3,5 @@ from __future__ import division as _division from .core import BaseSearchClass, ComputeFstat, Writer, SemiCoherentSearch, SemiCoherentGlitchSearch from .mcmc_based_searches import MCMCSearch, MCMCGlitchSearch, MCMCSemiCoherentSearch, MCMCFollowUpSearch, MCMCTransientSearch from .grid_based_searches import GridSearch, GridUniformPriorSearch, GridGlitchSearch, FrequencySlidingWindow from .injection_helper_functions import get_frequency_range_of_signal
 """ Code used with permissision from Sylvia Zhu to calculate the range in frequency space that a signal occupies due to spindown and Doppler modulations """ import numpy as np from astropy import units as u from astropy.coordinates import SkyCoord from astropy.time import Time # Assume Earth goes around Sun in a non-wobbling circle at constant speed; # Still take the zero longitude to be the Earth's position during the March # equinox, or March 20. # Each day the Earth moves 2*pi/365 radians around its orbit. def _eqToEcl(alpha, delta): source = SkyCoord(alpha*u.radian, delta*u.radian, frame='gcrs') out = source.transform_to('geocentrictrueecliptic') return np.array([out.lon.radian, out.lat.radian]) def _eclToEq(lon, lat): source = SkyCoord(lon*u.radian, lat*u.radian, frame='geocentrictrueecliptic') out = source.transform_to('gcrs') return np.array([out.ra.radian, out.dec.radian]) def _calcDopplerWings( s_freq, s_alpha, s_delta, lonStart, lonStop, numTimes=100): e_longitudes = np.linspace(lonStart, lonStop, numTimes) v_over_c = 1e-4 s_lon, s_lat = _eqToEcl(s_alpha, s_delta) vertical = s_lat horizontals = s_lon - e_longitudes dopplerShifts = s_freq * np.sin(horizontals) * np.cos(vertical) * v_over_c return np.amin(dopplerShifts), np.amax(dopplerShifts) def _calcSpindownWings(freq, fdot, minStartTime, maxStartTime): timespan = maxStartTime - minStartTime return 0.5 * timespan * np.abs(fdot) * np.array([-1, 1]) def get_frequency_range_of_signal(F0, F1, Alpha, Delta, minStartTime, maxStartTime): """ Calculate the frequency range that a signal will occupy Parameters ---------- F0, F1, Alpha, Delta: float Frequency, derivative, and sky position for the signal (all angles in radians) minStartTime, maxStartTime: float GPS time of the start and end of the data span Returns ------- [Fmin, Fmax]: array The minimum and maximum frequency span """ YEAR_IN_DAYS = 365.25 tEquinox = 79 minStartTime_t = Time(minStartTime, format='gps').to_datetime().timetuple() maxStartTime_t = Time(minStartTime, format='gps').to_datetime().timetuple() tStart_days = minStartTime_t.tm_yday - tEquinox tStop_days = maxStartTime_t.tm_yday - tEquinox tStop_days += (maxStartTime_t.tm_year-minStartTime_t.tm_year)*YEAR_IN_DAYS tStart_days = 280 - tEquinox # 7 October is day 280 in a non leap year tStop_days = 19 + YEAR_IN_DAYS - tEquinox # the next year lonStart = 2*np.pi*tStart_days/YEAR_IN_DAYS - np.pi lonStop = 2*np.pi*tStop_days/YEAR_IN_DAYS - np.pi dopplerWings = _calcDopplerWings(F0, Alpha, Delta, lonStart, lonStop) spindownWings = _calcSpindownWings(F0, F1, minStartTime, maxStartTime) return np.array([F0, F0]) + dopplerWings + spindownWings
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment