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Oliver Bock authoredOliver Bock authored
antenna.cpp 12.96 KiB
// Copyright Bruce Allen 2017
// Compile with gcc -o antenna antenna.c -lm
// REMAINING THINGS TO CHECK:
// (a) sign conventions for h, which arm is positive
// (b) direction and origin conventions for the polarization axis
// (c) double check the hand calculations
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <strings.h>
// Structure for passing information about the GW source and detectors
struct InputStruct {
// orbital orientation in degrees, 0 to 180. Zero degrees has
// orbital angular momentum pointing to the earth
double iota;
// orientation of long axis of ellipse, 0 to 360, in degrees CCW
// from North
double psi;
// orientation of detector arms away from actual, 0 to 360, in
// degrees CCW when viewed from directly overhead
// Ordering is LLO, LHO, VIRGO
double orientation[3];
};
// Structure for returning information about the response. The array
// elements are in the order LLO, LHO, VIRGO
struct OutputStruct {
// amplitude of sin function, dimensionless
double amp[3];
// phase of sin function, in degrees from 0 to 360
double phase[3];
// time delays, in milliseconds
double dt[3];
};
// Global variables for passing information. Ugly style but doesn't
// matter for this!
struct InputStruct inputdata;
// For converting degrees to radians
const double deg_to_rad = M_PI/180.0;
// For computing arrival time delays, need mean radius of the earth in
// milliseconds. Get this by dividing radius in km by speed of light in
// km/s.
const double radius_earth = 6371.0*1000.0/299792.458;
// Event time
// GPS 1187008882
// UTC: Thu 2017 Aug 17 12:41:04
// Julian Day 2457983.02852
// Modified Julian Day 57982.52852
// The convention in this code is that Lattitude is measured north of
// the equator. So Lattitude -10 means 10 degrees SOUTH of the
// equator. Longitude is measured East of Greenwich. So longitude
// -90 means 90 degrees West of Greenwich (somewhere in the USA).
// Galaxy NGC 4993 (from Wikipedia):
// Right ascension: 13h 09m 47.2s
// Declination: −23° 23′ 4″
// We will need to convert this to location over the Earth at the
// event time. It will turn out to be:
// Lattitude −23.3844 degrees (south of equator)
// Longitude 41.092981 degrees (east of Greenwich)