IFODELAY - find time delay for IFO from source sky location
samp = ifodelay(detID, theta, phi, sampFreq);
detId detector identifier string
cosTheta cosine of source co-declination angle
N.B. only cos(theta) for 0<=theta<=pi supported
phi source longitude in rad
sampFreq sampling frequency of IFO
samp number of samples to ADD for delay
SEE ALSO: GRAVEN, GETIFO0001 function samp = ifodelay(detId, cosTheta, phi, sampFreq) 0002 0003 % IFODELAY - find time delay for IFO from source sky location 0004 % 0005 % samp = ifodelay(detID, theta, phi, sampFreq); 0006 % 0007 % detId detector identifier string 0008 % cosTheta cosine of source co-declination angle 0009 % N.B. only cos(theta) for 0<=theta<=pi supported 0010 % phi source longitude in rad 0011 % sampFreq sampling frequency of IFO 0012 % 0013 % samp number of samples to ADD for delay 0014 % 0015 % SEE ALSO: GRAVEN, GETIFO 0016 0017 % $Id: ifodelay.m,v 1.9 2004/05/12 00:47:22 stuver Exp $ 0018 0019 % Theory: Find the projection of the vector pointing from the center of the 0020 % Earth to the detector onto the GW's unit vector (pointing from the center 0021 % of the Earth to the source's sky location) and convert this into time of 0022 % flight in units of samples. 0023 0024 % CHECK for errors 0025 % GET the WGS-84 X, Y & Z coordinates for detId 0026 % DEFINE the gravitational wave's unit vector from sky location 0027 % DETERMINE the number of samples to add to the start time 0028 0029 samp = []; 0030 0031 errorcheck(detId, cosTheta, phi, sampFreq); 0032 0033 % Get the WGS-84 coordinates for detId 0034 Cordnt = getifo(detId); 0035 % Make sure that Cordnt is not empty 0036 if isempty(Cordnt) 0037 Cordnt 0038 error('ifodelay: getifo returned empty Cordnt') 0039 end 0040 0041 0042 % Define the X, Y & Z WGS-84 coordinates for detId 0043 XIFO = Cordnt.WGS84(1); % m 0044 YIFO = Cordnt.WGS84(2); % m 0045 ZIFO = Cordnt.WGS84(3); % m 0046 0047 % From the given cosine of the source's co-dec to line-of-sight, 0048 % define the sine 0049 sinTheta = sqrt(1-cosTheta.^2); 0050 % N.B. only cos(theta) for 0<=theta<=pi supported 0051 0052 % Define the X, Y & Z coordinates of the GW's sky location 0053 xgw = sinTheta*cos(phi); 0054 ygw = sinTheta*sin(phi); 0055 zgw = cosTheta; 0056 0057 % Define the GW's unit vector 0058 gwhat = sqrt((xgw^2)+(ygw^2)+(zgw^2)); 0059 0060 % Define the speed of light 0061 C0=299792458; % m/s 0062 0063 % Determine the number of samples to add to the start time from the 0064 % definition of dot product, speed of light and sampling frequency 0065 % 0066 % t = -(XIFO*xgw + YIFO*ygw + ZIFO*zgw)/c*gwhat 0067 % samp = t*sampFreq 0068 0069 samp = -(((XIFO*xgw)+(YIFO*ygw)+(ZIFO*zgw))/(C0*gwhat))*sampFreq; 0070 0071 return 0072 0073 % ~~~ END MAIN ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 0074 0075 function errorcheck(detId, cosTheta, phi, sampFreq); 0076 0077 % ERRORCHECK - checks ifodelay's input data for errors and stops the code if 0078 % an error is found 0079 % 0080 % errorcheck(detId, cosTheta, phi, sampFreq) 0081 % 0082 % detId detector identifier string 0083 % cosTheta cosine of source co-declination angle 0084 % phi source longitude in rad 0085 % sampFreq sampling frequency of IFO 0086 0087 % CHECK variables for error 0088 0089 % detId must be a string 0090 if ~strcmp(class(detId), 'char') 0091 detId 0092 error('ifodelay: detId must be a string') 0093 end 0094 0095 % cosTheta must be real and bewteen -1 and 1 0096 if abs(cosTheta) > 1 | ~isreal(cosTheta) 0097 cosTheta 0098 error('ifodelay: cosTheta must be real and bewteen -1 and 1') 0099 end 0100 0101 % phi must be real and between -pi and pi 0102 if phi < -pi | phi > pi | ~isreal(phi) 0103 phi 0104 error('ifodelay: phi must be real and between -pi and pi') 0105 end 0106 0107 % sampFreq must be a real positive number 0108 if sampFreq <= 0 | isinf(sampFreq) | isnan(sampFreq) | ~isreal(sampFreq) 0109 sampFreq 0110 error('ifodelay: sampFreq must be a real finite number > 0') 0111 end 0112 0113 return