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Function: detector_site()

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void detector_site(char *detectors_file, int site_choice, float site_parameters[9], char *site_name, char *noise_file, char *whiten_file)
This function calculates the components of the position vector of the central station, and the components of the two vectors that point along the directions of the detector arms (from the central station to each end station), for a given choice of detector site, using information contained in an input data file. This function can also be used to obtain the latitude, longitude, arm orientations, and arm length of a detector site. This function also outputs three character strings that specify the site name, the name of a data file containing the detector noise power information, and the name of a data file containing information about the detector whitening filter, respectively.

The arguments of detector_site() are:

detectors_file: Input. A character string that specifies the name of a data file containing detector site information. This file is most likely the detectors.dat data file described in Sec. [*]. If the file is different from detectors.dat, it must have the same data format as detectors.dat, and it must reside in the directory pointed to by the GRASP_PARAMETERS environment variable (which you may set as you wish). If you want to use the detectors.dat file distributed with GRASP, use a command like:
setenv GRASP_PARAMETERS /usr/local/GRASP/parameters
to point to the directory containing this file. If you want to modify this file (e.g., to add another detector or to add another noise curve), then just copy the detectors.dat file to your own home directory, modify it, and set the GRASP_PARAMETERS environment variable to point to this directory.
site_choice: Input. An integer value used as an index into the input data file. The absolute value of site_choice should be chosen to match the site identification number for one of the detectors contained in this file. The integer can be positive or negative depending on whether the user wants the positions of the end stations (positive), or simply the latitude, longitude, arm orientation and length (negative).
site_parameters: Output. If site_choice was positive, site_parameters[0..8] is an array of nine floating point variables that define the position of the central station of the detector site and the orientation of its two arms. The three-vector site_parameters[0..2] are the $(x,y,z)$ components (in cm) of the position vector of the central station, as measured in a reference frame with the origin at the center of the earth, the $z$-axis exiting the North pole, and the $x$-axis passing out the line of $0^\circ$ longitude. The three-vector site_parameters[3..5] are the $(x,y,z)$ components (in cm) of a vector pointing along the direction of the first arm (from the central station to the end station). The three-vector site_parameters[6..8] are the $(x,y,z)$ components (in cm) of a vector pointing along the direction of the second arm (from the central station to the end station). If site_choice was negative, site_parameters[0] contains the site latitude (degrees north), site_parameters[1] contains the site longitude (degrees west), site_parameters[2] contains the orientation of the first arm (degrees CCW from North), site_parameters[3] contains the orientation of the second arm (degrees CCW from North), and site_parameters[4] contains the armlength (in cm). In this case, the unused elements site_parameters[5..7] are unchanged.
site_name: Output. A character string that specifies a convenient name (e.g., VIRGO or GEO-600) for the chosen detector site.
noise_file: Output. A character string that specifies the name of a data file containing information about the noise power spectrum of the detector. (See Sec. [*] for more details regarding the content and format of this data file.)
whiten_file: Output. A character string that specifies the name of a data file containing information about the spectrum of the whitening filter of the detector. (See Sec. [*] for more details regarding the content and format of this data file.)

detector_site() reads input data from the file specified by detectors_file. This file is searched (linearly from top to bottom) until the absolute value of site_choice matches the site identification number for one of the detectors contained in this file. The site location and orientation information for the chosen detector site are then read into variables local to detector_site(). If site_choice was negative, this information is returned in the array site_parameters[]; otherwise the values contained in the array site_parameters[] are calculated from these input variables using standard equations from spherical analytic geometry. (A correction is made, however, for the oblateness of the earth, using information contained in Ref. [37].) The site_name, noise_file, and whiten_file character strings are simply copied from input data file. If site_choice does not match any of the site identification numbers, detector_site() prints out an error message and aborts execution.

Authors: Bruce Allen, ballen@dirac.phys.uwm.edu, and Joseph Romano, romano@csd.uwm.edu
Comments: None.


next up previous contents
Next: Comment: noise power spectra Up: GRASP Routines: Stochastic background Previous: Data File: detectors.dat   Contents
Bruce Allen 2000-11-19