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/*****************************************************************************
* Johns Hopkins University
* Center For Astrophysical Sciences
* FUSE
*****************************************************************************
*
* Synopsis: cf_fifo_dead_time(fitsfile *header, long nevents,
* float *ptime, long nseconds, float *ttime, float *aic_rate,
* float *ids_dtc)
*
* Description: Searches high-count-rate observations for data drop-outs
* due to FIFO overflows. If found, calculates time-dependent
* scale factor to correct for lost photon events.
*
* Arguments: fitsfile *header Pointer to FITS file containing the
* header of the intermediate data file
* long nevents Number of photon events in the file
* float *ptime Detection time for each photon
* long nseconds The number of timeline values
* float *ttime Tabulated times in the timeline
* float *aic_rate Active Image Counter array
* float *ids_dtc IDS dead-time correction array
* (modified)
*
* Calls:
*
* Return: 0 on success
*
* History of cf_screen_fifo_overflow:
*
* 02/10/04 1.1 wvd Begin work
* 02/17/05 1.2 wvd Place parentheses around assignment
* used as truth value.
* 11/09/05 1.3 wvd In the current scheme, the rate_lif
* and rate_sic arrays contain values
* from the housekeeping file and do
* not reflect data loss due to FIFO
* overflows. Now we calculate the
* count-rate array directly from the
* photon time array.
* 02/23/06 1.4 wvd Change length of data_rate array
* from nevents to nseconds.
*
* History: 12/29/06 1.1 wvd Derived from cf_screen_fifo_overflow.
* 01/15/07 1.2 wvd When count rate is zero, correct one
* second before to two seconds after.
* 02/08/07 1.3 wvd If TTPERIOD = 0, set it to 1.
* 04/07/07 1.4 wvd Clean up compiler warnings.
*
****************************************************************************/
#include <stdlib.h>
#include "calfuse.h"
int
compute_count_rate(long nevents, float *ptime, long nseconds,
float *ttime, long **data_rate)
{
float delta_max = 1.0 + FRAME_TOLERANCE;
long j,k;
*data_rate = (long *) cf_calloc(nseconds, sizeof(long));
for (j=k=0; j<nevents; j++) {
while(ttime[k+1]-FRAME_TOLERANCE < ptime[j] && k+1 < nseconds) k++;
if ((ptime[j] - ttime[k]) < delta_max) (*data_rate)[k]++;
}
return 0;
}
int
cf_fifo_dead_time(fitsfile *header, long nevents, float *ptime,
long nseconds, float *ttime, float *aic_rate, float *ids_dtc)
{
char CF_PRGM_ID[] = "cf_fifo_dead_time";
char CF_VER_NUM[] = "1.4";
char elecfile[FLEN_VALUE];
int errflg=0, status=0;
int fifo_drain_rate;
int *flag_array, found_drop_out = FALSE;
long *data_rate, k;
float mean_ids_rate, ttperiod;
float mean_ids_dtc;
fitsfile *elecfits;
/* Exit if data were obtained in HIST mode. */
cf_error_init(CF_PRGM_ID, CF_VER_NUM, stderr);
cf_timestamp(CF_PRGM_ID, CF_VER_NUM, "Begin Processing");
if ((errflg = cf_proc_check(header, CF_PRGM_ID))) return errflg;
/* Read IDS drain rate from calibration file. */
FITS_read_key(header, TSTRING, "ELEC_CAL", elecfile, NULL, &status);
FITS_open_file(&elecfits, cf_cal_file(elecfile), READONLY, &status);
FITS_read_key(elecfits, TINT, "FIFO_DRN", &fifo_drain_rate, NULL, &status);
FITS_close_file(elecfits, &status);
cf_verbose(4, "fifo_drain_rate = %d", fifo_drain_rate);
/* Read interval between time stamps. */
FITS_read_key(header, TFLOAT, "TTPERIOD", &ttperiod, NULL, &status);
if (ttperiod < 1E-6) ttperiod = 1.0;
/* Compute mean IDS count rate. */
mean_ids_rate = 0.;
for (k=0; k<nseconds; k++)
mean_ids_rate += aic_rate[k];
mean_ids_rate /= nseconds;
mean_ids_rate += 1./ttperiod;
cf_verbose(4, "mean_ids_rate = %f", mean_ids_rate);
/* If mean IDS count rate > 3200, look for data drop-outs. */
if (mean_ids_rate > 3200 && nseconds > 4) {
compute_count_rate(nevents, ptime, nseconds, ttime, &data_rate);
flag_array = (int *) cf_calloc(nseconds, sizeof(int));
/* If count rate goes to zero, set flag_array. Where possible,
set flags from one second before to two seconds after. */
for (k=0; k<1; k++) if (data_rate[k] == 0)
flag_array[k] = flag_array[k+1] = flag_array[k+2] = TRUE;
for ( ; k<nseconds-2; k++) if (data_rate[k] == 0)
flag_array[k-1] = flag_array[k] = flag_array[k+1] =
flag_array[k+2] = TRUE;
for ( ; k<nseconds-1; k++) if (data_rate[k] == 0)
flag_array[k-1] = flag_array[k] = flag_array[k+1] = TRUE;
for ( ; k<nseconds; k++) if (data_rate[k] == 0)
flag_array[k-1] = flag_array[k] = TRUE;
for (k=0; k<nseconds; k++) if (data_rate[k] == 0) {
found_drop_out = TRUE;
break;
}
/* If there are any drop-outs, modify IDS dead-time correction. */
if (found_drop_out)
for ( ; k < nseconds; k++) if (flag_array[k])
ids_dtc[k] = (aic_rate[k] - 1./ttperiod) / fifo_drain_rate;
free(data_rate);
free(flag_array);
}
/*
* Calculate mean dead-time correction. Write to file header.
*/
if (found_drop_out) {
mean_ids_dtc = 0;
for (k = 0; k < nseconds; k++) mean_ids_dtc += ids_dtc[k];
mean_ids_dtc /= nseconds;
cf_verbose(1, "IDS FIFO overflow detected.");
cf_verbose(2, "Modified mean IDS dead-time correction: %f",
mean_ids_dtc);
FITS_update_key(header, TFLOAT, "IDS_DEAD", &mean_ids_dtc, NULL,
&status);
}
/*
* Clean up and go home.
*/
cf_proc_update(header, CF_PRGM_ID, "COMPLETE");
cf_timestamp(CF_PRGM_ID, CF_VER_NUM, "Done processing");
return 0;
}
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