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Diffstat (limited to 'src/libcf/cf_fifo_dead_time.c')
| -rw-r--r-- | src/libcf/cf_fifo_dead_time.c | 164 |
1 files changed, 164 insertions, 0 deletions
diff --git a/src/libcf/cf_fifo_dead_time.c b/src/libcf/cf_fifo_dead_time.c new file mode 100644 index 0000000..67ac065 --- /dev/null +++ b/src/libcf/cf_fifo_dead_time.c @@ -0,0 +1,164 @@ +/***************************************************************************** + * 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; +} |