HELP · SEE_ALSO
parthitz -- Locate particle events and compute dark rate.
parthitz input eetrailer mask table1 table2 dark
This routine locates particle events and determines the dark rate for the Goddard High Resolution Spectrograph (GHRS) science diodes. Particle events are located by determining the average count rate per diode using all data frames. Particle events are then identified as individual data points where the count rate is greater than a user-specified threshold (i.e., the pthresh parameter) above the average rate for the diode. If pthresh = 0.0, the program computes its value as pnsig times the standard deviation of the count rates for each diode over all frames of data. Consecutive diodes in the same frame that have a count rate above the threshold are considered to be part of the same event.
The dark rate is computed for each diode by averaging rates for all data frames. Points determined to be particle events are not used in the average. Noisy diodes are identified as those diodes having a dark rate greater than dthresh above the average for all diodes. If dthresh = 0.0 then it is computed as dnsig times the standard deviation of the rates of all diodes.
- input [file name template]
- File names of the input dark observations. These observations may be taken either from GHRS accumulated mode, or from direct downlink. The input images should contain the raw data with no further RSDP processing performed.
- eetrailer [file name templates]
- The extracted engineering trailer images for the input observations. These trailer images contain values for the 12 special diodes.
- mask [file name template]
- Optional data quality masks for each observation. If mask images are not specified (i.e., the mask parameter is passed a value of ""), all data are used. If mask files are used, the number of files passed to mask must be equal to the number passed to input.
- table= "events" [file name]
- Name of the output table that is to contain a summary of particle events.
There is one row for each event found. This table will have the following
'TIME' - Time of the event (char*24). 'FRAME' - Frame number in which the event occurred (integer). 'COUNTS' - Total counts in the event (integer). 'DIODES' - Number of consecutive diodes affected by the event (integer). 'FIRST_DIODE' - First diode affected by the event (integer).
- table= "frame_sum" [file name]
- Name of the output table into which to place the frame summary. It
will have one row for each data frame.
(Row numbers in the table correspond to the frame number in the input data
template.) This table contains the following columns:
'TIME' - Frame time (char*24). 'EVENTS' - Number of particle events in the frame (real). 'DIODES' - Number of diodes affected by particle hits (real). 'PCOUNTS' - Total particle event counts (real). 'DARK_RATE' - Average dark rate for the frame (real). 'ANTI_COIN' - Anti-coincidence counter for the frame (real). This value may not be useful for data taken in the accumulation mode. 'RADIATION' - Counts on the radiation diodes (real). 'SELECTED_DIODE'- Count rate of the diode selected by the 'dnum' parameter (real).
- dark = "dark" [file name]
- Name of the output image containing the average dark rate over all frames of data for each diode. It has a length of 500, corresponding to the number of science diodes.
- (pthresh = 0.0) [real]
- This parameter gives the threshold, in counts per second, for identification of particle events. A data point is considered a particle event if its count rate is greater than pthresh above the average count rate for the diode. If pthresh = 0.0, then a threshold is determined for each diode using the value of pnsig.
- (pnsig = 4.0) [real]
- This parameter is used to compute the threshold for each diode for identification of particle events; this parameter is ignored if a threshold is provided to the pthresh parameter. The thresholds are determined as the average count rate over all frames of data plus pnsig times the standard deviation of the count rates over all diodes.
- (dthresh = 0.0) [real]
- This parameter is the threshold in counts per second for identification of noisy diodes. If the average count rate for the diode over all frames of data (excluding particle event data points) is greater than dthresh, the diode is considered as noisy. If dthresh = 0.0, then the threshold is determined using dnsig.
- (dnsig = 4.0) [real]
- This parameter is used to compute the threshold for detection of noisy diodes when dthresh has a zero value. The threshold is set to dnsig times the standard deviation of the dark rate for all diodes.
- (dnum = 0) [integer, min=7, max=506]
- This parameter provides an analysis of an isolated diode; it is the science diode number to be analyzed. If this parameter is used, the average dark rate for the selected diode is displayed and a data set is created giving the dark rate for the diode for each frame of data.
1. Process one observation, darkobs, with an extracted engineering data image darket. The particle event and the noisy diode detection thresholds will be computed using pnsig and dnsig.
hr> parthitz darkobs[*] darket[*]
2. Rerun the task, this time using a particle event threshold of 0.001. Place the results in tables ev1.tab and fs1.tab.
hr> parthitz darkobs[*] darket[*] " " ev1 fs1 pthresh=0.001
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