HELP · SEE_ALSO
darksum -- Produce a report on dark count calibration spectra.
The darksum task computes various statistics and produces various plots based on dark count calibration data obtain from the Goddard High Resolution Spectrograph (GHRS). This task enables a user to monitor GHRS instrument health by monitoring dark calibration observations.
Calibrated data is used as input to this task, so all results are in count rates. However, if uncalibrated data is specified (i.e., .d0h files are used), results will be in total counts.
Dark count calibration proposals are broken down into sets of related observations (generally 16). Related observations will have similar STSDAS root file names (the first six characters will match). Each observation will generally consist of 7 groups.
darksum combines the results of the darkstat and hstpos tasks to produce a report of how the dark observations went during different portions of HST's orbit. This information is summarized in the tables specified by the group_stats, obs_stats, and total_stats parameters. Summaries of the group_stats table are also produced (in the file beginning with the string "summary_" followed by the root name and the ".txt" extension). The text summary and the tables are written to the directory specified by the summary parameter. If you wish, the task will produce a plot of orbit positions with a title showing the proposal ID and related observation name.
The contents of the tables specified by the parameters events, noisy, and dark are the same as that produced by darkstat. (See the darkstat help file for more information).
The three tables with statistics information will contain the following columns (see also the help files for darkstat and hstpos):
ROOTNAME - Root name of the observation (plus group identifier in group table). For the total table, this contains the first 6 characters of the observation root name. MEAN - Mean count rate for the group, observation, or all observations, depending on if table is for group, obs, or total, respectively. This is count rate unless uncalibrated data is used, in which case it is pure counts. SIGMA - Standard deviation from mean. MAX - Maximum count rate. SELECT_DIODE - Mean of selected diode. (Usually meaningless.) EVENT_RATE - Sum of diodes involved in particle hit. ANTI_COIN - Mean value of anti-coincidence counter. BACKGROUND - Mean value of four background diodes. RADIATION - Mean value of two radiation diodes. TIME - Time of observation (from EXPSTART keyword, if present, else from PKTTIME). For total table, this is taken from first observation in the set. LONGITUDE - Longitude in degrees east of Greenwich at time of observation. First observation in total table. LATITUDE - Latitude north of equator at observation time. First observation for total table. DATE-OBS - Day, month, and year of observation. Taken from TIME column (may not be present in older data). TIME-OBS - Time of observation.
The text file summaries produced by darksum is a printed version of the group_stats table, but only the columns ROOTNAME, MEAN, SIGMA, TIME, LONGITUDE, LATITUDE, DATE-OBS, and TIME-OBS.
When specifying output table names, keep in mind that if a specified table name already exists, new statistics will be appended to the existing data.
- input [file name list]
- Name of the image(s) that contain the science data for the dark count calibrations.
- (summary_dir = "") [file name]
- The directory where the output tables and text files should be placed. When specifying a directory, make sure that the directory separator, either $ or /, ends the name. (Again, if the files already exist, new data will be appended to existing data.)
- (group_stats = "group_stats.tab") [file name]
- Output table name for dark statistics for each group of input data. If the table doesn't exist, it will be created, otherwise data is appended.
- (obs_stats = "obs_stats.tab") [file name]
- Table that will contain the dark statistics for each individual observation of the input data.
- (total_stats = "total_stats.tab") [file name]
- Table that will contain the dark statistics for each set of related observations of the input data.
- (events = "events.tab") [file name]
- Output table for particle hit information
If no table is specified, no data will be written.
- (noisy = "noisy.tab") [file name]
- Output table for noisy data information.
If no table name is specified, no data will be saved.
- (dark = "dark.tab") [file name]
- Table for means of each diode for each observation set.
If no file name is specified, no data will be saved.
- (pthresh = INDEF) [real]
- If used, this represents
the absolute difference between
a diode and the mean for that diode among all the input that
constitutes it a being a victim of a particle hit.
If this parameter is not specified (i.e., value is INDEF), then the pnsig parameter is used.
- (pnsig = 4.) [real]
- If pnsig is specified and pthresh is not specified, this
parameter represents the
number of sigma difference a diode can be from the mean for that diode
among all observations before it is considered the victim of a
If pnsig is not specified (i.e., value is INDEF), no particle hit detection is done.
- (dthresh = INDEF) [real]
- If dthresh is specified, it represents the absolute difference between
the mean value of a diode for all related observations and the mean value of
all diodes for all related observations that constitutes whether the
If this parameter is not specified (i.e., value is INDEF), then dnsig is used.
- (dnsig = 4.) [real]
- If dnsig is specified and dthresh is not specified, it represents the number of sigma difference the mean of a diode for all related observations can be from the mean of all diodes for all related observations before it is considered noisy. If dnsig is not specified (i.e., value is INDEF), then no noisy diode checking is done.
- (plotpos = yes) [boolean]
- Plot HST orbit position?
- (device = "stdgraph") [string]
- Graphics device used to display plots.
- (marker = "box") [string]
- Type of marker used to plot HST position. (See help file for hstpos task for more information.
- (szmarker = 0.01) [real: from to 1]
- Size of the markers in Normalized Device Coordinates (NDC).
- (append = no) [boolean]
- Append new plot to previous plot?
- (verbose = yes) [boolean]
- Display information about particle hits and noisy diodes?
1. Produce a report about dark observations in the current directory.
cl> darksum *.c1h
2. Produce a report about the dark observations in the directory OBS and write the results to the directory summary$dark.
cl> darksum OBS$*.c1h summary=summary$dark/
3. For this set of observations, particle hits are know to have a count rate .4 higher than the mean.
cl> darksum *.c1h pthresh=.4
4. Do not perform particle hit or noisy diode detection.
cl> darksum *.c1h pthresh=indef pnsig=indef dthresh=indef >>> dnsig=indef
5. First determine statistics for a set of observations in directory PROP1 and then append the statistics from observations in directory PROP2.
cl> darksum PROP1$*.c1h cl> darksum PROP2$*.c1h
For assistance using this or any other tasks, please contact email@example.com or call the help desk at 410-338-1082.