| obsum | stsdas.hst_calib.hrs | obsum |
obsum -- Print various summaries of GHRS data.
obsum input title
The obsum task prints basic summary information for each group of a GHRS observation, ordered by increasing time when the packet was dumped. The groups are taken from the standard header information (SHP), found in files with the .shh extension, the unique data log (UDL), found in files with the .ulh extension, the extracted data, found in files with the .x0h extension, and the science data, found in files with the .d0h extension.
There are two options. The general order of all data groups produced can be generated with the show_groups = yes parameter. If one is just interested in the science data itself, i.e. a list of raw diode values and various engineering information, one should set the parameter diode = yes.
This tool is also used to determine which GHRS observations may have experienced a maximum Doppler compensation. This is necessary, since a problem with the on-board Doppler compensation was discovered in February, 1993. At the time this help file was originally written (October 1993), the problem was not resolved. In short, the problem was that at periods when the maximum Doppler compensation should be applied, the on-board flight software mistakenly applies NO correction. This situation will last for, at most, 60 seconds during any individual exposure. This task attempts to identify these periods and indicate the length of time that the non-correction occurred. See below for more details.
The output of task obsum is a text summary printed to standard output, i.e., the terminal. This can be redirected to a file using IRAF file redirection. See the EXAMPLES section below.
The text that obsum produces consists of the following:
The first line is the value of the parameter "title".
Next, if the parameter show_groups is "yes", a header line is printed. The fields in the header line are defined below.
Then, for each observation, a line is printed that lists the observation name and the number of groups of each type of data.
For each observation, one line is printed for each group from all the raw data files for that observation. The groups are printed in chronological order. The contents of each line are summarized below.
Fields common to all types of groups are:
TIME -- This is the time when this group was
produced by the instrument.
W11/14 -- For groups from the SHP file, this is the value
of the keyword "w11/14".
ZOBNUM -- 0-indexed counter of the pattern in the current
observation. Each SHP group delimits one complete
pattern taken by the instrument.
PTYPE -- The type of group represented in the current
line of output.
PFC -- The packet format code. For science groups, this
represents the type of science data stored in
the group.
The following fields only apply to science data groups.
SYS -- Which detector is in use. "1" for side 1,
"2" for side 2.
CARPOS -- The carrousel position for the current group.
INTE -- The number of integration periods for the current
group.
COADDS -- The number of coadditions that make up the current
group.
SUM -- Sum of the counts for the current group.
For lines representing SHP groups, the following fields apply:
PINFO -- The encoded proposal number.
DMP_IND -- Always "1".
For lines representing UDL groups, the following field applies:
FINCODE -- Value indicating the success of the observation.
Typical values are:
101 = Start of observation
102 = Successful end of observation.
Any other value indicates the observation had some
type of trouble.
If the parameter doppler is "yes", a check is made for each pattern (or "zobnum") of an observation to see whether it possibly crossed a maximum Doppler compensation point in the orbit. If the current pattern did not cross, nothing extra is printed. However, if the current exposure did cross, the following is indicated
CAL GROUP -- Which group of the calibrated data of
the current observation may be affected.
EXP -- Length of the exposure, in seconds.
OVER -- Extra time the exposure took due to
telescope operations, such as idling.
RSHIFT -- Estimated time, in seconds, the exposure
spent at zero Doppler compensation when it
should have been at maximum redshifted
compensation.
BSHIFT -- Estimated time, in seconds, the exposure
spent at zero Doppler compensation when it
should have been at maximum blueshifted
compensation.
DOPMAG -- The X deflection correction that would be
applied at maximum compensation.
Some notes about the above numbers. With the science data alone, there is no way of getting absolute timings about when events occur on the telescope, especially with events such as idling of the exposure due to Earth occultation of the target. Therefore, the task is designed to overestimate when maximum Doppler occurred and how often it occurred. In general, the following guidelines may be followed. The overhead usually should be about 2 seconds for uninterrupted exposures. In these cases, the rshift or bshift values should be fairly accurate. However, if the overhead time is large, on the order of a couple thousand seconds, then some external event interrupted the observation. In these cases, the time represented by rshift or bshift will be an over-estimation. In fact, due to time needed to re-acquire guide stars after an occultation, the observation may never experience the blue shift maximum, though certain geometries of the orbit plus target can still make this possible.
In short, the Doppler information is meant to be used as a guide to tell the user that a closer examination of the flagged observations is in order.
If the parameter diode is "yes", the following extra output will also be produced. If all the aforementioned parameters are set to "yes", the following will be printed after the doppler information. However, it is generally recommended that if diode = yes, all the other parameters should be set to "no".
The diode output is as follows:
Next, the value of all 512 diodes of the GHRS are printed. Remember that the first and last 6 diodes in the list are the "special diodes", i.e. background, focus, radiation, etc. detectors. The science diodes are number from 7 to 506. At the end of the dump, the total of the science diodes is printed.
Following the dump of the diode values, the following engineering information is printed:
1. Produce a summary of observation Z0Y30102T in the current directory.
cl> obsum z0y30102t
2. Produce a summary of all observations in the directory data$hrs.
cl> obsum data$hrs/*
3. Flag the observations in the current directory for possible maximum Doppler compensation.
cl> obsum * show_groups=no doppler=yes
4. Show all information about all observations in the current directory. Redirect the output to the file "obsum.report".
cl> obsum * doppler=yes > obsum.report
STSDAS Author: Jonathan Eisenhamer
The on-board Doppler compensation problem is described in Addendum 1 of the "Instrument Handbook for the Goddard High Resolution Spectrograph (GHRS)", version 4.1, January 1993, STScI GHRS Team.
The document describing the GHRS is "SI Systems Description and User's Handbook for the High Resolution Spectrograph (GHRS) for the Hubble Space Telescope (HST)", Ball Aerospace, SE-01.
For assistance using this or any other tasks, please contact help@stsci.edu or call the help desk at 410-338-1082.