HELP · SEE_ALSO
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:
- S. C. TIME
- This is the packet time when the science group was dumped from the spacecraft. This is the same value as found in the header keyword "PKTTIME".
- The number of segments containing fill data. This is the same value as found in the header keyword "FILLCNT".
- The number of errors in the data. This is the same value as found in the header keyword "ERRCNT".
- The Rootname of the observation being examined.
- The packet format code representing the type of data in the science file. This is the save value as found in the header keyword "PKTFMT".
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:
- "50MS CNTR"
- The 50 millisecond counter value.
- The On-The-Fly-Adder value.
- The next three fields represent the state of the anticoincidence
- The number of anticoincidence events encountered.
- The anticoincidence threshold.
- The analog noise sum flag. "1" if set.
- Flag indicating whether the anticoincidence circuit is enabled. "1" if enabled.
- The detector system in use, "1" or "2" for side 1 or side 2 respectively.
- The following values indicate the state of the test pulse hardware.
- The test pulse address.
- Flag indicating whether the test pulse circuit is enabled. "1" if enabled.
- Flag indicating whether the Digicon window heater is on. "1" if on.
- Flag indicating whether the threshold latch is enabled. "1" if enabled.
- The following values indicate the state of the carrousel.
- The carrousel position.
- State of the carrousel. The possible states are:
- Carrousel is "greater than" the commanded position.
- Carrousel is "equal to" the commanded position.
- Carrousel is "less than" the commanded position.
- Flag indicating whether the carrousel has achieved fine track lock. "1" if true.
- Position of the aperture shutter. It can have the following values:
- Shutter is closed.
- Shutter is open.
- The following indicate the state of the internal lamps.
- Lamp power relay 1 is on. "1" is on.
- Lamp power relay 2 is on. "1" is on.
- Spectral calibration lamp 1 relay on. "1" is on.
- Spectral calibration lamp 2 relay on. "1" is on.
- Flat field lamp relay on. "1" is on.
- HOR DFL
- The horizontal position commanded.
- VER DFL
- The vertical position commanded.
- The tweaking coil current level commanded.
- INT TIME
- The integration time commanded.
- The number of times the data has been co-added to this bin for normal science data. "-2" for field map data. "0" for direct downlink/rapid readout.
- input [file name]
- An observation template specification. Any file template specifying an observation or set of observations may be specified. It is not necessary to specify extensions.
- title [string]
- A one-line summary of why this report is being generated.
- (show_groups = yes) [boolean]
- If set to "yes", a line will be output for each group of the .shp, .udl, and raw science files of each observation found. (See the DESCRIPTION section for details on the output).
- (doppler = no) [boolean]
- Flag those observations that may have passed through a maximum point in the Doppler compensation?
- (diode = no) [boolean]
- Print detailed listing of the science groups and engineering information. If set to "yes", the user should set the other parameters to "no".
- (version = "8Oct93") [string]
- Date the current version of code was installed. Do not change this.
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.
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