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tastis stis


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SEE_ALSO

NAME

tastis -- Analyze STIS target acquisition images.

USAGE

tastis input

DESCRIPTION

The task tastis will print general information about each input target acquisition image, and will analyze both types of STIS target acquisitions: ACQs and ACQ/PEAKs.

The ACQ procedure is described in "STIS Onboard CCD Target Acquisitions (ACQ)" in the chapter on Target Acquisition (currently chapter 8) in the STIS Instrument Handbook. A section under "Target Acquisition Data" in the HST Data Handbook for STIS (currently Section 5.7.2) explains how to examine ACQ data.

The ACQ/PEAK procedure is described in "Onboard Target-Acquisition Peakups (ACQ/PEAK)" in the chapter on Target Acquisition (currently chapter 8) in the STIS Instrument Handbook. A section under "Target Acquisition Data" in the HST Data Handbook for STIS (currently Section 5.7.3) explains how to examine ACQ/PEAK data.

For an ACQ, target positions in global and local (subarray) coordinates and the total flux of the target in the maximum checkbox during both acquisition phases (coarse and fine) are displayed; the location of the reference aperture (used during the fine locate phase) is also displayed. For an ACQ/PEAK, the lowest flux measured during the peakup steps (the pedestal), the flux at each step after subtraction of the pedestal, and the total and pedestal-subtracted flux in the post-slew confirmation image are displayed.

The task will calculate the slews performed during the acquisition, check and compare fluxes measured in the images, and provide warnings of possible problems which could indicate a failure of the acquisition. Tests are made to find signs that the presence of more than one brightness peak confused the acquisition; to see if the images are either saturated or below the flux levels recommended for adequate signal to noise; to verify that the lamp illuminated the slit in the last stage of the ACQ; and to find indications of abnormal exposures in the telemetry.

If update=yes, keywords are added to the header to make problems easier to locate in batch processing. Warnings are given if the spt file is not present when tastis is run. In that case, for ACQs, some information will be missing from the printout and the value of the keyword DATAFLAG will be set to UNKNOWN; for ACQ/PEAKs, the processing will not occur. Keywords are populated and success or warning messages are given as follows:

____________________________________________________________________

ACQ:

ACQSTAT = OK and the following message is given if all of these conditions are met:

   ACQ_RAT  = OKRATIO  (0.75 < flux fits[4]/fits[1] < 1.25)
   ACQ_SLEW = OK_SLEW  (fine slew < 4 pix)
   ACQ_LAMP = OK_LAMP  (GOODMAX in raw.fits[7] > 1900 DN)
   ACQ_SAT  = UNSAT    (GOODMAX in raw.fits[4] < 32000 DN)
   DATAFLAG = TDF_Up   (OCSTDFX in spt.fits[1] = TDFUp)

Your ACQ appears to have succeeded, as the fluxes in the coarse and fine stages agree within 25% and the fine slews were less than 4 pixels as expected

ACQSTAT = FAILED (suspected failure that should be checked) and the appropriate message is given if any of these conditions is met:

ACQ_RAT = LORATIO, HIRATIO (flux fits[4]/fits[1] <0.75, >1.25)

The fluxes in the maximum checkbox in the fine and coarse stages differ by more than 25%. This may indicate a problem with your acquisition.

ACQ_SLEW = BIGSLEW (fine slew > 4 pix)

The fine slew (to center the target in the reference aperture) is larger than 4 pixels. This may indicate a problem with your acquisition.

ACQ_LAMP = LO_LAMP (GOODMAX in raw.fits[7] < 1900 DN)

The flux in the third image of the ACQ is lower than the typical value for the lamp; the image should be checked to see if the lamp was illuminated.

ACQ_SAT = SAT (GOODMAX in raw.fits[4] >32000 DN)

Saturation of pixels in the second image may have affected the final centering.

DATAFLAG = TDFdown (OCSTDFX in spt.fits[1] = TDFDown)

Telemetry indicates that the intended exposures may not have been performed. Check the images for signal.

____________________________________________________________________

ACQ/PEAK:

ACQSTAT = OK and the following message is given if all of these conditions are met:

   ACQP_FLX = OK_FLUX
   ACQP_RAT = OKRATIO
   ACQP_END = OK_END
   ACQP_SAT = UNSAT
   DATAFLAG = TDF_Up

The confirmation image has a flux between 0.8 and 2.0 times the maximum flux in the peakup, which is typical of a successful ACQ/PEAK.

ACQSTAT = FAILED and the appropriate message is given if any of these conditions is met:

ACQP_FLX=LO_FLUX for OBSTYPE=IMAGING (confirmation flux <1250 DN)

The flux in the confirmation image is __% of the recommended minimum of 1250 DN for a direct-light ACQ/PEAK. The signal-to-noise in the ACQ/PEAK may be inadequate for an accurate centering.

ACQP_FLX=LO_FLUX for OBSTYPE=SPECTROSCOPIC (confirmation flux <20000 DN)

The flux in the confirmation image is __% of the recommended minimum of 20000 DN for a dispersed-light ACQ/PEAK. The signal-to-noise in the ACQ/PEAK may be inadequate for an accurate centering.

ACQP_RAT = LORATIO, HIRATIO (confirm flux/max flux <0.8, >2.0)

The flux in the confirmation image is only __% of the maximum flux in the ACQ/PEAK scan. Percentages below 80% often indicate problems in the ACQ/PEAK.

The flux in the confirmation image is __% greater than the maximum flux in the ACQ/PEAK scan. An excess greater than 100% indicates problems in the ACQ/PEAK.

ACQP_END = HI_END

The maximum flux in the sequence occurred at one end. This may indicate that the target was beyond that end or that a neighboring object affected the acquisition.

ACQP_SAT = SAT (GOODMAX raw.fits[1] >32000 DN)

Some pixels in the confirmation image were saturated. If saturation also occurred in any of the peakup steps, it may have affected the centering.

DATAFLAG = TDFdown (OCSTDFX in spt.fits[1] = TDFDown)

Telemetry indicates that the intended exposures may not have been performed. Check the images for signal.

____________________________________________________________________

PARAMETERS

input [file name template]
The name of the input STIS target acquisition raw image; the spt file is also required for ACQ/PEAK files. It can take wildcards. Note that the task will ignore non-acquisition data when processing from a wildcard list.
(update = no) [boolean]
Update ACQSTAT keyword in input files? If update is set to yes, each input file will be opened read/write, and an ACQSTAT keyword will be written to the primary header. If a possible problem was detected for that file, the value for ACQSTAT will be "FAILED"; otherwise, ACQSTAT will be set to "OK". A keyword will also be created and populated for each test that is used to determine the value of ACQSTAT, as described above. These keywords are convenient when using hselect to print summary information for batch processing.

EXAMPLES

1. To run the task on all the files in the current directory. The task will only read the ACQ and ACQ/PEAK images sitting in the current directory.

cl> tastis *raw.fits
==========================================================================
O48X02TPQ       HST/STIS    MIRVIS     50CCD               ACQ/POINT
prop: 7721      visit: 2    line: 10   target: FEIGE110
obs date, time: 26/10/97    06:54:20   exposure time:  0.10
ACQ params:     bias sub: 1510   checkbox: 3      method: FLUX CENTROID
subarray (axis1,axis2):   size=(100,100)          corner=(488,467)
--------------------------------------------------------------------------
Coarse locate phase:           Target flux in max checkbox (DN): 11446

		       global          local
		    axis1 axis2     axis1 axis2
Target location:    541.0  530.9    54.0  64.9

		    axis1 axis2     axis1  axis2         V2      V3
		      (pixels)        (arcsec)            (arcsec)
Estimated slew:      5.6  14.2     0.285  0.723        0.713 -0.309
--------------------------------------------------------------------------
Fine locate phase:            Target flux in max checkbox (DN): 11002

		       global            local
		    axis1 axis2     axis1 axis2
Target location:    535.3  516.9    48.3  50.9
Ref ap location:    535.5  516.5    16.5  15.5

		    axis1 axis2     axis1  axis2         V2      V3
		      (pixels)        (arcsec)           (arcsec)
Estimated slew:     -0.2   0.4     -0.010  0.020       0.007 -0.022
--------------------------------------------------------------------------
Total est. slew:     5.4  14.6     0.275  0.743         0.720 -0.331
--------------------------------------------------------------------------
Your ACQ appears to have succeeded, as the fluxes in the coarse
and fine stages agree within 25% and the fine slews were less than
4 pixels as expected

==========================================================================
==========================================================================
O48X02TQQ       HST/STIS    MIRVIS        52X0.05             ACQ/PEAK-UP
prop: 7721      visit: 2    line: 20   target: FEIGE110
obs date, time: 26/10/97    07:01:51   exposure time:  0.10
ACQ params:     bias sub: 1510                  method: MAX-FLUX-CENTROID
subarray (axis1,axis2):   size=(32,32)          corner=(520,501)
--------------------------------------------------------------------------
Scan type: LINEARAXIS1                  Step size (mas): 36

       210       702      4622      4869      1246       466         0


		    axis1 axis2     axis1  axis2         V2   V3
		      (pixels)        (arcsec)           (arcsec)
Estimated slew:      2.1   0.0     0.107  0.000      0.075  0.075
Flux in post-slew confirmation image: (9377) - Pedestal: (3065) = 6312 DN
--------------------------------------------------------------------------
The confirmation image has a flux between 0.8 and 2.0 times the
maximum flux in the peakup, which is typical of a successful ACQ/PEAK.

==========================================================================

2. Here is an example where the acquisition may have failed.

cl> tastis o8gn10mmq_raw.fits

==========================================================================
o8gn10mmq       HST/STIS    MIRVIS     F28X50LP             ACQ/POINT
prop: 9619      visit: 10    line: 10   target: HZ43
obs date, time: 2002-06-08    09:04:56   exposure time:  0.90
dom GS/FGS: 0199601446F2    sub-dom GS/FGS: 0199600544F3
ACQ params:     bias sub: 1510   checkbox: 3      method: FLUX CENTROID
subarray (axis1,axis2):   size=(100,100)          corner=(485,467)
--------------------------------------------------------------------------
Coarse locate phase:           Target flux in max checkbox (DN): 2848

                       global          local
                    axis1 axis2     axis1 axis2
Target location:    516.3  505.0    32.3  39.0

                    axis1 axis2     axis1  axis2         V2      V3
                      (pixels)        (arcsec)            (arcsec)
Estimated slew:     -17.8  -11.7    -0.905 -0.593       -1.059 -0.221
--------------------------------------------------------------------------
Fine locate phase:            Target flux in max checkbox (DN): 4262

                       global            local
                    axis1 axis2     axis1 axis2
Target location:    530.0  471.3    46.0   5.3
Ref ap location:    537.8  515.4    21.8  14.4

                    axis1 axis2     axis1  axis2         V2      V3
                      (pixels)        (arcsec)           (arcsec)
Estimated slew:     -6.5  -44.1     -0.332 -2.240      -1.819  1.350
--------------------------------------------------------------------------
Total est. slew:    -24.3  -55.8    -1.237 -2.833        -2.878  1.129
--------------------------------------------------------------------------
The fine slew (to center the target in the reference aperture) is larger
than 4 pixels.  This may indicate a problem with your acquisition.

The fluxes in the maximum checkbox in the fine and coarse stages differ
by more than 25%.  This may indicate a problem with your acquisition.

==========================================================================

REFERENCES

STIS Instrument Handbook, chapter 8.
HST Data Handbook for STIS, sections 5.7.2 and 5.7.3.
'tastis' routines written by R. Katsanis & R. Downes, based on software
written by G. Hartig.

SEE ALSO


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