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Space Telescope Imaging Spectrograph
New Target Acq. Checking Procedure

New STIS Target Acquisition Checking Procedure

As of May 9th, manual reviews of STIS target acquisitions are no longer being performed on a daily basis. From now on, STIS ACQ and ACQ/PEAK data will be reviewed once a month. PIs of STIS GO programs (or their designated contact persons) should receive a warning by email at that time, if there appear to be problems with the acquisition. Note, however, that the ultimate responsibility to check STIS target acquisitions lies with the PIs, not with STScI.

The software which is used to evaluate the target acquisition data, IRAF/STSDAS task "tastis" in the stsdas.hst_calib.stis package, is available to observers. This program reports the location of the peak flux in each acquisition image, and the size of the telescope offset that was needed to center the target. It issues a warning if the fluxes of the apparent target measured at different stages within the ACQ or ACQ/PEAK are inconsistent, or if an unusually large telescope offset was needed in the final centering stage of the ACQ. Anomalies in the flux distribution encountered in the ACQ/PEAK sequence are also reported. The program is described in more detail in the help file of the "tastis" task.

The STIS target acquisition procedure is described in Chapter 8 of the STIS Instrument Handbook. The acquisition data products and the information that they contain are presented in section 5.7 of the HST Data Handbook for STIS. Both Handbooks are available through the STIS instrument webpage at

Note that observers have 90 days after delivery of their HST data to request any repeats for failed observations. This is done by filing a Hubble Observation Problem Report through the web at