This page in includes answers to some of the more common questions about PS1 data.  If you have suggestions for additional topics you would like to see addressed, please send email to archive@stsci.edu.

The Pan-STARRS project

What is Pan-STARRS?

...

The new MAST interface to the Pan-STARRS catalog supports queries to both the DR1 and DR2 PS1 catalogs. It also has an associated API, which is used in the script described here.

PS1 astrometry

How good is PS1 astrometry?

How can I search for moving solar system targets in the PS1 images and catalogs?

See the How to search for moving targets in PS1 images and catalogs page for a Python Jupyter notebook that demonstrates one approach to searching the PS1 archive for either images or catalogs that have observations of solar system targets.  A MAST interface is currently under development to make this kind of search easier.

PS1 astrometry

How good is PS1 astrometry?

The positions of DR1 sources were originally determined from the astrometric calibration of PanSTARRS using sources in common with the 2MASS The positions of DR1 sources were originally determined from the astrometric calibration of PanSTARRS using sources in common with the 2MASS catalog.  The systematic uncertainty in this calibration is not precisely known, but is likely to be close to 0.1".

...

We hope eventually to fix this issue (and some other problems described in the "FITS image format quirks" section of the PS1 DR2 caveats page), but since the PS1 archive includes 1.5 petabytes of PS1 images, the task of updating all the image files is not simple.

PS1 Timing

...

What is the time scale used for the PS1 observation times?  Why do the observation times in the image header and catalog

...

disagree?

The times in the warp image headers and in the catalog (e.g., the obsTime column in the Detection table) are defined using international atomic time (TAI) rather than UTC time.  Those times differ by the addition of leap seconds, which leads to header times that differ by 34 or 35 seconds from the UTC times. (See Rots et al. 2015 for more details.) If you are concerned with timing at this level, you may need to convert the times to UTC.  For the warp images, the fix for this is to insert the keyword TIMESYS = 'TAI' in the header.  FITS cutout images have a correct TIMESYS keyword (as of 2022 January 20), but full skycell FITS images do not have a TIMESYS keyword. For the database times, the fix is to add subtract 34 or 35 seconds (depending on the date) to from the TAI time to get the UTC time..  The astropy.Time module includes convenient functions for converting between TAI and UTC times.

Also note that the epoch given in the FITS header for the warp images is the start time of the observation, while the epoch in the database for Detection entries is the mean time of the observation, which is the start time plus 15 seconds (since the exposure time for PS1 images is 30 seconds).   So you should add 15 seconds to the warp header's MJD-OBS keyword value to get the equivalent value from the Detection.obsTime column in the PS1 database.

Thanks to Peter Van Wylen for discovering the TIMESYS issue and helping identify the fix. And thanks to Jules Halpern for pointing out an error in the original description of Thanks to Peter Van Wylen for discovering this issue and identifying the fix.