Pan-STARRS Photometric and Astrometric Calibration

TL;DR

The paper presents a comprehensive end-to-end calibration framework for Pan-STARRS1 3π data, detailing photometric Ubercal and relative photometry, as well as multi-stage astrometry that corrects for instrumental and atmospheric systematics. It describes real-time calibration pipelines, the PV3 DVO master database, and the integration of external catalogs including Gaia DR1 to anchor the photometric and astrometric solutions. The work reports millimagnitude photometric stability across the sky and milliarcsecond-level astrometric precision, achieving strong cross-consistency with Gaia while cataloging notable systematics such as the Koppenhöfer effect and DCR. These calibrations underpin robust, large-area PS1 DR2 products, enabling reliable measurements for wide-field astrometry and photometry over the $3π$ footprint. The methods lay groundwork for Gaia-based refinements in future releases and provide a blueprint for precision calibration in large ground-based surveys.

Abstract

We present the details of the photometric and astrometric calibration of the Pan-STARRS1 $3π$ Survey. The photometric goals were to reduce the systematic effects introduced by the camera and detectors, and to place all of the observations onto a photometric system with consistent zero points over the entire area surveyed, the ~30,000 square degrees north of $δ$ = -30 degrees. The astrometric calibration compensates for similar systematic effects so that positions, proper motions, and parallaxes are reliable as well. The Pan-STARRS Data Release 2 (DR2) astrometry is tied to the Gaia DR1 release.

Figures (11)

• Figure 1: High-resolution flat-field correction images for the 5 filters $grizy$.
• Figure 2: Consistency of photometry measurements across the sky. Each panel shows a map of the standard deviation of photometry residuals for stars in each pixel. The median value of the measure standard deviations across the sky is $(\sigma_g, \sigma_r, \sigma_i, \sigma_z, \sigma_y) = (14, 14, 15, 15, 18)$ millimags. These values reflect the typical single-measurement errors for bright stars.
• Figure 3: Illustration of overlapping skycells and the identification of the "primary" detections.
• Figure 4: Illustration of the Koppenhöfer Effect on chip XY04. Bottom left X-direction before correction. The solid line shows the measured mean residual for stars detected on this chip as a function of the instrumental magnitude / FWHM$^2$. Bottom right Y-direction before correction. Top left X-direction after correction. Top right Y-direction after correction.
• Figure 5: Map of the amplitude of the Koppenhöfer Effect on chips across the focal plane. In the affected chips, bright stars are up to 0.2 arcsec deviant from their expected positions. Bottom left X-direction before correction. Bottom right Y-direction before correction. Top left X-direction after correction. Top right Y-direction after correction.