Date: Mon, 18 Mar 2024 22:46:14 -0400 (EDT) Message-ID: <1620484322.11535.1710816374127@ploutercf.stsci.edu> Subject: Exported From Confluence MIME-Version: 1.0 Content-Type: multipart/related; boundary="----=_Part_11534_2074072025.1710816374124" ------=_Part_11534_2074072025.1710816374124 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Content-Location: file:///C:/exported.html
PS1 data processing includes many steps to go from raw image data to the a=
rchived data products. The raw images are detrended to remove instrument si=
gnatures, and then deprojected into images in a regular grid of projection =
cells. These "warps" are then combined into "stacks." Various forms of poin=
t-source and extended-object photometry are performed on the warps and stac=
ks.
The following information is taken from Magnier= et al. and Waters et al., which shoul= d be cited appropriately. The starting point for the PS1 data arch= ive is at Pan-STARRS1 data archive home page.
PS1 uses the 1.4 giga-pixel camera (see PS1 GPC1 camera) to image the sky north of = span>declination =E2=88=9230 degrees= . The camera detector system has 60 orthogonal transfer arrays (OTA) = devices, each of which has an 8 =C3=97 8 grid of = readout cells (each with 590=C3=97598 pi= xels). These images are reduced with the PS1 IPP pipeline. The Processing Version 3 (PV3) r= eduction, which all the publicly available data in this archive is based on= , represents the third full reduction of the PS1 data set. The first two re= ductions were used internally for pipeline optimization and the development= of the initial photometric and astrometric reference catalog, and are not = publicly available.
For the PV3 processing, large contiguous regions =
were defined, and the images for all exposures within that region launched =
for the processing (see paper by Waters et al. for more details). The proce=
ssing is divided into individual stages. The first step is the stage, in which the astrometry and photometry for the entire exposure i=
s calibrated by matching the detections against the reference catalog. This=
stage also performs masking updates based on the now-known positions and b=
rightnesses of stars that create dynamic feature.
The WARP stage is t=
he next to operate on the data, transforming the detector oriented <=
span>chip stage images onto common sky oriented PS1 Warp images that have fixed=
sky projections. Point-source and extended source photometry is performed =
on these warps. When all WARP stage processin=
g is done for the region of the sky, STACK pr=
ocessing is performed to construct deeper, fully populated&nbs=
p;PS1 Stack images from=
the set of warp images that cover th=
at region of the sky. Source detection and photo=
metry is performed on these stacks, which are then combined into objects (<=
span class=3D"confluence-link">see PS1 Stack objects and photometry). Sourc=
e detection and photometry is explained in more detail in the PS1 Source extraction =
and catalogs webpage.
Beyond the STACK st= age, a series of additional stages are performed. Transient features are id= entified in the DIFF stage, which takes input= warp and/or stack data= and performs image differencing. Further photometry is perfor= med in the STATICSKY and SKYCA= L stages, which add extended source fitting to the point sou= rce photometry of objects detected in the stack i= mages, and calibrate the results against the reference catalog. The = FULLFORCE stage takes the catalog output of the skycal stage, and uses the objects detected in that t= o perform PS1 Forced photometry of sources on the = individual warp images.
The PS1 Relative Photometric Calibration is det= ermined by the photometric calibration algorithm of Schlafly et al. (2012),= which refines the photometric calibration algorithm of Padmanabhan et al. = (2008), used in the Sloan Digital Sky Survey. The throughput of the system = is modeled with as a constant system throughput and atmospheric k-term each= night. The model is determined by finding the parameters of the model that= minimize the variance in flux of repeated observations of the same sources= . The photometric calibration also simultaneously fits for a low resolution= flat field correction vector and a trend in system throughput with PSF.
The PS1 Absolute photometric calibration combi= nes the use of a laser diode system to accurately and precisely determine t= he filter bandpass edges and throughput curves (roughly to 7 A in mean effe= ctive wavelength), with the PS1 observations of HST Calspec standards.
The PS1 Astrometry is anchored with the Gaia astrometry.
Schematic of the images and analysis processing stage of the PS1 IPP pipeline, described in Magnier et al.