Data Flow: Telescope to Catalogs
Introduction
The SDSS's primary data products are the survey photometry and the
spectroscopic measurements for the quasar, galaxy and star samples.
They can be accessed as binary (.fits) tables and images through the Data Archive
Server (see the archive access
page). The Data Archive Server also contains intermediate
data products.
The storage structure of the Data Archive
Server reflects the way in which the data are acquired and processed.
To help understand the archive structure and the logical relation
between the various data products, this section gives a high-level
description of the data flow from the telescopes through our pipelines
into the archives. The details of
our algorithms are described elsewhere.
Overview
The figure gives a simplified description of the
data flow. 
All observations are done at
Apache Point Observatory. There is a drift-scan
camera for 2.5m Imaging. Based on the imaging survey,
we select targets for the 2.5m Spectroscopy survey
carried out with a 640-fiber spectrograph. For photometric
calibration, there is a conventional CCD camera on the 0.5m
Photometric or Monitor Telescope (interchangeably
called PT or MT). The various pipelines produce nearly 100 different
types of data files (see the Data Model for a
description of all of them), both working files and scientific
outputs. Note that the names of files in the Data Archive Server
reflect their contents as well as the name of the pipeline which has
created them.
Photometric / Monitor Telescope (PT/MT)
