VIII. Post-Cryo Preliminary Data Release

1. Introduction

d. Cautionary Notes

WISE Post-Cryo Preliminary Release data products are subject to most of the same limitations and exhibit the same features as the April 2011 Preliminary Release Single-exposure image and extracted source data. We recommend that you begin by reviewing the Cautionary Notes for the Preliminary Release Single-exposure data before making use of the Post-Cryo Preliminary data products.

The WISE survey data acquisition strategy and data processing were designed to yield data products of high reliability and fidelity. However, the Post-Cryo data contained in this release were reduced using very early versions of the WISE Science Data System (WSDS) pipelines and instrumental calibrations that are known to be sub-optimal. This combined with the fact that these Post-cryo processed data did not receive the same level of scrutiny by the project's quality assurance scientists mean that there are a number of limitations and problems, known and unknown, that persist into the Post-Cryo Preliminary Release products.

Post-Cryo Preliminary Release Explanatory Supplement sections VIII.1.d.i through VIII.1.d.iii contain descriptions of known features and limitations that pertain to WISE Post-Cryo Preliminary Release products. Section VIII.1.d.i below contains a list of the most important things that you should know about the Release products to make the best use of them in your research. Click on any item in the list to see a more detailed discussion.

Section VIII.1.d.ii contains general information that pertains to all of the Post-Cryo Preliminary Release products. Sections VIII.1.d.iii and VII.1.d.iv contains Cautionary Notes for users who make use of the Post-Cryo Preliminary Single-exposure Source Database and Images. The Known Solar System Object Possible Association List is subject to the same limitations that apply to the All-Sky Release that are described in I.4.d.iv.

You are strongly encouraged to read and familiarize yourself with all of these Cautionary Notes before using the WISE Post-Cryo Preliminary Release data products.

i. Top 10 (or so) Things You Should Know About the WISE Post-Cryo Preliminary Release Data Products

1. The WISE Post-Cryo Preliminary Release data products were generated from first-pass data processing, and do not benefit from the calibration and algorithmic improvements and corrections that were in place to produce the All-Sky and 3-Band Cryo Data Releases.
2. The quality of the WISE Post-Cryo Preliminary Release data products is similar to, but generally not quite as good as that of the All-Sky Release products. The Post-Cryo measurements reach a similar depth as the full cryogenic measurements, but the achieved precision of photometric measurements is degraded because of the higher telescope and detector temperatures, and larger number of noisy pixels in the detectors.
3. The WISE All-Sky Release Catalog and Atlas are the most complete and uniform compendia of the mid-infrared sky. The Post-Cryo Preliminary Release Products are most useful as a resource to extract preliminary flux and position measurements for solar system objects found by the WISE Moving Object Pipeline System, and to obtain time-domain information about objects found in the All-Sky Release products, such as possible flux variability and proper motion.


4. The Post-Cryo Preliminary Release products do not include any measurements in the W3 (12 μm) and W4 (22 μm) bands.


5. The Post-Cryo observations covered approximately 70% of the sky.


6. The Post-Cryo Preliminary Release products include only the Single-exposure images and extracted source database. The Post-Cryo Single-exposure images were not coadded nor were deep source extractions made from coadded images.


7. The Post-Cryo Preliminary Release Single-exposure Source Database is not a highly reliable, well-vetted list of mid-infrared sources like the All-Sky Release Source Catalog. The Database contains multiple, independent detections of real astrophysical objects, as well as spurious extractions of image artifacts and transient noise events.



8. The Post-Cryo Preliminary Single-exposure Source Database photometry is up to 2% brighter in W1 and up to 11% brighter in W2 than the measurements of the same sources in the All-Sky Release Catalog. The photometric offsets vary with time, being strongest at the beginning of the Post-Cryo survey period, and diminishing towards the end of Post-Cryo operations.


9. Saturated pixels and sources may not be accurately flagged in the Post-Cryo Preliminary Release image and extracted source database because of the loss of on-board saturated pixel encoding. This results in erroneous flux measurements for saturated sources and incorrect flagging of spurious detections of by image artifacts from bright sources..


10. The WISE Post-Cryo Single-exposure image data will undergo second-pass processing with improved pipeline algorithms and instrumental calibrations. These improved data products will be released in early 2013 and will supersede this Preliminary Release at that time.

Last update: 2012 July 18