2MASS Facts

Many of the webpages referenced here are out of date, since this document has not been updated since 1998. For the latest official information, consult the 2MASS Explanatory Supplement. Some of the information referenced here has not made it into the Explanatory Supplement, or refers to problems that have later been fixed, or items of historical note. It is up to the reader to establish the currency of the information!!

Brief Table of Contents (Section Titles only)
Complete Table of Contents
Table of Contents for all 2MASS webpages
Update Log for 2MASS Facts

This document gives the key 2MASS Facts as they become available, with references to more complete write-ups when available. This document is far from the level of an Explanatory Supplement. It is intended as a working document for the benefit of the 2MASS Team, and in many cases requires knowledge not found in this document in order to make sense of the information presented herein.

An attempt is made to distinguish whether the source of the information is from the actual 2MASS Camera and Telescope or from the prototype camera on the KPNO 50" telescope. If the source is not identified, the reader should assume that the source is the prototype camera and KPNO telescope.

Also note that some of the information is outdated, irrelevant, or has been superseded by later information or a change in plans. This document will probably not be cleaned up until the first data release.

In a few places, topics in the Table of Contents are only placeholders waiting for the information to be supplied.

There is a lot of information that has not yet been incorporated into this document. Consult the comprehensive Table of Contents for all 2MASS webpages for further information, or use the Searchable Index to 2MASS Webpages. Rather than attempt to extract information from webpages, I am concentrating on adding information found only in email or from meetings.

If you reached this page through the [framed] IPAC or UMASS 2MASS Main webpage, and want to view this full-screen, paste the following address into the location field of your browser and hit return:

http://spider.ipac.caltech.edu/staff/tchester/2mass/facts/index.html

These 2MASS Facts have been obtained through the efforts of the 2MASS Team. Information has been stolen from any non-web document that could be found. In many cases, the information was taken from emails intended for a select audience or in response to a specific question which is no longer connected to the stolen portion presented here. Please take special care not to overinterpret what is presented here or to make sweeping conclusions from what may have been analysis of a small piece of early 2MASS data before the telescope was declared operational. The information on many topics in the Table of Contents is quite incomplete.

As a result of the mish-mash of information sources, there is no continuity of style, format, presentation, or anything else in this document. Don't expect for this document to be anything other than a collection of 2MASS facts which is incomplete.

We allow the public access to these pages for two reasons:

  1. The goal of 2MASS is to release data to the community as soon as possible, and therefore we feel it is only proper for interested people to be able to view the progress of the survey and the quality of the data.
  2. By making this information available, it makes it much easier for us to have others help us as needed with validation of the data.
Please keep in mind that all projects have problems at their beginnings that are later solved, and hence no conclusions about the quality of the in-the-end released 2MASS data should be made from anything in this document.

T. Chester is the compiler of this page. Please email him any comments, corrections, or suggested additions.

Brief Table of Contents (Section Titles only)
Complete Table of Contents

TABLE OF CONTENTS (Section Titles only)

The section titles link you directly to the section, except for the overview and data products section. If you want to go directly to a given subsection, use the Complete Table of Contents.

  1. 2MASS Overview
  2. Schedule
  3. Survey Level 1 Requirements
  4. Telescopes
  5. Cameras
  6. Basic Data Characteristics
  7. Survey Properties
  8. Survey Operations, Significant Operations Events and Notable Scans
  9. Calibration
  10. The Data Processing System (2MAPPS)
  11. Data Processing
  12. Data Products
    1. List of Products, Expected Number of Sources and Product Volumes
    2. Data products fundamental limits
    3. Expected detection limits for astronomical objects
    4. Colors of astronomical objects and extinction
    5. Point Source Catalog
    6. Extended Source Catalog
      1. Catalog Format and Definition of Fields
      2. Postage Stamp Atlas
    7. Image Atlas
  13. Data analysis results
  14. 2MASS Pictures on the Web
  15. Prototype camera processing caveats
  16. Funding Sources
  17. Things to add to this document
  18. Update Log for 2MASS Facts

    TABLE OF CONTENTS

    1. 2MASS Overview
    2. Schedule
    3. Survey Level 1 Requirements
    4. Telescopes
    5. Cameras
    6. Basic Data Characteristics
    7. Survey Properties
      • Image and Scan Sizes
        • Pixel Size
        • Number of pixels masked at edges of camera array
        • Useable Image Size for Single Camera Frame
        • Rotation of Array Relative to Scan Direction
        • Step Sizes Between Frames
        • Scan Parameters
          • Explanation of total cycle time per frame
          • Number of pad frames needed to cover a given true scan length to depth 6
      • Dithering Pattern
      • Survey Strategy
        • Number of Coverages
        • Extra Scan Overlap Due to Effect of Precession over 4 years
        • Scan Descriptions and Overlaps
        • Calibration observations
        • Coverage Rate and Time to Complete Survey
        • Observation Strategy
      • Completeness of objects of given size due to overlap size
    8. Survey Operations, Significant Operations Events and Notable Scans
    9. Calibration
    10. The Data Processing Software (2MAPPS)
    11. Data Processing
    12. Data products fundamental limits
    13. Data Products
    14. Data analysis results
    15. 2MASS Pictures on the Web
    16. Funding Sources
    17. Prototype camera processing caveats
    18. Things to add to this document
    19. Update Log for 2MASS Facts



    http://spider.ipac.caltech.edu/staff/tchester/2mass/facts/index.html
    Comments to: Tom Chester
    Last update: 25 May 1998 (Warning added 27 February 2001)