2MASS Facts

List of Data Products And Expected Sizes

Data ProductDescriptionSize1
Point Source Catalog~400 million sources
Catalog meets Level 1 Specs
Measured fluxes or upper limits at J, H, and Ks
Single band-merged position
Source quality, etc. flags
~120 GB
Extended Source Catalog~1 million sources
Catalog meets Level 1 Specs
Measured fluxes or upper limits at J, H, and Ks using several measures
Single band-merged position
Source quality, etc. flags
0.5 GB
Extended Source Catalog Image Atlas~1 million background-removed Atlas Images per band
corresponding to every source in Ext. Src. Cat.
Usual Image Sizes 101" x 101"
~120 GB
Digital Image Atlas1.3 million images per band
Each Image is 500x1024 1" pixels
Made from Individual Scans (not on regular grid through sky)
Resolution ~4"
(22 Atlas Images / Scan x 60,000 scans)
8,300 GB
Point Source Reject File~400? million sources
File does not meet Level 1 Specs
Measured fluxes or upper limits at J, H, and Ks
Single band-merged position
Source quality, etc. flags
~120? GB
Extended Source Reject File~10? million sources
File does not meet Level 1 Specs
Measured fluxes or upper limits at J, H, and Ks using several measures
Single band-merged position
Source quality, etc. flags
50? GB
Extended Source Reject File Image Atlas~3 million background-removed Atlas Images per band
corresponding to subset of sources in Ext. Src. Rej. File
Usual Image Sizes 101" x 101"
~360 GB
1 See next section for derivation of sizes

Examples of compressed 2MASS images (> 100 KB)

Data Volumes

 
Point Source Catalog
   ~120 GB (400 million sources x 300 bytes)

Extended Source Catalog
   0.5 GB (1 million sources x 500 bytes)

Extended Source Image Atlas
   ~120 GB (1 million sources x 101 x 101 x 4 bytes x 3 bands)

Digital Image Atlas of the Sky
   8.3 TB (60,000 scans x 22 images/scan x 512 x 1024 x 4 bytes x 3 bands)

Point Source Reject File (name tbd - may just be the source file)
   120? GB (400? million sources x 300 bytes)

Extended Source Reject File (name tbd - may just be the source file)
   50? GB (10 million sources x 500 bytes)

Extended Source Image Atlas for Reject File
   360 GB (~3 million sources x 101 x 101 x 4 bytes  x 3 bands)

R. Cutri has written up a Data Volume Profile,
giving the rate at which these products build up with time.  It also contains
the tape management plan for staging the data.




http://spider.ipac.caltech.edu/staff/tchester/2mass/facts/data_products.html
Comments to: Tom Chester
Last update: 25 May 1998