I spent some time exploring the IRSA site (Infrared Science Archive)
The IRSA archives include 2MASS, MSX (Midcourse Space Experiment), and
IRAS, plus the USNO-A (optical), NVSS (radio), and FIRST (radio) catalogs.
You have to go to the IPAC pages for additional information on 2MASS -
IRSA is focussed on archival access only. I found this a bit confusing.
The IPAC page also provides a link to ISO, info on WIRE (failed mission),
The 3 main IR missions include a variety of data products - various
catalogs, images, and some atlas images. Their catalog access is
provided through a query building tool called GATOR. I was a bit
disappointed that one could query only one catalog at a time. However
it provides a wide range of query alternatives including a user
specification option. This notes that you don't need to know SQL to
use, but it does have an SQL-like syntax you must use. GATOR also
allows one to set search limits on every field in the database, so
I rarely needed to use the user spec option. For some reason
GATOR runs only with Netscape, not Explorer as the web browser; this
seems like a serious limitation.
A process monitor page comes up so you can monitor the progress of
your query (which can be quite large). It lists your work area, so
don't delete it or you can't find your output! I did this and had
to rerun a couple of queries. It does warn you to bookmark the page.
The navigation is provided using frames and position sensitive links
from a top banner. I found this aggravating, since some text in the
banner is linked, some is not, so you have to check your web browser
page at the bottom to see if it's a real link. Highlighting a hot
link would help. I'm not found of frames either - to go back to a
previous page you must use the browser "back" function.
A small query on the 2MASS point source catalog took just a few seconds
to run. When I checked the status on the monitor page, it says "The
last job you submited is either finished or stopped. We display the
log file for you to check the status. If the status file doesn't
end with "EOF", it means there might be something wrong for some reasons."
Then one must page to the bottom to see if your query completed or not.
If it completes OK, it generates the message "Your Job Finished. Click
View Table to view your result." You may then view the resulting table
in a web page, from which you may save the results in a file. A better
way of giving the status would be highly desireable. The average user
won't be interested in the log file; at least put the "Job Finished"
message and link at the top of the page. When the query completes, you
are emailed a report; you have to wait for it to arrive and use your mail
utility to read it. This is probably most useful if you have run a
large, time-consuming query.
I also retrieved some of the 2MASS Survey Atlas images using the
2MASS Public Release Image Server, entering a target and using the
default settings. This searches for coadded images (a map on the
image search screen shows the current sky coverage), and displays
the resulting image in the J band (or K, L, or M if selected). For some
reason the default size is 9' (RA) by 18' (Dec). A grid is overplotted
in color - RA and dec in blue, filter glint artifacts with green
X's, and persistence artifacts with red X's. One may then download
the FITS data file and the overlay PostScript file. The displayed
image shows black stars on a white background and is quite nice.
I found that the search and display tools worked fine, but need some
work to be user friendly. I also found information difficult to find,
with few links to supporting documentation.