How do I download data from Spitzer?

The basics: Introduction and Terminology

Introduction

The Spitzer Heritage Archive (SHA) is the permanent home for all of the data collected during the Spitzer mission, plus all the documentation you need to understand it all. The SHA is formally part of IRSA's archive holdings (no longer 'owned' by the SSC). The SHA provides a web-based interface to the Spitzer archive, and it lives here: http://irsa.ipac.caltech.edu/applications/Spitzer/SHA/ Because it is web-based, you do not need to download and install software that is platform-dependent. It should "just work" in whatever browser you use (though, for really new or really old browsers, your mileage may vary)! There is online help for the SHA -- see the help menu in the upper right (of the red menu bar). There are also several other ways to get help; see here -- look under "Spitzer Heritage Archive Documentation". The cookbook's first few chapters has detailed step-by-step recipes (one of which was originally developed for a NITARP team), the User's Guide is a standalone PDF manual, and some instructional videos are linked in as both YouTube and Flash copies.

The software that used to be the primary mechanism for pulling data from the archive is called Leopard. There might be some lingering references to Leopard on the wiki, though we have tried to clean them all out.

Basic Terminology

An individual Spitzer observation sequence is an AOR, or Astronomical Observation Request. In certain cases (often calibration or sometimes science observations), you may also see an IER, or Instrument Engineering Request. Either one involves many individual frames, as well as observer name, date of observation, object or area of the sky observed, and instrument used (IRAC, MIPS, or IRS)-- these are all part of the AOR. All of Spitzer's operations (planning, scheduling, processing) have been centered around these units (AORs or IERs). Now, for the SHA, we are starting to move away from that, but there are some things that are still only available on an AOR basis, so we really can't escape them.

The rest of the new terminology has its origin in other similar terms used in other archives. I know, I know, hard to think about astronomers using the same terms to mean the same thing across multiple telescopes and wavelengths! But we're trying...

Raw data that are fundamentally unprocessed are "Level 0" data. As NITARP folks, you should never encounter (or want to encounter, really) Level 0 data.

The individual data frames that emerge, calibrated, from the Spitzer pipeline are "Level 1," or "Basic Calibrated Data," or "BCDs." New with the SHA, you can now get just the BCDs from a region that you want; you no longer have to download the whole AOR if it covers a much larger region than you want. As NITARP folks, you probably don't need these Level 1 data. But you might.

The products that come from combining these individual data frames (such as mosaics) are "Level 2," or "post-BCD," or "PBCD data." These still exist fundamentally on an AOR level, e.g., you can't get a Level 2 mosaic that is just a portion of an AOR. As NITARP folks, you probably want these data.

You can also get some higher-level processed products (which you might call "Level 3" data) through this interface. These products are supplemental data that are produced either by the SSC or donated to us by professional astronomers, and represent additional processing. For example, a Level 3 mosaic might combine data from 7 AORs into one big mosaic, with customized (as opposed to hands-off pipeline) processing of image artifacts. If you are familiar with the Legacy Enhanced Products, these are Level 3 data. See below for more on this.

All of the images come in FITS format. (Wondering what is FITS format?) (If you are really savvy, you might also care that they are mostly single-plane FITS files. Some Level 3 products will be/are multi-plane FITS.) The other format for some data is IPAC table files (.tbl extension). IPAC table format is really just plain text, with a special header. Once you get a file like this, just about anything (including Excel) can read it. (YouTube video on tbl files, how to access them, and how to get them into Excel (10min).)

Downloading Data: Using the SHA, short version

Please see the first recipe in the Spitzer Data Analysis Cookbook (direct link ought to work!). Or, see YouTube QuickStart video. Both these resources were developed for professional astronomers. Hopefully they make sense to you too. Let Luisa know if they don't.

Downloading Data: Using the SHA, long version

In more detail! Also see YouTube video, the long version.

Downloading Data: Using the SHA, a concrete example, very long version

Originally developed especially for the 2010 CG4 team, but then turned into a formal chapter for the professional astronomer's Data Reduction Cookbook. This demo covers the following tasks: Use the SHA to search the Spitzer Archive for all possible and relevant CG4 observations. Use the SHA to assess which observation will most quickly yield an image. Select data for download, and do it.

Recipe 2 from the Cookbook (direct link should hopefully work!!)

Downloading Data: How can I find already-reduced Spitzer data?

The SHA also includes polished mosaics and source lists, with more to come in 2011 and 2012! This is the "Level 3 Data" I mentioned above.

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Visualize AOR using Leopard (optional but useful if truly new at this)

The point of this is to see specifically where the telescope will be/was pointed for a given observation. If you have an observation that is a big mosaic, you can see where each individual pointing fell. This helps you understand why you have so many files when you download Spitzer data.

1. From Leopard's main window, select an AOR.
2. Under the Images menu, choose ISSA, and select a 5 degree image in the wavelength of your choice (25, 60, 100, 160 microns).
3. Under the Overlays menu, choose "AORs on image." (5th from the bottom on the Overlays menu.) Depending on your wavelength, each colored box may result in one or two data frames, each of which is a file you get from Leopard, as well as scads of associated files for each of those frames! (Note that there are lots of other overlay options to explore, and we encourage you to do so, but if you want to see where your observations fall on the sky, you need to pick "AORs on image.")

There is more information on visualization in the Spot and Leopard User's Guides.

Downloading Data: How can I find any prior observations for an object?

Has a particular target ever been observed with any of Spitzer's instruments? Or, would this target be a good proposal for a new project?

Downloading Data: How can I quickly get a mosaic of my object?

Get me a mosaic, quick! Don't bother me with preambles or complete explanations, I just want a picture. (Also see What is a mosaic and why should I care?)

Downloading Data: I need the image as a FITS file, how can I get this?

OK, I'm ready for a real fits file that doesn't have any losses due to compression.

Downloading Data: What should I do if there is more than one mosaic of the same object?

What to do if there is more than one imaging observation of your favorite target. Includes an example for finding the best possible image of a target, M16. If you have more than one image of a target that you need to combine, this naturally leads into mosaicking. An example is given for the ONC, including a link explaining how to combine (mosaic) the images.

Downloading Data: How can I get a spectrum of my object?

Spitzer is more than just imaging -- IRS and MIPS take spectra as well as images.

Downloading Data: I'm ready to advance to a highly technical and in-depth discussion on downloading Spitzer data.

This tells you how to start from the same place professional astronomers do. You will have to learn how to mosaic frames using the Spitzer tools developed for professional astronomers by the Spitzer Science Center. This needs a lot of disk space, and, well, a little bit of courage! And access to IDL would help a lot.

Questions to think about and things to try with Spot/Leopard

• This item is easiest to do with Leopard. Pick an object to search on, anything you want.
  • Which program(s) (if any) have observations? With which instruments?
  • Who requested the observations? (bonus: What are they investigating?)
  • Has Spitzer observed it yet?
  • When are the data going to be available to download? If they are available, download the post-BCD mosaics.
• Try the questions on this page using Spitzer data for the three color planes.
• This item can be done with Spot or Leopard, perhaps slightly easier with Spot than Leopard. You might find it useful to consult "Using Spot to get data from other wavelengths". For a given object, whether or not you can find Spitzer data, find images of the object from another mission or survey, in another (non-Spitzer) wavelength.
  • What wavelength(s) did you pick?
  • What features are more apparent in the other wavelength compared to Spitzer? Are there other differences?
• This item can be done with Spot or Leopard, perhaps slightly easier with Spot than Leopard. For a given object, on top of one of those images of an object from another mission or survey, pick a catalog (such as IRAS) to overlay on the image. Figure out how to just have it show the brightest or just the faintest things. Warning: if you choose to overlay the 2mass catalog over a large region, you will be waiting for several minutes while the computer renders many 1000s of points.
  • What other catalog(s) at what other wavelength(s) did you pick?
  • Were there a lot of sources in the region you picked, in the catalog you picked? Why? (You may wish to pick another catalog for comparison.)

Come up with your own answers and then discuss downloading data.

Possibly useful resources

• Leopard pocket guide
• Spot pocket guide
• Leopard User's Guide
• Spot User's Guide