HEASARC Cookbook

Finding and Downloading Data

Addressed in this section:

What data are available at the HEASARC?
Which X-ray satellites have looked at my favorite source?
Which satellite can do the science I'm interested in?
How do I download data from the HEASARC?
Can I look at standard data products or quick-look data products for the observation I'm interested in without downloading the data and analysis tools?
How do I decrypt data found in the HEASARC archive?

What data are available at the HEASARC?

The HEASARC archives contain data from high-energy astrophysics missions (X-ray and gamma-ray data mainly) in addition to catalogs at other wavebands. A listing of these 900+ data tables can be found in the Browse area. These tables are also available in ASCII format by visiting our FTP area.

Which X-ray satellites have looked at my favorite source?

You can use Browse to search observation catalogs for individual satellites. Or, by typing in a target name, clicking a single checkbox, and clicking Start Search, you can search all of the recent X-ray satellites for which we have archival data in a single step.

Let's say you're interested in X-ray data of the star HR 1099. From the main interface of Browse, you can type "HR 1099" into the object name box, select all the recent X-ray mission catalogs with one checkbox then click Start Search at the bottom. The results page returns a list of the individual observations made by ASCA, BeppoSAX, Chandra, ROSAT, RXTE, and XMM-Newton. At the bottom of this very extensive output, you'll find a list of tables searched that did not contain a match to your search criteria. The results include information (which varies slightly by mission) about the date, time and length of the observation, the RA and DEC, instrument/grating settings, the status of the observation (archived, planned, observed, etc.), and the offset of the center of the pointing from the RA/DEC of the source entered by you.

If the results of this search are too extensive to peruse, you can go back to the main Browse page and refine the search parameters using the More Options feature or you might just select fewer missions to search. More Options allows you to refine the parameters of the search (e.g., selecting particular observation dates, count rates, etc.) or to specify particular catalogs to search. Instructions on how to use Browse are available on the Browse website.

Which satellite can do the science I'm interested in?

The HEASARC maintains extensive documentation for nearly 100 missions and has a number of tables that compare the capabilities of the recent, current, and upcoming missions in areas such as energy range, effective area, energy resolution, angular resolution, and field of view.

Read about the science done using HEASARC data in the HEASARC's first decade.

How do I download data from the HEASARC?

The HEASARC's Browse service helps you find data by astronomical criteria and will help you create a tar file of interesting data. If you already know the structure of our archive, you can get all data directly through FTP.

In our previous example, suppose you selected some of the HR 1099 archived data from ASCA by checking on the box next to the observation on the Results Page (circled in this "Show Me" example). You could "Retrieve" or "Preview and Retrieve" and view GIFs or select specific products or files and Browse will create a tar file of the selected files that you can then download with just a click. A shortcut for clicking on a select box and clicking "Preview and Retrieve" is the "D" link in the data table row corresponding to the data set you're interested in (arrow in this "Show Me" example).

Users who know the mission and sequence or observation number of the data they want can go directly to the FTP area and download it. The rest of us use Browse.

Can I look at standard data products or quick-look data products for the observation I'm interested in without downloading the data and analysis tools?

You can look at stardard data products or GIF images of the some of the data before downloading. These products (spectra, light curves and images) can give you a good idea of the quality of the data and may help you determine if you want to download the dataset or not. Examples of where to find such data products are listed below.

ASCA has a set of pages with standard products for spectra, images, and light curves. Search by PI name, source location or name, or sequence ID, then click on "Plots and Images" link for the standard products. For the selected observation of HR1099 that's in the "Show Me" immediately above, you can see all these standard data products at http://adfwww.gsfc.nasa.gov/cgi-bin/asca_plot_index?22017000.pub
ROSAT - perform a Browse search on ROSAT (see the first "Show Me" for details) and click on the "D" on the results page for the dataset you are interested in. Images only.
RXTE - perform a Browse search on RXTE (see the first "Show Me" for details) and click on the "D" on the results page for the dataset you are interested in. Spectra and light curves only. Standard products are also available with a full download of the data products (only through the first half of the mission as of early 2002).
XMM-Newton - perform a Browse search on XMM-Newton (see the first "Show Me" for details) and click on the "D" on the results page for the dataset you are interested in. Images and RGS dispersion images only.

How do I decrypt data found in the HEASARC archive?

The script "decrypt_data.pl" allows you to decrypt data encrypted with a PGP (Pretty Good Privacy). Before to use this script you may need to know several things:

What do you need to decrypt the data?
How to test: the platform you are using; if you have PGP or GnuPG installed; the PGP or GnuPG version?
How to use decrypt_data.pl script?
Do you want to know more about PGP and GnuPG?

National Aeronautics and Space Administration

Goddard Space Flight Center

Sciences and Exploration

Search:

HEASARC Cookbook

Finding and Downloading Data