The Data and Software
Because X-rays do not penetrate the Earth's atmosphere, X-ray
telescopes must be placed in orbit above the atmosphere. A scientist
who studies X-rays cannot build (or, more importantly, afford) his or
her own X-ray satellite to collect the data needed. Satellites are
often built by a national institution (such as NASA), and many
scientists use each one. Scientists write proposals for what objects
they want to look at and for how long. To make sure that the data can
be accessed by scientists everywhere, the astronomical community has
developed a standardized way of storing the data, in so-called FITS
files (more on that later). Scientists use software developed
specifically to work with FITs data from high energy telescopes. The
Laboratory for High Energy Astrophysics (LHEA) has developed a suite
of software tools, called "ftools" (pronounced "eff-tools") for
working with X-ray data in FITS file format. There are ftools for
extracting information from the header, and for looking at and
manipulating the data in the body of the file, and many other useful
things.
Scientists at the LHEA (or working remotely from locations all over the globe!) are able to use the ftools on a Unix or Linux computer operating system. The data sets involved are huge, often several Gigabytes in size. Generally, Unix systems are used to work with such large data sets, as Windows or Mac systems are not flexible enough to do the job. Because of these constraints, LHEA programmers have developed a software program called "Hera" that allows users to install a small Hera module on their local machine and run ftools remotely on Goddard's machines. After setting up a Hera account, users can browse the LHEA archives for data they want to study, store data sets on computers at Goddard Space Flight Center and run ftools (using LHEA computers) on the stored data. Small files such as plots can then be saved to the user's local machine to study, print out and compare.
You will use a version of Hera adapted for use with this lesson. But
the software tools are the same ones that astronomers use.
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