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XMM-Newton Guest Observer Facility

How PIs Can Access Their Proprietary Data

Introduction

PIs can get their XMM-Newton data by FTP as soon as they have been processed and delivered to the GOF at GSFC. To provide for this ability we have encrypted proprietary data using GPG v1.4.x. Note that while anyone can download the files, only the person holding the GPG key can decrypt them. This way, PIs may download the pipelined versions of their data ("PPS") and/or the ODF data, which can be processed by the PI on their local computer using SAS. The PI may also share the data with co-Is simply by sending them the encryption key. These web pages tell you how to obtain and decrypt your data, and where to find the GPG encryption software, if you don't already have it.

Obtaining Your Data

  1. When a sequence has been delivered to the GOF and placed in the archive, the PI will be sent an e-mail message containing the key for that sequence. The key is a set of 40 alphanumeric characters required to decrypt that dataset.
  2. The PI can then obtain the data via anonymous FTP from legacy.gsfc.nasa.gov in the directory /xmm/data/ This is the U.S. XMM-Newton archive.
  3. GnuPG (GPG) software must be installed on the receiving system. If it isn't, see below.
  4. The files must be decrypted. The exact command to do this depends on the version of GPG you are using.
    • To decrypt a file using gpg v1.4.x:
           gpg --passphrase-fd 0 -d my_file.fits.gpg
    • To decrypt a file using gpg v2.x, add the --batch flag:
           gpg --batch --passphrase-fd 0 -d my_file.fits.gpg

    Wildcards (e.g. "*") will not work, so to decrypt many files with a single command it will be convenient to use a script. The GOF provides such scripts for Unix operating systems and Perl, depending on which GPG version you have, in the table below. Information on how to run these scripts can be found in their headers, or if downloading a "prepare_xmm_data*" package, the associated README file.

    Note that after downloading, the scripts will need to made executable, for example:
         chmod +x decrypt

    Also, for the Perl script, the first line may need to be altered if the Perl executable is not installed in /usr/bin/perl.

    GPG v1.4.x GPG v2.x Comment
    prepare_xmm_data.tgz prepare_xmm_data_v2.tgz decrypt and uncompress your data in Perl
    decrypt.csh decrypt_v2.csh decrypt your data in C or K shell
    decrypt.pl decrypt_v2.pl decrypt your data in Perl

Installing GPG

GnuPG is a free, open-source alternative to PGP, which many folks may not even remember. It is easy to get and install. GPG v1.4 works with the original scripts and GPG v2.x works with the newer scripts.

For v1.4.x,

  • Get the source tar file. If you are using CentOS/SL, click here. For other *nix systems, click here.
  • For MacOS:
         sudo port install gnupg1
  • For Debian/Ubuntu:
         sudo apt-get install gnupg1
For v2.x,
  • Get the source tar file.
  • MacOS:
         sudo port install gnupg2
  • Debian/Ubuntu:
         sudo apt-get install gnupg2

If you have any questions concerning XMM-Newton send e-mail to xmmhelp@lists.nasa.gov