NICER Archive: Getting started

General

The NICER science data are organized by sequence (10 digit number), where a sequence corresponds to an observation of one day in lenght. The sequences are located in the HEASARC NICER data archive area in the /obs directory which is divided in one month interval subdirectories named YYYY_MM (YYYY year MM month). The sequences are located in the YYYY_MM. The archive structure is therefore:

 
                              /obs
 
         2017_06/  2017_07/  2017_08/  2017_09/    .....
                               |
                   1020140114/ 1020270115/ .....
                                   |
                         auxil/ log/ xti/
                                      |
                                event_uf/ event_cl/ hk/ 


Archive access : Web, wget, download script

At the HEASARC the NICER archive can be accessed using the web interfaces Browse or via anonymous FTP or via Wget.

  • Access via Web : The archive access via the Web makes use of database table to search for the science data. The database table is nicermastr which records high-level information for each NICER observation. This table can be queried for position, time and several other parameters, and from the result page it is possible to select and retrieve the data files.

  • Wget : If you have wget installed, and the observation id is already known, the data can be retrieved via 'wget'. For example using the HHTP protocal, if the user wants to retrieve the sequence '100001010' observed in August 2016, she/he can retrive the entire sequence (see Example 1) or data for a single instrument (see Example 2)
    Example 1 
     
       wget -q -nH --cut-dirs=5 -r -l0 -c -N -np -R 'index*' -erobots=off --retr-symlinks http://heasarc.gsfc.nasa.gov/FTP/nicer/data/obs/2017_08/1020270115/ 
    
    Example 2
       wget -q -nH --cut-dirs=5 -r -l0 -c -N -np -R 'index*' -erobots=off --retr-symlinks http://heasarc.gsfc.nasa.gov/FTP/nicer/data/obs/2017_08/1020270115/xti/ 
    
    

  • download_wget : donwload_wget is a PERL script that uses the wget protocol, similarly to the example above, but simplify the command and allow for more flexility. You can retrive the download_wget and place it in your local machine
     
     Here are  two exmaples of how to run it  
    
    A) To downaload a specific sequence type:  > download_wget.pl http://heasarc.gsfc.nasa.gov/FTP/nicer/data/obs/2017_08/1020270115 
    
    B) To downaload range of sequences type:   > download_wget.pl http://heasarc.gsfc.nasa.gov/FTP/nicer/data/obs/2017_08/102027011[56] 
    
    
    To get help type :  > download_wget.pl help