NICER Archive: Getting started
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:
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 , Wget and the download script.
- 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)
wget -q -nH --cut-dirs=5 -r -l0 -c -N -np -R 'index*' -erobots=off --retr-symlinks https://heasarc.gsfc.nasa.gov/FTP/nicer/data/obs/2017_08/1020270115/
wget -q -nH --cut-dirs=5 -r -l0 -c -N -np -R 'index*' -erobots=off --retr-symlinks https://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
Examples of how to run the script:
A) To downaload a specific sequence type: > download_wget.pl https://heasarc.gsfc.nasa.gov/FTP/nicer/data/obs/2017_08/1020270115
B) To downaload range of sequences type: > download_wget.pl https://heasarc.gsfc.nasa.gov/FTP/nicer/data/obs/2017_08/102027011
To get help type : > download_wget.pl help