Setting Up a NICER Analysis Environment
Like all X-ray astronomy missions, NICER requires a combination of software, calibration data, and observation data to produce science results. This document describes how to set up an environment for NICER data analysis.
Read this thread if you want to: Set up NICER software and calibration.
Last update: 2021-04-16
Like all X-ray astronomy missions, NICER requires a combination of software, calibration data, and observation data to produce science results. To get the consistent and correct results, the analyst's computer should be set up properly. This document describes how to set up an environment for NICER data analysis.
The key components for analysis are:
This document gives an overview of how to install software and calibration data. Where appropriate, we will link to HEASARC's web pages for further instructions.
Here is what is needed:
You should typically download the most recent version of HEASoft.
On the download page, you have several choices. We recommend that you download the source code distribution. However, you can choose to retrieve a precompiled software package for some computer operating systems. The selection of pre-compiled software is limited, and users have reported compatibility issues in the past with this method. However, if you are just getting started, pre-compiled binaries may be the quickest and easiest way to try things out.
You will also have to select which components to retrieve. It is often easiest to retrieve "everything." At the very minimum, you should select "NICER," "General-Use FTOOLS," and "Xspec." Click submit and the software will begin to download.
Please follow the instructions to install HEASoft on your computer.
When you have completed building and installing the software, you will still need to be sure that it is initialized properly in every session that you use. Typically this involves adding some commands to your startup file (.tcshrc or .bashrc). The installation instructions have more information about how to do this.
When you have completed the installation instructions, you can verify the installation by typing the following command:
What is Installed with HEASoft?
It is difficult to describe the full breadth of software that is available within HEASoft, since it supports tens of missions.
A key component is NICERDAS, or the NICER Data Analysis System, which has all NICER-specific data analysis software tools. When you start analyzing NICER data, you will be using NICERDAS tools. A list of NICERDAS software tasks, with task-specific documentation, can be found here.
You will also be using the mission-generic tool called XSELECT. XSELECT provides capability to extract light curves, spectra, and detector images. XSELECT uses a processing engine called "extractor" to do most of its work behind the scenes.
After extracting NICER spectra, you will likely use the spectral modeling software called XSPEC, which included as a part of HEASoft.
Finally, for temporal analysis you may try to use XRONOS. It has tasks for plotting light curves, estimating power spectra and folding pulsar periods.
Installing Calibration Data
NICER analysis software requires calibration data to produce scientific results. Like many missions, NICER uses the HEASARC's Calibration Database (CALDB) system to catalog and distribute calibration data.
CALDB provides not only a way to archive and distribute calibration data, but it also provides a way to "tag" each calibration data set with a unique release identifier. This tagging capability provides a way for analysts to describe in the papers the source of their calibration data.
To install your own local copy of CALDB, you will first download a "framework" and install it, followed by NICER-specific files. For more information, see the installation instructions:
As per the installation instructions, once you have the generic framework installed, you need at least one mission's calibration data: NICER's! Visit the following page:
Updating NICER CALDB data to a new version. There may be a time when you wish to download a new version of NICER CALDB data. The steps remain the same. Follow the instructions above, i.e. use the "Retrieve NICER XTI caldb tar file" link to download NICER CALDB again, and install it according to the standard instructions. It is standard practice to never delete "obsolete" calibration files from CALDB. Obsolete files will still be present but marked as "bad" in the calibration index file.
To test that you have properly installed NICER CALDB, you can type the following command:
Once you have completed these steps, you should have a functioning NICER analysis environment. You are ready to find and download data from the archive and begin analysis.
Please see the thread titled Calibration Recommendations for more information about recommended calibration practices for NICER analysis.
The thread titled nicerl2 provides standard way to analyze any NICER observation.