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There are three primary data products that can be created using gPhoton.
There are three primary Python modules you will use.
The Galaxy Evolution Explorer (GALEX) mission surveyed the sky in the ultraviolet for approximately ten years between April 2003 and June 2013. Its two microchannel plate (MCP) detectors recorded the position and time-of-arrival of incident photons ("photon events") with a time resolution of 5 thousandths of a second. Due to storage space and processing limitations, however, these data have previously been released and archived almost exclusively as integrated images (with visit- and coadd-level depths of minutes or more). The gPhoton database and associated software tools now give researchers the means to use photon-level GALEX data up through General Release (GR) 6/7.
The corpus of GR 6/7 photon data is composed of more than 79 billion FUV and over a trillion NUV photon events. On disk, the gPhoton database is approximately 130 TB. The gPhoton command line tools permit users to search for coverage within this database and create calibrated light curves, images, or movies, with the flexibility to set time and spatial ranges or cuts across the entire mission. This enables studies of variability at timescales shorter than the GALEX visit files, customization or refinement of the calibration, and simplifies the fusion of data across mission phases, surveys and modes. When imported as Python modules, gPhoton permits even more detailed work with the data, including analysis at the level of individual photons.
There are two ways to install the gPhoton software.
Option 1: Install via pip.
Option 2: Install via GitHub.
This section is intended as a "quick start" guide. For more details about how to install the gPhoton software, or its software dependencies, consult the gPhoton User's Guide documentation.
If you installed via pip:
If you installed via github:
The gPhoton software is intended to be a friendly, easy-to-use service to the community. However, like any large data set there are caveats, pitfalls, and "gotchas" that can sometimes be identified only through experience and careful examination of your results. We strongly recommend that all users read the GALEX technical documentation, and we also recommend that users read the GALEX mission overview paper Morrissey et al. 2007, ApJS, 173, 682. You should also read through the gPhoton User's Guide, which will be continuously updated and improved by the gPhoton team.
The gPhoton project is a work-in-progress, and is continually updated and improved. Below we note a few important items to be aware of when using our software.
Gotchas: Or Things To Be Aware Of When Analyzing Your gPhoton Results
We have compiled a list of important effects to be aware of when analyzing your gPhoton results, such as data artifacts, known issues with the Python software, or frequently asked questions. Visit our gPhoton Gotchas Page. You are encouraged to email the gPhoton team with any questions or strange features and behaviors. This helps us fix bugs, improve calibration, and compile this list for other members of the gPhoton community.
gPhoton is available as a public release. We will continue to update gPhoton, e.g., improved backend stability, query efficiency, better calibration, and adding new features to the Python software. If you have comments, suggestions, questions, or problems -- or if you would like you be added to our "users" email list -- please contact the team using the MAST help desk email (archiveBe sure to include the word "gPhoton" in the subject line.@ stsci.edu).
The gPhoton project is under active development on GitHub (https://github.com/cmillion/gPhoton). We welcome contributions from the community.
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