GSoC 2016 Application Parikshit Sakurikar: Implement PSF photometry for fitting several overlapping objects at once
Project Title: Implementing PSF photometry for fitting several overlapping objects at once.
Project Description: The task of photometry involves the measurement of the brightness of a source point of light. Each imaged source point however is captured as a finite sized disk based on a particular point-spread-function (PSF). Usually, establishing the correct PSF for every source point is possible by PSF fitting, provided that the spread of each source point was undisturbed by other source points. This is not always possible in a practical setting. Every set of source points in a dense star cluster will spread enough to interfere with nearby PSFs and thus a multi-PSF fitting is required to correctly establish the brightness of each source point individually.
Project Solution: The brute force approach for overlapping PSF fitting is not a good solution. I presume this is for two reasons: 1) The problem can be computationally very expensive. 2) It would always be better to start with some prior over the data such as assumptions on known brightness of some points, known geometric arrangement of nearby points, known grouping of points (which can be fit together) etc. While these priors may be unavailable, it might be possible to split detected source poinst with initial guessed parameters and refine that decision based on some precision metric for our estimated PSF spreads (as suggested here). Based on this, I would like to understand the relevant literature (DAOPHOT and others) and build a flexible code which is able to perform overlapping-PSF-fitting based on provided input parameters.
Expected Timeline: April,May 2016: Understand the scope of the problem and familiarize myself with the existing codebase - DAOPHOT, T-PHOT, extenstions over DAOPHOT based on neural-nets etc. During this time, I expect to have a fully structured pseudo-code and identify the exact algorithm as clearly as possible.
May-July 2016: With an active communication with the mentors, I expect to complete the coding phase of the project during this time, based on the strategy and algorithm devised earlier, with any necessary changes as they might arise.
July-August 2016: Will spend time in documentation, testing, optimization etc. to make the code ready for use by the community.