Overview of the Frames Pipeline

Table of Contents

Flow Through the Frames Pipeline

Start

Initialise Modules, Read Plan/Parameter Files

Foreach frame {
    Read Known Objects

    Foreach color {
        Read Frame, and add on overlap with next frame

	Correct Frame

	Fix Cosmic Rays
    }

    Foreach color {
	Find Bright Objects
    }

    Merge Bright_Objects

    Foreach Bright_Object {
	Measure Object
    }

    Subtract Star Wings

    Foreach binning-scale {
	
	Bin Frame

	Foreach color {
	    Estimate and Subtract Local Sky

	    Find Faint Objects
	}

       Merge Faint Objects, adding them to object list

    }

    Write Corrected Frame, Mask, and Binned Image

    foreach object {
	Measure Object

	Write parameters and atlas image

	Deblend

	Foreach child {
	    Measure Object

	    Write parameters and atlas image
	}
    }

    Write remaining outputs
}

Cleanup

End

Input to the Frames Pipeline

In the list below, we give representative values for several parameters (for example, overlap region size) that are not fixed and may change in practice; they are indicated by an italic font.

Before it can run, the Frames Pipeline requires various inputs; for details see Correct Frame's discussion of inputs. For each frame, it needs:

• CCD hardware specs for each chip, including its readout noise, gain, list of any defects, etc.
• raw frames for each color, which are a different size than corrected frames: they lack overlap regions between frames, and hence have a smaller number of rows (1354 vs. 1489; 10%); and they have extra columns from the overclock region on both ends (2128 vs. 2048).
• a bias vector appropriate for each chip.
• a flatfield vector for each chip.
• a CALIB1 structure for each frame, which includes the filter name, sky value and slope, bias values for each amplifier, approximate flux calibration (in the form of ``the number of DN which equal magnitude 20.0''), a model for the point-spread-function, and the coordinate transformation to convert pixel coordinates in this frame to great-circle coordinates (frames uses these to find the transformation from one band to another, so which great circle coordinates is not important).