Change Record Version Date Description Owner name 1 1/28/2011 Update Document to reflect Model based on Data Challenge 3 J. Kantor 2 7/12/2011 Update Document to reflect Model based on Data Challenge 3B PT1 R. Allsman 3 8/18/2011 General updates R. Allsman 4 9/11/2013 Final Design updates (revision 1.125) R.Allsman 5 9/26/2013 Formatting updates and WBS inclusion R. Allsman 6 10/10/2013 Returned SDQA to the Apps model (revision 1.144); TCT approved R. Allsman
.....done: done: After all Detector Segment(s) have been illuminated with the spot, analyze the collected Raw Exposure(s). The Crosstalk Correction Matrix element (i, j) can be directly determined as the ratio of the flux measured in Segment j to the flux measured in Segment i, at the corresponding Pixel Coordinates. fin: AltPath: Data from Survey data or Star Raster Scan Exposures Identify Pixel(s) affected by bright point Source(s), whose cross-talk affected counterparts contain nothing more than the background Compute the ratio of fluxes of those Pixel(s), per amp-amp pair Average the measurement over all data collected in a period of time shorter than the timescale of cross-talk changes on the Camera Basic Path step:9 Produce Master Bias Exposure WBS: 02C.01.02.04 Create Master Bias Exposure from individual Bias Exposures Scenario Steps Summary Rejoins at Basic Path Combine the Bias Exposure(s) to form the Master Bias Exposure Store the Master Bias Exposure into the Calibration Database Produce Master Dark Exposure WBS: 02C.01.02.04 Create Master Dark Exposure from individual Dark Exposures Scenario Steps Summary Rejoins at Basic Path Combine the Dark Exposure(s) to form the Master Dark Exposure Store the Master Dark Exposure into the Calibration Database Produce Master Fringe Exposures WBS: 02C.01.02.04 For each Observing Filter, the Monochromatic Dome Flat Exposures will be used to construct the
Atmospheric Model, skip defringing Path step:8 Assemble CCD WBS: 02C.03.01 Assemble per-amplifier Trimmed Exposures into a per-CCD Trimmed Exposure. Scenario Steps Summary Rejoins at Basic Path Load all per-amplifier Trimmed Exposure(s) Write them into a single per-CCD Trimmed Exposure Detect Sources WBS: 02C.03.01 This process identifies the Sources that are present in the Raw. The process outputs a list of Sources and the Pixels occupied by those Sources (i.e., a detection Mask). The detected and measured Sources need not necessarily be persisted. Scenario Steps Summary Rejoins at Basic Path Subtract Sky Background Model Correlate the Raw Exposure with its PSF, producing a detection likelihood Mask Plane. Find all Pixels above the specified S/N threshold in the detection likelihood Mask Plane. Decompose those Pixel(s) into spatially isolated groups and find peaks within the Footprint(s). The positions of the peaks will represent the nominal locations of detected Source(s), until a better Centroid is determined by later measurement. Determine Aperture Correction WBS: 02C.03.01 Determine Aperture Correction factors for the Raw Scenario Steps Summary Rejoins at Basic Path Select bright, isolated, point Source(s) Estimate Aperture Correction
Determine Photometric Zeropoint WBS: 02C.03.01 Determine initial Photometric Model of the Raw Exposure, by using the detected Sources to determine the Photometric Zero Point. This model may further be refined by later processing steps, for example by taking into account the Exposures from adjacent CCDs. Scenario Steps Summary Rejoins at Basic Path Detect bright point-like Source(s) Measure instrumental PSF Flux Match the detected Source(s) to AstroObject(s) in the Level 2 AstroObject Catalog. Until Level 2 coverage of the entire sky is in place, External Catalog(s) will be used as a reference. Fit the constant Photometric Zero Point minimizing the difference between recalibrated instrumental and cataloged fluxes Determine PSF WBS: 02C.03.01 Determine the shape and variation of the Point Spread Function ( PSF) on the Exposure based on a sampling of high signal-to-noise stars. Scenario Steps Summary Rejoins at Basic Path Subtract Sky Background Model from Raw Exposure Detect point-like Source(s) using an approximate PSF model Model the PSF given detected high-S/N Source(s) Determine Sky Background Model WBS: 02C.03.01 Determine the Sky Background Model for the Calibrated Exposure. Scenario Steps Summary Rejoins at Basic Path Subdivide the Raw Exposure into 128 by 128 pixel bins (or similar) For each bin: .....Estimate the sky level by computing a robust statistic (e.g., median) of observed Pixel values: done: Fit a function to the resulting grid, resulting in a Sky Background Model. Determine WCS