NIR Stacked Frame

$SetSchemaPath nir/euc-test-nir-StackedFrame.xsd

Data product name

$PrintDataProductName

Data product custodian

$PrintDataProductCustodian

Name of the Schema File

$PrintSchemaFilename

Last Edited for DPDD Version

1.1

Processing Elements Creating / Updating / Using the Product

Creators:

  • NIR

The DpdNirStackedFrame data product components are created by different tasks during the execution of the NIR_ProcessField_Pipeline:

  • The MEF file is created by the NIR_DostackProgram task of the NIR_Stacking project

  • The PSF model and image are created by the NIR_PSFModelling task of the NIR_PointSpreadFunction project

  • The data product xml is written by the final NIR_ProcessField_Pipeline step that is NIR_CreateScientificDpds of NIR_Utilities project

Consumers:

  • NIR

Into the NIR_ProcessField_Pipeline the MEF file is used as input for the NIR_CatalogExtraction PE to create the NIR Stacked Frame Catalog containing source extracted.

Processing Function using the products

This is one of the output of the NIR_ProcessField_Pipeline.

In the pipeline the MEF file is used as input for the NIR_CatalogExtraction PE to create the NIR Stacked Frame Catalog with source extracted.

  • PF-NIR

Proposed for inclusion in EAS/SAS

This product is proposed for inclusion in the SAS: yes

Data Product Elements

$PrintDataProductElements

Detailed Description of the Data Product

The DpdNirStackedFrame is one of the output of the NIR_ProcessField_Pipeline applied to wide survey observations and in general to “scientific” pointings (i.e. Self Calibration).

It is the result of the stacking process of a set of input images, 4 in case of wide, the nominal survey strategy. It could be created also in some specific cases with more exposures. A single stacked image is provided at the end of each NIR_ProcessField_Pipeline run.

../../_images/nirStackedFrame.png

Fig. 20 : Graphical representaton of Data section structure for DpdNirStackedFrame

The main elements inside the Data section are:

  • Filter: The filter name (e.g. NIR_Y, NIR_J, NIR_H)

  • WCS: The description of the WCS for the image. This field mirrors values in the FITS header

  • ZeroPoint: The effective photometric zero point of this stack of single images

  • ImgSpatialFootprint: This spatial area defines the spatial footprint of the image in a series of vertex

  • ObservationId: Image Observation Id

  • TargetPointing: Coordinates of target pointing

  • DataStorage: FITS file name containing the Stacked image FITS file

  • PsfStorage: Reference to the PSF files (Model and FITS)

  • QualityParams (optional):Data Quality Parameters

    • Min: Minimum image pixel value

    • Max: Maximum image pixel value

    • Mean: Average image level (mean of all image pixel values)

    • Median: Median image level (median of all image pixel values)

    • StDev: Sample standard deviation of the image pixel values

    • MaskedPixelFraction: The fraction of masked pixels

The DpdNirStackedFrame data product contains the link to 3 files:

  • a MEF file with the science image

  • a PSF model measured from science frames

  • a PSF image of the model

Scientific image FITS file

The main result of the stacking process is a MEF file stored into the DpdNirStackedFrame in the Data.DataStorage field.

The file is composed by four layers:

Layer name

Data Format

Units

Content

PRIMARY

Main headers

SCI

float32

microJy

Scientific data

RMS

float32

microJy

RMS data

DQ

int32

Data Quality mask
../../_images/stacked_frame.png

Fig. 21 : Graphical representation of 3-layer structure of NIR stacked frames

Primary layer

The primary layer is an header dedicated to store global infomation on pointings and parameters used by SWarp for resampling and stacking (i.e. starting from COMBINET, RESAMPT1 up to PSCALET2 in the next table) together with the inverse sensitivity value PHOTFNU needed to convert pixels in [microJy].

$PrintPrimaryHeader fit/euc-nir.xml nir.stackedImage

Scientific Layer

The scientific layer, named SCI, stores the data obtained combining togheter all images used as input to the NIR Pipeline.

The header contains some basic image definition keywords together with the GAIN and the SATURATE keywords derived by SWarp for resampling and stacking.

$PrintExtensionHeader fit/euc-nir.xml nir.calibratedScienceFrame DETn.SCI

RMS Layer

The RMS layer is

DQ Layer

The DQ layer is

PSF files description

The Point Spread Function (PSF) is measured from the image. It is provided into two formats: a .psf file containing model parameters and a .fits file with an instance of model.

A PSF model is extracted from the scientific image by PSFEx software. This solution is provided both as model and as image.

The PSF model is produced as .psf file, an Astromatic format that can be directly provided to SExtractor for catalogue extraction. The model can track wavelength and focal plane position dependencies.

The PSF image is a FITS file with a primary and a single data layer containing a PSF image.

PSF Model file

This is a model file

PSF image file

The PSF primary header contains information on Observation Id in OBS_ID.

Because of the FITS structure is in common with the one used on NIR Calibrated Frame definition some keywords are meaning-less in case of stacked frame. As in example DITHOBS could be ignored and PSFTYPE is fixed to “Inflight” value because the PSF is always extracted from images.

$PrintPrimaryHeader fit/euc-test-nir.xml nir.psfImage

The detector header collects basic image keywords with the coordinates of PSF image center in pixel space (X_CENTR and Y_CENTR) and the effective wavelength (EFF_WAVE).

$PrintExtensionHeader fit/euc-test-nir.xml nir.psfImage DETECTOR.n