.. _VisStackedFrame:

Vis Stacked Frame Product
-------------------------

Data product name
=================
.. DataProductNameStart

VisStackedFrame

.. DataProductNameEnd

Data product custodian
======================
.. DataProductCustodianStart
 
VIS

.. DataProductCustodianEnd

Data model tag
==============
.. DataModelTagStart

9.0.2

.. DataModelTagEnd

Name of the Schema file
=======================
.. NameSchemaStart

euc-test-vis-VisStackedFrame.xsd

.. NameSchemaEnd

Schema documentation tag
========================
.. SchemaDocTagStart

emphasis:`Documentation for data product element DpdVisStackedFrame:`

Output of the Science Pipeline for the StackedFrame. The VIS PF provides stacked images which individual VIS dither is combined using SWarp with the option COMBINE TYPE=WEIGHTED

:emphasis:`Documentation for data product element Header:`
    
The generic header of the product.   

.. SchemaDocTagEnd

Data product elements
=====================
.. DataProductElementsStart

Header of type: sys:genericHeader

Data of type: vis:visStackedFrame

Parameters of type: ppr:genericKeyValueParameters
   
.. DataProductElementsEnd

Processing Element(s) creating/using the data product
=====================================================
.. PECreatorStart

.. PECreatorEnd

Processing function using the data product
==========================================
.. PFUsingStart

MER processing function.

.. PFUsingEnd

Detailed description of the data product
========================================
.. DetailedDescStart

.. Comment by Editor (MS): I have made changes in the use of latex to include the command
   \propto. Otherwise it was not possible to have a proper latex output. I have also significantly
   changed the use of the figure directive, and introduced markup for references instead of explicit
   references. This way figure numbering is consistent throughout the document. I also think you
   need to check the usage of the reference directive: it does not show either in the html or in the
   latex output (this Calabretta ref).

The VIS processing function provides a Stackedframe product consisting of 3 FITS files; a **stacked VIS image**, and the corresponding **PSF model** and **background**.

The **stacked VIS image** is the combined result of calibrated VIS individual dither(s) using **SWarp** with the option “COMBINE TYPE=WEIGHTED”, i.e. the output flux F over i images is given by:

F = :math:`\frac{\sum \omega_i p_i f_i}{\sum \omega_i}`

where f_i is the flux in each calibrated VIS individual image, :math:`p_i` the flux scaling factor
(currently set to 1 for all images) and, as for a calibrated frame, :math:`w_i` the individual
weight for each image expressed in terms of relative inverse variance, :math:`w_j \propto \frac{1}{{\sigma_{j}}^{2}}` , where :math:`\sigma_j` is the standard deviation (or “RMS” of the :math:`j_th` pixel).

The tangent point ([Calabretta & Greisen 2002]_) of the output image is computed by **SWarp** software with the option “CENTER_TYPE all”. Therefore, the size of this image and its tangent point is for the moment not pre-defined, and can vary based on the coverage of the input dithers.
The output tangent point is approximately equal to the geometric average of the tangent point of the input images.

The input data products (SCI, RMS, and FLG) are resampled to constant pixel scale over the focal plane of 0.1” / pixel. The images are background subtracted with a sliding window using the following parameters BACK_SIZE=64 and BACK_FILTERSIZE=3.

We will now describe the content of each extension of the **stacked VIS image**:

**SCI extension**

The fluxes in each pixel of the SCI extension are rescaled to have a zero point of 23.9 AB magnitudes with an effective exposure time of 1s.

**RMS extension**

As for the calibrated VIS individual images, the RMS map contains standard deviation at each pixel in the corresponding Science image, expressed as the absolute standard deviation.

**FLG extension**

For the stacked images, the value of the Flagmap is 0 for good data, 1 otherwise. Flags are stored as eight-bit unsigned integers.

Calabretta & Greisen 2002] Calabretta, M. R. & Greisen, E. W. 2002, A&A, 395, 1077

Primary Header:

+--------+-----------+---+--------------+
| SIMPLE |           | / |              |
+--------+-----------+---+--------------+
| BITPIX |           | / |              |
+--------+-----------+---+--------------+
| NAXIS  |           | / |              |
+--------+-----------+---+--------------+
| EXTEND |           | / |              |
+--------+-----------+---+--------------+
| END                                   |
+--------+-----------+---+--------------+

Extension Header:


.. DetailedDescEnd