A Mosaic Pattern is a specification in APT of a sequence of offsets for mosaicking a Roman Observation. The Mosaic Plan is built in the Mosaic Pattern Form.

Mosaic Pattern Overview

A Mosaic Pattern forms a grid pattern defined by its rows and columns of identical Tiles. Mosaic patterns are created by entering the number of rows and columns on the Mosaic Pattern form to build a grid of Tiles. A wide range of mosaic shapes can be created by applying row or column shifts, and/or disabling individual Tiles using the Mosaic Tile Editor. A Mosaic Pattern is not specific to a Target and may be used and re-used for any Observation (see Pass Plans). All of the Tiles in a Mosaic Pattern are observed at the same orientation. An example is given in the Figure Showing the Mosaic Pattern Editor.

An example 5 Tile by 3 Tile Mosaic Pattern built using the APT Mosaic Pattern form. To aid the user, a the graphic illustrates what each mosaic tile (the rectangle) represents. This is approximately 0.7 deg by 0.4 deg on the sky. Rather than representing the outer extent of the WFI footprint, the rectangle represents interlocking tiles which is more useful for designing mosaics, e.g. to avoid creating unintended gaps between tiles.

Mosaic Plan Parameters

A Mosaic Pattern has the following parameters.

Number

APT Parameter Field NUMBER

A number that designates the Mosaic Pattern. Required (incremental numbers are added by default but may be changed by the user).

Label

APT Parameter Field LABEL

A name that identifies the Mosaic Pattern. Not required. The label identifies the Mosaic Pattern in the hierarchical editor and in drop-down lists.

Number of Rows

APT Parameter Field NUMBER OF ROWS

The number of rows in the Mosaic Pattern (required). Default is 1. Allowed range is APT Range Field 1 TO 100

Number of Columns

APT Parameter Field NUMBER OF COLUMNS

The number of columns in the Mosaic Pattern (required). Default is 1. Allowed range is APT Range Field 1 TO 100

Number of Tiles

The number of Tiles in the Mosaic Pattern (Example: for an 8x4 layout the number of tiles is 32). This value is calculated from the APT Parameter Field Number of Rows x APT Parameter Field Number of Columns minus any tiles disabled with the Mosaic Tile Editor.

Row Overlap %

APT Parameter Field ROW OVERLAP %

The percent overlap for rows (required). Default is 10%.

Column Overlap %

APT Parameter Field COLUMN OVERLAP %

The percent overlap for columns (required). Default is 10%.

Row Shift (deg)

APT Parameter Field ROW SHIFT (DEG)

The shift in degrees for rows (required). Default is 0 degrees.

Column Shift (deg)

APT Parameter Field COLUMN SHIFT (DEG)

The shift in degrees for columns (required). Default is 0 degrees.

Slew Back to Start

APT Parameter Field SLEW BACK TO START

Determines the slew order for successive Observations.

When APT Parameter Field SLEW BACK TO START is selected, the next Observation begins at the first Tile traversed.
When APT Parameter Field SLEW BACK TO START is not selected (default), the next observation begins at the last Tile traversed.

Mosaic Tile Editor

Mosaic Patterns are created by entering the number of rows and columns on the Mosaic Pattern Form. Once the initial grid is created, the pattern is represented in the Mosaic Tile Editor.

Irregular patterns may be created by applying row or column shifts, and/or disabling one or more tiles. To disable a tile, click it in the Mosaic Tile Editor (click again to enable it). Disabled Tiles are shown with a diagonal line. The Figure showing functions of the Mosaic Tile Editor shows an example of removing tiles.

If you change APT Parameter Field NUMBER OF ROWS or APT Parameter Field NUMBER OF COLUMNS , a new grid is created with all Tiles enabled.

Sequence labels (numbers) are displayed on each tile by default. To hide sequence labels, select the Hide Sequence Labels checkbox.

An example Mosaic Pattern that is 48 Tiles in an approximately circular shape built using the APT Mosaic Pattern form. In this case, the default mosaic pattern has been edited using the Mosaic Tile Editor to remove the corners of the rectangular to better fit a circular shape. This visual tool shows how disabled tiles (1, 2, 9, 10, 11, 20, 41, 50, 51, 52, 59, and 60) are marked with a red diagonal line.

For additional questions not answered in this article, please contact the Roman Help Desk at STScI.

Latest Update	15 Dec 2023	Updated screen captures.
Publication	15 Dec 2022	Initial publication of the article.

Mosaic Patterns