Aladin Visualization
Aladin is a visualization tool integrated with APT that allows you to view program targets and instrument apertures displayed on sky images.
Aladin is already in use with APT for HST and JWST programs.
Starting Aladin
To view a program element in Aladin, select the program element in the left pane, then click the View in Aladin button on the top APT toolbar.
With this version of APT, the program elements you can visualize with Aladin are:
- Fixed Targets
- Region Targets
- Pass Plans
- Selected observations within a Pass Plan
Aladin Controls
To control the opacity (shading) of the aperture, use the Opacity slider in the lower right panel.
To load background sky images from the Digitized Sky Survey (DSS), click the DSS button on the APT Aladin Controls toolbar.
To load a color full-window DSS image, click the DSS button on the Aladin window (not on the APT Aladin Controls Toolbar). Many other image sources are available within Aladin using File> Load Astronomical Image.
- To adjust the image, use the Pixel tool in the right pane of the Aladin window.
To zoom in or out, do one of the following:
- Use the mouse wheel
- Use the Zoom slider on the lower right panel
- Click the 'Z' tool on the left panel - a highlighted square appears. Drag the highlighted square over the image, then click to zoom in, or Shift-click to zoom out.
To re-center the view at a default zoom level, Control+click anywhere in the inset square on the lower right panel.
Managing Level of Detail
APT performance can be greatly slowed down when Aladin displays complex programs. For that reason, APT provides several ways to control the level of detail displayed.
- Single Aperture button (on the APT Aladin Controls toolbar). Displays the outline of each full WFI footprint in the selection, without showing the 18 individual detectors (see Simple Pass Plan).
- Single Mosaic button (on the APT Aladin Controls toolbar). Displays the approximate outline of each mosaic footprint with no internal detail (see Pass Plan with Mosaic).
- Automatically reduce detail. APT provides an option to automatically reduce the level of detail Aladin displays when a selection is too complex to display in an acceptable amount of time. This option is "Automatically adapt level of detail for Roman observations" and is available in the View in Aladin menu (under the Aladin Display submenu). This option is enabled by default but may be turned off by the user.
- Select one or more or more observations in a Pass Plan (instead of selecting the entire Pass Plan).
View Pass Plans in Aladin
To view a Pass Plan in Aladin, select a Pass Plan in the left panel, then click the View in Aladin button.
All pass plans of fixed targets are currently displayed at a default orient of 0 degrees. Future versions of APT will include the ability to display Survey Steps so the default orient can be the mid point of any requested Orient. Pass plans of region targets are displayed at the Planned Orient by default.
Simple Pass Plan
Figure of a Simple Pass Plan
This pass plan shows a simple pass with the characteristic "batwing" footprint of the WFI aperture. Note that there are gaps between the 18 detectors which can be covered by using dithers. However, no dithering is used in this example, and only a single WFI aperture is shown. The image on the right shows the same pass but with Single Aperture selected so individual detectors are not shown, although the gaps between detectors are still present.
Simple Pass Plan with Dithers
Figure of a Simple Pass Plan with Dithers
This Pass Plan adds a 4-point dither (BOXGAP4) to cover the gaps between detectors.
Pass Plan with Mosaic
Figure of a Pass Plan with a 2x1 Mosaic
Pass Plan with 2x1 mosaic and a 4-point dither (BOXGAP4). The level of detail shown may be controlled with the Single Aperture and the Single Mosaic button (from Roman Demonstration Program 960). Each image shows the same mosaic at a different level of detail:
- The left image shows the outline of each detector (Single Aperture and Single Mosaic both off).
- The center image shows each tile in the mosaic but not each detector (Single Aperture on, Single Mosaic off).
- The right image shows the footprint of the entire mosaic with no internal detail (Single Mosaic on). Note that the outer perimeter is displayed as an approximation and should be checked at a higher level of detail.
Pass Plan with Region Target
Figure of a Pass Plan with a Region Target
. 
This Pass Plan uses a Region Target with 15 points to cover the Large Magellanic Cloud. Each point in the region is covered by a 3x3 mosaic (from Roman Demonstration Program 961).
Both images show the same Pass Plan at a different level of detail:
- The left image shows the tiles inside each of the 15 mosaics (Single Mosaic off).
- The right image shows only the footprint of each mosaic with no internal detail (Single Mosaic on).
View Targets in Aladin
To view a target in Aladin, select a target in the left panel, then click the View in Aladin button.
- For a fixed target, Aladin displays a small blue reticle (resembling a plus sign) for the target coordinates.
- For a region target, Aladin displays a reticle at the fiducial point of each of the coordinates in the target.
Figure showing Region Target in Aladin
In this example, Aladin displays a Region Target with 15 points, with a small blue reticle (plus sign) at each point.
For additional questions not answered in this article, please contact the Roman Help Desk at STScI.