This article contains information related to the use of a Jupyter notebook to quickly preview Field of View Overlays for Roman.

The Barbara A. Mikulski Archive for Space Telescopes (MAST) has developed infrastructure to overlay the locations and shapes of instrument apertures on images, and to perform spatial footprint queries on catalog databases. These tools have been bundled into a Jupyter notebook hosted on the MAST Notebooks Github repository hosted by Space Telescope. Specifically, the display footprint tool is a multi-mission Jupyter notebook with supplemental python files (see the display_footprints directory).

The notebook allows the user to input a celestial position and uses pysiaf and ipyaladin to combine the instrument footprint with astronomical observations and catalogs. Once a telescope/instrument/aperture combination is selected (Roman's WFI is the default), the user can retrieve and display the instrument footprint, as well as retrieve and display sources from the available catalogs within the footprints. The notebook defaults to displaying the Digitized Sky Surveys (DSS) as the background sky image. However, Sloan Digital Sky Survey (SDSS) and the Galaxy Evolution Explorer (GALEX) imagery are also available. As the notebook is well documented and self contained, we give only a brief overview of the installation, highlight the features, and provide some helpful tips.

Installation

The easiest way to get started is to download all contents from the display_footprints repository to the desired location. For those familiar with git commands, it may be beneficial to clone the entire mast_notebooks repository to take advantage of all the notebooks also provided. Within the display_footprints directory, all the required packages can easily be installed using pip. After the packages are installed, the Jupyter notebook can be opened in many different ways. We present one installation and opening method on a Unix-like operating system using a Conda environment manager in a shell below:

$ conda create -n <environment_name> python
$ conda activate <environment_name>
$ pip install -r requirements.txt
$ pip install jupyter
$ jupyter notebook display_footprints.ipynb

Features 

The two main features of this notebook are to:

1. Overlay an STScI instrument footprint on a region of the sky as seen by a select number of surveys
2. Use an STScI instrument footprint to query an astronomical catalog

Below one example for each of these features is shown, utilizing two Roman WFI pointings to cover the majority of the Andromeda Galaxy. 

Helpful Tips

Here are some helpful tips when it comes to using the Jupyter Footprint Viewer for Roman:

• The telescope position angle is defined relative to the a telescope's V-axes (see the pysiaf RDox page for the axes definitions). Thus a position angle of 0 will cause the WFI footprint to appear tilted at a 60 degree angle to horizontal. 
• To specify targets by name and/or lookup coordinates from SIMBAD (Set of Identifications, Measurements, and Bibliography for Astronomical Data) or the NASA/IPAC Extragalactic Database (NED), use the following:
  
  

from astroquery.mast import MastClass
Mast = MastClass()
coords = Mast.resolve_object("M101")

• Although the example notebook only walks through a single WFI footprint, the same code can be duplicated to overlay many different pointings as shown in the examples above.

• When using ipyaladin for your work or research, please cite it with the following acknowledgment:

This research made use of ipyaladin, developed by CDS, Strasbourg Astronomical Observatory, France (DOI: 10.26093/kpaw-kb74).

2020ASPC..522..117B - ipyaladin: Enabling Aladin Lite in Jupyter Notebooks (Boch T. et al.)

• And finally, as stated in the notebook, footprints will not appear until the Aladin display is manipulated so either mouse over the preview window or change the box (e.g. change the image size) to force them to appear.

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

References

• MAST Notebooks repository (https://github.com/spacetelescope/mast_notebooks)
• ipyaladin: Enabling Aladin Lite in Jupyter Notebooks (Boch T. et al.) (2020ASPC..522..117B), developed by CDS, Strasbourg Astronomical Observatory, France (DOI: 10.26093/kpaw-kb74).