1. General Software Considerations
The astronomy software community is investing heavily in Python and in particular in the astropy suite. While we do not exclude other languages, applications developed in Python and compatible with astropy are more likely to be easily installed and usable by a broad audience.
External dependencies are sometimes necessary but each extra one adds maintenance overhead and often limits the potential user base; they should therefore be used judiciously.
Software-savvy astronomers will want to access the software by calling libraries (typically Python ones). However, less software-aware astronomers (both professional and amateur) will need command-line or web-based end-to-end tools which wrap these libraries in a simple interface. We must support both of these communities. In particular, a simple browser-based interface to the PassPredict and TrailMask tools discussed below (at least in their simple mode) is strongly recommended. We should also provide interfaces to planetarium applications (World Wide Telescope, OpenSpace, Stellarium).
If the software is to be used widely by astronomers, it should if at all possible be open-source, free, and free of restrictive licences. We should support a software ecosystem in which centrally developed reference implementations may exist, but interfaces are simple and well documented so that alternative implementations can be swapped in — this will allow us to leverage innovation by the community.
We encourage support of International Virtual Observatory Alliance (IVOA) protocols, and specifically pyVO, for retrieval of test datasets (and possibly of satellite prediction data if appropriate protocols exist). However, programs should always also allow import of datasets from a local disk.
Where appropriate (e.g., for satellite reflectance models) the software architecture should allow for user-model plugins (i.e., users can write their own model and have the software use that instead of the presupplied one).
1.1. Distribution and Documentation
The software will require user documentation and support. The obvious place to serve as a portal for software and documentation is the SatHub proposed in the Observations Working Group Report. We also recommend the development of related educational materials such as lesson plans to engage the school and university student communities.
