SSB jwst trac wiki home

Plans for the development of tools to replace artdata-related functionality within IRAF as well as JWST instrument/telescope simulations.

At a high level, these tools may be broken down into these categories:

1) Source models (both spatial and spectral). The ability to generate a 3d cube for a source.

2) Generating sets of sources either through user interaction or generation of a random set of sources according to specified distributions (spatial, type, luminosity, etc)

3) Source detector projection. Turning the source cube into what the detector sees.

4) Instrumental and noise effects.

It has been pointed out that there are some simulation tools along these lines at, namely skymaker and stuff that are reasonably easy to distribute (they are C-based executables). Unfortunately neither has any real documentation. And perhaps worse, they fall into the big black box approach to simulation, whereas we would prefer a more modular and extensible set of tools. E.g., make it easy to add a new distribution of sources not in the standard set, or a new source model.

So for the time being the planning will assume we will develop our own tools for all of this. Much of steps 1-4 can be worked on in parallel, where more models, distributions, detector projections, noise models, and instrumental effects are added in time. The priorities of each of the specific items may change as the project needs dictate (while these tools are to be generic and not specific to JWST, of course JWST needs will receive priority as they arise).

Detailed initial plan

1) Extend pysynphot tools to encompass spatial information. Most likely this will be layered on pysynphot rather be part of it (though I wonder if it makes sense to allow pysynphot like objects that support analytic models in all 3 dimensions). This will entail a generic class design to handle spatial information, such as a spatially dependent PSF. Initial model will be point source only supporting all pysynphot supported spectra.

2) Develop initial distribution models for generating collections of sources. Initial supported distributions will be:

a) uniform spatial

b) power law luminosity

3) Source projection initial models will be simple spatial integration (normal imaging mode), and a simple slit model for spectroscopy.

4) Initial instrumental effects will be support for the needed noise models for HST and JWST detectors, namely CCD, MAMA, and IR noise models.

The APIs developed after this initial iteration will be tentative and not finalized. It is not yet possible to estimate the amount of work necessary to accomplish the first iteration (we will do that after general acceptance of this approach and specific items).

The second iteration will include:

1) Support for galaxy spatial models

2) support for clustered spatial models, spectral and galaxy distribution models

3) slitless and IFU projection models

4) Cosmic-Rays

The third iteration will include:

Detailed detector effects possibly including:

  • intra-pixel QE variations (IR)
  • inter-pixel charge coupling (IR)
  • charge bleeding/trailing (CCD)

  • CTE (CCD)

Level 5 Proposed Requirements

Last modified 5 years ago Last modified on 03/06/14 15:12:01