Goals
- Retire aXe
- Retire aXeSIM
- Leverage the JWST infrastructure
- just crds, gwcs and asdf?
- Enable common "Grismconf" infrastructure for:
- pyLINEAR
- grizli
- EM2D, and Nor's other modules
- JWST pipeline
- (WFIRST)
- Ensure that users can do all the flavors of geometric transformations (and can understand them)
- Make sure calibration (files) are consistent with the approach to geometry
- Support the following HST modes:
- WFC3/IR
- ACS
- WFC3/UVIS?
- Compatible with JWST pipeline outputs of WFSS modes (NIRISS and NIRCam)
Use-Cases / Workflows
1D spectral extraction for perfectly registered & perfectly calibrated data
Story: As an impatient astronomer, I just want to extract a 1D spectrum for a single source given perfectly registered images and assuming calibrations are correct. I want it fast and I don't want to think about forward modeling.
What do I need as inputs?
- Direct and slitless images with perfect WCSs
- catalog information
- Exposure times?
- Noise model? Or components of the noise model (gain, exptime, read noise, subtracted background)?
- Or is this already in an uncertainty array?
- Detector signatures already removed (e.g. CALWEBB_DETECTOR1)
- Identification of the pixels in the direct image corresponding to "the source" (e.g. from a segmentation map)
- Identification of any pixels in the direct image corresponding to contaminating sources
What does this step do for me?
- Maps pixels in the direct image to x,y, wavelength
- Accumulates the flux at each wavelength (onto some wavelength grid)
- Perhaps weighted by the flux in the direct image at this cross-dispersion location
- Accumulates uncertainties at each wavelength
- Accumulates some kind of contamination flag at each wavelength
Why would I not want to do this?
- This doesn't do much to address contamination
- This mixes together wavelength and position more than a forward-modeling approach.
- Uncertainties are likely to be quite misleading
Epics
Identify and match data sets
- Should this be part of Astrogrism, or outside the package (e.g. in a notebook, as a tutorial)?
- Archive queries via API for both direct and slitless observations
- Build associations
- Can/should we use the JWST pipeline machinery for such associations?
Geometric transformations
Direct image: x,y ↔ RA, DEC
Slitless image:
ra, dec, wavelength → x, y
x,y | RA, dec → wavelength
- x,y | wavelength → ra, dec
Astrometric registration
Simulations
Contamination
Background Subtraction
Flatfielding
1D Spectral Extraction
2D Spectral Extraction
1D Forward modeling
2D Forward modeling
Combine spectra single PA
Combine spectra multiple orients
Documentation
- Getting Started (landing page)
- Installation
- Overview
- Input/Output
- images
- spectra
- catalogs and tables
- reference files
- Matching direct and slitless observations
- Astrometric registration
- Background subtraction
- Spectral extraction
- Contamination
- Combining spectra
- Simulations and forward modeling
- Using Astrogrism with other packages
- specutils
- grizli
- pylinear
- EM2D
- MIRAGE?
- Terminology:
- Use "slitless" instead of grism?