Merging branch 2026.2.x into main

This branch includes all new notebooks and workflows, updated notebooks, and requirement files in support of release Nexus 2026.2. 

All CI tests pass now.

Author: rizeladiaz

.github/workflows/notebook-on-demand.yml

@@ -336,4 +336,3 @@ jobs:
 
 
 
-

.gitignore

@@ -2,4 +2,3 @@
 .DS_Store
 mastDownload
 *.asdf
-*.ecsv

CITATION.cff

@@ -0,0 +1,78 @@
+cff-version: 2026.2
+message: "If you use these notebooks in your work, please cite it using the following metadata."
+authors:
+- family-names: "Barnes"
+  given-names: "Amethyst"
+  orcid: "https://orcid.org/0009-0001-0447-0793"
+- family-names: "Bianco"
+  given-names: "Sam"
+  orcid: ""
+- family-names: "Cherinka"
+  given-names: "Brian"
+  orcid: "https://orcid.org/0000-0002-4289-7923"
+- family-names: "Choi"
+  given-names: "Ami"
+  orcid: ""
+- family-names: "Desjardins"
+  given-names: "Tyler"
+  orcid: "https://orcid.org/0000-0001-6905-1859"
+- family-names: "Diaz"
+  given-names: "Rosa"
+  orcid: "https://orcid.org/0000-0002-2269-239X"
+- family-names: "Dutkiewicz"
+  given-names: "Thomas"
+  orcid: "https://orcid.org/0009-0003-8874-4679"
+- family-names: "Han"
+  given-names: "Eunkyu"
+  orcid: "https://orcid.org/0000-0001-9797-0019"
+- family-names: "Khandrika"
+  given-names: "Harish"
+  orcid: "https://orcid.org/0000-0002-9011-0216"
+- family-names: "Lajoie"
+  given-names: "Charles-Philippe"
+  orcid: "https://orcid.org/0009-0003-3993-8338"
+- family-names: "Louie"
+  given-names: "Dana"
+  orcid: "https://orcid.org/0000-0002-2457-272X"
+- family-names: "Mehta"
+  given-names: "Vihang"
+  orcid: "https://orcid.org/0000-0001-7166-6035"
+- family-names: "Morris"
+  given-names: "Brett"
+  orcid: "https://orcid.org/0000-0003-2528-3409"
+- family-names: "Otor"
+  given-names: "Justin"
+  orcid: ""
+- family-names: "Price"
+  given-names: "Sedona"
+  orcid: "https://orcid.org/0000-0002-0108-4176"
+- family-names: "Sánchez"
+  given-names: "Javier"
+  orcid: "https://orcid.org/0000-0001-8514-4350"
+- family-names: "Schultz"
+  given-names: "Will C."
+  orcid: "https://orcid.org/0000-0003-1796-9849"
+- family-names: "Shahbandeh"
+  given-names: "Melissa"
+  orcid: "https://orcid.org/0000-0002-9301-5302"
+- family-names: "Sharma"
+  given-names: "Sanjib"
+  orcid: "https://orcid.org/0000-0002-0920-809X"
+- family-names: "Wilson"
+  given-names: "Robby"
+  orcid: ""
+- family-names: "Wu"
+  given-names: "John F."
+  orcid: "https://orcid.org/0000-0002-5077-881X"
+
+abstract: " The Roman Notebooks. Jupyter notebooks "
+repository-code: "https://github.com/spacetelescope/roman_notebooks"  
+
+
+title: "Roman Notebooks"
+version: 2026.2.0
+doi: 10.5281/zenodo.17179608
+license: BSD-3-Clause
+date-released: 2026-09-15
+type: software
+url: "https://github.com/spacetelescope/roman_notebooks"

images/crds_workflow.jpg

@@ -0,0 +1,15 @@
+# Introduction to the Nancy Grace Roman Space Telescope
+
+The Nancy Grace Roman Space Telescope (Roman) is a NASA flagship mission with an expected launch in mid-2026. Roman is equipped with the Wide Field Instrument (WFI) as its primary instrument, as well as the Roman Coronagraph. The WFI has a large field of view, approximately 200 times larger than that of the Hubble Space Telescope Wide Field Camera 3 infrared detector. When compared to other space observatories, like Hubble Space Telescope, the scale of data collection will be magnitudes larger than what has been possible before. For example, in the first five years of operations, the estimated volume of Roman's data archive is 20 petabytes (PB), which is roughly 20,000 terabytes (TB), compared to Hubble's 172 TB during 30 years of operations.
+
+During its mission, Roman will conduct different surveys of the sky including the Galactic Bulge Time-Domain Survey, High-Latitude Time-Domain Survey, High-Latitude Wide-Area Survey, and the Galactic Plane Survey. Each of these surveys will contribute to our understanding of the Universe, as well as serving Roman's primary missions of studying and discovering exoplanets, and measuring dark matter and dark energy. 
+
+Data from Roman will be stored and available to users via the Roman Archive in the Barbara A. Mikulski Archive for Space Telescopes (MAST), with WFI data stored in Advanced Scientific Data Format (ASDF). Instructions on how to access and utilize the Roman data is available throughout the Roman Nexus Workflows and Tutorial Notebooks.
+
+Welcome to the Nancy Grace Roman Space Telescope!
+
+
+## For Additional Information About Roman’s Mission Explore:
+- [Roman Documentation (RDox)](https://roman-docs.stsci.edu/)
+- [Roman's Mission](https://science.nasa.gov/mission/roman-space-telescope/)
+- [Roman Space Telescope](https://www.stsci.edu/roman)

images/wfi-data-sim.jpg

@@ -19,7 +19,7 @@ Below is the current set of Notebook Tutorials available in the Nexus. Each tuto
 
 ### Data Access and Exploration
 
-- [**Catalog Database Access**](../notebooks/cayalog_database_access/catalog_database_access.ipynb)  
+- [**Catalog Database Access**](../notebooks/catalog_database_access/catalog_database_access.ipynb)  
 
   Access and query a wide diversity of Roman catalogs from MAST databases.
 
@@ -60,6 +60,15 @@ Below is the current set of Notebook Tutorials available in the Nexus. Each tuto
   Combine multiple Level 2 data products into a Level 3 distortion-corrected and co-added image using the Roman WFI science calibration pipeline, RomanCal.
 
   *Science Workflow(s)*: [WFI Data Simulation](./workflows/wfi-data-sim.md)
+
+- [**CRDS Reference Files**](../notebooks/crds_reference_files/README.md)
+
+    - Understand the structure, content, and usage of Calibration Reference Data System. 
+    - Learn How to get reference files from CRDS
+    - Explore each major reference file type in detail.
+      
+  
+  *Reference Files Workflow*: [**CRDS Reference Files Exploration**](./workflows/crds-reference-files.md)
 
 - [**WFI TVAC Bright Star Data**](../notebooks/ground_test_analysis/wfi_tvac_brightstar.ipynb)
 

markdown/roman_Intro.md

@@ -6,17 +6,20 @@ Workflows are designed to help users explore Roman-style analysis patterns in th
 
 ## WFI Workflows (Early Access)
 
-The Early Access release currently includes three WFI-focused Science Workflows: 
+The Early Access release currently includes four WFI-focused Science Workflows: 
+
+- [Quickstart Workflow](./workflows/Intro_Workflow.md)
 - [WFI Data Simulation](./workflows/wfi-data-sim.md)
 - [WFI Data Analysis](./workflows/wfi-data-analysis.md)
 - [WFI Observation Planning](./workflows/wfi-obs-plan.md)
+- [CRDS Reference File Exploration](./workflows/crds-reference-files.md)
 
-Together, these workflows demonstrate how Roman tools can be used for pipeline-level data simulation, exploratory analysis of simulated WFI products within the Nexus environment, and proposal planning. 
+Together, these workflows demonstrate how Roman tools can be used for pipeline-level data simulation, exploratory analysis of simulated WFI products and calibration reference data within the Nexus environment and proposal planning. 
 
-Each workflow highlights a different aspect of the platform ecosystem—from generating synthetic data and processing them through the Roman calibration pipeline to performing basic measurements on exposure-level products and evaluating observing strategies. While the current materials focus on WFI-imaging investigations, they also include an introductory spectroscopic example within the Data Analysis workflow, with additional spectroscopic content planned for future updates. Two further workflows—one covering **time-domain analysis** and another focused on **WFI TVAC data**—are in development and expected to be added in **early 2026**.
+Each workflow highlights a different aspect of the platform ecosystem—from generating synthetic data and processing them through the Roman calibration pipeline to performing basic measurements on exposure-level products and evaluating observing strategies. While the current materials focus on WFI-imaging investigations, they also include an introductory spectroscopic example within the Data Analysis workflow, with additional spectroscopic content planned for future updates. One further workflow covering **time-domain analysis** is in development and expected to be added in **summer 2026**.
 
 ## Using Workflows
 Workflows are composed of individual [Notebook Tutorials](./tutorials.md), each focused on a specific tool or analysis step. Users may work through an entire workflow sequentially or use the tutorials independently, depending on their goals. If you would like to modify the material for a custom workflow, first copy it into your personal home directory or team home directory. 
 
 ---
-*Last Updated: December 2025* 
+*Last Updated: July 2026* 

markdown/tutorials.md

@@ -0,0 +1,41 @@
+# Intro Nexus Workflow
+Welcome to the Roman Research Nexus, an open platform which brings data from NASA's flagship missions, the Nancy Grace Roman Space Telescope (Roman), into the hands of everyone. Whether you're getting your start in citizen science, completing course work, or just wanting to look at some new images from Roman, this is the place to start.
+
+This workflow has preselected tutorial notebooks which are best suited for people either outside of the field of astronomy, or just beginning their astronomy education. These tutorial notebooks will teach the process by which one can access, filter, and visualize Roman data.
+
+- [**Jupyter Notebook Tutorial)**](../../markdown/jupyter.md)
+
+  Start here if you haven't already. Explore the basics of working in Jupyter and learn all the skills you'll need to be able to run the notebooks.
+
+## Workflow Overview
+
+- [**Roman Mission Introduction**](../../markdown/roman_Intro.md)
+
+  Before we start utilizing the data, let's learn about where the data comes from. Explore this mission and get an idea of the type of technology and instrumentation we'll be working with. Gain a background on the purpose and details of the Roman Mission and its goals.
+
+- [**Data Discovery and Access**](../../notebooks/data_discovery_and_access/data_discovery_and_access.ipynb)
+
+  Now that you know what Roman is, let's figure out how to find its data. Due to the vast amount of data which we will be receiving from the telescope, scientists working with data from Roman will utilize cloud-based storage processing. These cloud services are limited to registered MyST users only; regardless, this notebook will teach you how to search for and retrieve data from Roman's Wide Field Instrument (WFI), as well as data from other missions (such as the Hubble Space Telescope) from the Barbara A. Mikulski Archive for Space Telescopes (MAST). With this notebook you'll be able to search for observations of celestial objects in MAST, and allow you to take the data you found into the next notebooks.
+
+- [**Working With ASDF**](../../notebooks/working_with_asdf/working_with_asdf.ipynb)
+
+  Now that we have found our data let's figure out how to open and handle it. Roman stores its data using the Advanced Scientific Data Format (ASDF), so in this notebook you will learn about tools allowing you to search, load, and read ASDF files. Additionally learn about the process by which Roman Data are formatted and categorized as you explore ASDF metadata. By the end of this notebook you'll have an understanding of the structures and functions related to the data produced by Roman, enabling you to take on new data yourself.
+
+- [**Data Visualization**](../../notebooks/data_visualization/data_visualization.ipynb)
+
+  You've learned about how find the data and how the products are formatted; now let's start to work with those data products. In this notebook, you will take the methods you learned to access data and apply it to methods of visualization so that we'll be able to look at the images and data Roman is providing.  Additionally, you will learn about some known instrument artifacts that can occur with the WFI. Explore different visualization techniques to gain all the tools you'll need to look at all the amazing images from Roman.
+
+
+- [**Footprint Visualization**](../../notebooks/footprint_visualization/footprint_visualization.ipynb)
+
+  Now, let's explore the kinds of science Roman will do. In this notebook, you will learn about the various surveys that the Roman Space Telescope will complete during its mission. Furthermore, you will be able to visualize Roman survey footprints on the sky to determine whether, when, and how Roman may observe an astronomical source. With this final tutorial in the workflow, take the step towards your own science and explore with these sources and tools yourself.
+
+  
+
+## Caveats and Limitations
+- This workflow is primarily for individuals who do not have advanced degrees in astronomy, providing a curated selection of tutorials utilized by professional astronomers, and additionally providing explanations of concepts when possible to make certain ideas more accessible.
+- It is highly recommended to explore the resources linked throughout the notebooks in order to gain a better grasp of the ideas and concepts discussed in this workflow.
+
+
+---
+*Last Updated: July 2026* 

markdown/workflows.md

@@ -0,0 +1,70 @@
+# CRDS Reference Files
+
+This science workflow guides users through understanding the structure, content, and
+usage of Calibration Reference Data System (CRDS) reference files for the Roman Wide
+Field Instrument (WFI).
+
+The notebooks in this workflow are designed as standalone tutorials but can
+be followed sequentially for a complete introduction to how reference files are
+retrieved, inspected, and visualized.
+
+## Workflow Overview
+
+### General CRDS Introduction
+
+- [crds_reference_files.ipynb](../../notebooks/crds_reference_files/crds_reference_files.ipynb)
+
+   - Learn what CRDS is, how reference files are matched and delivered, and how to use `crds.getreferences()` and `crds.getrecommendations()`.
+
+### Reference File Inspection Fundamentals
+
+- [crds_reference_files.ipynb](../../crds_reference_files/crds_reference_files.ipynb) (first part) + individual reference file notebooks
+
+Understand the common structure of Roman reference files using `roman_datamodels` and the `.info()` method.
+
+### Individual Reference File Notebooks
+
+Explore each major reference file type in detail:
+
+| Reference File | Purpose | Key Concepts Covered | Notebook |
+|----------------|---------|----------------------|----------|
+| **MASK** (Bad Pixel Mask) | DQ flags and bad pixel identification | `dq` array, bitwise flags, flagged pixel statistics | [bad_pixels_mask_reffile.ipynb](../../notebooks/crds_reference_files/bad_pixels_mask_reffile.ipynb) |
+| **DARK** | Dark current correction | Pixel-by-pixel and frame-by-frame dark current values per detector readout mode | [dark_reffile.ipynb](../../notebooks/crds_reference_files/dark_reffile.ipynb) |
+| **SATURATION** | Saturation thresholds | Per-pixel thresholds, flag handling | [saturation_reffile.ipynb](../../notebooks/crds_reference_files/saturation_reffile.ipynb) |
+| **REFPIX** | Reference pixel correction | Frequency-dependent coefficients (`alpha`, `gamma`, `zeta`) | [reference_pixel_reffile.ipynb](../../notebooks/crds_reference_files/reference_pixel_reffile.ipynb) |
+| **DISTORTION** | Astrometric distortion model | Astropy `CompoundModel`, grid evaluation, vector fields | [distortion_reffile.ipynb](../../notebooks/crds_reference_files/distortion_reffile.ipynb) |
+| **PHOTOM** | Photometric calibration | conversion factors for putting pixel values into physical units | [photom_reffile.ipynb](../../notebooks/crds_reference_files/photom_reffile.ipynb) |
+| **GAIN** | DN to electrons conversion | Per-pixel gain maps, amplifier structure | [gain_reffile.ipynb](../../notebooks/crds_reference_files/gain_reffile.ipynb) |
+| **READNOISE** | Read noise characterization | Per-pixel read noise maps | [readnoise_reffile.ipynb](../../notebooks/crds_reference_files/readnoise_reffile.ipynb) |
+| **AREA** | Pixel solid angle | Pixel area maps in steradians | [area_reffile.ipyn](../../notebooks/crds_reference_files/area_reffile.ipynb) |
+| **PSF / ePSF** | Empirical point spread function | Multi-dimensional ePSF stamps, extended PSF | [psf_reffile.ipynb](../../notebooks/crds_reference_files/psf_reffile.ipynb) |
+| **LINEARITY** family | Non-linearity correction | `LINEARITY`, `INVERSELINEARITY`, `INTEGRALNONLINEARITY` (per-amplifier lookup tables) | [linearity_reffile.ipynb](../../notebooks/crds_reference_files/linearity_reffile.ipynb) |
+
+
+## Suggested Learning Path
+
+1. Start with the general **CRDS Reference Files** notebook.
+3. Go through the individual reference file notebooks in roughly this order:
+   - MASK -> DARK -> SATURATION -> FLAT (foundational)
+   - GAIN -> READNOISE -> AREA -> DISTORTION (detector characterization)
+   - LINEARITY family (important for flux accuracy)
+   - PHOTO (photometric calibration)
+   - REFPIX, PSF/ePSF (more specialized)
+4. Return to the general CRDS notebook as needed for context.
+
+
+<img src="https://raw.githubusercontent.com/spacetelescope/roman_notebooks/refs/heads/main/images/crds_workflow.jpg" alt="CRDS Workflow" width="250" />
+
+
+## How to Use This Workflow
+
+- Work through the notebooks sequentially for a comprehensive understanding.
+- Use individual notebooks independently when you need to inspect a specific reference file.
+- All notebooks follow a consistent structure
+
+## Related Workflows
+
+- **WFI Data Simulation** — Uses many of these reference files via Roman-I-Sim and CRDS.
+- **WFI Data Analysis** — Uses calibrated data products that depend on these reference files.
+- **Exposure Pipeline** tutorial — Shows where these reference files are actually applied in `romancal`.
+