Use Case Catalog

Primary use cases that exercise the JWST Data Analysis Application across all architectural views. Each use case references which views it touches and which architectural components are involved.

4+1 View: +1 Scenarios — these use cases tie the Logical, Process, Development, and Physical views together.

Actors

Actor	Description
Astronomer	Authenticated user who imports, analyzes, and visualizes JWST data
Visitor	Unauthenticated user browsing public data and featured targets
Admin	User with elevated privileges for data management
MAST Portal	External STScI archive providing JWST observations
Processing Engine	Internal Python service performing scientific computation

---

Primary Use Cases

UC-1: Discover and Import JWST Data

Goal: Astronomer finds interesting JWST observations and imports them for analysis.

Trigger: User navigates to Discovery page.

Flow: 1. Frontend loads featured targets from backend (GET /api/discovery/featured) 2. User selects a target (e.g., "Carina Nebula") or searches by name/coordinates 3. Backend queries Processing Engine, which queries MAST via astroquery 4. Results displayed with instrument/filter metadata and preview thumbnails 5. User selects observations to import 6. Backend creates an import job (POST /api/mast/import) → JobTracker assigns job ID 7. Processing Engine downloads FITS files from STScI archive (chunked, resumable) 8. Files stored via IStorageProvider (S3 or local), metadata saved to MongoDB 9. SignalR pushes progress updates (bytes downloaded, files completed) 10. Job completes → data appears in user's library with full lineage (L1→L3)

Views Exercised: - Logical: JwstData, JobStatus, FeaturedTarget, MastObservation entities - Process: Async job queue, SignalR push, chunked download with resume - Physical: Frontend → Backend → Processing Engine → MAST (external) - Development: All three services coordinate

Error Scenarios: - MAST timeout → retry with exponential backoff - Download interrupted → job marked resumable, user can restart - Disk full → job fails with storage error, no partial records saved

---

UC-2: Create Multi-Band Color Composite

Goal: Astronomer combines multiple JWST filter images into a single RGB color image.

Trigger: User clicks "Create Composite" or follows a recipe suggestion.

Flow: 1. User selects 2+ FITS images from their library, assigns each to a color channel 2. Per-channel controls: stretch algorithm, black/white points, gamma, tone curve, weight 3. Color assignment via hue angle, explicit RGB, or luminance (LRGB mode) 4. User can apply a preset (auto, natural, NASA, high-contrast, faint-emission, scientific) 5. Frontend submits composite request (POST /api/composite/n-channel) 6. Backend validates inputs, creates job, forwards to Processing Engine 7. Processing Engine: loads FITS → WCS alignment → per-channel stretch → color mapping → stack → post-processing 8. Result stored as PNG/JPEG blob, job marked complete 9. SignalR notifies frontend → composite displayed in viewer 10. User can adjust parameters and re-render, or save to library

Views Exercised: - Logical: JwstData (inputs), CompositeRequest, ChannelConfig, JobStatus - Process: Compute-intensive job, progress stages, result as blob - Physical: CPU-bound work on Processing Engine container

Quality Attributes: See QA-1 (performance) — composite of 4 channels at 4096x4096 should complete in < 30s.

---

UC-3: Build WCS-Aligned Mosaic

Goal: Astronomer combines multiple overlapping JWST pointings into a single seamless mosaic.

Trigger: User selects multi-pointing observations, or recipe indicates requiresMosaic = true.

Flow: 1. User selects 2+ FITS files with WCS headers 2. Backend requests footprint analysis from Processing Engine (POST /api/mosaic/footprints) 3. Footprints displayed on a sky coordinate overlay (RA/Dec corners, bounding box) 4. User configures: combine method (mean/sum/first/last/min/max), stretch, colormap, output size 5. Frontend submits mosaic request (POST /api/mosaic/create) 6. Processing Engine uses reproject library for WCS-aware reprojection and combination 7. Result can be PNG/JPEG (for viewing) or FITS (for further analysis, saved as L3 data) 8. Saved mosaics link back to source files via DerivedFrom

Views Exercised: - Logical: JwstData (inputs + output), MosaicRequest, MosaicFileConfig, footprints - Process: Memory-intensive reprojection, DoS limits enforced (MAX_MOSAIC_OUTPUT_PIXELS) - Physical: RAM-constrained on Processing Engine container

---

UC-4: Guided Discovery Experience

Goal: New user follows a step-by-step wizard from target selection to finished composite.

Trigger: User clicks a featured target card on the Discovery home page.

Flow: 1. Featured target cards load with thumbnails, categories, and composite potential ratings 2. User selects a target → system queries MAST for available observations 3. Processing Engine analyzes available filters and suggests ranked recipes 4. User picks a recipe (e.g., "Pillars of Creation — NASA-style RGB") 5. System checks which data is already imported; imports missing observations 6. GuidedCreate wizard pre-fills channel assignments from the recipe's color mapping 7. User can accept defaults or customize before rendering 8. Composite created (UC-2 flow) → result displayed → user can save or share

Views Exercised: All views — this is the end-to-end "golden path" through the application.

---

UC-5: Analyze Astronomical Data

Goal: Astronomer performs quantitative analysis on imported FITS data.

Trigger: User opens a data file and selects an analysis tool.

Subflows:

5a. Region Statistics: - User draws a rectangle or ellipse on the image - Backend forwards region to Processing Engine - Returns: mean, median, std, min, max, sum, pixel count

5b. Source Detection: - User configures threshold (sigma), FWHM, minimum pixels - Processing Engine runs photutils-based detection - Returns: detected sources with centroids, flux, sharpness, roundness

5c. Table/Spectral Viewer: - FITS tables displayed with pagination and column metadata - Spectral data plotted as interactive charts (wavelength vs. flux)

Views Exercised: - Logical: JwstData, AnalysisModels (region stats, source detection, table/spectral) - Process: Synchronous request-response (no job queue for simple analysis) - Physical: Processing Engine CPU for source detection

---

UC-6: Upload and Manage Local Data

Goal: Astronomer uploads their own FITS files and organizes their data library.

Trigger: User clicks "Upload" or drags files into the application.

Flow: 1. Frontend validates file type and size client-side 2. File uploaded via multipart POST to backend (POST /api/jwstdata/upload) 3. Backend validates FITS headers, extracts metadata (instrument, filter, WCS) 4. File stored via IStorageProvider, metadata document created in MongoDB 5. Thumbnail generated asynchronously 6. User can tag, describe, archive, and share uploaded data 7. Data appears in library with IsPublic = false (private by default)

Supporting Operations: - Search by filename, tags, target, instrument, filter - Semantic search across metadata fields - Archive/unarchive, version tracking - Bulk operations (tag, delete, share)

---

UC-7: Authenticate and Manage Account

Goal: User creates an account and manages their session.

Flow: 1. Register with username, email, password (+ optional display name, organization) 2. Login → backend issues JWT access token + refresh token 3. Access token used for API calls (short-lived) 4. Refresh token extends session without re-login 5. Admin can manage user accounts and access public data 6. All user data scoped by UserId — users see only their own data + public data

Architectural Note: Auth flow is currently fragile — documented as a known limitation. Extra care required for changes.

---

Use Case Map

graph LR
    subgraph Actors
        A[Astronomer]
        V[Visitor]
        AD[Admin]
    end

    subgraph "Core Use Cases"
        UC1[UC-1: Discover & Import]
        UC2[UC-2: Create Composite]
        UC3[UC-3: Build Mosaic]
        UC4[UC-4: Guided Discovery]
        UC5[UC-5: Analyze Data]
        UC6[UC-6: Upload & Manage]
        UC7[UC-7: Authenticate]
    end

    A --> UC1
    A --> UC2
    A --> UC3
    A --> UC4
    A --> UC5
    A --> UC6
    A --> UC7
    V --> UC4
    V --> UC1
    AD --> UC6
    AD --> UC7

    UC4 -->|includes| UC1
    UC4 -->|includes| UC2
    UC2 -->|may include| UC3

---

Traceability to Architecture Views

Use Case	Logical View	Process View	Development View	Physical View
UC-1: Discover & Import	JwstData, JobStatus, FeaturedTarget	Async jobs, SignalR, chunked download	All 3 services	Frontend → Backend → Engine → MAST
UC-2: Create Composite	CompositeRequest, ChannelConfig	Compute job, progress push	Backend + Engine	CPU on Engine container
UC-3: Build Mosaic	MosaicRequest, JwstData lineage	Memory-intensive job, DoS limits	Backend + Engine	RAM on Engine container
UC-4: Guided Discovery	All entities	Full async pipeline	All 3 services	Full stack + MAST
UC-5: Analyze Data	Analysis models	Synchronous request-response	Backend + Engine	CPU on Engine container
UC-6: Upload & Manage	JwstData, User	File upload, thumbnail gen	Frontend + Backend	Storage provider
UC-7: Authenticate	User, tokens	JWT lifecycle, refresh	Frontend + Backend	Stateless (no session store)

---

Back to Architecture Overview