Aladin Lite: a brief summary over the years

• Aladin Lite was released in 2013
• Multi-resolution image viewer
• Uses the HiPS IVOA standard based on HEALPix tesselation of the sphere
• The more you zoom, the more you see



• JS Canvas 2D rendering
• Lightweight: less than 100kB at the time when gzipped and minified
• Easy to embed
• No plugins, installation required
• Just a few JS snippet of code to use
• JS API aiming to be simple and very light CSS (can be overriden easily)

Aladin Lite: Some users of Aladin Lite

Aladin Lite: Some users of Aladin Lite

• ~30000-40000 startups per day
• Some over-usage for special events (e.g. 100k startups when the first JWST image was released)

Aladin Lite: a brief summary over the years

• Although efficient, Aladin Lite v2 is getting old:
• New data vizualization challenges coming (SKA, LSST, ...)





• Improved embeddable visualization - a priority for the ESCAPE project
• Big FITS image support needed
• Big data cube e.g. SKA data challenge2: 1TB simulated datacube
• Powerful new technologies are now available
• WebGL, much more well supported than in 2013








• Rust, a new safe, performant system language, can be compiled to WebAssembly easily!

E-OSSR integration

• The source code (link github)
• A bunch of user examples (contained in the repo here)
• The API documentation - here
DOI link:

Aladin Lite v3: A short video

Aladin Lite v3: The added value

• WebGL2 new graphical engine
• FITS HiPS tiles support and dynamic client-side cutouts changes
• All-sky projections support: Aitoff, Mollweide, Azimuthal, Gnomonic, Mercator - more to come
• Multiple image survey overlays
• Better MOC support
• Can display MOCs up to max HEALPix order 29 (~0.4 milli-arcsecond HEALPix cells)
• Thanks to the use of performant Rust librairies cds-moc and cds-healpix
• New coordinate grid overlay - more customisations to come!
• Smartphones/tablets enhanced experience: pinched rotation and zoom, move with inertia
• Still lightweight
• ~500kB for the whole project, bigger than v2 but still OK for nowadays
• E.g. a single 512x512 FITS tile storing float precision values: 512x512x4=1Mo large

Easy embedding

• Replacing v2 with the v3 (line 7)
• CSS not needed anymore but JQuery still a dependency
• Aladin instantiation wrapped inside a init promise (ensuring the WASM file is loaded) (lines 13-20)

Javascript API: Enhanced displacements

• Change the projection: setProjection
  • Aitoff, Orthographic, Azimuthal, Mollweide, ...see Representations of celestial coordinates in FITS, Calabretta, M. R., Calabretta, M. R. paper
• Turn around the cursor: setRotation, zoom in/out: setFov, move to a location: setRaDec

Javascript API: Meerkat survey display

• Aladin.createImageSurvey returns an HpxImageSurvey object
• New methods are available on it: setCuts, setColormap, setOpacity, toggle
• Add multiple overlays with the Aladin.setOverlayImageLayer method

Javascript API: Planetary survey display

• longitudeReversed optional keyword: reverse the longitude axe for planetary surveys
• Catalog overlays API: A.catalog, Catalog.addSources, Aladin.addCatalog

Javascript API: GWs multi-order maps display

Probability confidence region plots of gravitational waves. Credits to ESCAPE EGO/VIRGO partner G. Greco

Javascript API: Additive blending mode

Add the colors of multiple image surveys together, with the optional additive keyword

Available through a jupyter notebook python API

Development cycle

• Developments on GitHub: https://github.com/cds-astro/aladin-lite
• Pull requests, issues, release
• Documentation, API and examples: https://aladin.u-strasbg.fr/AladinLite/doc/
• GPLv3 License

Software requirements/services

• Requirements
• Runs on any web browsers with WebGL2 compatibility (~94% user support taken from caniuse)
• GPU not mandatory but suggested
• Services & libraries
• Services: mocserver, HiPS nodes
• Librairies: cds-healpix, fitsrs, cds-moc, wcs

Some last words

• Aladin Lite v3 beta is available
• You now have instructions how to use it
• And how to embed it
• Contact us for feedback, bug reports, questions, feature ideas
• By mail at: cds-question@unistra.fr
• On the official Aladin Lite repository
• Releasing date: January 2023
• Development continues
• FITS general image support, WCS parser & analyser - work in progress
• HiPS cube support in the frame of SKA Science Region Centre visualization prototyping
• OpenGL graphical backend for making it a desktop application
• Looking forward releasing a google play/apple store app

Useful links

• The Aladin portal: https://aladin.u-strasbg.fr/AladinLite/
• Aladin Lite documentation (News, API, snippet examples)
• Link to the slides https://aladin.u-strasbg.fr/AladinLite/ADASS2022 for you to play with it
• Our contact
• By mail at: cds-question@unistra.fr
• On the official Aladin Lite repository

Thank you!