Self hosted NASA Astronomy Picture of the Day (APOD) viewer written with Ionic 8 / Angular 22 (client) and Java (server).

https://apod.rasc.ch/

Technology

Server

Written in Java 25 with Spring / Spring Boot. Periodically polls the NASA Science APOD API, stores the information in a Xodus database, downloads JPEG images and recompresses them with jpeg-recompress to save bandwidth. The API's url is an article link; hdurl supplies the image used for both normal and high definition views. Credits and explanations are converted from HTML to plain text. Video and non-JPEG entries are skipped.

The NASA Science API does not require an API key. Its base URL can be overridden with app.nasa-api-url (default: https://science.nasa.gov/wp-json/wp/v2/apod-basic/). Provides a Protocol Buffer endpoint (/apods) for the clients.

Libraries:

• Spring 7
• Spring Boot 4
• Xodus
• jsoup
• OkHttp
• protobuf-java
• kryo

Client

Written in TypeScript, CSS, HTML and the Ionic framework.
The app consists of 3 pages:

• Home: Displays a list of images for each APOD entry. Shows detail page when user taps on image.
• Detail: Displays the image and underneath the explanation. Shows full page when user taps on image.
• Full: Displays the high definition image in a scrollable view.

Apod data is stored in IndexedDB. The application accesses the IndexedDB through Dexie.js. Visited images are stored by the service worker in the cache. The application assets are also cached, the app therefore runs when offline. In offline mode the applications shows only entries and images that the user visited before and are therefore cached.

Libraries

• Ionic
• Dexie.js
• ProtoBuf.js
• Workbox

Icon

Source: https://www.shareicon.net/science-stars-education-astronomy-universe-telescope-795293
Various sized icons generated with: http://cthedot.de/icongen/

Build tools

• bread-compressor-cli: Pre-compresses assets
• Vite: Builds the custom service worker
• workbox-cli: Precache the application resources

Run locally

• Install Node.js https://nodejs.org/en/

• Install Java 25

• Download jpeg-recompress for your operation system https://github.com/imagemin/jpeg-recompress-bin/tree/master/vendor/

• Clone the project and install the dependencies

  git clone https://github.com/ralscha/apod.git
  cd apod/client
  npm install
  

• Open server/src/main/resources/application-development.properties and change the path to the jpeg-recompress binary.

• Download some test data. The following command will download the last 10 days.

  cd apod/server
  ./mvnw spring-boot:run -Dspring.profiles.active=development -Dspring-boot.run.arguments=import10
  

• Start the server

./mvnw spring-boot:run -Dspring.profiles.active=development

• Start the client and service worker build watcher

cd apod/client
npm run dev

Backfill missing dates

The scheduled import checks the latest four days. To recover a longer gap, stop the running server, replace its JAR with the rebuilt server/target/apod.jar, and run the following with the same configuration and data paths as the service:

java -jar apod.jar import-range --from=2026-09-29 --to=2026-10-18 --spring.main.web-application-type=none

Both dates are inclusive; --to defaults to today. Existing database entries are skipped. The command imports oldest first and can be rerun after a failure. Run it before restarting the service so clients receive the missing dates before newer entries. Clients that already synchronized newer dates will need their local APOD data refreshed to pick up older backfilled entries.

Build and test the server with Java 25 or later:

cd server
./mvnw verify