• Mars Rover
  • MarsRover.Console
    • Dependencies
    • Build/Run
    • How It Works
  • MarsRover.WebApi
    • Dependencies
    • Build/Run
    • How It Works

This .NET Core console application pulls images taken by all rovers on a given date by calling the NASA Mars Rover Photo API.

• .Net Core SDK 2.2 (Download Here)

• From Visual Studio
  • Open MarsRover.sln
  • Set MarsRover.Console as default startup project
  • Build
  • Debug/Run
• From CLI
  • cd to MarsRover\MarsRover.Console directory
  • dotnet build
  • dotnet run

1. Read in input file

   1. Read input file name from appsettings.json
      • Default to input.txt
      • Assumptions
        • file is in same directory as executable
        • file consists of line seperated date string
   2. Parse dates in each line and persist

2. Retrieve rover manifest for curiosity, opportunity, spirit

   • Rover manifest is used primarily for the Landing Date and Recent Photo Date properties

3. Retrieve photo pages

   • For each rover
     • For each date parsed from input file
       1. Check if Landing Date <= parsed input date >= Recent Photo Date
       2. Retrieve numOfPagesToRequest photo pages.
          • Configurable from appsettings.json
          • Default to 1

4. Download photos

   • For each rover
     • For each date
       • For each photo page
         • Download the first 10 images to the {executable_dir}/Photos/{rover_name}/{date}/ directory

5. Write photo pages to json

   • Serialize the photo pages by rover and write to {executable_dir}/output.json

• .Net Core SDK 2.2 (Download Here)

LIVE DEMO: Here

• From Visual Studio
  • Open MarsRover.sln
  • Set MarsRover.WebApi as default startup project
  • Build
  • Debug/Run
  • index.html will launch in new browser
• From CLI
  • cd to MarsRover\MarsRover.WebApi directory
  • dotnet build
  • dotnet run
  • Navigate to https://localhost:5001 or https://localhost:5000 in browser

1. Check if mars-rover.db exists
   • If the sqlite database doesn't exists, the WebApi will generate a new mars-rover.db file with the expected schema for the WebApi.
2. Upload a date input file
   • Dates must be input into the WebApi by means of a file consisting of line separated date strings. Which is prompted at the Upload Date File section of the web page.
   • Once a file is uploaded to the WebApi, each line is read and the WebApi will persist each line that was read and will track what lines were invalid date string.
   • For valid lines the WebApi will check if the date exists in the mars-rover.db
     • If the date does not exist the line will be inserted into the PhotoDate table in ISO8601 date string format. (SQLite expects dates stored in a TEXT field to be ISO8601 strings "YYYY-MM-DD HH:MM:SS.SSS")
       • The WebApi will track that this line was added into PhotoDate
     • If the date exists, the WebApi will skip inserting it into PhotoDate
       • The WebApi will track that this line already exists in the database.
   • The web page will display lists for lines that were Read, Invalid, Exists, and Added
3. Rover Manifsts
   • On page load, an api call is made to /api/v1/rovers to retrieve rover options for the dropdown list
     • The WebApi checks if any records exists for the rovers currently available from the NASA Mars Rover API (curiosity, spirit, opportunity)
       • If the rover doesn't exist, the rover's Name, LandingDate, and RecentPhotoDate is inserted into the Rover table with LastUpdated of a timestamp of insertion.
       • If the rover exists, a check is made on the LastUpdated field to see if the rover's manifest has been updated within 24 hours.
         • This is to reduce api calls being made to the NASA API
         • It's redundant to call the https://api.nasa.gov/mars-photos/api/v1/manifests/{rover_name} endpoint multiple times a day to update RecentPhotoDate
4. Rover Photos
   • In the Rover Photos section of the web page, select the desired rover and date from the respective dropdown lists.
   • When Get Photos is clicked, and api call is made to /api/v1/rovers/{rover_id}/photos?photoDate={ISO8601_photo_date_string}
     • Checks are made to validate the rover_id and ISO8601_photo_date_string
       • If either of these values don't exist in the database, 404 Not Found will be returned from the API
   • The WebApi will then check if any photo records are currently in the RoverPhoto table for the requested rover_id
     • If there are photo records, the api will return the entire collection in the databse.
     • If there are no photo records, an api call is made to https://api.nasa.gov/mars-photos/api/v1/rovers/{rover}/photos?earth_date={yyyy-M-d} to retreive ALL photos for the rover on the requested date.
       • Each photo is then stored into the RoverPhoto table
         • The field RoverCameraInfo is a JSON string of the NASA API response photo[n]:camera property.
         • The field PhotoUrl is the direct image url for that camera.
         • FK References
           • RoverId
           • PhotoDateId
     • The web page will then display all images in 200x200px thumbnails in rows of 7.
       • Clicking on a thumbnail will open a new tab of the full image for better viewing.