NASA Image Downloader

Download images from the NASA Image & Video Library API into a local folder structure, store each image’s metadata in a JSON file, and automatically resume where the last run stopped. The script is idempotent and runs safely as a nightly job or as a manual command.

Description

Queries NASA’s public “Image and Video Library” API for all images between a start and an end date.
Downloads each image to an images/ directory.
Saves the raw API response for each item to a companion index‑<nasa_id>.json file in metadata/.
Keeps a last_run.txt file with the date of the most recent successful run; subsequent executions automatically pick up from that date.
Skips files that already exist locally, so the script can be called multiple times without re‑downloading anything.
Optional time‑budget: stops after a configurable maximum run time (2 h by default).
Graceful error handling – printing failures to STDERR but continuing the entire run.

Prerequisites

Python 3.7 or later (the shebang is /usr/bin/env python3).
Python packages:
- requests
- tqdm (optional; if missing the script falls back to a plain list)
```
pip install requests tqdm
```

Usage

python downloader.py [--start YYYY-MM-DD] [--end YYYY-MM-DD] [--output BASE_DIR]

Argument	Description
`--start`	Start date (inclusive). If omitted, the script reads the date from
`last_run.txt`; if that file does not exist it defaults to three days ago.
`--end`	End date (inclusive). Defaults to today.
`--output`	Base directory where `images/` and `metadata/` folders will be
created. Default is the current working directory.

The script prints progress to the console and records the last successful end date in last_run.txt (or in the chosen output directory).

Examples

Below are valid calls that demonstrate typical use‑cases.

# 1. Default run – uses last_run.txt for the start date (or defaults to
#    3 days ago) and downloads everything up to today.
python downloader.py

# 2. Override date range – gather images created in the first week of July 2023.
python downloader.py --start 2023-07-01 --end 2023-07-07

# 3. Recent images only – start is yesterday, end is today.
python downloader.py --start $(date -u +%Y-%m-%d --date='-1 day') \
                     --end $(date -u +%Y-%m-%d)

# 4. Output everything under a specific directory tree.
python downloader.py --output /Users/me/Nasa

# 5. Custom state directory: images and metadata will live inside `/tmp/nasa_imgs/`.
python downloader.py --start 2023-06-20 --output /tmp/nasa_imgs

# 6. Combine date range and custom output base.
python downloader.py --start 2023-01-01 \
                     --end 2023-01-05 \
                     --output /Projects/nasa_imgs

Output Structure

After a successful run:

images/
├── <high‑res‑image‑1>.jpg
├── <high‑res‑image‑2>.png
└── ...

metadata/
├── index-XYZ123.json
├── index-ABC456.json
└── ...

last_run.txt

Each index‑<nasa_id>.json contains the full API response for the image.
The images folder holds the highest‑resolution image that NASA offers for each item.

Author

Created by Jarian Cottingham.

License

This project is released under the MIT License. See LICENSE for details.

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