This is a Python package to access CMB data from the Legacy Archive for Microwave Background Data (LAMBDA).

Command line

Installing the package puts a lambdaquery command on your PATH:

lambdaquery experiments                  # list every experiment
lambdaquery datasets WMAP                # list one experiment's datasets
lambdaquery fetch WMAP <dataset> -o ./data

fetch writes each file under the output directory (-o, default: the current directory), mirroring its LAMBDA /data/... path — so the same file referenced by several datasets is stored, and downloaded, once. Downloaded paths go to stdout and progress goes to stderr, so lambdaquery fetch ... > files.txt gives you a clean list of paths. Pass -q to silence progress. Files already present are skipped.

The listing commands print one name per line and pipe into grep — useful, since WMAP alone has several thousand entries:

lambdaquery datasets WMAP | grep 9yr

python -m lambdaquery ... works the same way if the script directory isn't on your PATH.

Try it

uv sync
uv run jupyter lab notebooks/lambdaquery_demo.ipynb

notebooks/lambdaquery_demo.ipynb is a guided tour of the package — browsing the catalog, inspecting an entry, and downloading a file — with a scratch section at the end for your own experiments. It's the easiest way to kick the tires and it's where feedback is most welcome.

For a terminal session instead, uv run ipython.