Abstraction Layer for Ephemerides (ALE)

This library allows for the position, rotation, velocity and rotational velocity tracking of multiple bodies in space, especially in relation to one another. It makes extensive use of NAIF's SPICE data for such calculations.

Using ALE to generate ISDs

To generate an ISD for an image, use the load(s) function. Pass the path to your image/label file and ALE will attempt to find a suitable driver and return an ISD. You can use load to generate the ISD as a dictionary or loads to generate the ISD as a JSON encoded string.

isd_dict = load(path_to_label)
isd_string = loads(path_to_label)

You can get more verbose output from load(s) by passing verbose=True. If you are having difficulty generating an ISD enable the verbose flag to view the actual errors encountered in drivers.

Setting up dependencies with conda (RECOMMENDED)

Install conda (either Anaconda or Miniconda) if you do not already have it. Installation instructions may be found here.

Creating an isolated conda environment

Run the following commands to create a self-contained dev environment for ALE (type y to confirm creation):

conda env create -n ale -f environment.yml

For more information: conda environments

Activating the environment

After creating the ale environment, we need to activate it. The activation command depends on your shell.

• tcsh: conda activate ale

You can add these to the end of your $HOME/.bashrc or $HOME/.cshrc if you want the ale environment to be active in every new terminal.

Building ALE

After you've set up and activated your conda environment, you may then build ALE. Inside of a cloned fork of the repository, follow these steps:

python setup.py install
cd build
cmake ..
make

Keep in mind that you will need to clone the repository with the --recursive flag in order to retrieve the gtest submodule for testing. If you have already cloned without the --recursive flag, running the following command will retrieve the gtest submodule manually:

git submodule update --init --recursive

Adding the ALESPICEROOT environment variable

If an ale driver is going to be used that leverages SPICE data, it is necessary to set the ALESPICEROOT. One can do this using normal shell syntax, e.g.:

export ALESPICEROOT=/path/to/ale/spice

or inside of a conda environment:

conda env config vars set ALESPICEROOT=/path/to/ale/spice.

Adding ALE as a dependency

You can add ALE as a dependency of your CMake based C++ project by linking the exported CMake target, ale::ale.

For example:

add_library(my_library some_source.cpp)
find_package(ale REQUIRED)
target_link_libraries(my_library ale::ale)

Running Tests

To test the c++ part of ALE, run:

ctest

from the build directory.

To test the python part of ALE, run:

pytest tests/pytests