Introduction#

VSPEC (Variable Star PhasE Curve) is a powerful tool designed to simulate observations of exoplanets orbiting variable stars.

VSPEC uses a dynamic model of stellar spots, faculae, flares, and granulation combined with simultations from the Planetary Spectrum Generator (PSG, Villanueva et al., 2018) to simulate phase resolved observations of planetary spectra.

Recent observations with JWST have shown stellar contamination can cause signals similar to exoplanet atmospheres [Moran et al., 2023]. Similarly, the future Habitable Worlds Observatory will gather reflected-light spectra of earth-like exoplanets over a very long baseline. To understand these challenges and develop data analysis that can mitigate them, we need a robust and flexible modeling suite.

This package was initially designed to simulate data for the Mid-IR Exoplanet CLimate Explorer mission concept (MIRECLE, Mandell et al., 2022), but has since been refactored to be a general-use tool. It builds off of PSG and supports reflcted, thermal, and transmission spectroscopy as well as the use of a coronagraph for direct imaging spectroscopy.

Installation#

VSPEC can be installed via pip.

pip install vspec

You can also clone our repository. This would be great if you are interested in contributing.

git clone https://github.com/VSPEC-collab/VSPEC.git
cd VSPEC
pip install -e .[dev,plot]

Note that adding [dev,plot] will install additional dependecies for development and plotting.

Running PSG#

While it is not 100% necessary to run PSG locally in order to use VSPEC, it is highly recommended. Luckly, PSG is easy to install and run. Detailed instructions can be found in the PSG handbook (see page 153).

We recommend using Rancher Desktop to run the PSG Docker container, as it is free for all use. If you do not have administrative (sudo) access to your computer, uncheck ‘Administrative Access’ in Rancher Desktop settings.

Note

Rancher Desktop is not necessary if running on Linux. The docker engine command line interface is sufficient. It can be installed by following these instructions.

VSPEC assumes you have installed PSG using the commands (Handbook page 154):

docker logout
docker pull nasapsg/psg
docker tag nasapsg/psg psg

docker run -d --name psg -p 3000:80 psg

VSPEC interfaces with PSG through the pypsg library, so if you change any setting from the default (e.g. the port that PSG runs on), make sure to change the appropriate setting in pypsg.

Importantly, pypsg assumes that a container named psg exists to run PSG locally, and if this container is not found the code will complain even if PSG is installed and http://localhost:3000/api.php is reachable.

VSPEC has been tested with the following PSG packages installed:

  • BASE

  • SURFACES

  • ATMOSPHERES

  • LINES

  • EXO

  • CORRKLOWMAIN

Note

Users who wish to run simulations with resolving powers higher than R=500 must install the CORRKMEDMAIN package (up to R=5000).