Apollo

APOLLO is an astronomical alert and broker system. APOLLO consists of several Python functions that compose both a listener and scheduler. The listener employs the GCN Kafka Client for Python to receive classic and JSON notices from the NASA General Coordinates Network (GCN).

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Overview

Code Structure

The code is run from the main APOLLO directory through a set of scripts that pull functions from module libraries. The scripts currently available include:

• GCN listener (gcn_listener.py)
• Survey simulator (survey_simulator.py)

Running APOLLO

To run the GCN listener, navigate to the main APOLLO directory, and run the following command:

$ python -m scripts.gcn_listener

Installation

Setup APOLLO

First, download a copy of APOLLO and navigate to the main directory. Open the configuration file (config.py) and change the following parameters to suit your specific environment:

• APOLLO_DIRECTORY
• DELPHI_DIRECTORY

Then, in a terminal and from the main APOLLO directory, run the following command:

$ python -m scripts.setup_apollo

This will create the Delphi directory at the specified location in the configuration file. The Delphi directory is the place for saving alert contents, analysis files, catalogs, and logs.

Select Observatory

There are currently a few observatories supported in the code. One may freely add their own observatories to the code (in the observatory.py library). To select an observatory, choose one that is successfully encoded by setting the OBSERVATORY parameter in the configuration file.

Download Catalogs

Apollo's scheduler uses the latest GLADE catalog (https://glade.elte.hu/) for selecting galaxy targets to follow up. Download the catalog as an ASCII text file (i.e. GLADE+.txt), and save it to the directory ~/Delphi/analysis/survey.

Create GCN Account

One requires an account on the GCN platform (https://gcn.nasa.gov/). The parameters CLIENT_ID and CLIENT_SECRET are uniquely generated per user, and must be plugged into the configuration file in order to use the listener.

Create Email Account

The GCN listener sends alerts to a mailing list from a specified email client. Set the email that will send the alerts via the parameter EMAIL in the configuration file. You can add email addresses to the MAILING_LIST parameter in order to send alerts to willing participants.

Development

Platform

I have developed APOLLO on the Ubuntu 24.04.1 LTS operating system using a Conda environment and Python 3.12.2.

Testing

I have not written any tests of APOLLO yet. Suggestions are always welcome!

References

• G. Dálya et al. (2022), GLADE+: An Extended Galaxy Catalogue for Multimessenger Searches with Advanced Gravitational-Wave Detectors, MNRAS, Volume 514, Issue 1, https://doi.org/10.1093/mnras/stac1443

• LVK Collaboration (2022), LIGO/Virgo/KAGRA Public Alerts User Guide, https://emfollow.docs.ligo.org/userguide/

• NASA, General Coordinates Network (GCN): NASA's Time-Domain and Multimessenger Alert System, https://gcn.nasa.gov/

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19 Jul 2023
Last update: 14 Nov 2024

Richard Camuccio
[email protected]