National Aeronautics and
Space Administration

General
Coordinates
Network

NASA’s Next Generation Time-Domain and Multimessenger Alert System

A service of the Astrophysics Science Division at NASA’s Goddard Space Flight Center

https://gcn.nasa.gov

Realtime Alerts Born of Necessity

GCN Enabled Seminal Breakthroughs in Astrophysics

There are two kinds of GCN data products:

The Changing Scientific Landscape

The Changing Technological Landscape

Introducing
the new GCN

## What is special about GCN's Kafka cluster?
            **It's special because it's so ordinary!** It's a plain 3-broker Kafka cluster
            * No custom auth extensions to side-load into the server
            * No vendor lock-in: we use [Confluent Platform](https://www.confluent.io/product/confluent-platform/), but we could use open-source [Apache Kafka](https://kafka.apache.org) or fully managed solutions like [Confluent Cloud](https://www.confluent.io/confluent-cloud/) or [Amazon MSK](https://aws.amazon.com/msk/)

We use standard [OpenID Connect (OIDC)](https://openid.net/connect/) for single sign-on
            * We use [Amazon Cognito](https://aws.amazon.com/cognito/), one of many off-the-shelf OIDC auth solutions
            * We use the same auth system across our web site and our Kafka broker
            * We have a straightforward path to adopting [SciTokens](https://scitokens.org) (an HPC single sign-on infrastructure based on OpenID Connect, adopted by LIGO)

Why switch to the new GCN?

	GCN Classic	GCN Classic over Kafka
Self-service	NO. Users need to contact administrator in order to make account and subscription changes	YES. Manage your own account and subscription settings through the web site
Open standards	NO. Notices are sent using three custom protocols	YES. Notices are sent using one standard protocol, Apache Kafka
Open source	NO. Custom software needed to receive notices	YES. Receive notices using open-source software
Highly available	NO. Notices are broadcast by a single server	YES. Notices are broadcast by a cluster of highly-available Kafka brokers in the cloud
Secure	NO. Notices are sent as plaintext	YES. Notices are protected with SSL/TLS

Streaming GCN
Notices in Python

## Migrating GCN Circulars from GCN Classic

On April 17, 2023, GCN Circulars moved from the old site to the new one. If you had an account on the old system, then you already have an account on the new one!

### GCN Circulars Migration Cheat Sheet

<table class="why-switch">
  <thead>
    <tr>
      <th></th>
      <th>Old</th>
      <th>New</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <th>
        <img src="https://cdnjs.cloudflare.com/ajax/libs/uswds/2.13.3/img/usa-icons/local_library.svg" alt="">
        Web archive
      </th>
      <td><a href="https://gcn.gsfc.nasa.gov/gcn3_archive.html">https://gcn.gsfc.nasa.gov/<wbr>gcn3_archive.html</a></td>
      <td><a href="https://gcn.nasa.gov/circulars">https://gcn.nasa.gov/<wbr>circulars</a></td>
    </tr>
    <tr>
      <th>
        <img src="https://cdnjs.cloudflare.com/ajax/libs/uswds/2.13.3/img/usa-icons/mail.svg" alt="">
        Emails come from
      </th>
      <td>gcncirc@capella2.gsfc.nasa.gov</td>
      <td>no-reply@gcn.nasa.gov</td>
    </tr>
    <tr>
      <th>
        <img src="https://cdnjs.cloudflare.com/ajax/libs/uswds/2.13.3/img/usa-icons/send.svg" alt="">
        Submit Circulars by email to
      </th>
      <td><a href="mailto:gcncirc@capella2.gsfc.nasa.gov">gcncirc@capella2.gsfc.nasa.gov</a></td>
      <td>
        <div><a href="mailto:gcncirc@capella2.gsfc.nasa.gov">gcncirc@capella2.gsfc.nasa.gov</a></div>
        <div><a href="mailto:circulars@gcn.nasa.gov">circulars@gcn.nasa.gov</a> <small style="vertical-align: baseline">(recommended)</small></div>
      </td>
    </tr>
    <tr>
      <th>
        <img src="https://cdnjs.cloudflare.com/ajax/libs/uswds/2.13.3/img/usa-icons/language.svg" alt="">
        Submit Circulars by web form
      </th>
      <td><span style="color: gray">(not supported)</span></td>
      <td><a href="https://gcn.nasa.gov/circulars/new">https://gcn.nasa.gov/circulars/new</a></td>
    </tr>
  </tbody>
</table>

Tutorial:
Receiving GCN Circulars

Tutorial:
Submitting GCN Circulars

Screen shot of a GCN Circulars submit sign in

Screen shot of a GCN Circulars peer endorsement process

What’s next for GCN?

Screen shot of New Notice Producers Documentation

## Unified schema and alert format for GCN Kafka
        * JSON schema with common core fields
        * Instrument/mission/observatory specific fields where needed
        * <a href="https://github.com/nasa-gcn/gcn-schema">https://github.com/nasa-gcn/gcn-schema</a>

JSON example (in development):
        ```
        {
          "$id": "https://github.com/nasa-gcn/gcn-schema/blob/main/gcn/notices/fermi/gbm/Trigger.schema.json",
          "$schema": "https://json-schema.org/draft/2020-12/schema",
          "title": "Trigger",
          "description": "fermi gbm Trigger",
          "type": "object",
          "properties": {
            "alert_info": {
              "$ref": "https://github.com/nasa-gcn/gcn-schema/blob/main/gcn/notices/core/AlertInfo.schema.json"
            },
            "identifiers": {
              "$ref": "https://github.com/nasa-gcn/gcn-schema/blob/main/gcn/notices/core/Identifiers.schema.json"
            },
            "event_info": {
              "$ref": "https://github.com/nasa-gcn/gcn-schema/blob/main/gcn/notices/core/EventInfo.schema.json"
            },
            "datetime": {
              "$ref": "https://github.com/nasa-gcn/gcn-schema/blob/main/gcn/notices/core/DateTime.schema.json"
            },
            "localization": {
              "$ref": "https://github.com/nasa-gcn/gcn-schema/blob/main/gcn/notices/core/Localization.schema.json"
            },
            "statistics": {
              "$ref": "https://github.com/nasa-gcn/gcn-schema/blob/main/gcn/notices/core/Statistics.schema.json"
            },
            "hardness_ratio": {
              "$ref": "https://github.com/nasa-gcn/gcn-schema/blob/main/gcn/notices/core/HardnessRatio.schema.json"
            },
            "comments": {
              "$ref": "https://github.com/nasa-gcn/gcn-schema/blob/main/gcn/notices/core/Comments.schema.json"
            },
            "specific": {
              "$ref": "Specific.schema.json"
            }
          }
        }
        ```