How to view images using CARTA on AWS

Follow the instructions below to use CARTA on AWS from a web browser on your local machine. This can be useful for visualizing large images stored on AWS without needing to download them first.

Prerequisites

An account on AWS and access to the headnode
Pre-configured Spack environment on AWS on an interactive compute node. See How to start an interactive compute node on AWS and How to load Spack modules on AWS.
A fits image to open on AWS

Warning

Using CARTA to open large images on the headnode is not recommended. Make sure you are on an interactive compute node before following the steps below.

Steps

On an interactive compute node, navigate to the folder containing your images (CARTA will open the file browser in this directory by default but you can navigate to other directories as needed).
Make a note of the compute node host name (you will need this later). You can find this by running the command:
```
hostname
```
Load the carta module:
```
module load carta
```
Choose a unique port number (e.g. 12345) - if your chosen port is already in use you will need to choose a different port.
Start CARTA with the --no_browser option and your chosen port:
```
carta --no_browser --port 12345
```
Copy the url and token that this will print (it will look something like this: http://10.192.5.113:12345/?token=9ee0f256-7e62-4114-a983-9c26f87548c1)
On your local machine, open a new terminal window and start a new subshell with temporary AWS credentials:
```
aws-vault exec dp-hpc-headnode
```
Set up a tunnel to the compute node via the headnode to access CARTA and map the port you used above to a port on your machine (you can use the same number).
```
PORT=12345
ssh -L localhost:${PORT}:<compute-node-hostname>:${PORT} dp-hpc-headnode
```
Open a web browser on your local machine and navigate to the url you copied in step 5, replacing the IP address with localhost (e.g. http://localhost:12345/?token=9ee0f256-7e62-4114-a983-9c26f87548c1).

Verification

You should see the CARTA interface in your web browser. You can use the file browser to navigate to and open your fits image stored on AWS.

FAQ

Q: Where can I find more information about using CARTA?

A: See the official CARTA documentation for more details.