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WIP: Figuring out how to intercept telemetry from James Web Telescope

Today I wondered if I could detect a data stream from the JWST.

I've done this with ham radio satellites and INMARSAT, but what about objects much further away?

This thread will be a running tally of the project. So it is less of a how-to, and more a public notepad for you guys to follow along in case you were interested, or had something to add.

There are a few challenges as I see them now

  1. JWST is far away, orbiting around Earth-Sun L2 (a million miles) so signal might be very weak and hard to detect with small antennas.
  2. The spacecraft uses frequency bands outside of shack capabilities
  3. Once the freq is discovered, we need to design and build an antenna
  4. We still need to figure out where it is to point the antenna

A search produced some frequency ranges to answer for #2:

JWST uses S-band at 2270.5 MHz to transmit telemetry. The science data will be transmitted in K-band at 25.9 GHz, with a rate of up to 28 Mbps.​

The best SDR I have is the SDRPlay2, which tops out at 2ghz. The RTL v4s only go to 1.7ghz. I'm going to need a receiver with higher range or a block down converter.

#4 is pretty easy to solve. NASA does it for us.

We can use a planetarium application and a script, along with NASA data, to plot the position of points important to this project.

The program I am using is called Stellarium. It is free and feature-rich.

This repo contains a Stellarium script to plot the position of the James Webb Space Telescope (JWST) and the Sun-Earth-Moon-Barycenter L2 Lagrange (SEMB-L2) point using coordinates from the Nasa Horizons service.

This is the plot for ~10pm tonight.


The JWST will be fairly high to the east, clear of trees and obstructions. I'll have to adjust the data of course when we're ready for a measurement attempt.

You can see Sun-Earth L2 point in yellow off to the right. The JWST orbits these points.

L2 or the LaGrange Point 2 is a point in the solar system where objects can be placed and not have to use much or any fuel to stay in orbit.

In red, I've plotted Earth-Moon L4. This is for another experiment I've been planning since the bottom of last solar cycle, but since I just figured out this script, I thought I'd try mapping other points.

So it appears I have enough to at least start finding the RX gear and planning the antenna.

The coffee can antenna comes to mind, but I am thinking it won't be enough gain.

I do have a 22 inch dish with a 5ghz feed. This might be suitable with a custom 2.2ghz feed. Only way to know is to get an RX and test it out.

I'll update as I make some progress.
Lots of other projects lately, but I haven't forgotten. I'll get back to it soon.