DSPIRA Lessons

Digital Signal Processing in Radio Astronomy

Build a radio telescope. Point it at the Galaxy.

51 free lessons. You fold the antenna out of insulation board, solder your own amplifier, and then use the thing to measure how fast the Milky Way turns. The high school teachers who wrote these did all of it first.

Start at lesson one See all 51 lessons

The seven modules

Start at the top and they take you from a flat sheet of insulation board to a velocity curve of the Milky Way. Or take any one on its own; most stand up as a couple of weeks of classroom material.

  1. Module 1

    Horn Construction

    Foil-faced insulation board, aluminium tape, dimensional lumber, and a paint-thinner can for the throat. The finished stand is 75 cm across, so it fits through a classroom door.

    All 5 lessons

  2. Module 2

    Receiver Electronics

    The amplifier is what decides how good your telescope is, so it is the part worth taking time over. Build the DSPIRA board for about $30 in parts, or buy one ready-made and get on with the observing.

    All 5 lessons

  3. Module 3

    Software Setup

    Ubuntu, GNU Radio, and the DSPIRA blocks. The flash-drive route turns any Windows machine into a spectrometer without touching its hard disk.

    All 11 lessons

  4. Module 4

    Observing

    It works in daylight, in the rain, and from a school car park. All it needs is open sky and somewhere to sit.

    All 10 lessons

  5. Module 5

    Digital Signal Processing

    Six lab exercises that build a spectrometer in GNU Radio one block at a time: sampling, Fourier analysis, filters, and finally correlation, the trick that turns two horns into an interferometer.

    All 8 lessons

  6. Module 6

    Astronomy

    The part it is all for. Where to point, what hydrogen looks like at 21 cm, and how a rotation curve ends up as an argument for dark matter.

    All 8 lessons

  7. Module 7

    Community Labs

    Schools, clubs and students who built the hardware and then went somewhere the curriculum does not: cosmic rays, motorised mounts, and checking the thing against the literature.

    All 4 lessons

What the telescope is

A horn telescope has three parts: the antenna, a pyramidal horn folded from foil-faced insulation board; the stand, built from dimensional lumber; and the back-end electronics, a low-noise amplifier and a software-defined radio dongle. Parts run to a few hundred dollars, and everything can be sourced from a hardware store and a couple of online suppliers.

Pointed at the sky, it detects the 21 cm line of neutral hydrogen — enough to map the hydrogen in the Milky Way and measure how fast the Galaxy turns.

A pyramidal horn antenna of foil-faced insulation board, mounted on a wooden cradle and stand in a field.
The whole instrument: horn, cradle, stand and feed can.

Where these came from

DSPIRA was a National Science Foundation Research Experiences for Teachers site at West Virginia University, run with the Green Bank Observatory. Over three summers, fifteen high school teachers built these telescopes, learned the signal processing behind them, observed with them at Green Bank, and then wrote these lessons from what they had done.

The cohort programme concluded in 2019. The lessons are still here, still free, and still maintained. More about the programme.

The Milky Way over the Green Bank Observatory site, with DSPIRA written in the air by a hand-held light.
Green Bank, West Virginia, where the cohorts observed.

Also here

  • Telescope kits

    Educators and community organisers can request a starter kit of the parts that are hardest to source — an SDR dongle and a 21 cm amplifier.

  • Who these are written for

    Every lesson is tagged for school teachers, students or hobbyists. This is the same 51 lessons sorted by who they were written for.

  • Associate research labs

    Classrooms and hobbyist groups that have taken this hardware and these lessons and built their own programmes on them.

  • LightWork Memos

    An informal numbered memo series on citizen science with radio telescopes, covering design, construction and operation.

  • The forum

    Questions, build reports and troubleshooting, running on GitHub Discussions. Threads go back to 2020.

  • Contribute a lesson

    The whole site is Markdown in a public repository. This is how to add your own lesson to it.