The first summer

Nine teachers spent six weeks learning digital signal processing, building a radio telescope each, and taking it to Green Bank.

9teachers
5states
6weeks
Morgantown + Green Bank

A horn antenna built by DSPIRA teachers set up on the grounds of the Green Bank Observatory — A teacher-built horn antenna at the Green Bank Observatory.

Who was here

The 2017 cohort

Nine teachers came from five states. All of them teach science in grades 8 through 12, and all of them went home with a working radio telescope.

The 2017 DSPIRA teacher cohort assembled outdoors — The 2017 cohort.

Jamie Avalos TX
Howard Chun RI
Denise Gipson WV
Eric Goff WV
Wendy Lee WV
John Makous NC
Adam Osborne WV
Shane Price WV
LaShonda Torbert MD

Foundation

The point of the program was to send teachers home able to run digital signal processing projects with their own students — so the first four weeks were daily lectures building a foundation in astronomy and DSP.

The astronomy covered the celestial sphere, astronomical and solar time, Kepler's laws, the H–R diagram, galaxies, and cosmology topics including dark matter and galaxy rotation curves. The signal processing track was modeled on an undergraduate DSP course, running from signal basics through to the fast Fourier transform.

Hands-on learning

Every lecture was followed by a lab. The labs took the abstract parts of DSP and made them tangible, which software-defined radio is unusually good at: GNU Radio is free and open source, it runs on cheap off-the-shelf radio hardware, and it is the same tool the lab uses on real instruments. The structured labs ended with each teacher writing their own software spectrometer — a component every radio telescope needs.

Then they built the telescope. That meant soldering a low-noise amplifier out of very small components and fabricating a horn antenna, in a design deliberately constrained to materials and tools you can buy at a hardware store. The horns were built in the industrial design workshop at WVU.

The whole group got their LNAs working, several of them having never soldered before. The horn construction turned into an assembly line. Between the spectrometer, the LNA and the horn, every teacher had a working radio telescope by the end of the four weeks in Morgantown.

GNU Radio — free, open source, and the same stack the lab uses on real instruments.

A surface-mount amplifier component a couple of millimeters across, balanced on a fingertip above a printed assembly sheet — The amplifier parts are a couple of millimeters across. Several teachers had never soldered before.

Two teachers working a metal cylinder into shape at a bench in the WVU workshop — Fabricating the feed, in the industrial design workshop at WVU.

A completed horn antenna on its wooden mount standing in a field under a blue sky — The finished article. Horn, mount, amplifier and spectrometer — four weeks, from nothing.

Field experiments

The horn antennas were tested in Morgantown, then taken to the Green Bank Observatory.

At WVU

Several tests confirmed the telescopes worked before they traveled. LNA performance was measured in the lab, with the noise figure taken inside the Faraday cage in the RF room. A trial observing run with one of the horns was conducted on the roof of the Engineering Sciences Building.

At Green Bank Observatory

The last two weeks were spent on site. The teachers went through the observatory's full suite of outreach activities, including training on the 40 Foot telescope — and then tapped its signal, routing it through the SDR dongle and the GNU Radio spectrometer they had written at WVU. They also took the intermediate-frequency signal from the Green Bank Telescope through the same spectrometer and compared the result against the VEGAS back end.

Mostly, though, the time went on planning and executing observations with the horns. The teachers wrote their own observing plan to map the whole sky. Hot–cold measurements gave the gain and system temperature of the horn system, work on the antenna probe and the LNA continued in the GBO electronics lab, and workshops on site covered reducing the data the spectrometer produced.

Bench test equipment in the WVU RF room showing a measurement on red LED displays — Measuring the noise figure, in the RF room at WVU.

Time-lapse of a horn antenna undergoing measurement in the laboratory — Hot–cold measurements, to get the system temperature of the horn.

A horn antenna set up on the rooftop of the Engineering Sciences Building at WVU, the valley stretching away behind it — The trial run, on the roof of the Engineering Sciences Building.

The 40 Foot telescope sign at the Green Bank Observatory with the dish standing behind it — The 40 Foot, whose signal the teachers routed through their own spectrometer.

Four horn antennas on wooden mounts lined up on the grass outside the Green Bank Science Center, with the Reber Telescope towering behind them — Four horns on the lawn outside the Science Center, under the Reber Telescope.

Two teachers working by lamplight with horn antennas beneath the Reber Telescope against a deep blue dusk sky — The same spot at dusk. Mapping the Galaxy took the observing into the night.

Students and lessons

The Green Bank trip overlapped with the PING summer camp, which gave the teachers a room full of students to try the material on. They wrote and ran digital signal processing activities pitched at school-age children — the first version of what became the DSPIRA curriculum.

In the classroom. Introducing PING campers to digital signal processing.
Group exercises. Every module ended in one.
Sampling discretely. Sampling and quantization — the cornerstone of the whole subject.
Campers working through one of the activities.
On encoding. A basic exercise in digital encoding.
An outdoor activity. Filtering, outside the Green Bank Science Center.

What it opened up

The summer gave teachers research experience in engineering and radio astronomy, but it also made a wider point about amateur radio astronomy. The hardware is cheap and the design uses materials anyone can find — home insulation, paint thinner cans — so the barrier to entry is mostly curiosity. It also means a teacher can build more telescopes back at their own school without much logistical burden.

And these simple systems can do more than one thing. An aperture array built from several horns, for instance, opens up time-domain radio astronomy — a thread the 2018 cohort's undergraduates picked up directly.

Four teacher-built horn antennas lined up side by side on their wooden mounts as a small aperture array — Four horns as a small aperture array — the starting point for the next summer's pulsar work.

Everything they used

Use the lessons online

51 lessons covering the astronomy, the hardware, the signal processing and the labs—free and maintained by the DSPIRA community.

Open the lessons site

← DSPIRA program Cohorts 2017 2018 2019