Global Citizen Radio Astronomy Powered By You
Join a worldwide network of radio astronomers learning to observe the cosmos from your location. Detect hydrogen line emissions, monitor solar radio bursts, and participate in educational radio astronomy with affordable RTL-SDR hardware.
What is RadioSky?
A distributed radio telescope network turning consumer hardware into scientific instruments
Your Personal Radio Telescope
Connect an RTL-SDR dongle to your Android device or computer. Point an antenna at the sky. Start collecting radio frequency data from space.
Real-Time Spectrum Analysis
Built-in FFT processing displays power spectral density in real-time. See hydrogen lines, detect interference, visualize cosmic radio emissions.
Join the Global Network
Share your observations with the community. Contribute to a growing database of educational radio astronomy data and learn from others worldwide.
Detect Transient Events
Observe bright transients like solar radio bursts, meteor scatter reflections, and satellite signals. Learn to identify and characterize radio phenomena.
Open Source & Free
Built on open standards and free software. All data processing happens locally. Cloud sync is optional. Your science, your data.
Learn Radio Astronomy
Perfect for students, educators, and hobbyists. Understand radio waves, signal processing, and the electromagnetic universe through hands-on observation.
Distributed Radio Telescope Array
Combining collecting area from stations worldwide
Interactive station map loading...
How We Compare to SKA
The Square Kilometer Array (SKA) is the world's largest radio telescope with 1 km² of collecting area from 197 dishes. RadioSky is a distributed network of citizen scientists contributing to a global radio astronomy effort.
0.2% of SKA collecting area
Observation Capabilities
Educational radio astronomy tools for hands-on learning with consumer hardware
Hydrogen Line (21cm)
Detect the 1420 MHz spectral line emitted by neutral hydrogen throughout the galaxy. Learn radio spectroscopy fundamentals with real observations.
- 1420.405 MHz center frequency
- Doppler shift detection
- Qualitative velocity measurements
- Automated drift scan mode
Solar Observations
Monitor solar radio emissions across multiple frequencies. Track solar flares, coronal mass ejections, and space weather.
- Multiple solar frequency bands
- Flare detection and alerts
- Space weather monitoring
- Time-series analysis
Meteor Scatter
Detect ionized meteor trails as they reflect distant radio signals. Count meteor rates during major showers.
- Forward scatter detection
- Automatic meteor counting
- Shower peak prediction
- Historical shower data
Satellite Tracking
Observe satellites, track ISS passes, decode weather satellite imagery, and monitor spacecraft transmissions.
- TLE-based pass prediction
- Doppler correction
- NOAA/Meteor APT decoding
- Automated satellite recording
Android App
Native Android application with USB OTG support for RTL-SDR. Observe anywhere with your smartphone.
- USB OTG RTL-SDR support
- Real-time FFT processing
- Background observation service
- Offline operation
Web Dashboard
Monitor your station remotely, browse network observations, explore event detections, and analyze historical data.
- Real-time station status
- Global observation map
- Event timeline
- Data export and API
Current System Limitations
Honest assessment of what consumer RTL-SDR hardware can and cannot do
⚠️ Educational Focus
RadioSky is designed primarily for educational outreach and citizen science learning, not as a replacement for professional radio astronomy facilities. Consumer-grade RTL-SDR hardware has significant limitations compared to professional equipment.
Hardware Limitations
- ±1 ppm frequency drift limits velocity measurements to ±1-2 km/s
- 8-bit ADC: 48 dB dynamic range (vs. 72-96 dB professional)
- Temperature-dependent gain variations (±3 dB)
- Limited 2 MHz bandwidth
Calibration Limitations
- No calibrated noise sources
- Unknown antenna beam patterns
- Pointing accuracy only ±5-10°
- 30-50% flux calibration uncertainty
Data Quality
- 40-70% RFI contamination in urban areas
- Cannot detect sources weaker than ~100 Jy
- No angular resolution (beam FWHM >10° for dipoles)
- Velocity uncertainty 10-100× worse than professional
✓ What RadioSky IS Good For
- Education: Hands-on learning of radio astronomy techniques and signal processing
- Bright transients: Detection and alerting for solar bursts, meteor scatter
- Temporal monitoring: Continuous coverage where absolute calibration is less critical
- Technology development: Testbed for distributed observation coordination
- Community: Connect with amateur radio astronomers worldwide
RadioSky is complementary, not competitive with professional facilities. Data quality currently requires professional validation for scientific publication.
Frequently Asked Questions
What hardware do I need?
+An RTL-SDR dongle ($25-40), USB OTG cable for Android, and a basic antenna. For hydrogen line observations, a dish antenna or helical antenna is recommended.
Can I use RadioSky without hardware?
+Yes! The web dashboard lets you browse observations from the global network, explore event detections, and analyze data even without your own station.
Is RadioSky really free?
+Yes, RadioSky is open source and free to use. The Android app, web dashboard, and backend server are all available on GitHub.
What can I actually observe?
+Hydrogen line emissions from the Milky Way (qualitative detection), bright solar radio bursts, meteor scatter reflections, satellite signals, and some strong cosmic radio sources. Consumer RTL-SDR hardware is limited to detecting bright sources (>100 Jy) and provides educational demonstrations rather than precision measurements.
Do I need a license?
+No license required - you're only receiving radio signals, not transmitting. RTL-SDR is a passive receiver that's legal to use worldwide.
How accurate is RTL-SDR?
+RTL-SDR hardware is suitable for educational radio astronomy but has significant limitations: ±1 ppm frequency drift (velocity uncertainty ±1-2 km/s), 48 dB dynamic range (vs. 72-96 dB professional), temperature-dependent gain variations (±3 dB), and 30-50% flux calibration uncertainty. It can detect strong signals like the hydrogen line and solar bursts, but cannot compete with professional facilities for precision measurements.
Can I contribute to real science?
+RadioSky focuses primarily on educational outreach and hands-on learning. You can contribute to transient detection (bright solar bursts, meteor scatter) and temporal monitoring studies. However, data quality requires professional validation for scientific publication due to calibration limitations, RFI contamination (40-70% in urban areas), and hardware constraints. RadioSky is complementary to professional facilities, not competitive with them.
Where is my data stored?
+All observations are stored locally by default. You can optionally upload to the RadioSky network to share with the community. Data is compressed and includes metadata like location, frequency, and timestamp.
How do I set up an antenna?
+Start with a simple dipole for general observations. For hydrogen line, build or buy a small dish (60cm+) or helical antenna. Point at zenith or use equatorial mount for tracking.
Can I use this for education?
+RadioSky is perfect for STEM education! Students can learn about radio waves, signal processing, astronomy, and scientific data collection through hands-on observation.
Start Observing the Radio Universe
Join the global network of citizen radio astronomers. Download the Android app or access the web dashboard to begin your journey.
Open Source • RTL-SDR Compatible • Free Forever