Upcoming Passes
Predictions for your location based on current orbital elements
Share your location
Required to calculate when the ISS will fly over you
Amateur Radio
ISS frequencies, modes, and scheduled transmissions
Frequencies
APRS / Packet Digipeater
Automatic Position Reporting System — relays ground station packets worldwide
145.825
MHz
UP/DOWN
Voice Downlink
Crew voice, ARISS school contacts, SSTV events. FM narrow (±5 kHz deviation)
145.800
MHz
DOWN
Cross-Band Repeater — Downlink
Pairs with 437.800 MHz uplink. Active during crew off-hours when enabled by crew. PL tone: 67.0 Hz
145.800
MHz
DOWN
Cross-Band Repeater — Uplink
UHF uplink for cross-band repeater. Use 67.0 Hz CTCSS tone. ISS re-transmits on 145.800 MHz
437.800
MHz
UP
Voice Uplink — Region 1
Europe, Middle East, Africa. Used during ARISS school contacts directed from the ground
144.490
MHz
UP
Voice Uplink — Region 2
North and South America
144.200
MHz
UP
Voice Uplink — Region 3
Asia and Pacific
145.200
MHz
UP
Doppler Shift Reference
The ISS travels at ~27,600 km/h, causing significant Doppler shift. Tune your radio accordingly:
FrequencyMax shift (AOS/LOS)At TCA
145.800 MHz±3.7 kHz0 Hz
145.825 MHz±3.7 kHz0 Hz
437.800 MHz±11.2 kHz0 Hz
TCA = Time of Closest Approach (maximum elevation). Many modern radios with satellite tracking mode handle this automatically.
Slow Scan Television (SSTV)
SSTV Image Transmissions
Transmitted on 145.800 MHz downlink
PD120
Primary mode — 320×496 color, 126 sec/frame
PD180
High-res variant — 640×496 color, 187 sec/frame
Robot 36
Occasional — 160×120 color, 36 sec/frame
Known event windows
~12 Apr
Yuri's Night / Cosmonautics Day — annual multi-day event
~Nov
ISS anniversary events (station launched Nov 1998)
Ad hoc
Russian space milestone commemorations
ARISS School Contacts
ARISS (Amateur Radio on the ISS) facilitates scheduled contacts between ISS crew and schools, museums, and science centers worldwide. During a contact:
- Students ask the crew questions live over amateur radio
- Anyone within the ISS footprint can listen on 145.800 MHz FM
- Passes typically last 10 minutes — preparation and setup are critical
- Low-elevation passes (<10°) may be too noisy for reliable copy
Listening Tips
Equipment
A simple handheld VHF/UHF FM radio or SDR (e.g., RTL-SDR) works. A directional Yagi antenna greatly improves results for low passes.
Timing
Be ready 2 minutes before AOS. APRS packets arrive in short bursts. Voice contacts are brief — the entire pass is the contact window.
APRS Software
Use Direwolf (PC), APRSdroid (Android), or APRS.fi to decode packets. ISS digipeats packets from the ground — your station can be gated to the internet.
SSTV Decoding
Use MMSSTV (Windows), Robot36 (Android), or Black Cat SSTV (iOS/Mac). Hold your radio near the mic input or use a cable for best results.