APRS through the ISS

Everything on this page except the VIA ISS mark in the packet log needs APRS Connect Pro.

The International Space Station carries an amateur radio packet digipeater, run by ARISS (Amateur Radio on the International Space Station). It listens and transmits on 145.825 MHz, 1200 baud AFSK, worldwide, and repeats any packet whose path asks for it. A station on the ground can hear it, and be heard by it, only while the station is above the horizon: a pass lasts about ten minutes, and there are several a day.

The ISS screen is in the drawer.

Where it is

The screen says whether the station is above your horizon right now, how high it stands and in which direction, and where it is over the earth. The numbers are computed on the phone from the station's published orbit, a two-line element set from CelesTrak. It is fetched when there is a connection and refreshed about twice a day. A fetched orbit is kept and used for days, so the screen works with no signal once it has one. The line under the position says how old the orbit is.

Whether the station is above you needs your own position, which the screen asks for the same way the map does. A line under the position says how old the orbit is, and Update orbit data fetches a fresh one on demand; for an hour after a fetch the button is absent and the line says when it returns, as a courtesy to CelesTrak's free service.

Show on the map turns on the Space station map layer and centres the map on the station. The layer draws three things: the station itself as the APRS satellite symbol, updated every couple of seconds; the dashed circle of ground from which it is currently above the horizon, which is the area it can hear a packet from; and its ground track for the next orbit. Tap the symbol to open the ISS screen. The layer is also in the map's LAYERS panel, and off by default.

Next passes

The screen lists the next three passes over your position: when each starts, how long it lasts, how high it gets and in which direction. A pass under way is listed first with the time it ends. Passes that peak under 10° above the horizon are not listed; a handheld does not hear them. The Elevation line, set on a pass's sky chart, moves that limit. Next 5 days of passes opens the rest, grouped by day.

The same passes can sit on the Dashboard: add its Next ISS pass tile, and make it bigger to list more than one.

Every pass has a Notify button. Tapping it asks for a notification before that one pass, at the times set under Minutes before a pass, whatever the other settings below say; tapping again withdraws it.

A pass on the sky chart

Tap a pass, in either list, to see it drawn across the sky. The circle is the sky over you: its edge is the horizon and its centre is straight up, with rings at 30° and 60°. North is at the top and east is on the right, as on a compass. The line is the station's path, with an arrowhead showing which way it goes. The Sun and the Moon are drawn where they will be, if they are up. The (i) in the corner of the chart says the same in the app.

Under the chart a table gives the time, elevation and direction of the rise, the highest point and the set. While the pass is under way, a dot on the line marks where the station is and a Now row gives its elevation and direction each second.

The dashed ring is the Elevation line: how high you want the station before you count on working it. It starts at 10°, and the setting under the table changes it to 5°, 15° or 20°, or turns it off. The table gains two rows for it, the time the station climbs above the line and the time it drops below it. A pass that never gets that high has no such rows.

The line is also the limit for the lists: a pass that peaks under it is left out of Next passes, the five-day list and the Dashboard tile. With the line off, the limit is 10°. Notifications do not use it. They have their own limit, Only above.

On a phone, a pointer on the edge of the circle shows where the top of the phone points. Hold the phone flat and turn until the pointer is in line with the dot: the top of the phone then points toward the station. The pointer comes from the phone's compass. To calibrate it, move the phone in a figure eight pattern. A computer has no compass, so the pointer is not shown in a browser or in the desktop app.

SSTV pictures during a pass

In the Android, iPhone and desktop apps, Receive SSTV on the ISS screen and on a pass opens the SSTV screen with this chart beside the picture, for receiving the pictures the ISS sends during ARISS events. See SSTV pictures.

Notifications

Every pass posts a notification before each pass that fits two limits: Only above sets the peak elevation a pass has to reach (10°, 20°, 30° or 45°), and Between sets the local times of day you are willing to be notified in. The same time in both boxes means any time of day; a window that ends before it starts runs through midnight. Tap a time to open a picker with a box at the top for typing a time instead. The picker offers twelve hours and AM or PM on a 12-hour clock, or twenty-four hours on a 24-hour one, and then five-minute steps. Times follow the app's clock setting. Minutes before a pass sets how far ahead the notification comes: 2, 5, 10, 15 or 30 minutes, with 5 the default. Pick more than one to be notified more than once. For example, 10 and 2 gives one notification ten minutes before each pass and another two minutes before. At least one stays picked.

The notification carries the duration, the peak, the frequency and the path. Notifications are off by default, ask for permission when first switched on, and have their own Android notification channel, ISS passes, so they can be silenced on their own. They are scheduled from the orbit and your position when a setting changes, when the app returns to the foreground, and when a fresh orbit arrives, and they fire whether or not the app is running.

Beaconing through it

A packet asks the station to repeat it with the path ARISS, and nothing after it. When the station repeats a packet it writes its own callsign into the path as the used hop, RS0ISS*, the way a terrestrial digipeater does with WIDE1-1.

Add ISS beacon creates a beacon profile with that path, a fixed rate of once a minute, and only your radio channels selected, then opens it in the editor. It is an ordinary beacon otherwise, and it is created switched off. Once a profile with the ISS path exists, the screen shows that profile in place of the button.

Send during passes is the switch that sends it. With it on, the ISS beacon goes out once a minute while the station's orbit puts it above your horizon, and whenever anything it repeated is heard on your radio, whether that is its own beacon or anyone's packet with RS0ISS* in the path. Nothing is sent between passes, and the profile itself stays switched off. The channel is shared by every station under the footprint, so once a minute is the accepted rate. The radio has to be on 145.825 MHz; the app does not tune it.

Heard via ISS

The bottom of the screen lists every station whose packets the ISS has repeated, from the packet log, newest first, with a count and when it was last heard. Your own station is highlighted. Tap a row to open the station, or Show in packet log to see the packets themselves under the log's Via ISS filter.

The same fact appears in three other places: a VIA ISS tag in the packet log's left-hand gutter on each packet the station repeated, a Via ISS row on a station's page once it has been heard that way, and a VIA ISS chip in the view filter's Show only row that narrows the map, the Stations list and the packet log to stations the space station has repeated. All three are free.

Only a packet that came back down counts. A packet that asked for the station but was not repeated still has ARISS unmarked in its path. That is the usual outcome of transmitting at a satellite, and those packets are not listed. The list reaches back as far as the packet log is kept; see how long the log is kept.

Links

The screen links to three sites. spaceaprs.com is a live map of every station the space station has repeated, worldwide, heard through the internet gateways rather than your own radio; it is run by APRS Connect. ariss.org is ARISS's own site, and the third link is ARISS's page on the current status of the station's radios. The digipeater is switched off during some crew activities; the app only knows what it has heard, and the status page is where ARISS says so. The links tell each website that the visit came from APRS Connect, and nothing else about you.

Beaconing: everything else about a beacon profile.
Map: the Space station layer beside the other layers.
Packet log: where the repeated packets are.
Stations: the station page and its Via ISS row.

Last updated 8 October 2026