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IoT Network Service



Astrocast, in partnership with Airbus and Thuraya, is building a network of leading-edge nanosatellites in Low Earth Orbit to provide cost-effective IoT services to the 90% of the world not covered by cellular systems.

An uplink message is a message transmitted from an Astronode S module to an Astrocast satellite.

User data

Each uplink message may include between 0 and 160 bytes as user data.

User data
0 - 160 Bytes


Geolocation dataUser data
8 Bytes0 - 160 Bytes

Geolocation data

It is possible to transmit geolocation data with an uplink message. By using this feature, your asset location will appear on the Astrocast Portal and the Astrocast API will return latitude and longitude properties on messages retrieved.

Byte offsetFormatNameDescription
0Int32LatitudeDegrees latitude * 107
The valid range is between -90° to 90°
4Int32LongitudeDegrees longitude * 107
The valid range is between -180° to 180°


The satellite sends an ACK message back to the module to confirm it received the uplink message.

A command is a downlink message transmitted from an Astrocast satellite to an Astronode S module.


A command always follows an uplink message.

User data

Each command may be 8 or 40 bytes as user data.

User data
8 or 40 Bytes


The Astronode S module sends an ACK message back to the satellite to confirm it received the downlink command. The acknowledgment will then be available in the Portal/API (Received Date).

End-to-end Latency

The current satellite constellation can provide a latency of maximun 24 hours to any device on the planet.

The Astrocast Latency represents the following:

  • Your asset enqueues a message in the Astronode S
  • The Astronode S wait for the next satellite pass
  • The message is stored onboard a satellite
  • A ground station download the message
  • The message is decoded into the Astrocast Data Service
  • The message is delivered in the Astrocast Portal and API

Astrocast aims to provide a latency of up to 15 minutes with its full constellation.

Radio Frequencies

L-band spectrum

Astrocast is the only NewSpace IoT LEO network with access to the L-band spectrum.​


L-band is the radio spectrum from 1 to 2 gigahertz (GHz)​ and it is the most efficient spectrum for Satellite M2M/IoT communication.​

It has superior performance characteristics for IoT, such as​ smaller antenna​s, lower-cost RF components​, better signal propagation (no rain fade, lower power requirements)​, and fewer interference risks than other bands.

RF PathFrequence MinFrequence Max
Uplink (Tx)1626.5 MHz1660.5 MHz
Downlink (Rx)1525.0 MHz1559.0 MHz


Ephemerides are used by the modules to calculate next passes and avoid seeking/searching for a satellite continuously.

This feature is active by default but can be deactivated.

The command details can be found here: CFG_W Configuration Write.

High-level operation

At each pass, the satellite broadcasts the following to all modules in range:

  • Current UTC Time
  • Number of satellites in the constellation

A module updates its ephemerides information every time it receives a broadcast message.

When an asset requests to send a message, the module wakes up only in the time windows it expects a satellite to be in range. If after 24 hours a message has not been sent, the module will wake up and continuously search for a satellite pass.


The ephemerides system should be deactivated in 2 cases:

  • If the device has access to a power supply and therefore has no power consumption constraints. It will provide the best possible latency.
  • If the device is mobile from a protocol perspective - see below.

What is a mobile asset from a protocol perspective?

A mobile device is a device that is moving more than 1,000 kilometres between 2 communications.

A fixed device is either a stationary device or a device that is moving in a region smaller that 1000 km diameter.


This distinction is important when deciding to use or not use the ephemerides feature:

  • If the ephemerides feature is ON and the device is moving great distances, then the device may not wake up when there is a satellite pass.
  • If the ephemerides feature is OFF and the device is not moving, then its power consumption could increase significantly unnecessarily.

Time synchronization

  • Time information is included in the broadcast message.
  • The local RTC is synchronized with every satellite broadcast message that is demodulated.
  • The RTC in the module is continuously running, the RTC time is updated in flash memory every time a new message is created.
  • Initial time: Frame Number starts at Astrocast Epoch (1st January 2018 at 00:00:00).

Portal & API

Astrocast provides a web portal for Device Management, User Management and API Tokens Management.

An API is also available to retrieve your messages to your own platform.


Astrocast is using a state-of-the-art secure protocol to keep your devices and transmissions secure. Each Astronode S has a private and unique encryption key. Messages are encrypted both at the application and a transport layers with industry AES 256-bit encryption.


The Astrocast Network provides by default encryption, authentication and integrity.

Astronode S

  • Messages are encrypted and authenticated based on AES GCM 256.

Ground system

  • Communications between the ground stations and the Astrocast Data Management (DM) platform and portal are encrypted and authenticated to insure data privacy and integrity.

Astrocast Portal

  • Users are required to log in using Multi-Factor Authentication (MFA).
  • The portal runs on an encrypted connection secured by SSL/TLS (HTTPS).

Astrocast API

  • API authentication is performed with a random token.
  • The API runs on an encrypted connection secured by SSL/TLS (HTTPS).