The ORBCOMM system provides global asset monitoring and messaging using a constellation of low Earth orbit satellites and ground infrastructure. It consists of 36 operational satellites in low Earth orbit, a network of gateways and their earth stations, and subscriber communicators. The satellites use TDMA and QPSK to communicate with the gateways and subscribers. The gateways process messages and provide connectivity to the public switched telephone network. This allows the system to offer positioning, messaging and monitoring services on a global scale.

1. ORBCOMM Satellite System
Cairo University
Faculty of Engineering
Comm. & Elec. Department
4th Year - 2nd semester
Satellite Communication Course’s Project

2. Introduction
• Orbital Communications (ORBCOMM) is a company that
offers global asset monitoring , messaging and position
determination services.
• ORBCOMM system is a low Earth orbit (LEO) satellite
system.

3. Introduction
• System Description.
• Ground Infrastructure.
• Space Segment.

4. System Description

5. System Description
Dynamic Channel Activity Assignment System:
• DCAAS uses a scanning receiver to measure the
interference power across the entire uplink band.
• Identifies clear channels and assigns them for uplink use
by SCs.
• Scanning evaluated at intervals of 5 seconds or less.

6. System Description
Position Determination Capabilities:
• The SC measures the satellite downlink frequency to
determine the Doppler shift.
• The Doppler shift, time, satellite position, and satellite
velocity represent one data point.
• After enough data points are gathered, the SC can calculate
the Doppler position.
• Some SCs are equipped with internal GPS receivers and
associated GPS antennas.

7. Ground Infrastructure
Overview of ORBCOMM Gateway:
• An ORBCOMM licensee requires a Gateway to connect to
ORBCOMM satellites in view of its service area.
• The principal role of the ORBCOMM Gateway is to provide
message processing and subscriber management for a
defined service area.

8. Ground Infrastructure
Overview of ORBCOMM Gateway:

9. Ground Infrastructure
Gateway Message Switching System:
• Contains the software that performs the actual message
processing, routing, and conversion between the SC and the
ORBCOMM Message Switch (OMS) to traditional Mail
protocol.

10. Ground Infrastructure
Monitoring & Control:
• Audio alarming for all critical system failures.
• Collection and storage of system fault and performance
data.
• Graphical interfaces for most system administration tasks.
• Real-time displays of OMS and GES information.

11. Ground Infrastructure
Gateway Earth Station:
• Provides an RF communications link between the OMS and
the satellite constellation.
• It consists of medium gain tracking antennas, RF and modem
equipment, and communications hardware and software for
sending and receiving data packets.

12. Ground Infrastructure
GES-to-GCC Channels:
• GES-to-GCC links will operate over 56-kbps or 64-kbps
data lines.
• The GES process communicates with the GMSS process
using TCP/IP UDP packets.

13. Ground Infrastructure
GES-to-Satellite Channels:
• A single 57.6-kbps uplink and downlink channel using
the TDMA protocol.
• This protocol permits simultaneous RF links between a
single satellite and several GES installations within the
satellite footprint.

14. Ground Infrastructure
Subscriber Communicator:
A wireless VHF modem that transmits messages from a user to the
ORBCOMM System for delivery to an addressed recipient, and
receives messages from the ORBCOMM System intended for a
specific user.

15. Space Segment
Constellation Coverage and Availability:
Plane designation A, B, C, D F G E
Number of orbital planes 4 1 1 1
Number of satellites in each
orbital plane
8 4 4 7
Inclination angle 45 70 108 0
altitude (km) 815 740 785-875 975

16. Space Segment
System Redundancy:
• The ORBCOMM System provides redundancy at the system level
due to the number of satellites in the constellation.
• In the event of a lost satellite, ORBCOMM will optimize the
remaining constellation to minimize the time gaps in satellite
coverage.

17. Space Segment
Orbcomm Link Budget:
Gateway-satellite Satellite-subscriber
Uplink Downlink Uplink Downlink
Frequency, MHz 149.4 137.2 148.95 137.5
[EIRP], dBW 40 6.5 7.5 12.5
Misc. losses, dB 7.3 7.3 11.3 11.3
[G/T], dBK-1
-33.3 -12.8 -26 -28.6
Data rate, kbps 57.6 57.6 2.4 4.8

18. Space Segment
Satellite Description:
Each satellite utilizes the popular TDMA multiplexing scheme
and QPSK modulation. Orbcomm is the only current satellite
licensee operating in the 137-150 MHz VHF band.

19. Space Segment
Satellite Description:

20. Abstract
• Orbital Communications (ORBCOMM) is a company that
offers global asset monitoring , messaging and position
determination services.
• The ORBCOMM System consists of the ground
infrastructure, a space segment, and a subscriber
segment.

21. Abstract
• An ORBCOMM Gateway consists of a Gateway Control
Center and one or more Gateway Earth Station sites, as
well as the network components.
• Subscriber Communicators.
• 45 ORBCOMM satellites have orbited Earth.

22. Questions / Comments

23. Thank You
By: Akram Ahmed