rbcomm

ORBCOMM offers affordable global wireless data and messaging communications services from space. Click here for more information.

Frequency Allocation
The ORBCOMM system uses 137-138 MHz and 400 MHz frequencies for transmissions down to mobile or fixed data communications devices; and 148-150 MHz frequencies for transmissions up to the satellites. These frequencies, approved for use by LEO satellite systems at the World Administrative Radio Conference in February 1992, were allocated by the FCC to Little LEO mobile satellite services in January 1993. The FCC granted ORBCOMM a U.S. commercial license in October 1994.

System Description
The ORBCOMM system uses LEO satellites instead of terrestrial fixed site relay repeaters to provide worldwide geographic coverage. The system is capable of sending and receiving two-way alphanumeric packets, similar to two-way paging or e-mail. The three main components of the ORBCOMM system are: the space segment - the constellation of satellites; the ground segment - gateways which include the Gateway Control Centers (GCCs) and Gateway Earth Stations (GESs) and the Network Control Center (NCC) located in the United States; and subscriber communicators (SCs) - hand-held devices for personal messaging, as well as fixed and mobile units for remote monitoring and tracking applications.

ORBCOMM System Architecture Diagram

Space Segment
ORBCOMM currently has 35 satellites in its constellation. An additional launch is planned for 2000, enhancing coverage in the equatorial regions of the world.

The main function of ORBCOMM's satellites is to complete the link between the SCs and the switching capability at the NCC in the U.S. or a licensee's GCC. The satellites are "orbiting packet routers" ideally suited to "grab" small data packets from sensors in vehicles, containers, vessels or remote fixed sites and relay them through a tracking Earth station and then to a GCC.

Satellite Characteristics

- Weight: 90 lbs.
- Solar Array Power BOL: 160 watts
- Transmitters:

VHF (subscriber links) 1

VHF (feeder links) 1

UHF 1
- Receivers:

VHF (subscriber links) 7 -
1 DCAAS Receiver and 6 Subscriber Receivers

VHF (feeder links) 2
- Propulsion: N2
- Guidance: Autonomous/GPS

More ORBCOMM Satellite Facts

ORBCOMM Satellite Element Sets

Ground Segment
The ground segment, which has most of the intelligence of the ORBCOMM system, is comprised of GCCs, GESs and ORBCOMM's NCC, which is located at ORBCOMM's headquarters in Dulles, VA. The NCC also serves as North America's GCC. Additionally, within the US, there are four GESs located in Arizona, Georgia, New York State and Washington State.

Gateway Control Center (GCC)
Located in a territory that is licensed to use the ORBCOMM system, the GCC provides switching capabilities to link mobile SCs with terrestrial-based customer systems via standard communications modes including X.400, X.25, leased line, dial-up modem, public or private data networks, and e-mail networks including the Internet. Interfaces to the GCC enable reliable, efficient and cost effective integration of the ORBCOMM system into existing or new customer MIS systems.

Gateway Earth Station (GES)
ORBCOMM's GESs link the ground segment with the space segment and will be in multiple locations worldwide. The GESs provide the following functions:

Acquire and track satellites based on orbital information from the GCC

Transmit and receive transmissions from the satellites

Transmit and receive transmissions from the GCC or NCC

Monitor status of local GES hardware/software

Monitor the system level performance of the satellite "connected" to the GCC or NCC

The GES is redundant and has two steerable high-gain VHF antennas that track the satellites as they cross the sky. The GES transmits to a satellite at a frequency centered at 149.61 MHz at 57.6 kbps with a nominal power of 200 watts. The GES receives 3-watt transmissions from the satellite at 137-138 MHz range. These up and downlink channels have a 50 KHz bandwidth.

Network Control Center (NCC)
The NCC is responsible for managing the ORBCOMM network elements and the U.S. gateways through telemetry monitoring, system commanding and mission system analysis. It provides network management of ORBCOMM's satellite constellation and is staffed seven days a week, 24 hours a day by ORBCOMM-certified controllers.

The NCC provides the following functions:

Monitor real-time and back-orbit telemetry from the ORBCOMM satellites
Send real-time and stored commands to the satellites
Provide the tools and information to assist engineering with resolution of satellite and ground anomalies
Archive satellite and ground telemetry for analysis
Monitor performance of the U.S. Gateway Earth Stations (GESs)
Monitor status of the ORBCOMM U.S. Message Switch (OMS) and related software
Provide daily and weekly performance totals

For more information on ORBCOMM's Network click here.

Subscriber Communicator (SC)
There are several types of SCs. ORBCOMM's SC for fixed data applications uses low-cost VHF electronics. The simple antenna design and small package provide installation flexibility. The low-power electronics allow for extended operations using batteries, a solar panel or available power.

The SC for mobile two-way messaging is a hand-held, stand-alone unit. Typically, the units have an alphanumeric keyboard and small display screen.

Click here for more information on ORBCOMM Subscriber Communicator manufacturers.

Source: Orbcomm Website

About MobileWorld

Advertising