Architecture of ORBCOMM Little LEO Global Satellite System for Mobile and Personal Communications

This article describes the ORBCOMM system, a wide area packet switched and global two-way data transfer network providing mobile satellite communication (MSC), tracking, monitoring, control and logistics services between mobile, remote, semi-fixed units and other mobile or fixed subscribers via ORBCOMM space and ground segments. It includes the concept of the ORBCOMM Little low earth orbit (LEO) MSC System as well as the architecture of the ORBCOMM Little LEO MSC Network Space, Ground and User segments. ORBCOMM satellite communication, tracking and monitoring terminals, heavy equipment management terminals and ORBCOMM maritime satellite automatic identification system (S-AIS) terminals are also described.

The ORBCOMM MSC system concept originated in 1989 by Orbital Sciences Corporation. The $810 million ORBCOMM Company became operational in 1998 and then filed for Chapter 11 bankruptcy protection in September 2000. Shortly thereafter, ORBCOMM Company was purchased by a new group of investors in April 2001 for an estimated $5 to $10 million.

The ORBCOMM Global, L.P. Company, Dulles, Va., U.S., equally owned by Teleglobe and the Orbital Sciences Corporation, provides global services via the world's first Little LEO satellite-based data and messaging satellite communications system. The U.S. Federal Communications Commission granted ORBCOMM a commercial license in October 1994 and commercial service began in 1998. Orbital Sciences is the prime contractor for satellite design.

The ORBCOMM Company owns and operates a network consisting of Little LEO satellites and several ground earth stations (GES) deployed around the world, connecting small, low power and commercially proven subscriber terminals to private and public networks, including the Global System for Mobile Communication (GSM), cellular systems and the internet.

ORBCOMM is one of the first LEO commercial communications satellite systems to reach orbit and begin service. Offering paging, messaging and data transfer services, the first two of a planned 36-satellite constellation were launched in April 1995.

The constellation was designed to maximize coverage over heavily populated regions, particularly between 60 degrees North and 60 degrees South latitudes. Trade studies were performed to evaluate an optimal constellation configuration for coverage of this region. A total of 35 first generation satellites (OG1) were launched between 1995 and 1999 using the Pegasus and Taurus launch vehicles, establishing the operational satellite constellation for the ORBCOMM Global communications infrastructure. The unlaunched satellite, original designation ORBCOMM FM-29, was cannibalized for parts for a capability demonstration satellite and then rebuilt as TacSat-1 for the U.S. military. 

ORBCOMM Generation 2 (OG2) second generation satellites supplement and will eventually replace the first generation constellation. Eighteen satellites were ordered by 2008 nominally intended to be launched in three groups of six from 2010 to 2014, and by 2015 have all 17 satellites launched. These satellites were launched by SpaceX on the Falcon 9 launch vehicle.

ORBCOMM provides constellations of Little LEO communication satellites for mobile applications, such as maritime, land (road and rail) and aeronautical communications. Apart from service for mobile applications, ORBCOMM provides service for fixed applications, industrial IoT, machine-to-machine (M2M) communications hardware, software and services designed to track, monitor and control fixed and mobile assets in markets including transportation, heavy equipment, maritime, containers, oil and gas, utilities and government. The company provides hardware devices, modems, web applications and data services delivered over multiple satellite and cellular networks.¹

ORBCOMM SYSTEM

As of 30 June 2021, ORBCOMM had more than 2.3 million billable subscriber communicators, serving original equipment manufacturers such as Caterpillar Inc., Doosan Infracore America, Hitachi Construction Machinery Co., Ltd., John Deere, Komatsu Limited and Volvo Construction Equipment, as well as other corporate and private customers, such as J. B. Hunt, C&S Wholesale Grocers, Canadian National Railways, C.R. England, Hub Group, KLLM Transport Services, Marten Transport, Swift Transportation, Target, Tropicana, Tyson Foods, Walmart and Werner Enterprises. ORBCOMM Company is headquartered in Fort Lee, New Jersey and has a Network Control Center in Dulles, Va.

By means of a global network of LEO satellites and accompanying ground infrastructure, ORBCOMM’s low-cost and reliable two-way data communications products and services track, monitor and control mobile and fixed assets in four core markets: commercial transportation, heavy equipment, industrial fixed assets and marine/homeland security. The company’s products are installed on trucks, containers, marine vessels, locomotives, backhoes, pipelines, oil wells, utility meters, storage tanks, small craft, camera cargo sensors, tractor ID sensors for trailers, wireless door sensors, wireless temperature sensors, next generation of cellular and IoT telematics and other assets.

ORBCOMM is continuously updating its network to improve global coverage and enhance its performance and reliability for customers around the world. With the launch of new and more capable next generation OG2 satellites, ORBCOMM took its service to the next level. Each OG2 satellite is the equivalent of six OG1 satellites, providing faster message delivery, larger message sizes and better coverage at higher latitudes, while significantly increasing network capacity.

ORBCOMM owns and currently operates a global network of 31 LEO communications satellites and accompanying ground infrastructure including 16 GESs, or gateways, in 13 countries to track and establish two-way satellite communications, tracking and monitoring systems.

From robust web reporting applications to turnkey IoT solutions and enablement, ORBCOMM’s portfolio includes the tools developers, system integrators, value added reseller (VAR) partners and enterprise users need to remotely monitor and control fixed and mobile assets around the world. These include trailers, reefers, containers, cargo ships, fishing vessels, cargo security and fleet management.

In addition, ORBCOMM’s Satellite Automatic Identification System (S-AIS) is an important solution for ship tracking and safety and security in navigation. Taking into consideration all mentioned services, the ORBCOMM system could be classified as a subsystem of the Global Maritime Distress and Safety network and its equipment.

A framework for opportunistic navigation with the multi-constellation ORBCOMM Little LEO satellite signals is proposed via Doppler. A receiver architecture suitable for processing both time division multiple access (TDMA) and frequency division multiple access (FMDA) signals from ORBCOMM can produce Doppler frequency measurements from multi-constellation LEO satellites. An extended Kalman filter based estimator is formulated to solve for a stationary receiver’s position using the resulting Doppler measurements.^1,2

LITTLE LEO MSC NETWORK ARCHITECTURE

The ORBCOMM system and network is a wide area packet switched network with two-way data transfer and messaging providing satellite communication, tracking and monitoring services between mobile, remote, semi-fixed or fixed satellite communication units (SCUs), GESs or gateway control centers (GCCs) accomplished via the constellation of Little LEO satellites and network control centers (NCCs).

An ORBCOMM mobile or fixed terminal delivers information to and from virtually anywhere in the world on a nearly real-time basis via ground and space segments to the terrestrial telecommunication network and its ground subscribers. The ORBCOMM OG1 ground segment and subscriber transmitters (Tx) are capable of providing a continuous 4.8 Kb/s stream of uplink packet data and 9.6 Kb/s stream of downlink packet data to the receivers (Rx) and vice versa.

At first, the OG2 satellites operated at an uplink speed of 4.8 Kb/s and a downlink speed of 7.2 Kb/s, while the currently the OG2 satellites can provide higher data rate transmission capabilities, with subscriber downlink speeds of up to 86.4 Kb/s in the uplink and up to 172.8 Kb/s in the downlink. More importantly, a proposed modified OG2 satellite deployment plan will improve overall network coverage and capacity (particularly in mid and higher latitude coverage areas), so ORBCOMM can meet an expected increased demand for its services.

RF communication within the ORBCOMM network operates in the very high frequency (VHF) portion of the frequency spectrum between 137 and 150 MHz. The system can send and receive two-way alphanumeric packet messages, like well-known two-way paging, SMS or e-mail transmissions.

The ORBCOMM network enables two-way monitoring, tracking and messaging services through the world’s first commercial Little LEO satellite slow data communications system. Applications include tracking mobile assets such as oceangoing ships, fishing vessels and barges, containers, vehicles, trailers, locomotives and rail cars, heavy equipment and small craft as well as monitoring and controlling fixed sites.

Fixed services include supervisory control and data acquisition (SCADA) or M2M of electric utility meters, water levels, oil and gas storage tanks, wells, pipelines and environmental projects and a two-way messaging service for consumers, commercial and government entities.

Small, low power and commercially proven SCUs can connect to private and public networks, including the Internet, via ORBCOMM satellites and gateways. Through this network, ORBCOMM delivers information to and from virtually anywhere in the world on a nearly real-time basis.

Vital messages generated by a variety of applications are collected and transmitted by appropriate mobile or fixed SCU terminals to a satellite in the ORBCOMM constellation. The satellite receives and relays these messages down to one of four U.S. GES terminals. The GES then relays the message via satellite link or dedicated terrestrial line to the NCC station. The NCC routes the message to the final addressee, through the Internet via e-mail to a personal computer or through terrestrial networks to a subscriber communicator, pager, dedicated telephone line or facsimile.

The ORBCOMM space and ground network with GESs, GCCs and SCUs and with the OG1 and OG2 generation of satellites is shown in Figure 1. Messages originating outside the U.S. are routed through international GCCs in the same way to their final destinations. Messages and data sent to a remote SCU can be initiated from any computer using common e-mail systems, internet and X.400. The GCC or NCC then transmits the information using ORBCOMM’s global telecommunications network.

ORBCOMM serves customers through VARs that provide expertise in specific industries. These ORBCOMM VARs provide whole-product solutions and customer support to end-users. Different customers from around the world rely on the ORBCOMM satellite network for a wide range of mobile, farming and fixed site data applications including:

1) Monitoring and controlling assets at remote or rural sites for oil/gas extraction, pipeline operations, storage, custody transfer and electric power generation and distribution;
2) Messaging for truck fleets, owner operators and remote workers;
3) Tracking and managing construction equipment, locomotives, rail cars, trucks, trailers, containers, vessels, small craft and locating and recovering stolen vehicles and cargo and
4) Weather data for general aviation.^2,3,4

Figure 1 ORBCOMM system overview.²

SPACE SEGMENT

The ORBCOMM system allows users to track, monitor and control remote assets via a satellite network that provides near global coverage with OG1and OG2 satellite constellations.

First Generation of ORBCOMM OG1 Satellites

Through a network of LEO OG1 satellites and regional GESs, users can communicate with their mobile or fixed assets anywhere in the world (see Figure 2). ORBCOMM offers low-cost and high-quality service dedicated to fulfilling the specific needs of all potential users.

Figure 2 ORBCOMM OG1 satellite coverage.⁵

The ORBCOMM communication network’s first generation operational OG1 satellites are in Little LEO orbit at about 825 km above the Earth’s surface (see Figure 3a). The main function of ORBCOMM’s satellites is to complete the link between an SCU and the switching capability at the NCC in the U.S. or a licensee’s GCC in other countries.

1) Planes A, B and C are inclined at 45 degrees to the equator and each contains eight satellites in circular orbits at an altitude of approximately 815 km.
2) Plane D is also at 45 degrees containing seven satellites in circular orbits at an altitude of 815 km.
3) Plane F is inclined at 70 degrees and contains two satellites in a near-polar earth orbit (PEO) at an altitude of 740 km.
4) Plane G is inclined at 108 degrees and contains two satellites in a near-PEO at an altitude varying between 785 km and 875 km. Plane E is in circular equatorial orbit.

Figure 3b shows the main parts of a fully deployed OG1 satellite. Each spacecraft carries 17 data processors and seven antennas, designed to handle 50,000 messages per hour.

Figure 3 ORBCOMM OG1 satellite constellation (a) and components of the OG1 satellite (b).²

Undeployed, the ORBCOMM OG1 satellite resembles a circular disk and weighs about 43 kg. It measures approximately 1 m in diameter and 16 cm in depth. Circular panels hinge from each side after launch to expose solar cells. These panels articulate on one axis to track the Sun and provide 160 W.

The satellite’s electrical power system is designed to deliver about 100 W, on an orbit-average basis, near its expected end-of-life in a worst-case orbit. The satellite solar panels and antennas fold up into the disk (also called the “payload shelf”) with the remainder of the payload during launch and deployment. Once fully deployed, the spacecraft length measures about 3.6 m from end-to-end with a 2.3 m span across the solar panel disks. The spacecraft long boom is a 2.6 m VHF/UHF gateway antenna.

The ORBCOMM network depends on the number of satellites and gateways in operation and the user’s location. As the satellites move with the Earth, so does the approximately 5.100 km diameter geometric footprint of each satellite. This system provides redundancy at the system level, due to the number of satellites in the constellation. Thus, in the event of a lost satellite, ORBCOMM will optimize the remaining constellation to minimize time gaps in satellite coverage. Consequently, the constellation is tolerant of degradation in the performance of individual satellites.

ORBCOMM satellites constantly move, so large obstructions do not prohibit available coverage in remote rural areas. In comparison, GSM (cellular) coverage depends on tower location, usually centered on major highways and cities and cannot reach remote areas, and the geostationary earth orbit (GEO) satellite system requires large space constructions and costly/ power-intensive hardware. Due to slow data transfer, however, large data files (such as graphics) or emergency response latencies are not appropriate applications for ORBCOMM.

Its satellite transponder receives 2400 b/s at 148 to 149,9 MHz and transmits 4800 b/s at 137 to 138 MHz and 400.05 to 400.15 MHz. The OG1 satellite system uses X.400 of the Consultative Committee on International Telephony and Telegraphy (CCITT 1988). Addressing and message size is typically 6 to 250 bytes (no maximum).

The communication subsystem is the principal payload flown on the satellite, consisting of five major parts:

1. The Subscriber Communications Section is the main payload part consisting of one subscriber Tx, seven identical Rxs and associated Rx and Tx filters and antennas. Six of the Rxs are used as subscriber receivers and the seventh is used as the Data Center as a Service (DCAAS) Rx. The subscriber Tx is designed to transmit an operational output power of up to about 40 W, although the output is less during normal operation. The power of each Tx can vary over a 5 dB range, in 1 dB steps, to compensate for aging and other lifetime degradations. Symmetrical Differential Phase Shift Keying (SDPSK) modulation is used on the subscriber downlink at a data rate of 4800 b/s. (It is capable of transmitting at 9600 b/s.). The satellite uplink modulation is SDPSK with a data rate of 2400 b/s. Raised cosine filtering is used to limit spectral occupancy.

2. The ORBCOMM Gateway Communication Section contains both the gateway satellite’s Tx and Rx. Separate right-hand circular polarization antennas are used for Tx and Rx functions. The gateway Tx is designed to transmit 5 W of RF power. The 57.6 Kb/s downlink signal to the GES is transmitted using an offset quadrature phase shift keying (OQPSK) modulation in a TDMA format. The gateway Rx is designed to demodulate a 57.6 Kb/s TDMA signal with OQPSK modulation. The received packets are routed to the onboard satellite network computer.

3.The Satellite Network Computer receives the unlinked data packets from the subscriber and the ORBCOMM gateway Rxs and distributes them to the appropriate Tx. The computer also identifies clear uplink channels via the DCAAS Rx and algorithm and interfaces with the GPS Rx to extract information pertinent to the communications system. Several microprocessors in a distributed computer system aboard the satellite perform the satellite network computer functions.

4.The UHF Tx is a specially constructed 1 W Tx that emits a highly stable signal at 400.1 MHz. The Tx is coupled to a UHF antenna designed to have a peak gain of about 2 dB.

5.The Satellite Subscriber Antenna Subsystem comprises a deployable boom containing three separate circularly polarized quadrifilar antenna elements.

The attitude control system is designed to maintain both nadir and solar pointing. The satellite must maintain nadir pointing to keep the antenna subsystem oriented toward the Earth. Solar pointing maximizes the amount of power collected by the solar cells. The satellite employs a three-axis magnetic control system that operates with a combination of sensors, which also obtains its position through its onboard GPS receiver.

Satellite planes A/B/C are designed to maintain a separation of 45 ± 5 degrees between satellites in the same orbital plane. Planes D/E provide 51.4 degrees spacing between satellites, while highly inclined satellite planes (F/G) are spaced for 180 ± 5 degrees apart.

The springs used to release the satellites from the launch vehicle give them their initial separation velocity. A pressurized gas system is used to perform braking maneuvers when the required relative in-orbit satellite spacing is achieved. An Orbital Sciences Corporation formation-keeping technique maintains the specified satellite intra-plane spacing. One of the benefits is that, unlike GEO satellites, it does not affect the satellite’s life expectancy in fuel usage.^2,4,5

Second Generation of ORBCOMM OG2 Satellites

ORBCOMM in May 2008 signed a next generation satellite constellation contract with Sierra Nevada Corporation (SNC) to build 18 modern ORBCOMM Generation 2 (OG2) satellites with an option to purchase up to 30 additional OG2 satellites to augment its existing satellite constellation (see Figure 4).

Figure 4 ORBCOMM OG2 satellite coverage.⁶

As prime contractor, SNC is an experienced integrated space team with unique and established space heritage, resources and performance record, including Boeing Intelligence and Security Systems (I&SS), ITT Space Systems and MicroSat Systems. The integrated space team also includes several other key subcontractors and industry leaders with unparalleled experience in both the design and construction of complex communications systems and satellites.

SNC, Boeing and ITT provide oversight, systems engineering, technical management, integration and mission assurance functions to assure the successful performance of the OG2 program. MicroSat Systems (MSI), a wholly owned subsidiary of SNC, leveraged its experience on the TacSat-2 mission to design the spacecraft and perform integration and test activities for the OG2 satellites.

In June 2008, SNC selected Argon ST to develop and deliver the satellite payloads for the OG2 satellite constellation. Each OG2 satellite is equipped with an enhanced communications payload designed to increase subscriber capacity by up to 12 times over the OG1 satellites. ORBCOMM customers can transmit data over the OG2 satellites at greater speeds and send larger data packets using future modems.

From 8 October 2012 to 22 December 2015, 18 next generation OG2 satellites were launched, but only 17 became operational. Figure 5 shows the ORBCOMM OG1 spacecraft (a), ORBCOMM OG2 spacecraft (b) and ORBCOMM OG2 orbital satellite constellation (c).

The OG2 satellites are backward compatible with OG1, so that existing subscriber communicators function seamlessly with the OG2 satellites. In addition, all OG2 satellites are designed with S-AIS payloads to receive and report transmissions from AIS-equipped oceangoing vessels. In fact, ORBCOMM markets this S-AIS data to the USA and international coast guards and government agencies, as well as maritime companies engaged in security or logistics businesses for tracking shipping activities or for other navigational purposes.

The ORBCOMM LEO satellites are “orbiting packet routers” ideally suited to “grab” small data packets from mobile or fixed sensors and relay them through a tracking Earth station and then to a GCC.

The current satellite constellation, OG1 and OG2, provides one central location for the two-way delivery of data over multiple carriers to customer back-office applications via the Internet, cellular wireless, satellite and dual-mode cellular and satellite services; however, more than 42 percent of the market share of ORBCOMM's current satellite system provides M2M service to users for fixed and mobile applications.^6-8

Figure 5 ORBCOMM OG1/OG2 satellites: OG1 spacecraft (a), OG2 spacecraft (b) and ORCOMM OG2 orbital satellite OG2 coverage (c).⁸

GROUND SEGMENT

The ORBCOMM ground segment, which contains most of the system intelligence, comprises gateways or GESs, control centers and both mobile and fixed SCU customer terminals. The space segment of satellite constellations and orbits are controlled by one satellite control center (SCC).

Gateways, which include the GESs, GCCs and the NCC, are located at ORBCOMM headquarters in Dulles. Within the USA, there are four other GESs located in Arizona, Georgia, New York State and Washington State. The NCC also serves as North America’s GCC and manages the overall system worldwide. ORBCOMM gateways are connected to dial-up circuits, private dedicated lines or the Internet. The SCU handheld devices for personal messaging are fixed and mobile units for remote monitoring, control and tracking applications.

GES

ORBCOMM continues the deployment of additional regional GESs to provide near-real-time service for all major areas of the world, as well as developing and launching a new generation of satellites that will enhance and expand the current system’s capabilities. All ORBCOMM’s GES terminals link the ground segment with the space segment and are in multiple locations worldwide.

The GES acquires and tracks satellites based on orbital information from the GCC, links ground and space segments from multiple worldwide locations, transmits and receives transmissions from the satellites, transmits and receives transmissions from the GCC or NCC, monitors the status of local GES hardware and software and monitors satellite system level performance “connected” to the GCC or NCC (see Figure 6).

The GES terminal is redundant and has two steerable high-gain VHF antennas that track the satellites as they cross the sky. It transmits to a satellite at a frequency centered at 149.61 MHz at 56.7 Kb/s with a nominal power of 200 W. It receives 3 W transmissions from the satellite in the 137 to 138 MHz range. These up-and-downlink channels have 50 KHz bandwidths.

The mission of the GES is to provide an RF communications link between the ground and the satellite constellation. It comprises medium gain tracking antennas, RF and modem equipment and communications hardware and software for sending and receiving data packets. An ORBCOMM licensee requires a gateway to connect to satellites in view of its service area. Namely, the gateway consists of a GCC and one or more GESs, as well as the network components that provide inter-facility communications.^2,9,10

Figure 6 Diagram of ORBCOMM GES.¹⁰

GCC

The GCC is the operations center for ORBCOMM gateway activities. Auxiliary systems such as subscriber management and business support systems are typically located in the GCC. GCC terminals are in territories licensed to use the ORBCOMM system. They locate wherever ORBCOMM is licensed, link remote SCUs with terrestrial-based systems, communicate via X.400, X.25, leased line, dial-up modem, public and private data networks and E-mail networks including the Internet and efficiently integrate the ORBCOMM infrastructure with new or existing customer management information system solutions.

The GES transmits messages over a dedicated line to the GCC that places them on the public switched network for delivery to the receiver subscriber’s PC Internet provider. The GCC Local Area Network (LAN) and GES LAN are considered part of the global OCCNet Wide Area Network (WAN).

The OCCNet is the overall, worldwide WAN hardware network that ties together the ORBCOMM LAN hardware in GCC stations of ORBCOMM gateways established throughout the world. Thus, it consists of the routers, bridges, modems and interconnecting circuits over which command and control telemetry passes.

Within the context of an ORBCOMM gateway, the OCCNet also consists of the routers, bridges and modems by which the ORBCOMM gateway elements (in particular, the NMS, GMSS, and GES) are interconnected. The OCCNet functions include: 1) providing message transport between an ORBCOMM gateway, GMSS and NMS, 2) providing message transport between an ORBCOMM gateway, GCC and its GES terminals and 3) providing message transport with the GCC.^1,2

NCC

The NCC is responsible for managing the ORBCOMM communications network elements and the USA gateways through telemetry monitoring, commanding and mission system analysis. It monitors real-time and back-orbit telemetry from the ORBCOMM satellites, sends real-time and stored commands to the satellites, provides the tools and information to assist engineering with resolution of satellite structure and ground anomalies, archives all satellite and ground telemetry data for analysis and monitors performance.

The NCC manages the entire ORBCOMM satellite constellation and its processes and analyzes all satellite telemetry. It is responsible for managing the ORBCOMM system worldwide. Through OrbNet, the NCC monitors message traffic for the entire ORBCOMM system and manages all message traffic that passes through the U.S. gateway. The NCC is staffed 24 hours a day, 365 days a year from Dulles, Va. A backup NCC system was established in 2000, which permits the recovery of critical NCC functions in the event of an NCC site failure.^1,5

SCC

The SCC serves in territories licensed to use the ORBCOMM system and provides control of the ORBCOMM Little LEO satellite constellation. The SCC terminal is owned and operated by ORBCOMM and co-located with the U.S. NCC in Dulles, Virginia.

SCU

The SCU equipment comprises both mobile and fixed terminals used for connection to the ORBCOMM satellite network through gateway stations. The SCU terminal is 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.

Manufacturers have different proprietary designs. Each model must be approved by ORBCOMM and adhere to the ORBCOMM Air Interface Specification, Subscriber Communicator Specifications and ORBCOMM Serial Interface Specification (if an RS-232 port is available). Different versions of SCU terminals are currently available, which include “black-box” industrial units that have RS-232C ports for data uploading and downloading. Current options on several SCUs include internal GPS receivers and/or additional digital and analog input and output ports.

User Segment

The ORBCOMM satellite system is designed to enable short communications between different, often unmanned remote fixed or mobile modems, positions and customer information hubs as a part of the User Segment. The main unit is an SCU. ORBCOMM hardware and software components comprise a global, packet switched two-way data communication service optimized for short messages and small file transfers.

The ORCOMM SCU mobile or fixed satellite terminals are full-feathered compact, light-weight devices with their own power supplies, or are supplied from other sources if installed on some mobile means of transport, such as ships, road or rail vehicles and small craft. Many have RS-232 data ports and some are integrated (black-box versions) with GPS receivers, lap-tops and palm-top computers and other systems.

Data transmissions can be encrypted by application software using standard digital encryption standard computer chips using the same methodology used by STU-111s to encrypt classified conversations over the public telephone network.

The ORBCOMM system provides a less accurate geolocation capability that combines the Doppler frequency shift available from a LEO satellite with the satellite onboard GPS receiver to calculate position within less than 100 meters. This may be sufficient for many U.S. or other country armed forces requirements.^1,5

Second Generation of ORBCOMM SCU Terminals

There are many first and next generation SCU satellite terminals that use the ORBCOMM satellite network, but in this context, two terminals from ORBCOMM’s second generation of SCU terminals will be introduced. Before that, the Magellan GSC 100 satellite modem was developed as the first generation of handheld satellite terminals in the world that allows sending and receiving text and e-mail messages to and from anywhere in the ORBCOMM coverage area (see Figure 4).

1. Stellar DS300 Terminal – The DS300, designed by Stellar and Delphi Electronics, and Safety and manufactured by Delphi, is a two-way satellite communicator for use with the LEO ORBCOMM satellite network. It is a complete hardware solution combining a satellite transceiver and GPS receiver for companies using a wide variety of applications to track, monitor and communicate with their fixed and mobile assets around the globe (see Figure 7a).

The DS300 terminal is a complete hardware solution for companies using a wide variety of applications to track, monitor and communicate with fixed and mobile assets around the globe. It features a satellite modem using a VHF transmit frequency of 148 to 150.05 MHz and a receive frequency of 137 to 138 MHz. Dynamic Range is 40 dB minimum. Its power supply is 12 VDC for both the transceiver and GPS receiver. It transmits at a speed of 120 Kb/s, and has a user-programmable application processor, an integrated 16 channel GPS receiver, adequate software configurable input/output (I/O) options and a battery charger packaged in a rugged, automotive-grade enclosure.

The design and stable performance make the DS300 a reliable satellite device for transportation, heavy equipment, marine, aeronautical and many other markets. The satellite modem is configurable with eight input or output digital channels, four input analog channels and 8 GPS receiving channels.

2. Quake Q4000 Terminal – This satellite three-mode (ORBCOMM, Iridium and GSM) mobile terminal is one of the initial generations of cost effective and fully programmable ORBCOMM transceivers and GSM (cellular) receivers. It operates at a VHF transmit frequency of 148.000 to 150.050 MHz and a receive frequency of 137.000 to 138.000 MHz with a 50-channel GPS receiver for a global tracking capability (see Figure 7b).

It uses the ORBCOMM satellite network and it has almost the same technical characteristics as the Iridium Q4000i for the Iridium Big LEO satellite network. It can be used for SCADA (M2M) and business-to-business Internet links with marine, land (road and rail) or aeronautical based assets and fixed M2M heavy equipment, transportation and oil and gas applications anywhere in the world.

This is a robust industrial modem in a compact form factor that is small enough to hold in one’s hand. It is also designed to meet exacting standards regarding automotive power conditioning requirements and features a low power draw load for battery operated applications of 10.5 VDC.

The Q4000 uses an application programming interface (API) that empowers developers to integrate its functions and build customized onboard mobile applications. Various mobile and fixed clients are given a wide array of fully customizable options, including multiple inputs/outputs, antenna detection, J1939 CAN Bus, memory and network accessibility based on their M2M technical and functional requirements.^{11, 12}

Figure 7 ORBCOMM second generation of SCU modems: Stellar DS300 (a) and Quake Q4000 (b).^11,12

Next Generations of ORBCOMM SCU Terminals

1. ORBCOMM OG2-GPS Modem – This tracking unit delivers connectivity over the LEO ORBCOMM VHF satellite network for transportation maritime, land (road and rail) and aeronautical, heavy equipment, agricultural and other markets (see Figure 8a). It measures 40 × 70 x 0.5 mm and has a Mini PCI Express 52-pin edge connector with a 0.8 mm pitch. Its input voltage is 2.8 to 15 VDC. Input current in transmit mode is 1.6 A, GPS draws 35 mA and receive mode uses 70 mA.

ORBCOMM's OG2 and OGi satellite modems share the same electrical and application interfaces. This allows for seamless plug-and-play satellite connectivity over either network with no additional time or resources spent on development and integration. The OG2 satellite modem supports low power consumption for improved longevity in battery-powered applications, and its modems do not require a fixed line of sight with the satellites. The GPS version includes a built-in accelerometer and is well-suited for use in mountainous terrain and dense urban areas.

2. ORBCOMM GT 1100 Modem – This unit enables full control of mobile assets and containers (see Figure 8b). It allows complete visibility and control of fixed and mobile assets. As part of a comprehensive solution that includes sensor technology, powerful Web and mobile applications and reliable cellular and satellite connectivity options, the GT 1100 helps businesses optimize operational efficiencies and reduce costs. It is available as a cellular or dual-mode satellite-cellular version powered by solar rechargeable batteries for low power consumption and long service life in the field. It operates autonomously and requires minimum maintenance, no battery changes and can externally interface to a GPS receiver.^13,14

Figure 8 OG2 and GT 1100 SCU terminals: OG2-GPS Modem (a) and GT 1100 Modem (b).^{13, 14}

3. ORBCOMM MT 5000 Modem – This is reliable small craft and shipborne tracking device for safety, security and compliance that ensures secure, consistent and reliable M2M vessel fleet location (see Figure 9a). The MT 5000 is a class B transmitter, broadcasting Radio – AIS (R-AIS) messages to nearby vessels and coastal AIS stations, along with ORBCOMM’s S-AIS network. This unique combination delivers more reliable and comprehensive fleet location data. It brings the power of reliable tracking to smaller vessels.

It uses rechargeable lithium manganese batteries with very low self-discharge. It can be charged from 9 to 32 V DC or by means of universal 12 V AC/DC adapter. It operates at 4 VHF AIS frequencies, two for R-AIS and two for S-AIS with a minimum 2 to 3 W EIRP. It also uses 50 Global Navigation Satellite System (GNSS) channels for GPS satellite-based augmentation systems, such as WAAS, EGNOS and MSAS and non-augmented GNSS networks such as GPS, GLONASS, Galileo and BeiDou.

4. ORBCOMM GT 700 Modem – This unit provides reliable satellite-based asset detection, tracking and security in the transportation and distribution, oil and gas and other industrial markets (see Figure 9b). It supports a security cable that wraps around container-locking bars or other latching mechanisms to ensure cargo security. The device delivers alarms when the cable seal is broken or disconnected to help deter theft.

It uses a lithium internal (primary battery) that lasts five years at two messages per day. It provides simplex (one way) transmission via circular polarization division multiplexing and adaptive transmission modulation over the LEO satellite constellation and tracking with a GPS receiver operational to 1,000 knots (515 m/s) in service for ships and aircraft tracking as well.^15,16

Figure 9 MT 5000 (a) and GT 700 (b) SCU terminals.^15,16

Satellite Communication, Tracking and Monitoring Terminals

To enhance safety and security in transportation systems it is necessary to implement satellite asset tracking (SAT) for all mobile solutions, especially for ships and small craft via two-way data transfer devices in portable sizes. With their reduced power consumption of main, solar or battery power, these portable units are an effective way of remotely collecting position, velocity and time (PVT) data from ships, containers, vehicles, locomotives with wagons and small craft for transmission to the tracking control station (TCS). In this article only two ORBCOMM SAT and fleet management terminals will be discussed, global transportation management and heavy equipment management terminals.

1. ORBCOMM PT 7000 Modem – This unit integrates cellular and optional satellite trackers in cases where monitoring units are outside of ORBCOMM satellite coverage (see Figure 10a). It provides comprehensive monitoring and control for heavy equipment and vehicles used in the construction, mining, rail and utility industries. As part of a comprehensive telematics solution that includes sensors, connectivity and applications, the PT 7000, available as a cellular or dual-mode satellite-cellular version, gives customers complete visibility and control of their heavy equipment fleet and allows them to manage their operations more effectively by enabling access to real-time data and analytics.

It receives asset status updates and engine alerts, configures reporting intervals, responds to requests for asset positions and more. A satellite connectivity option is available for critical applications to ensure alarm delivery and response. It also receives real-time alarms when specific conditions are detected or thresholds are exceeded and an asset has been turned on, an engine reading has exceeded a threshold, an asset has entered or exited a geofence, low oil pressure is detected and more. It provides accurate status and position information along with key operational metrics so all users can proactively manage their fleets anywhere in the world.

By leveraging equipment utilization and maintenance reports, customers know where their equipment is, if it is productive or needs maintenance, if oil pressure is within limits and how it is being used to better allocate resources and improve operational efficiency. In addition, equipment alerts including unauthorized movement or out-of-spec sensor readings such as loss of oil pressure or high coolant temperature can be quickly communicated to a mobile device to ensure a timely response.

Necessary time to provide alert delivery is 30 seconds and poll response time is 2 to 3 minutes. The terminal provides reporting interval position, motion start/stop, condition-based fault codes, engine/idle hours, fuel consumption, battery voltage, antenna connect/disconnect and pre-defined event triggers. It interfaces four digital inputs, two digital outputs, two pull-up, two pull-down, four analog inputs, 4 1(/2) CAN/J1939 bus ports, 2(/1) Serial ports, LED and Bluetooth low energy.^17,18

2. Global Transportation Management RT-6000 Terminal – This terminal can be used for integrated GPS with dual-mode cellular and satellite tracking and management and has many interfaces for monitoring sensors (see Figure 10b). The ruggedized RT 6000+ provides visibility, control and decision rules to dispatch and operations centers, maintenance organizations and operational managers of transportation companies worldwide.

Using a unique direct interface to any refrigerated asset it provides comprehensive temperature and fuel management, maintenance, logistical and management applications services to revolutionize refrigerated transportation operations (see Figure 11). Transport customers can make immediate, important decisions about their reefers or any other vehicles, allowing for smarter investments in transportation system operations, logistics and immediate savings as well as improved end-to-end operations. With two-way interfaces, this solution delivers the most effective refrigeration and fleet management tools in the industry for maximum compliance, efficiency and return-on-investment.^2,10

Figure 10 Heavy equipment and transport management: PT 7000 Modem (a) and RT-6000 Terminal (b).^17,18

Figure 11 Tracking sensors onboard a truck.²

Maritime Satellite AIS (S-AIS) Terminals

The ORBCOMM LEO operator provides a new and more reliable satellite automatic identification system (S-AIS) via VHF frequencies for oceangoing ships with onboard broadcast systems. Ship identification, position and other critical data received from the GES can be used to assist in navigation and improve maritime safety and security at sea. In a similar way, the S-AIS system can be used for aeronautical applications so that aircraft position and other critical data can be used to assist in-flight operations and improve aeronautical safety.

The most current terrestrial-based Radio AIS (R-AIS) system implemented by the International Maritime Organization provides only VHF limited coverage nearby shorelines; it is not able to provide global coverage. The ORBCOMM satellite system overcomes this due to a fully Satellite AIS (S-AIS) data service that can monitor maritime vessels well beyond coastal regions and the horizon in a cost effective and timely fashion and send this data via GES to the Coastal Surveillance Center or TCS.

An AIS receiver using satellites can extend the VHF range of R-AIS systems considerably and makes it easier to monitor ship ocean navigation and fishing areas. ORBCOMM was the first commercial satellite network to begin operations with S-AIS data service. In 2008, ORBCOMM launched the first LEO satellites specially equipped with the capability to collect AIS data with plans to include these capabilities on all future satellites for ongoing support of global safety and security initiatives.

Figure 12 shows the space and ground configuration of S-AIS integrated with R-AIS. In fact, all ships receive GNSS PVT signals from the US GPS (1) or Russian GLONASS (2), then ships out of R-AIS coverage send via service link (3) PVT data to an AIS satellite. This data is transmitted via a feeder link to the GES (gateway) terminal (4).

All ships inside of R-AIS coverage send GNSS PVT data to the R-AIS base station (BS) via radio link (5), while all ships have AIS data communication via inter-ship links (6). Received AIS data from the GES and AIS BS is forwarded via terrestrial links (7) to the SCS terminal for processing. In this way, AIS data with positions of all ships in a certain sailing region can be displayed on a radar-like screen and used for collision avoidance.^1,2

Figure 12 ORBCOMM Satellite AIS (S-AIS).²

CONCLUSION

The versatile ORBCOMM products and Little LEO satellite constellation support multiple modes of communication, leveraging extensive experience to provide a broad portfolio of satellite, cellular and dual-mode IoT connectivity. The platform’s capacity has been expanded exponentially to process more than 100,000 messages per second, which is an increase of over 1000x in message throughput over legacy systems. With the ORBCOMM satellite network, it is possible to provide increased processing capability. Customers can continue to expand their deployments, access a higher level of visibility and enable more sophisticated solutions in a 5G sensor-enabled IoT ecosystem integrated with satellite solutions.

References

1. Mobile Satellite Communication Systems, CNS Systems, 2019.
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10. Orbcomm System Overview, ORBCOMM LLC, 2008.
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12. Q4000 Multi-Network Communications Device, Quake Global,  Web: https://www.quakeglobal.com/products/q4000.
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14. W. Leavitt, “ORBCOMM Unveils Solar-Powered Tracking Device,” FleetOwner, October 2013, Web; https://www.fleetowner.com/technology/article/21688294/orbcomm-unveils-solarpowered-tracking-device.
15. Hardware Data Sheet, MT 5000, Reliable small craft tracking for safety, security and compliance, ORBCOMM, Web: https://vmsmea.com/wp-content/uploads/2021/09/MT-5000_letter_Eng.pdf.
16. GT 700, Singapore Technologies Group, Web: https://www.singtechgp.com/telematics/devices/orbcomm/.
17. PT-7000 Rugged Telematics, ORBCOMM LLC, Web: https://www.orbcomm.com/en/solutions/heavy-equipment/hardware/pt-7000.
18. RT 6000+ Global Transportation Management Systems, Industry Leading Tracking and Monitoring Solutions for Refrigerated Assetts, ORBCOMM LLC, Web: https://www.orbcomm.com/PDF/datasheet/RT-6000-Reefer-Tracking.pdf.