ORBCOMM FM-3 and ORBCOMM FM-4 are American low altitude communications spacecraft that were launched by a Taurus rocket from Vandenberg AFB at 13:20 UT. These ORBCOMM FM fleet of satellites enable global voice and data links to/from fixed or mobile industrial sites such as oil rigs, cargo trucks and ships. Initial orbital parameters were period 101.5 min, apogee 878 km, perigee 784 km, and inclination 108.0 degrees.
These satellites were part of a commercial venture to provide global messaging services using a constellation of 26 low-Earth orbiting satellites. The planned system was designed to handle up to 5 million messages from users utilizing small, portable terminals to transmit and receive messages directly to the satellites. The first 2 satellites of the constellation (95-017A + B) experienced communication problems after launch, but were recovered and placed into operational status. The nominal 26 satellite constellation was to be deployed by 1997, with the potential for an additional 8 satellite plane and 2 more polar orbiters depending on demands for increased coverage. The vehicles were controlled from a single control center located in Dulles, VA.
The spacecraft was a circular shaped disk. Circular panels hinged from each side after launch to expose solar cells. These panels articulated in 1-axis to track the sun and provide 160W. Deployed spacecraft measured 3.6 m from end to end with 2.3 m span across the circular disks. VHF telemetry was at 57.6 kbps. The spacecraft contained an on-board GPS navigation and timing system, and 14 volt power system. Gravity gradient stabilization provided 4 degs control with magnetic torques for damping cold gas (nitrogen) propulsion system.
The spacecraft carried 17 data processors and 7 antennas and was designed to handle 50,000 messages per hour. The long boom was a 2.6 meter VHF/UHF gateway antenna. Receive: 2400 bps at 148 - 149.9 MHz. Transmit: 4800 bps at 137 - 138 MHz and 400.05 to 400.15 MHz. The system used X.400 (CCITT 1988) addressing. Message size was 6 to 250 bytes typical (no maximum).
Facts in Brief
Launch Date: 1998-02-10
Launch Vehicle: Taurus
Launch Site: Vandenberg AFB, United States
Mass: 41.0 kg
Nominal Power: 160.0 W