Our Technology
Space Segment
ORBCOMM operates a network of low Earth orbit (LEO) satellites that provide worldwide coverage. These satellites are relatively small
in size, weighing less than one hundred pounds and measuring only forty-two
inches in diameter and six inches in height before deployment. The relatively
small size of our satellites is made possible by the fact that they do not
require a propulsion system to maintain the satellites in the appropriate
orbit and have significantly lower power requirements as compared to geostationary
satellites.
Each satellite is equipped with a VHF and Ultra High Frequency, or UHF, communication
payload capable of operation in the 137.0-150.05 MHz and the 400.075-400.125
MHz bands. The use of the system uplink (Earth-to-space) spectrum is managed
by an on-board computer that employs the ORBCOMM-pioneered Dynamic Channel
Activity Assignment System, or DCAAS. DCAAS continuously scans the authorized
spectrum, identifies frequencies in use by other users of the frequency band
and assigns subscriber communication uplink channels to minimize interference.
DCAAS changes the uplink frequency at least every 15 seconds, which allows
our system to coexist with the current users of the VHF frequency band, and
limits interference to acceptable levels. The gateway earth stations
and the subscriber communicators communicate with the satellites in the same
VHF band, thus eliminating the design complexity, as well as the associated
bulk, power and cost of supporting multiple communication equipment on a
single satellite. Our satellites also contain packet-routing communications
capability, including a limited store-and-forward capability.
Sun-Nadir Steered Configuration
- Vertical disk-shaped body with nadir-oriented quad helix antennas
- Single-axis, dual panel solar array deployed normal to body
Vital Statistics
- 92 pounds
- 41” diameter x 6.5” high (stowed configuration)
- 170” long x 88” high (antenna and solar array deployed)
Bus Subsystem
- Peak power tracking with GaAs solar array
- Wheel-augmented gravity gradient / magnetic 3-axis ACS
- GPS state vector determination
- Cold gas propellant / differential drag stationkeeping
- Central flight computer for data / command storage