Flight modem demonstrates feasibility of “launch vehicle as a node” for real-time tracking using commercial satellite-based positional data without traditional ground and flight telemetry infrastructure. The flight modem uses commercial off-the-shelf (COTS) equipment capable of full duplex communications at 2,400 baud to augment or replace low-bandwidth telemetry tracking and control (TT&C) mission requirements. The flight modem can be combined with an onboard global positioning satellite (GPS) receiver as a vehicle locator and effectively eliminate the need for downrange radar tracking.

The flight modem has an onboard iridium modem that can either work as a dial-up modem to a landline or can call another iridium modem. If the dial-up method is used, the modem can be used to access the Internet and the delay will be about 2 seconds. If two modems are used, the propagation delay can be as little as 100 milliseconds. The iridium modem is tied to an onboard GPS receiver via a PC-104 computer. The iridium modem will answer incoming calls and automatically start sending GPS data to the call modem that initialized the call.

The benefits of the flight modem include reduced ground station infrastructure; elimination of inherit scheduling conflicts, sustaining engineering, and antenna equipment costs; reduced mission costs by an order of magnitude; drastic reduction in logistical issues; and worldwide access to low-rate TT&C data.

The iridium flight modem will use sounding rocket-related activities as a springboard to prototype GPS launch support systems. Other vehicle test platforms include balloons, unmanned aerial vehicles (UAV’s), and aircraft. The technologies and processes involved include data communications, support hardware and software, safety and launch support processes, GPS, mission modeling, and analysis.

Ongoing development efforts include combining two iridium modems to increase the data rate to 4,800 bits per second, using one antenna for both iridium and GPS instead of two separate antennas, and developing a Sounding Rocket Antenna. The technologies involved in this project are the commercial satellite data services; the GPS receiver and potential other sensors (e.g., accelerometers); the Internet protocol (IP) communications and software tools; and the compact COTS bus architecture and local Ethernet ports.

Benefits of this project include:

• Reduction and possibly elimination of radar dependence.
• Easy configuration of ground hardware.
• Easy addition of new monitoring sensors or payload data interfaces.
• Easy configuration of inexpensive Internet-based ground software.
• Elimination of inherent scheduling conflicts on satellites.
• Reduction of ground station infrastructure and antenna equipment tracking costs.