Session
Technical Session II: New Components and Software
Abstract
The present-day emphasis on smaller, lower cost spacecraft missions has generated significant interest in higher levels of integration for spacecraft electronics. One of the more effective approaches is to integrate the core electronics, including the RF hardware, into a single card-based chassis commonly referred to as an Integrated Electronics Module (IEM). This approach has been adopted for the TIMED spacecraft, currently being built for NASA by the Johns Hopkins University Applied Physics Laboratory. Breaking from traditional approaches, TIMED incorporates the S-band transmitter and receiver functions into the IEM along with the spacecraft digital electronics. These RF functions are integrated with portions of the command and data handling system, thus blurring the traditional boundaries between subsystems and resulting in two plug-in cards (uplink and downlink) that perform high level functions for the spacecraft. Although designed for S-band operation, the architecture of the cards is scaleable, permitting them to be adapted to X-band for deep space or high data rate applications. In addition, the cards are capable of performing highly accurate two-way Doppler tracking. Using a noncoherent technique recently developed at APL, velocity accuracy has been demonstrated at the 0.1 mm/s level, thus meeting the stringent requirements of a deep space mission.
A Highly Integrated S-Band Transceiver System with Two-Way Doppler Tracking Capability
The present-day emphasis on smaller, lower cost spacecraft missions has generated significant interest in higher levels of integration for spacecraft electronics. One of the more effective approaches is to integrate the core electronics, including the RF hardware, into a single card-based chassis commonly referred to as an Integrated Electronics Module (IEM). This approach has been adopted for the TIMED spacecraft, currently being built for NASA by the Johns Hopkins University Applied Physics Laboratory. Breaking from traditional approaches, TIMED incorporates the S-band transmitter and receiver functions into the IEM along with the spacecraft digital electronics. These RF functions are integrated with portions of the command and data handling system, thus blurring the traditional boundaries between subsystems and resulting in two plug-in cards (uplink and downlink) that perform high level functions for the spacecraft. Although designed for S-band operation, the architecture of the cards is scaleable, permitting them to be adapted to X-band for deep space or high data rate applications. In addition, the cards are capable of performing highly accurate two-way Doppler tracking. Using a noncoherent technique recently developed at APL, velocity accuracy has been demonstrated at the 0.1 mm/s level, thus meeting the stringent requirements of a deep space mission.
