Integral Systems, Inc. (Nasdaq:ISYS) announced at the 2010 National Space Symposium that its wholly-owned subsidiary, RT Logic, has successfully delivered its next generation Tracking and Data Relay Satellite System (TDRSS) Cross Link Simulator (TSIM) to multiple civil government and commercial customers over the past year, with additional deliveries pending. The new TSIM is based on RT Logic's T400 and T501 product lines.

Customers are provided with an economical platform to verify operation of space vehicles or transponders designed to access NASA's Space Network (SN) while on orbit. The TSIM receives command data and generates the TDRSS spread spectrum forward link signal. The forward link signal contains the command data modulo-2 added to a command Pseudo-random Noise (PN) sequence and a ranging PN sequence. The two PN sequences are modulated in an unbalanced Quadrature Phase-Shift Keying (QPSK) format. The TSIM receives the return link RF signal and demodulates either the Data Group 1 (spread) or Data Group 2 (non-spread) modes.

The return link signal is modulated in a staggered QPSK format known as Staggered Quadriphase PN (SQPN), and allows data to be placed on both the I and Q phases. The TSIM recovers this data and outputs data and clock for both I and Q streams. Epochs from the forward and return links are used to calculate range measurements. A Doppler simulator allows any Doppler profile to be easily simulated. The TSIM can also simulate the Point A side of the space-to-space link.

As a fully integrated system, the TSIM includes an intuitive, user-friendly graphical user interface for equipment configuration and status. The modularity and configurability of the underlying software-defined architecture allows for tailoring of the standard TSIM to specific customer requirements.