Simulation and Evaluation System (SEVS)
   SEVS 1.25316455696

Date manufactured: 1980

Period/Dates when in use: 1980-2010

Description: The Collins Avionics & Communications Division of Rockwell International (now Rockwell Collins, Inc.) designed and built the Simulation and Evaluation System (SEVS) as a way to test early Global Positioning System (GPS) technology. SEVS consisted of a multiple-channel signal generator (MCSG), an interface simulator, a magnetic tape system for input and output data, a Digital Equipment Corp. (DEC) Program Data Processor (PDP) 11/60 computer, a Texas Instruments LXY-11 line printer and a DECwriter printing terminal. A single channel version of the SEVS was developed in the early 1980s for factory use where the MCSG was replaced with a single channel signal generator (SCSG).

Item History: SEVS was one of the first satellite simulators in the early development and testing of GPS user equipment. At the time, four prototype satellites were in orbit, providing only a few hours of coverage each day – often at very inconvenient times. Simulating the satellite signals in a range of programmable, repeatable scenarios enabled GPS developers to evaluate their systems without being hampered by the availability of orbiting-satellite signals.

In its qualification testing capacity, SEVS powered, controlled and monitored GPS receivers, providing interface signals, coordinated satellite data and host vehicle aiding data such as inertial, baro altimeter and precise time. SEVS simulated real-time flight scenarios, during which the GPS receiver would transmit its performance data into the SEVS data recording system for post-test evaluation against truth data.

SEVS simulation capabilities included:

  • Masking – both terrain and body
  • Antenna – different kinds of antenna technology
  • Jammer – stationary or moving using closed-circuit simulation, with a maximum of two types of jammers at any time
  • Satellite – up to 24 satellites (up to six at a time), with truth data used to generate satellite motion, satellite clock offset and ionospheric delay
  • Host vehicle motion – predefined motion (i.e., no pilot), with separately computed attitude. Motion simulation included coordinated turns for fixed-wing aircraft, ship’s motion models and vectors fixed by velocity for land vehicles.

Submission authored by:
John Nielson
Rockwell Collins
855 35th Street NE
Cedar Rapids, IA