An application of the "virtual spacecraft" concept in evaluation of the Mars Pathfinder Lander low gain antenna

The virtual spacecraft concept is embodied in a set of subsystems, either in the form of hardware or computational models, which together represent all, or a portion of, a spacecraft. This paper describes a simulation designed to evaluate a communications link between the Earth and the Mars Pathfinder Lander module as it descends under a parachute through the Martian atmosphere toward the planet´s surface. This link includes a transmitter and a low gain antenna on the spacecraft and a receiving antenna and receiver on the Earth as well as a simulation of the dynamics of the spacecraft. The transmitter, the ground station antenna, the receiver and the dynamics are all simulated computationally while the spacecraft antenna is implemented in hardware on a very simple spacecraft mock-up. The dynamics simulation is a record of one output of the ensemble of outputs of a Monte Carlo simulation of the descent. Additionally, the antenna/spacecraft mock-up system was simulated using APATCH, a shooting and bouncing ray code developed by Demaco, Inc. The antenna simulation, the antenna hardware, and the link simulation are all physically located in different facilities at JPL separated by several hundred meters and are linked via the local area network (LAN).