Passive EVA tracking system using a pair of 3-element microstrip patch arrays

There exists no method for tracking an astronaut in extravehicular activity (EVA) except for having a colleague onboard stand by the window and watch. When considering the use of any conventional radar system for tracking an EVA, there is the danger of radiating the target with high levels of microwave energy when the range is short. The authors discuss some preliminary design and analysis work which has been done on a passive tracking system to provide range and direction of upto five EVAs out to a few hundred meters. There are no EVA safety hazards since the passive system is receive only. That is, there is no transmitted radar energy to radiate the astronaut. Instead, the tracking system uses the voice communication signals already available from the backpack. This system will be compatible with the new time division multiple access (TDMA) system which uses continuous phase frequency shift keying (CPFSK) modulation at a carrier frequency of 414.2 MHz with frequency deviation 358.4 kHz.