Lunar Astro-Track


Design

   The Astro-track functional design is        presented along with design                considerations.  Below are a list of        topics that are included in this                section. Click on any links below to        jump to a topic.

   Design Topics:


       Design Goals

            Objectives and Requirements

       Astro-Location

            RFID Waypoint
            RFID Interrogator
            Portable Array

       Astronaut / Lunar Lander Link

            One-Way High Speed Link

                    
            

Astro-Location (RFID Interrogator)

RFID Waypoint RFID Interrogator Portable Array
The Lunar Astro-Track RFID interrogator is made up of 5 dipole antennas: One for transmission and four for reception.  The four receiving antennas are used together as a phased array to perform DF.

The transmit antenna situated above the receiving elements to achieve a better line of site to the RFID and to minimize leakage into receive antennas.  Behind each of the receive antennas a very narrow, deep notch filter is used to null out RFID tone (could be a stub).  Due to the spread spectrum nature of the RFID waypoint waveform, this nulling will have a minimal affect on the ability to detect a RFID waypoint even though it is in the same band.


 
Periodically the interrogator will send out short duration bursts of energy at 1.15 GHz to activate the RFID Waypoints.  After a RFID is powered up by incident pulse from the interrogator, it will immediately transmit a direct sequence spread spectrum sdignal.  The signals spreading sequence will be unique to a paricular waypoint.  When an RFID's return signal is detected, the return time and interrogation burst time are used to compute the range ring.  The thickness of the range ring is adjusted by cross-correlation levels, a priori system noise knowlege, and timing uncertainty.