Operations
The main mission sequence is composed of six distinct phases: Launch, Launch Vehicle Separation, Initial Acquisition, GPS Onboard Relative Navigation, Onboard Single Antenna GPS Attitude Determination and Micro-discharge Plasma Thruster Operation, and Amateur Radio Operations. In the first phase, the two nanosatellites will be launched on the Department of Defense Space Test Program STP-S26 Mission from Kodiak Launch Complex (KLC) in Kodiak, Alaska. They will be transported to a 72 degree inclination circular low Earth orbit with an altitude of 650 km by a Minotaur IV rocket. Initially, the two nanosatellites will be in a stacked configuration. Once the rocket reaches the desired orbit, the satellites will be powered on by the launch vehicle before finally separating from the launch vehicle. The third phase will begin once the two nanosatellites are ejected from the rocket. During this phase, there will be a 30-minute period where the satellites will go through a check out and initialization process. After this period, the satellites will begin transmitting beacon messages containing telemetry information that will help determine each satellite's status. During this phase the ground station will attempt to establish first contact with the satellites and perform a check out procedure to make sure all the subsystems on board are working correctly. It is expected that this checkout procedure will take several hours or even a few days depending on the duration of the communication passes with the ground station. Once the operators are satisfied with the status of the satellites, the satellites will be commanded from the ground to separate, finalizing the third phase of the mission. When the satellites have successfully separated, the primary mission will begin, signaling the start of fourth phase. First, the satellites will autonomously establish a cross-link, or in other words, they will communicate with each other through UHF/ VHF bands. The satellites will then exchange GPS data through this cross-link in order to calculate on-orbit real time relative navigation solutions. The fifth phase will activate a micro-discharge plasma thruster with a command from the ground that will autonomously operate when the thrusting vector is within a 15 degree cone of the anti-velocity vector. The thruster operation will be dependent on the on-orbit real-time single antenna GPS attitude determination solution. After this phase is over, a command from the ground station will disable the thruster on FASTRAC 1. The final phase of the mission will start once the communication architecture of the satellites is reconfigured from the ground to work with theSubsystems
Structure
The structure of the FASTRAC satellites is a hexagonal iso-grid design that is composed of two titanium adapter plates, aluminum 6061 T-6 side panels, six hollow outer columns with inserts and six inner columns. The mass of the two nanosatellites is approximately 127 lbs with all of the components included.Communication Architecture
The communications architecture is based on a system flown on PCSat2. The FASTRAC implementation consists of two receivers, one transmitter, a terminal node controller (TNC), a transmitter relay board, and a receiver relay board. On FASTRAC 1 “Sara Lily”, two R-100 VHF receivers and one TA-451 UHF transmitter from Hamtronics are used. On FASTRAC 2 “Emma”, two R-451 UHF receivers and one TA-51 VHF transmitter from Hamtronics are used. The TNC used is a KPC-9612+ from Kantronics. Both the transmitter and receiver relay boards were designed and manufactured in house.Command & Data Handling
The command & data handling (C&DH) system is composed by four distributed AVRs which were developed by Santa Clara University. Each AVR has an Atmega 128 microcontroller and controls an individual subsystem on the satellite (i.e.: COM, EPS, GPS, and THR or IMU). The AVRs communicate with each other through the I2C bus.GPS Subsystem
The GPS position and attitude determination system was designed and built by student researchers at The University of Texas' GPS Research Lab. The system utilizes GPS code measurements, as well as antenna signal-to-noise ratio (SNR) and 3-axis magnetometer measurements to provide estimates of position, velocity, and attitude. Each satellite will have redundant ORION GPS receivers, dual cross-strapped antennas with RF switching and splitting hardware.Power System
The power system for each satellite is composed of eight solar panels, a VREG box, and a battery box. The battery box is made from black anodized aluminum and holds 10 Sanyo N4000-DRL D-cells provided to the team by AFRL. Both the solar panels and the VREG board were designed and made in-house. On each satellite, the VREG board distributes power from three VICOR VI-J00 voltage regulators, and also charges the batteries with the power collected from the solar panels.Separation System
There are two separation systems for the FASTRAC satellites, both designed and manufactured by Planetary Systems Corporation (PSC), which will be used to separate the satellites in their stacked configuration from the Launch Vehicle and then to separate the two satellites while they are in orbit. The PSC Lightband Separation System is composed of two spring-loaded rings and a motorized release mechanism.Micro-Discharge Plasma Thruster
The micro-dischargeInertial Measurement Unit (IMU)
On FASTRAC 2 “Emma”, instead of using a thruster, an Inertial Measurement Unit (IMU) MASIMU01 from Micro Aerospace Solutions is used to measure the separation of the two satellites.Amateur Radio Participation
The FASTRAC satellites transmit and receive data (GPS, Health, etc.) on amateur radio frequencies. All amateur radio operators are encouraged to downlink data from either satellite and upload the data to the radio operator section on thOperation Frequencies
References
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