Student Ground Station

Overview

The Student Ground Station (SGS) is a satellite command and telemetry station designed and operated by students in the Space Systems Engineering Program. The ground station is used to communicate with satellites built by the Space Systems Engineering Program, or other missions that need additional ground support.

The ground station has three major subsystems: Tracking, UHF, and S-Band. The tracking subsystem locates the target satellite as it passes overhead, and controls the tower rotors to aim the antennas at the satellite. The UHF system communicates with satellites in the 430-440 MHz frequency range. It is capable of receiving information from the satellite and commanding the satellite. The S-Band system receives information from satellites at frequencies around 2400 MHz.

The ground station is located at the NOAA Fairbanks Command and Data Acquisition Station (FCDAS), near Gilmore Creek. NOAA generously provides a tower and building for SSEP to house the SGS, and provides support for SSEP when needed. The FCDAS site is ideal for its quiet radio environment.

Design and Operation

Tracking

The tracking system uses the Systems Tool Kit (STK) to retreive satellite orbital parameters provided by the North American Aerospace Defense Command (NORAD). NORAD tracks any satellite in low-earth orbit and provides the satellites' oribital parameters for public use. After retrieving the orbital parameters for the desired satellite, STK calculates the azimuth and elevation angles between the ground station and the satellite, as well as the frequency correction for Doppler shift. It passes the results to a student written LabVIEW program that commands the rotators to aim the antennas. The program also makes doppler shift corrections in the radio.

UHF

The UHF (Ultra-High Frequency) system is used to receive satellite health beacons and transmit satellite commands. The system uses a software defined radio programmed via LabVIEW. All of the signal processing and decoding is done in software.

Incoming signals are received at the antenna, fed through a preamplifier at the top of the tower, and then down the tower into the equipment housing building. A power amplifier with a radio frequency (RF) switch passes the received into the software defined radio. The radio demodulates the RF signal into bits that are processed by the computer.

During transmission, the radio received the desired bits from the computer, and modulates those bits into RF signals. The RF signal is then fed into the power amplifier which amplifies the signal before sending it to the antenna to be broadcasted. The computer also notifies the power amplifier that amplifier that a transmission is coming, so that the power amplifier can swith into transmission mode and tell the preamplifier to also switch.

S-Band

The S-Band system is only used for high-capacity data downlink. The signal is received at the anetnnas, downconverted to a lower frequency, and received by the software defined radio that demodulates the signal and sends the bits to the computer for processing.