1. Earth Station and Communications Infrastructure
University of Kentucky
Space Systems Laboratory
Earth Station and Communications Infrastructure
*Earth Stations Operated By the University of Kentucky’s Space System Laboratory (SSL) Lab Director/Advisor: Dr. Jim Lumpp Lead Earth Stations Operator: Steve Alvarado Certified SSL Operators: Meetra Torabi, Jason Rexroat, Josh Evans, Max Bezold, Zach Jacobs
GENSO - Global Education Network for Satellite Operations
Introduction
The Space Systems Laboratory at the University of Kentucky has two operational UHF/VHF earth stations, each with the capabilities for low earth orbit (LEO) satellite communications.
Earth Station Hardware
The Space System Laboratories’ two earth stations consist of several critical hardware elements that allow for efficient telecommunications. Among these hardware systems are the Yagi-Uda directional antenna array, radio transceiver, power supplies/amplifiers, digital decoding/encoding hardware and centralized computer connected that inter connects all these sub systems.
GENSO is a global earth station network infrastructure designed to provide LEO satellite operators with an expansive network of worldwide earth stations for data collection.
Strength in Numbers
A LEO satellite orbits the earth approximately once every 90 minutes. This means that a quality satellite “pass,” the time period a satellite is within acceptable
Radio Equipment and Power Systems
Identified as ground stations
Uniform and Kilo, both
stations were constructed in
conjunction with the development of KySat-1, Kentucky’s first orbital satellite, to provide active ground support and data collection right from the University’s main campus.
SSL earth stations are equipped with an ICOM IC-910H dual band fm transceiver. Digital communication, are handled though a digital/analog interface called the Terminal Node Controller (TNC). The TNC performs audio frequency-shift keying (AFSK) modulation/demodulation to transform analog signals into formatted digital data packets and data packets into modulated analog signals to be transmitted by the transceiver. TNC digital data is sent to the ground station computer over serial connections. Receive preamplifiers are used to
Figure ft. UHF/VHF Directional Antenna Atop the FPAT Building at The University of Kentucky
communication range of a stationary earth station, using typical earth station equipment will often last less than minutes. GENSO connects multiple earth stations around the world via TCP/IP (internet) protocol, with each earth station “node” in the network collecting and forwarding data to LEO satellite owners
who typically cannot afford multiple stations. Not only does this significantly reduce costs, but the expansive network also provides an invaluable method for collecting large amounts of value data. From multiple locations around the world.
SSL Mission Control and Communication Consoles
UK’s two main earth stations are
operated from the SSL Mission
Control & Satellite Communications
room located in 553 FPAT on UK’s
main campus. Both station consoles
are equipped with a variety of
software suites that can perform
a multitude of digital, analog,
mathematical, and hardware control functions including: digital packet decoding/encoding, incoming and outgoing signal analysis, software signal modulation/demodulation, computer-hardware interfaces,
satellite orbital prediction and communication systems updates.
enhance low fidelity signals and 50 Amp/13 volt Astron power supplies allows for up to 100 watts of power to be transmitted over VHF. Antenna rotator controllers and radio level converters allow for autonomous antenna control and radio frequency Doppler-shift correction.
Figure 2.0 Ground Station Uniform Equipment Console. Located in 553 FPAT
GENSO Software (GSS)
Earth station operators install
software packages at their station
consoles that make tracking satellites
in the GENSO database completely
autonomous. During a scheduled pass,
the GSS software calculates the projected
orbit based on Keplerian elements. It then directly controls the radio transceiver—continuously adjusting the frequency to compensate for Doppler shifts, communicates with the hardware TNC, and pilots the antenna azimuth/elevation rotator controller for accurate , autonomous, directional pointing for antennas. Data collected during a pass is immediately forwarded to the main AUS server where it is processed and sent to the appropriate location.
Earth Station Directional Antenna Arrays
Satellite Tracking Software
Figure 5.0: 2mcp22 UHF antenna array used by SSL earth stations
Figure 6.0: GSS Software autonomously controlling earth station directional antenna
Specialized software (e.g., SatPC32) performs orbit propagation calculations of earth orbiting satellites based on publicly available radar tracking data from the North American Aerospace Defense Command (NORAD). NORAD maintains a database with mathematical representations of all
Figure 4.0: 3-Dimensional Radiation Pattern of a 70cm UHF Yagi-Uda Antenna
High gain circularly, polarized Yagi- Uda antenna
2 m is dBd 70 cm is 16.8 dBd
Half Power Beam Width
α = 2 m
α = 70 cm
For safe transmission, VSWR < 2 is required
VSWR = 2 m
VSWR = 70 cm
Elements
No. of elements : 2 m
No. of elements : 70 cm
Type : 3/16" Alum Rod
Power 2 m is 1.5 KW
70 cm is 1 KW
Ground stations Kilo and Uniform each control one high gain, UHF/VHF, Yagi-Uda directional antenna both of which are stationed atop the FPAT building (Figure 1.0). The Yagi antenna’s inherent signal polarization, gain properties, radiation propagation characteristics and optimal frequency range provide for an ideal earth station antenna with LEO satellite communication capabilities. Both antennae are circularly polarized to minimize the signal loss that is often experienced by transmitting satellites due to atmospheric attenuation and high relative orbital velocity. The SSL Yagi-Uda Antennae have an optimal frequency range of 144MHz-148MHz VHF and MHz UHF--also known as the amateur radio 2m and 70m bands. These bands are heavily utilized by university and amateur-built LEO satellites.
Figure 3.0 Image of SATPC32, A Software Suite That Provides LEO Satellite Orbital Information and Autonomous Ground Station Satellite Tracking
UK, SSL - Breaking New Ground
In May of 2011, ground station Uniform
autonomously collected data from FASTRAC-1, a university built satellite from the University of Texas at Austin, and successfully relayed the data to GENSO’s main server in Vigo, Spain. The University of Kentucky became just the 5th university in the world to have a GENSO-compatible earth station.
objects in space called Keplerian or “two-line” elements. The Keplerian elements precisely describe the orbit of the satellite that tracking software can use to determine the current and future “footprint” of the satellite, and can automatically set the azimuth and elevation of the tracking antennas and adjust the frequencies of the radios to compensate for the Doppler shift due to the relative motion of the satellite antennas (18,000 mph velocity for LEO satellites).
Figure 7.0: 21m , parabolic antenna at Moorehead State University. SSL communications partner and fellow member of Kentucky Space.