2007:089 MASTER'S THESIS - Semantic ScholarABSTRACT Design, Development and Operation of a student...
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2007:089 MASTER'S THESIS Design, Development and Operation of a Student Ground Station Anura Wickramanayake Luleå University of Technology Master 's thesis Space Science Department of Space Science, Kiruna 2007:089 - ISSN: 1402-1552 - ISRN: LTU-DUPP--07/089--SE
Transcript of 2007:089 MASTER'S THESIS - Semantic ScholarABSTRACT Design, Development and Operation of a student...
2007:089
M A S T E R ' S T H E S I S
Design, Development and Operationof a Student Ground Station
Anura Wickramanayake
Luleå University of Technology
Master's thesis Space Science
Department of Space Science, Kiruna
2007:089 - ISSN: 1402-1552 - ISRN: LTU-DUPP--07/089--SE
Design, Development and Operation of a Student Ground Station
A.B.A.T Wickramanayake June 2007
ABSTRACT Design, Development and Operation of a student ground station is a Master thesis project
done at the Department of Space Science (IRV), Luleå University of Technology,
Sweden. The Objective of this degree project is to develop and operate the IRV student
ground station that operates within amateur radio bands (VHF and UHF). Hardware and
software were selected after studying the existing student ground stations. Tokyo
University CubeSat XI-IV, CUTE-1 and XI-V were used for testing of the uplink and
downlink performance. Those experiments gave good results for Ax.25 packets and for
CW signals. Handover experiments were carried out to determine the importance of the
IRV ground station in a possible student ground station network. The results showed that
IRV ground station has a unique advantage due to its location. SWR measurements were
carried out for VHF and UHF antenna systems that gave results below 2. It is observed
that noise levels due to external electromagnetic interferences in amateur radio bands are
negligible. Currently the IRV ground station is fully functional in VHF and UHF bands
and has the option of expanding to S band
ii
INDEX ABSTRACT......................................................................................................................... i
INDEX ................................................................................................................................ ii
LIST OF FIGURES ............................................................................................................ v
LIST OF TABLES............................................................................................................ vii
CHAPTER 1 ....................................................................................................................... 1
INTRODUCTION .............................................................................................................. 1
CHAPTER 2 ....................................................................................................................... 3
GROUND STATION TECHNOLOGY............................................................................. 3
Hardware..................................................................................................................... 4
Software ...................................................................................................................... 4
People.......................................................................................................................... 5
Operations................................................................................................................... 5
Decoding ratio................................................................................................................. 7
Student Ground Stations and Student Satellites.............................................................. 7
Comparison of Student Ground Station Technology...................................................... 9
Hardware..................................................................................................................... 9
Software .................................................................................................................... 11
Hardware selection........................................................................................................ 12
Software selection......................................................................................................... 13
Cost of finance .............................................................................................................. 14
Antenna theory.............................................................................................................. 15
Polarization ............................................................................................................... 15
Standing Wave Ratio (SWR).................................................................................... 16
Antenna bandwidth ................................................................................................... 17
Impedance ................................................................................................................. 17
Directivity of the antenna and antenna beamwidth................................................... 17
Radiation Pattern....................................................................................................... 18
Gain of the antenna ................................................................................................... 18
Omnidirectional antennas ......................................................................................... 18
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Yagi antennas............................................................................................................ 20
Digital communication.................................................................................................. 22
Link Budget .................................................................................................................. 23
Link margin............................................................................................................... 23
Calculation of (C/N)ach.............................................................................................. 24
Equation needed to calculate the (C/N)req for detail link budget .............................. 25
Receiver figure of merit ............................................................................................ 26
Losses........................................................................................................................ 26
Global Educational Network for Satellite Operation (GENSO)................................... 31
CHAPTER 3 ..................................................................................................................... 33
IRV GROUND STATION STATUS ............................................................................... 33
Ground station specification ......................................................................................... 33
Description of used hardware and software.................................................................. 35
Tower and antennas .................................................................................................. 35
Transceivers .............................................................................................................. 35
Rotor and rotor controller ......................................................................................... 36
Preamplifiers ............................................................................................................. 37
Radio Computer Interface......................................................................................... 38
Rotor Computer Interface ......................................................................................... 38
Power controller switch ............................................................................................ 39
The UEK-200SAT receive converter ....................................................................... 39
Power supply............................................................................................................. 40
SWR & Power meter ................................................................................................ 41
Audio Noise Reduction filter .................................................................................... 42
Cables........................................................................................................................ 42
Connection of hardware................................................................................................ 43
Software setup............................................................................................................... 44
Pre-pass software ...................................................................................................... 44
Real time software .................................................................................................... 44
Past-pass software..................................................................................................... 44
Operational Procedure .................................................................................................. 45
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CHAPTER 4 ..................................................................................................................... 46
IRV GROUND STATION PERFORMANCE ANALYSIS ............................................ 46
Preliminary link budget ............................................................................................ 46
CUTE-1 FM operation to find out the decoding ratio of IRV ground station .......... 51
XI-IV FM operation to find overall data download ratio ......................................... 52
Interference monitoring ............................................................................................ 54
Testing of the SWR for the antenna systems ............................................................ 54
CHAPTER 5 ..................................................................................................................... 55
DISCUSSION AND FUTURE WORK............................................................................ 55
CHAPTER 6 ..................................................................................................................... 57
CONCLUSION................................................................................................................. 57
CHAPTER 7 ..................................................................................................................... 58
REFERENCE.................................................................................................................... 58
APPENDIX 1: Detail specification of hardware .............................................................. 60
ICOM IC-910H Specifications ..................................................................................... 60
General...................................................................................................................... 60
Transmitter................................................................................................................ 60
Receiver .................................................................................................................... 61
Audio Noise Reduction Filter ....................................................................................... 62
Cable specifications ...................................................................................................... 63
APPENDIX 2: Glossary ................................................................................................... 67
v
LIST OF FIGURES
Figure 01: Relationship between Space segment, Ground system and Data users............. 3
Figure 02: A block diagram of a basic ground station........................................................ 5
Figure 03: Picture of a student ground station (LTU ground station)................................. 7
Figure 04: Picture of a student satellite............................................................................... 7
Figure 05: E-field variation of Linear and Circular polarization. ..................................... 15
Figure 06: Definition of antenna beamwidth .................................................................... 17
Figure 06: Omnidirectional antenna (Discone type)......................................................... 18
Figure 07: Discone antenna elevation radiation patterns for 145 MHz............................ 19
Figure 08: Discone antenna elevation radiation patterns for 145 MHz............................ 19
Figure 09: Skeleton slot fed Yagi antenna........................................................................ 20
Figure 10: Cross Yagi antenna.......................................................................................... 21
Figure 11: Voltage polar diagram and gain against VSWR for Yagi antennas ................ 21
Figure 12: Worst case distance between the satellite and the ground station................... 25
Figure 13: Clear sky radio signal attenuation due to oxygen and water vapour in the
atmosphere ........................................................................................................................ 26
Figure 14: Galactic and tropospheric noise temperatures at various ground antenna
elevations (δ)..................................................................................................................... 27
Figure 15: Ground station receiver noise.......................................................................... 28
Figure 16: Attenuation Lrain and noise temperature due to rainfall at 30 deg elevation
above the local horizon ..................................................................................................... 29
Figure 17: UHF/VHF Yagi antennas ................................................................................ 35
Figure 18: Picture of the ICOM IC-910H transceiver ...................................................... 36
Figure 19: Rotor and Rotor controller .............................................................................. 36
Figure 20: AG-25/AG-35 preamplifier............................................................................. 37
Figure 21: ARR GaAsFET Preamplifier........................................................................... 37
Figure 22: ICOM CT-17 Radio Computer Interface ........................................................ 38
Figure 23: GS-232B Rotor Computer Interface................................................................ 38
Figure 24: Power controller switch................................................................................... 39
Figure 25: UEK-200SAT receive converter ..................................................................... 39
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Figure 26: Kenwood PS-52 Power supply........................................................................ 40
Figure 27: SAGA 300 Power supply ................................................................................ 40
Figure 28: SWR & Power meter (1.8 – 150 MHz) ........................................................... 41
Figure 29: SWR & Power meter (140 -450 MHz)............................................................ 41
Figure 30: Audio Noise Reduction filter .......................................................................... 42
Figure 31: Hardware connection....................................................................................... 43
Figure 32: Plot of time stamps of decoded packet at each ground station........................ 51
Figure 33: Comparison of downloaded data at each pass................................................. 52
Figure 34: The integration of obtained data at each operation time. ................................ 53
Figure 35: The ratio of obtained data at each ground station ........................................... 53
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LIST OF TABLES Table 1: Satellites Modes.................................................................................................... 6
Table 2: Hardware comparison with other Universities ................................................... 10
Table 3: Software comparison with other Universities..................................................... 11
Table 4: Hardware Selection............................................................................................. 12
Table 5: Software selection............................................................................................... 13
Table 6: Cost of finance as at 2006................................................................................... 14
Table 7: IRV ground station specifications ...................................................................... 34
Table 8: Preliminary downlink budget for 70 cm antenna ............................................... 47
Table 9: Preliminary downlink budget for 2 m antenna ................................................... 48
Table 10: Preliminary uplink budget for 70 cm antenna .................................................. 49
Table 11: Preliminary uplink budget for 2 m antenna ...................................................... 50
1
CHAPTER 1
INTRODUCTION
The Objective of this degree project is to develop and operate the IRV student ground
station that operates within amateur radio bands (VHF and UHF). IRV ground station
was first established in 1990’s but since 1996 it has not been functional due to the lack of
experience staff (for operations and maintenance) and due to the out-of-date instruments.
In 2006, Dr Priya Fernando (senior lecturer at IRV and Project manager, Ground Station
Project) started the Ground Station Project to re-establish the IRV Ground Station with
the aid of European Union Development fund. During this degree project, the IRV
ground station build from scratch to its current fully functional state. This degree project
was carried out under the supervision of Dr. Priya Fernando. In this thesis the chapter 2
is about the ground station technology related to student ground stations and it covers
hardware and software comparison and selection, antenna theory and link calculation etc.
The chapter 3 is about the IRV ground station status and it covers the detail description of
used hardware and software, hardware and software setup, operational procedure etc. The
chapter 4 is about the IRV ground station performance analysis and it covers the
preliminary link calculations and the results of the experiments. Chapter 5 is the
discussion and future work and chapter 6 is the conclusion. Owing to its location in the
northern hemisphere at a latitude of 67.7 degree north, the IRV ground station at Kiruna
has the great advantage of having more passes for polar satellites. Secondly, the ground
station is located at a considerably flat area with very low population around, so almost
no interference from electromagnetic disturbances or blocking from high rise buildings,
giving it a very good contact at even low elevations. With the plan of launch of its
Cubesat by IRV, it’s very important to have an operational ground station. Till the
Cubesat project is launched, a considerable experience in satellite communication and
operation can be achieved by working on this ground station. after comparing the existing
student ground stations, “CUE DEE 15X 144” VHF antenna, “CUE DEE 17 X 432” UHF
antenna, “YAESU 5400B” rotor controller, “ICOM 910H” transceiver, “AG-35” and
“AG-25” preamplifiers ,“Nowa for Windows” software, “Winorbit” software, “GMS
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(Ground Station Management Service)” software, “Packet Engine Pro” a software based
TNC (Terminal Node Controller), terminal program (AGWTERMINAL), “Hamscope”
software and “CWget” software are selected for the project. Tokyo University Cubesat
XI-IV, CUTE-1 and XI-V were used for testing of the uplink and downlink performance
and obtain good results for Ax.25 packets and for CW signals. During the experiments it
is observed that packet downloading and decoding can be done at very low elevation
angles like 5-degrees and also found that the ground station has a data decoding rate
around 40% (48.25 % CUTE-1 and 32.1% for the XI-IV). Handover experiments were
carried out to determine the importance of the IRV ground station in a student ground
station network. From these experiments showed that the IRV ground station has a high
data downloading capacity for polar satellites (twice as university of Tokyo). SWR
measurements were carried out for VHF and UHF antenna systems and both
measurements are below 2. Noise levels in amateur radio bands are negligible due to
external electromagnetic interferences. The preliminary link calculation shows that IRV
ground station can receive the telemetry of a satellite which has a minimum EIRP of -19
dB in 70 cm or -28 dB in 2m band. Also it can upload telecommand to a satellite which
has an antenna with a minimum gain of -267 dB in 70 cm band or – 275 dB in 2 m band.
Currently the IRV ground station is fully functional in VHF and UHF bands.
3
CHAPTER 2
GROUND STATION TECHNOLOGY A ground station is an earth-based point of communication with the spacecraft/Space
segment. They are the source for our interaction with the satellites; hence play an
important part for any satellite related operation and it is very important to have a good
communication link between the ground station and the satellite/space segment. Usually a
ground segment/ground system involves following tasks. (Ref 6, page 477)
• Tracking and determine the position of the satellite orbit
• Telemetry operations to acquire and record satellite data and status
• Commanding operations to interrogate and control the various functions of the
satellite
• Controlling operations to determine orbital parameters, to schedule all satellite
passes and to monitor and load the on-board computer
• Data processing operations to present all the engineering and scientific data in
the formats required for the successful progress of the mission
• Voice and data links to other worldwide ground stations and processing
centres
Figure 01: Relationship between Space segment, Ground system and Data users.
Data Relay
Spacecraft and payload support
Ground System Command and tracking data
Telemetry
Mission Data
4
Figure 01 shows the relationship between space segment ground segment/ground system
and data users (Ref 5, page 623). Normally a ground segment can be divided in to 4 main
components. (Ref 6, page 477)
• Hardware
• Software
• People
• Operations
Hardware Basically the hardware section consists of antennas, rotors, transceivers, computers,
power supplies, peripherals, data recorders etc.
Software There are mainly 3 different kinds of software uses in the student ground station
operations
• Pre-pass software
• Real time software
• Post-pass software
(Normally in a commercial ground station there are 4 different kids of software involves,
including the onboard software which needed for the space craft. At present most of the
student satellites does not have the function to upgrade onboard software using the uplink
from the ground station. Therefore the onboard software is not an essential item in a
student ground station.)
Pre-pass software The software which is required in advance of the pass of the spacecraft to
• Determination and prediction of the orbit
• Observation planning and scheduling
• Command list generation and simulation.
5
Real time software The software which is required during the spacecraft is visible to the ground station. This
include the antenna tracking software, computer control software, command and data
handling software etc
Post-pass software Post-pass software are the software that needs for Housekeeping, quality control and
health assessment, data processing and orbit determination and for data analysis.
People In a commercial ground station people are involved in many different areas of
responsibilities such as site and project management, operation shift staff, hardware staff,
software staff, data and engineering support staff, administration, specialist engineers and
scientists. However in a student ground station all the operations are carried out by few
staff members and couple of students.
Operations This brings hardware, software and people together. The operations team is the
fundamental human unit that integrates the mission software and hardware into on
effective routine process.
Figure 02: A block diagram of a basic ground station
Ref 06
6
For a ground station to operate successfully with a satellite, the communication
equipments should be in compatible with the selected satellite modes. The satellites
modes are the combination of uplink frequency, downlink frequency, and transmission
modes. Table 01 shows a list of common satellite modes. (Ref 14)
Mode
Description
A This mode requires a 2 meter SSB/CW transmitter and a 10 meter
SSB/CW receiver and supports CW and voice.
B This mode requires a 70 cm SSB/CW transmitter and a 2 meter SSB/CW
receiver and supports CW and voice. Some satellites also support RTTY
and SSTV in this mode.
K This mode requires a 15 meter SSB/CW transmitter and a 10 meter
SSB/CW receiver and supports CW and voice. This mode is unique in
that it can be done with a simple HF rig.
JA This mode stands for J Analog and requires a 2 meter SSB/CW
transmitter and a 70 cm SSB/CW receiver and supports CW, voice.
JD This mode stands for J Digital and requires a 2 meter FM transmitter and
a 70 cm SSB/CW receiver and supports packet.
S This mode requires a 70 cm SSB/CW transmitter and a 2.4 GHz
SSB/CW receiver and supports CW and voice.
T This mode requires a 15 meter SSB/CW transmitter and a 2 meter
SSB/CW receiver and supports CW and voice.
Table 1: Satellites Modes
Some satellites have dual modes that operate simultaneously. For example, AO-13
(Amsat Oscar 13) (Ref 14) can operate in mode BS which means that it can operate in both
modes B and mode S simultaneously. Other common dual modes are KT and KA.
7
Decoding ratio Ground station decoding ratio is defined as the ratio of decoded packets in the ground
station to packets sent from the satellite. Packets sent from a satellite are estimated from
duration of pass time and the interval of packet output. The interval of packet output is a
property of the satellite.
Student Ground Stations and Student Satellites
Figure 03: Picture of a student ground station (LTU ground station)
The student ground stations (Ref 11-16) are mainly design to communicate with student
satellites. Most of the universities have their own satellite programs to give experience to
the students about the design of satellites. Most of these satellites are weighing less than 5
kg and communicate via UHF and VHF bands using Ax.25 packets (communication
protocol).(Ref 4- page 256, Ref 8) Cubesat (a small satellite of 10 x 10 x 10 cm cube and weigh
less than one kg ) is a popular satellite program among the universities (Ref 12).
Figure 04: Picture of a student satellite
Ref 16
8
Currently there are number of student satellites in orbit. Tokyo University XI-IV, XI-V,
CUTE-1(Ref 15), California Polytechnic State University (CalPoly) CP-3, CP-4 (Ref 16) are
some examples. Since most of the student satellites communicate via the UHF/ VHF
amateur radio bands, the minimum requirement of a student ground station is the ability
to communicate via UHF/VHF amateur radio bands. But, some universities are
developing satellites which can communicate via S band (Ref 15), so in the future student
ground stations may need the equipments to communicate via S band as well.
9
Comparison of Student Ground Station Technology
Hardware Hardware University of Tokyo ,
Japan (Ref 15) California Polytechnic State University , USA (Ref 16)
JMUW, Germany (Ref 10)
Tower • Creative Design CR-30
• Rohn JRM23810
• JRM23810
• Hummel Teletower Jumbo III
Antenna 1 (2m -VHF) • x213 : VHF (Creative Design)
NDA • M2 2MCP22
Antenna 2 (70 cm -UHF)
• x727 : UHF (Creative Design)
• M-squared 436CP42
• M2 436CP42U/G
Antenna Rotor • Elevation Rotator
ERC5A (Creative Design)
• Azimuth Rotator RC5A-3 (Creative Design)
• Yaesu G-5500 • Yaesu G-5500
Rotor controller NDA • Yaesu G-5500 controller
Yaeau G-5500 controller
Rotor computer interface
• Yurin (Original control system use PIC)
• GS-232B • WinRotor
Rotor computer interface driver
• RS-232 NDA • WinRotor XP
Transceiver • IC-910D (ICOM) • Yaesu 847 • ICOM IC-910H
• ICOM IC-910H
Preamplifier 1 ( for VHF)
• AG-25 NDA • LNA-145, SLN Series
Preamplifier 2 ( for UHF)
• AG-35 • SP-7000 • LNA-145, SLN Series
Radio computer interface
• CT 17 • CT-17 NDA
Radio computer interface driver
• RS-232 CI-V interface
NDA NDA
10
Power controller switch • Original hardware High power Solid State Relay (OMRON)and relay interface system (RBIO series/Kyoritsu RBIO-4S
NDA NDA
Power controller switch interface driver
• USB NDA NDA
1200 MHZ – 144 MHz down converter
NDA - NDA
Power supply 1 • GSS1200 Diamond Antenna
NDA • Microset 13.5 V
Power supply 2 • GSV3000 Diamond Antenna
NDA • Microset 13.5 V
SWR & power meter 1 • SX-400 (Diamond)
NDA NDA
DSP • Downlink: TNC-555 (Tasco)
• Uplink: TNC-505 (Tasco)
NDA NDA
Noise filter NDA NDA NDA Cables • 10D-FB coax
(Fujikura co. ltd.) • LMR-400 coax • LMR-600 coax
NDA
PC 1 • DELL NDA • Fujitsu Siemens
PC 2 NDA NDA • Fujitsu
Siemens
Wide screen NDA NDA NDA Table 2: Hardware comparison with other Universities
11
Software Software
University of Tokyo , Japan (Ref 15)
California Polytechnic State University , USA (Ref 16)
JMUW, Germany (Ref 10)
Operating system Windows XP Linux - Pre-Pass software • Virtual
Ground Station
• MacDopplerPRO X
• SatPC32 • Predict
• Mercury GS system
• Predict
Real time software • Virtual Ground Station
• GMS 6 • GMS Client • CS
• MacDopplerPRO X
• SatPC32 • Predict • InstantTrack
• Mercury GS system
• Predict
Past-pass software CS NDA
NDA
Software TNC NDA MixW NDA Table 3: Software comparison with other Universities Remarks:
1. CS - Custom software 2. NDA - No Data Available
12
Hardware selection Hardware selection was carried out considering the current and future requirements
(communicate via S band) of the IRV ground station, weather conditions in Kiruna,
already available equipments and the available budget. Advice and recommendations
from collaborative universities/ industries were taken into account during the decision
making.
Hardware 1st selection 2nd selection Remarks
Tower CUE DEE - aa Antenna 1 (2m -VHF) CUE DEE 15 X 144 - aa Antenna 2 (70 cm -UHF) CUE DEE 17 X 432 - aa Antenna Rotor YAESU G-5400 B - aa Rotor controller YAESU G-5400 B - aa Rotor computer interface GS 232B - Rotor computer interface driver
RS-232 Winrotor
Radio ICOM IC-910H YAESU FT 736R sa Preamplifier 1 ( for VHF) ICOM AG-25 ARR P144VDG sa Preamplifier 2 ( for UHF) ICOM AG-35 ARR P435VDG sa Radio computer interface CT-17 - Radio computer interface driver
RS-232 CI-V interface -
Power controller switch RBIO-4S - Power controller switch interface driver
RS-232 -
1200 MHZ – 144 MHz down converter
UEK-200SAT - aa
Power supply 1 PS 52 SAGA 300 aa Power supply 2 PS 52 SAGA 300 aa SWR & Power meter DAIWA CN-460M - aa Noise Filter DSP-59 + - aa Cables aircom puls 50 ohm
cables Nokia communication cables
aa/sa
PC 1 Dell, Intel GHz, 1GB Ram, 80 GB HDD
-
PC 2 Dell, Intel GHz, 1GB Ram, 80 GB HDD
-
Wide screen HITACHI 42 Inch - Table 4: Hardware Selection Remakes:
1. aa- Already available in the ground station 2. sa- Some parts/amount are already available
13
Software selection Software selection was carried out considering the current and future requirements
(ground station networking) of the IRV ground station, available hardware and the
available budget. Advice and recommendations from collaborative universities/ industries
were taken into account during the decision making.
Software
1st selection 2nd selection Remarks
Operating system Windows XP Linux - Pre-Pass software Nova for Windows
Virtual Ground StationWinorbit
-
Real time software Nova for Windows Virtual Ground Station GMS GMS Client AGWTERMINAL CWget
Winorbit Winorbit Hamscope
-
Past-pass software AGWTERMINAL CWget
Hamscope
-
Software TNC Packet Engine Pro - - Table 5: Software selection
14
Cost of finance
Item Cost (SEK)
Tower 15000* Antenna 1 (2m -VHF) 1272 Antenna 2 (70 cm -UHF) 1080 Antenna Rotor 5000* Rotor controller - Rotor computer interface 5200 Rotor computer interface driver - Radio 18000 Preamplifier 1 ( for VHF) 1500 Preamplifier 2 ( for UHF) 1540 Radio computer interface 840 Radio computer interface driver - Power controller switch 2000 Power controller switch interface driver - 1200 MHZ – 144 MHz down converter - Power supply 1 2000* Power supply 2 2000* SWR & Power meter 1 1750 Noise filter - Cables 10000* PC 1 10000 PC 2 10000 Wide screen 18000 GMS - GMS Client - Packet Engine pro 500 Nova for windows 500 Hamscope - CWget - AGWTERMINAL - TOTAL 106182
Table 6: Cost of finance as at 2006 Remarks:
1. Most of the prices are taken from the invoices and some are from the internet 2. *: Approximate value
15
Antenna theory
Antennas are the most important part of a ground station. They are the essential link
between free space and the transmitter or receiver and play a vital part in determining the
characteristics of the complete system. Design of antennas and its working environment
will decide the effectiveness of any given ground station (Ref 16). In this section attention
is given only to the UHF and VHF antennas.
Polarization
Figure 05: E-field variation of Linear and Circular polarization.
The polarization of the signal is identified from the direction of the e-field vector. Mainly
there are two kind of polarization.
• Linear polarization
• Circular polarization
If the e-field vector exists in vertical plane then the polarization is liner and vertical. If
the e-field vector exists in horizontal plane then the polarization is liner and horizontal.
Simple way to identify which polarization an antenna communicate when it transmit (or
is most sensitive for which polarization during receiving) is to note the direction of the
radiator elements (figure 05). For vertical polarization the radiator elements are vertical
and for horizontal polarization the radiator elements are horizontal. (Ref 1, Ref 3, Ref 20)
Radiator elements
Ref 20
16
If the signal is composed of two plane waves of equal amplitude but differing in phase by
90°, then the signal is said to be circularly polarized. The tip of the electric field vector
appears to be moving in a circle. If the electric vector of the electromagnetic wave
appears to be rotating clockwise (as it coming toward), the wave is said to be right-
circularly polarized. If it rotates counter clockwise, then it is said to be left-circularly
polarized. (Ref 3, Ref 2)
Standing Wave Ratio (SWR) SWR is a measurement of how efficiently the antenna system will radiate the power
available from the radio. In simple terms, the radio would like to radiate all of its power,
but can only do so if the other components cooperate. Bad coaxial cables and mounts, or
inefficient antennas and ground plane can cause system bottlenecks.
There are several methods to measure SWR.(Ref 1) Measuring the maximum and minimum
voltage along the line and using equation 1 can calculate the “Voltage Standing Wave
Ratio” (VSWR).
Or it is possible to calculate by comparing the antenna feedpoint resistive impedance (ZL)
to the transmission line characteristic impedance (Z0). Equation 2 or 3 can be use for
impedance comparing.
It is possible to measure the forward power (PF) and reflected power (PR) to calculate the
SWR (by using equation 4).
VSWR = VMAX VMIN (1)
(ZL > Z0 ) VSWR = ZL
Z0 (3)
(Z0 > ZL ) VSWR = Z0
ZL (2)
+
-SWR =
√PF √PR
√PR √PF (4)
17
Antenna bandwidth Bandwidth of an antenna refers generally to the range of frequencies over which the
antenna can be used to obtain a specified level of performance. The bandwidth is often
referenced to some SWR value. But SWR bandwidth is not always related to gain
bandwidth. (Ref 1)
Impedance The impedance at a given point of the antenna is determined by the ratio of the voltage to
the current at that point. Antenna impedance may be either resistive or complex
depending on whether the antenna is at resonant at the operating frequency. (Ref 1)
Directivity of the antenna and antenna beamwidth All antennas are exhibit directive effects, means, some directions will have more
radiation compare to other directions. This property is called as the directivity of the
antenna. A directional antenna radiates and receives through a main lobe and several side
lobes (as shown in figure 06). The side lobes are usually undesirable, as they attract
spurious noise, and efforts are made through the antenna design to suppress them. As
shown in the figure 06 the antenna beam width is the 3 dB angle respect to its bore site
maximum power. (Ref 3)
Figure 06: Definition of antenna beamwidth
Ref 03
18
Radiation Pattern A graphical representation of the intensity of the radiation of the antenna plotted against
the angle (from the perpendicular axis). The graph is usually circular, the intensity
indicated by the distance from the centre. (Ref 8, Ref 9)
Gain of the antenna The gain of an antenna is a combination of directivity and efficiency when compared
with a reference antenna. Normally the reference antenna will be an isotropic one.
Omnidirectional antennas Omnidirectional antennas are the simplest one that can use in a ground station. It will
simplify the building of the ground station tremendously, as no rotors or rotor interface
are needed. Most of the amateur satellites can be heard by using omnidirectional
antennas. The “Discone” antenna (figure 06) is often used where a single omnidirectional
antenna covering several VHF/UHF bands is required. The Discone antenna consist of a
disc mounted above a cone, and ideally should be constructed from sheet material. There
will be a small loss of performance if the components are made of rods or tubes. At least
8 or preferably 16 rods are required for the disk and cone for reasonable results. This kind
of antenna is capable of covering the 70,144 and 432 MHz bands or 144, 432, 1290 MHz. (Ref 8)
Figure 06: Omnidirectional antenna (Discone type)
Disk
Cone
Rods
Ref 08
19
Antenna can be operate over roughly a 10:1 frequency range. Since the antenna is radiate
harmonics present in the transmitter output, it is needed to use suitable filters for
attenuation. These antennas have VSWR of less than 2:1 over the octave range. Figure 07
and 08 shows the radiation patterns of a Discone antenna for 145 MHz and 435 MHz
bands. (Ref 1, Ref 3, Ref 7, Ref 9, Ref 10)
Figure 07: Discone antenna elevation radiation patterns for 145 MHz
Figure 08: Discone antenna elevation radiation patterns for 145 MHz
Ref 08
Ref 08
20
Yagi antennas Since most of the student satellites produce low strength (due to the low power) circular
polarized waves (due to the spinning of the satellites) it is preferred to use Yagi antennas.
The number of elements on a Yagi and array length is directly proportional to the gain of
the antenna. More elements mean more gain but smaller beamwidth. The array length is
of greater importance than the number of elements, within the limit of a maximum
element spacing of just over 0.4λ.
The antenna should mount considering the polarization of the wave. The difference
between horizontal and vertical polarization is (theoretically) infinite. If the orbiting
antenna is horizontally polarized and ground station antenna is vertically polarized,
nothing will receive. If the orbiting antenna circularly polarized and ground satiation
antenna linearly polarized then maximum loss will be 3 dB. But if the orbiting and
ground satiation antennas are circularly polarized then maximum loss can be 10 dB due
to the polarization mismatch. (Ref 1, Ref 3, Ref 7, Ref 9, Ref 10)
Figure 09: Skeleton slot fed Yagi antenna
The simplest way of being able to select polarisation is to mount a horizontal Yagi and a
vertical Yagi on the same boom giving the cross Yagi antenna configuration (shown in
Ref 08
21
figure 10). Separate feeds to each section of the Yagi brought down to the operation
position enable the user to switch to either horizontal or vertical polarization.
Figure 11 shows the voltage polar diagram and gain against VSWR of Yagi antennas for
six and eight elements. (Ref 8)
Figure 10: Cross Yagi antenna
Figure 11: Voltage polar diagram and gain against VSWR for Yagi antennas
Ref 08
Ref 08
22
Digital communication
In the context of TT&C digital communication is much more interest than the analog
communication. Specially most of the student satellites are communicating via JD
satellite mode.
In digital communication the Bit Error Ratio (BER) is the primary quality criterion. BER
must be keet at minimum to obtain a better link quality. Normally suitable modulation
methods and forward error correction (FEC) methods are using to minimize the BER.
FEC will give a considerable coding gain and therefore FEC acts like a virtual
amplifier(Ref 3).
Where
C: Carrier power
N: Noise power
(C/N): Carrier to noise ratio
(5)
(6)
(7)
(8)
N0 = N/B (9)
23
Eb: Amount of energy manage to pack in to the each bit in a digital data stream (C/r) r: Bit rate ( bits per second)
N0: Normalize noise power with respect to the bandwidth (Noise spectral density)
B: Frequency Bandwidth
(C/N)req : Required carrier to noise ratio
(C/N)ach : Achieved carrier to noise ratio
Link Budget A link budget is the accounting of all of the gains and losses from the transmitter to the
receiver in a satellite communication system. When calculating the link budget, it is in
practice to calculate both preliminary and detail link budgets. Normally preliminary link
budget is calculated to find out the rough value of the link margin. When calculating the
preliminary link budget the losses are not taking in to account. For the telemetry the
system noise temperature (Tsys) is decided by considering only the galactic and
tropospheric noise temperatures (commonly is taken as 80 K) and it is used to determine
the carrier-to-noise ratio. In the detail link budget, the noise and attenuation due to
various sources are taken in to account (Ref 3).
To achieve an acceptable quality signal, following requirement must be fulfilled.
Link margin Is the difference between ‘Achieve (C/N) and required (C/N) in dB for a particular BER
The Minimum required link margin for a good reception is approximately 3 dB in a detail
link budget and 10 dB for the preliminary link budget (in case of unexpected link losses)
(Ref 3)
(10)
Link margin = (C/N)ach (dB) – (C/N)req (dB) (11)
24
Calculation of (C/N)ach
In a satellite communication system the received power can be expressed as following
relationship
Where
Pt: is transmitted power in Watts
Pr: is received power in Watts
Gt: is transmitter antenna gain
Gr: is receiver antenna gain
λ: is the wave length
d: is the distance between satellite and the ground station
To distinguish the received signal from the noise it is important to know the relationship
between carrier power (C), induce noise power (N); and from that it is possible to
calculate the carrier-to-noise ratio (C/N) (Equation 12).
Where
k: Boltzman constant ( 1.38 x 10-23 J/K)
T: Noise temperature
c: Speed of light ( 3.108 m/s)
f: Frequency
2
4⎟⎠⎞
⎜⎝⎛=
dGGPP rttr π
λ (12) [Watts]
(13)
(14)
(15)
25
EIRP: Equivalent Isotropic Radiated Power (transmit power (Pt) multiply by the transmit
antenna gain (Gt))
Equation needed to calculate the (C/N)req for detail link budget Where
And L1, L2 are the losses causes due to the weather, antenna pointing errors, polarization
mismatch etc.
Figure 12: Worst case distance between the satellite and the ground station
Here “d” is the worst case distance when the elevation angle δ.
For the non-zero elevation angle, the distance is “d’”
(16)
(17)
Ref 03
26
Receiver figure of merit Gr/T: the amount of thermal noise picked up by the antenna side lobes
Losses
Free space loss The quantity of {λ/ (4πd)} 2 is know as the free space loss (from equation 12); the amount
of the radio signal dissipated in free space.
Losses due to the O2 and Water vapour Figure 13: Clear sky radio signal attenuation due to oxygen and water vapour in the
atmosphere
Note : Thickness of the O2 layer ~ 5 Km, thickness of the H2O layer ~2 km. O2
attenuation loss Latm can be obtain by using the figure 13 and calculating the path length
of the signal through the O2 layer (by using equation 18, here h=5 km).
(18)
Ref 03
27
System noise temperature
During the telecommand the satellite antenna is looking down at earth. Therefore it sees
the earth surface and some surrounding space. During the telemetry the ground station
antenna looks up and sees sun, moon, outer space, the ionosphere, the troposphere,
surrounding topography etc.
Where
Tsys: System noise temperature
Tant: Noise temperature collected by the satellite antenna due to the earth radiation during
the telecommand and noise temperature collected by the ground station antenna due to
various sources (sun, moon etc) during telemetry.
Lline: Resistive noise contribution from the signal line (between antenna and receiver)
Trx: Noise temperature depending on chosen frequency and receiver technology
Figure 14: Galactic and tropospheric noise temperatures at various ground antenna
elevations (δ)
(19)
Ref 03
28
Figure 14 shows galactic and tropospheric noise temperatures at various ground antenna
elevations δ. Here it assumes that, the ground station antenna never sees sun or moon
during the telemetry.
Noise temperatures due to hot bodies If the ground station antenna sees the sun or moon during the telemetry then the noise
temperatures should take in to account (equation 20). The sun is treated as a hot body
with a temperature of 5805 K and moon is treated as a hot body of temperature of 200K.
Where α is the fraction that heat source occupies within the antenna coverage (3 dB beam
width)
Ground station receiver noise Ground station receivers produce noise depending on their technology. Figure 15 shows
the relationship between ground station technology, noise temperature and frequency.
Figure 15: Ground station receiver noise
(20)
Ref 03
29
Noise and attenuation due to Rain Rain fall introduces attenuation by absorption and scattering of signal energy, and the
absorptive attenuation introduces noise.
Figure 16 shows the attenuation loss due to rain (Lrain) and the corresponding noise
temperature (Train) where rain rate measured in mm/h and it is assumed that the cloud
temperature is 290K and the antenna boresight elevation angle is 30 deg above the local
horizon.
Figure 16: Attenuation Lrain and noise temperature due to rainfall at 30 deg elevation above the local horizon
The thickness of the rainy part of the atmosphere is 3 km at elevation angle 90 deg. The
equation 22 gives the elevation dependent thickness.
(21)
(22)
Ref 03
30
Equation 23 gives the induce loss due to rain according to the elevation angle.
Line noise and attenuation A typical coaxial cable causes a signal loss of 0.5 dB per meter. Therefore a 1 meter
cable represents a loss [Lline] =0.5 dB, corresponding to Lline=1.1. This loss also gives rise
to an equivalent noise temperature. Equation 24 shows the relationship between line
losses to the noise temperature.
Polarization loss The maximum polarization isolation between an antenna with linear polarization and one
with circular polarization is 3 dB. Equation 25 gives the relationship between the
polarization loss and the mismatch angle. The equation 26 shows the relationship
between the signal frequency and the average day time Faraday rotation angle (Ref 3).
Where Ф is the mismatch angel and/or average day time Faraday rotation angle
Antenna pointing loss
(23)
(24)
(25)
(26)
(27)
31
Where
θ3dB : is the antenna beamwidth in degrees
ε : is the pointing error in degrees
Implementation losses 0.5 to 3 dB due to the frequency dependent losses in the hardware
Summary of sources of Noise and Losses
Here Ts is the sum of all noise temperature contributions. Lline1, Lline2 and Lpoint1 and
Lpoint2 represent the line and pointing losses in both transmitter and receiver sides.
Global Educational Network for Satellite Operation (GENSO)
GENSO is a project that initiated under the auspices of the International Space Education
Board (ISEB). This board consists of the Education Departments of the Canadian Space
Agency (CSA), the European Space Agency (ESA), the Japan Aerospace Exploration
Agency (JAXA) and the National Aeronautics and Space Administration (NASA).
Currently the project is managed by the Education Projects Division of ESA. It is expect
to run a first pilot phase of the project in the summer of 2007. The main objectives of this
GENSO project are (Ref 18)
• To provide unparalleled near-global levels of access to educational spacecraft in
orbit,
• To allow remote access for operators to real-time mission data, even in cases
when their local ground station is experiencing technical difficulties,
• To provide remote control of all participating ground stations,
• To optimise uplink fidelity by calculation of real-time link budgets and uplink
station selection,
• To perform downlink error-correction by comparing multiple data streams,
(28)
32
• To define and implement a global standard for educational ground segment
software,
• To define and instantiate an optional well-defined standard solution for
educational ground-segment hardware (in order to expedite participation in
GENSO),
• To support a common interface for applying for frequency allocation and
coordination.
33
CHAPTER 3
IRV GROUND STATION STATUS
Ground station specification Ground station name SK2UL University Luleå University of Technology City Kiruna Country Sweden Altitude 382 m Latitude 67.7 N Longitude 20.3 E Tower CUE DEE Operating frequencies 144-146 MHz, 432-438 MHz Antenna 1 (2m –VHF) (Gain: 13 dB) (Beamwidth: 44 deg)
CUE DEE 15 X 144
Antenna 2 (70 cm –UHF) (Gain: 14 dB ) (Beamwidth: 40 deg )
CUE DEE 17 X 432
Antenna Rotor Yaesu G-5400B Rotor controller Yaesu G-5400B Rotor computer interface Yaesu GS 232B Rotor computer interface driver RS 232 Radio 1 ICOM 910H Radio 2 YAESU FT-736 R Preamplifier 1 ( for VHF) (Gain: 15 dB )
ICOM AG-25
Preamplifier 2 ( for VHF) (Gain: 24 dB)
ARR P144VDG
Preamplifier 3 ( for UHF) (Gain: 15 dB)
ICOM AG-35
Preamplifier 4 ( for UHF) (Gain: 24 dB)
ARR P435VDG
Radio computer interface CT-17 Radio computer interface driver RS-232 CI-V interface Power controller switch RBIO-4S Power controller switch interface driver RS 232 1200 MHZ – 144 MHz down converter UEK-200SAT Power supply 1 Kenwood PS-52 Power supply 2 SAGA 300 SWR & power meter 1 DAIWA CN-101L SWR & power meter 2 DAIWA CN-460M Noise filter DSP-59 +
34
Cables ECOFLEX-10 LAGFORLUST Nokia telecommunication cables aircom puls 50 ohm cables
PC 1 Dell, Intel 3 GHz, 1GB Ram, 80 GB HDD
PC 2 Dell , Intel 3 GHz, 1GB Ram, 80 GB HDD
Wide screen HITACHI 42 Inch Operating system Windows XP Pre-pass software Nova for Windows
Winorbit Virtual Ground Station
Real time software Nova for Windows Winorbit Virtual Ground Station GMS GMS Client AGWTERMINAL Hamscope CWget
Past-pass software AGWTERMINAL Hamscope CWget
TNC software Packet Engine pro Table 7: IRV ground station specifications
35
Description of used hardware and software
Tower and antennas
Figure 17: UHF/VHF Yagi antennas Antennas are the transducers that convert the wave signal into an electrical signal and
vice versa. The present configuration uses two antennas mounted on a 4 m high
aluminium tower. These are:
CUE DEE 15X 144 Antenna used for a frequency range of 144 to 146 MHz
CUE DEE 17 X 432 Antenna used for a frequency range of 432 to 438 MHz
Transceivers ICOM IC-910H (All Modes) transceiver is used. The IC-910H is a 144 MHz /440
MHz/1.2 GHz all mode satellite radio. It features a powerful 100 W of output on 2 meter
band, and 75 W on 70 cm band. The IC-910H has two data sockets for simultaneous two
band packet communications. High speed PLL lockup time makes 9600 bps high speed
packet communications possible.
36
Figure 18: Picture of the ICOM IC-910H transceiver
Rotor and rotor controller The Yaesu G-5400B provide 360 deg azimuth and 180 deg elevation control of medium
and large-size unidirectional satellite antenna arrays under remote control from the
station operating position. The two factory-lubricated rotator units are housed in weather-
proof melamine resin coated die-cast aluminium. Rotor contains a thermal sensor to
prevent damage from overheating during periods of high usage.
The controller unit is a desktop unit with dual meters and direction controls for azimuth
and elevation.
Figure 19: Rotor and Rotor controller
37
Preamplifiers Both “ICOM AG” and ARR GaAsFET type of preamplifiers are used in the ground
station. The “ICOM AG” type preamplifiers are water proof all weather type with
improved S/N ratio and receiver sensitivity, and make DX-communication possible. The
coaxial cable is working also as the DC cable.
Figure 20: AG-25/AG-35 preamplifier
ARR GaAsFET preamplifiers have been specifically designed for amateur use. Each unit
is housed in a completely shielded, rugged, custom aluminium enclosure. To maintain a
high degree of RF shielding a feed-through type capacitor is provided for the DC ground
connection. These preamplifiers are suitable for fixed, mobile, or portable operations.
Power supply requirements are 10-16 Volts DC supply with 15 mA current.
Figure 21: ARR GaAsFET Preamplifier
38
Radio Computer Interface ICOM CT-17 is using to connect the transceiver to the PC via the PC's RS-232C port.
This allows to control the Radio from the PC and/or transfer the data from the receiver to
the PC. Control is provided via ICOM's CI-V communication interface.
Figure 22: ICOM CT-17 Radio Computer Interface
Rotor Computer Interface The GS-232B provides digital control of Yaesu antenna rotators from the serial port of an
external personal computer. The async serial line can be configured for serial data rates
from 1200 to 9600 baud. Firmware of the GS-232B supports either direct key board
control, or commands from programs written specially to support it.
Figure 23: GS-232B Rotor Computer Interface
39
Power controller switch
Figure 24: Power controller switch RBIO-4S power switch is used to switch on/off all the hardware via computer command.
Computer serial interface is used to connect to the PC and “OMRON” 10 A, 264 VAC
solid state relays are using as the switches.
The UEK-200SAT receive converter The UEK-200SAT is an S-band receive converter. UEK-200SAT provides
approximately 50 MHz of RF bandwidth starting at 2400 MHz as well as 50 MHz
bandwidth starting at 144 MHz. The UEK-200SAT is constructed on Teflon printed
circuit board material to achieve low losses and excellent noise figure at 2400 MHz.
Figure 25: UEK-200SAT receive converter
40
Power supply “Kenwood PS-52” and “Saga 300” power supplies are used to power the hardware.
Kenwood PS-52 (13V, 20 Amp) is used to power the transceiver, the CT-17
communication interface and the GS-232B Rotor computer interface. Saga 300 (13.8 V, 3
Amp) is used to power the ARR GaAsFET preamplifiers (when they used instead of
ICOM AG preamplifiers).
Figure 26: Kenwood PS-52 Power supply
Figure 27: SAGA 300 Power supply
41
SWR & Power meter
Figure 28: SWR & Power meter (1.8 – 150 MHz)
SWR and power indicators are installed in single meter unit. One scale will indicate
forward power; another scale reflected power and SWR is indicated at the crossing point
of the 2 needles. This unique feature makes it possible to read forward power, reflected
power, and SWR all at the same time.
Figure 29: SWR & Power meter (140 -450 MHz)
42
Audio Noise Reduction filter The DSP-59 + is an audio noise filter for amateur radio voice, data and CW operation.
This filters and reduces noise and interference to improve the radio reception. The DSP-
59+ uses digital signal processing technology to implement algorithms that perform three
basic filter functions
1. Random noise reduction
2. Adaptive multi-tone notch filtering ( Tone noise reduction)
3. Band-pass / High-pass / Low-pass filtering
Push-button switches permit simultaneous selection of these three functions
Figure 30: Audio Noise Reduction filter
Cables “ECOFLEX-10 LAGFORLUST” Co-axial cables, “Nokia” telecommunication cables
and “aircom puls” 50 ohm coaxial cables are used (details in appendix 1). The length of
the cable is about 25 m from the antenna to the transceiver.
43
Connection of hardware
Figure 31: Hardware connection
Rotor
Computer
IC 910HCT-17
PS-52
GS-232B
G-5400B
AG-35
UHF Antenna VHF Antenna
AG-25
44
Software setup
Pre-pass software Nova for windows software, win orbit software, and “Virtual Ground Station” software
(developed by the Tokyo University) are using as pre-pass software to determine the
Satellite AOS, LOS, azimuth and elevation angels.
Real time software Nova for windows software, win orbit software, and “Virtual Ground Station” software
are used to determine the Satellite crossing times, elevations and azimuth angles
according to the satellite position.
GMS (Ground Station Management Service) (Ref 12) software (developed by the Tokyo
University) is used to control the radio and the antennas autonomously according to the
satellite position.
The “Packet Engine Pro” a software based TNC (Terminal Node Controller) and a
terminal program (AGWTERMINAL) are used to decode and encode the AX.25 packets
in real time. The “Hamscope” software and “CWget” software are used to decode the
CW beacons in real time.
Past-pass software The “Packet Engine Pro” a software based TNC (Terminal Node Controller) and a
terminal program (AGWTERMINAL) are used to decode the AX.25 packets from a
recorded satellite downlink. The “Hamscope” software and “CWget” software are used to
decode the CW beacon from a recorded downlink CW signal.
45
Operational Procedure
This section gives a brief detail of how the entire system works and can be controlled.
1. Identify the target satellite.
After knowing the satellite, its beacon, uplink and downlink frequencies can be
obtained from the satellite webpage or satellite detail sheet.
2. To obtain the updated TLE (Two Line Elements)
The updated TLE of the satellite can be obtained from internet (Ref 17)
3. To determine the AOS, LOS, azimuth and elevation angles.
The updated TLE is used in the Nova for windows software, “Virtual Ground
Station” software or “Winorbit” software to determine the AOS, LOS, azimuth and
elevation angles.
4. Controlling the antenna rotor and the transceiver
For this the “GMS” software is used. The satellite details and the ground station
details are fed in to the GMS client program. First the frequency of the transceiver is
fixed to the beacon frequency to detect the satellite when it’s in range. Then the
transceiver is fixed to the telemetry and telecommand frequencies to communicate via
AX.25 packets.
5. To start the communication via AX.25 packets, the software TNC program and
the terminal (AGWTERMINAL) program are used.
6. To start the communication via CW, the “Hamsocpe” program or “CWget”
program is used.
46
CHAPTER 4
IRV GROUND STATION PERFORMANCE ANALYSIS
During the IRV ground station performance analyses following tasks were carried out.
1. Calculating the preliminary downlink budget for 70 cm antenna system
2. Calculating the preliminary uplink budget for the 70 cm antenna system
3. Calculating the preliminary downlink budget for 2 m antenna system
4. Calculating the preliminary uplink budget for the 2 m antenna system
5. Experiments to find out the data decoding ratio of the ground station
6. Experiments to find out the overall data downloading ratio compare to other
ground stations
7. Experiments to find out the required minimum elevation angle (δ)
8. SWR measurements in 70 m antenna system
9. SWR measurements in 2 m antenna system
10. Monitoring the external electromagnetic interferences in amateur radio bands
Preliminary link budget The preliminary link budget is calculated to get a rough idea about the required minimum
EIRP for a successful downlink and/or uplink. Since the ground station EIRP is directly
known from its antenna gain and transmitter power, it is possible to calculate the required
minimum antenna gain for the spacecraft. Or for a known spacecraft it is possible to
calculate the required minimum EIRP from the ground station and check whether the
ground station EIRP is sufficient for successful uplink. For the calculation the earth
radius has taken as 6371 km and the Noise temperature (T) assumed as 80 K. Here it is
assumed that the required link margin is 10 dB and required minimum ground station
elevation angle (δ) is 10 degrees for a successful communication. The bit error rate for
AFSK modulation is assumed as 10-5.
47
No Parameter Liner value
dB Remarks
1 Max satellite altitude h ( km) 850.00 2 Radial distance (km) 7221.00
3 Bit rate (bps) 1200.00 4 Bit error rate 1.00E-05 Assumed 5 Modulation method AFSK 6 Min elevation angle (deg) 10.00 7 Link frequency (MHz) 450.00 8 Ground station antenna gain (dB) 14.00 9 Ground station antenna beamwidth
(deg) 40.00 70 cm
antenna 9 Noise temperature T ( K) 80.00
10 Boltzmann constant μ (J/K) 1.38E-23 (C/N) req
11 Bandwidth B ( Hz) 2.70E+03 Ref 19 12 Eb/N 4.01E-03 Eq 6 13 Eb/N0 1.08E+01 Eq 8 14 C/N req 4.81E+00 6.82 Eq 7
(C/N) ach
15 Max distance d (km) 2.47E+03 Eq 18 16 Wave length (m) 6.67E-01 Eq 15 17 Max free space loss 4.62E-16 -153.35 Eq 12
18 Required link margin (dB) 10.00 Assume 19 (C/N) ach ( Required) 16.82 Eq 11 20 GS Noise Power N 2.98E-18 -175.26 Eq 14
21 GS received power (Required) -158.44 19+20
22 Minimum EIRP ( Required from SC) -19.09 Eq 12
Table 8: Preliminary downlink budget for 70 cm antenna
48
No Parameter Liner value
dB Remarks
1 Max satellite altitude h ( km) 8.50E+02 2 Radial distance (km) 7.22E+03
3 Bit rate (bps) 1.20E+03 4 Bit error rate 1.00E-05 Assumed 5 Modulation method AFSK 6 Min elevation angle (deg) 1.00E+01 7 Link frequency (MHz) 1.44E+02 8 Ground station antenna gain (dB) 13.00 9 Ground station antenna beamwidth
(deg) 4.00E+01 70 cm
antenna 9 Noise temperature T ( K) 8.00E+01
10 Boltzmann constant μ (J/K) 1.38E-23 (C/N) req
11 Bandwidth B ( Hz) 2.70E+03 Ref 19 12 Eb/N 4.01E-03 Eq 6 13 Eb/N0 1.08E+01 Eq 8 14 C/N req 4.81E+00 6.82 Eq 7
(C/N) ach
15 Max distance d (km) 2.47E+03 Eq 18 16 Wave length (m) 2.08E+00 Eq 15 17 Max free space loss 4.51E-15 -143.45 Eq 12
18 Required link margin (dB) 10.00 Assumed 19 (C/N) ach ( Required) 16.82 Eq 11 20 GS Noise Power N 2.98E-18 -175.26 Eq 14
21 GS received power (Required) -158.44 19+20
22 Minimum EIRP ( Required from SC) -27.98 Eq 12
Table 9: Preliminary downlink budget for 2 m antenna
49
No Parameter Liner
value dB Remarks
1 Max satellite altitude h ( km) 850.00 2 Radial distance (km) 7221.00
3 Bit rate (bps) 1200.00 4 Bit error rate 1.00E-05 Assumed 5 Modulation method AFSK 6 Min elevation angle (deg) 10.00 7 Link frequency (MHz) 450.00 8 Ground station antenna gain (dB) 14.00
Ground Station Transmitter Power (W)
7518.75
9 Ground station antenna beamwidth (deg)
44.00 70 cm antenna
9 Noise temperature at receiver T ( K) 80.00 10 Boltzmann constant μ (J/K) 1.38E-23
(C/N) req
11 Bandwidth B ( Hz) 2700.00 Ref 19 12 Eb/N 4.01E-03 Eq 6 13 Eb/N0 1.08E+01 Eq 8 14 (C/N) req 4.81E+00 6.82 Eq 7
(C/N) ach
15 Max distance d (km) 2.47E+03 Eq 18 16 Wave length (m) 6.67E-01 Eq 15 17 Max free space loss 4.62E-16 -153.35 Eq 12
18 Required link margin (dB) 10.00 Assume 19 (C/N) ach 16.82 Eq 11 20 SC Noise Power N 2.98E-18 -175.26 Eq 14
21 GS EIRP 262.51 19+20
22 Minimum required SC antenna gain -267.59 Eq 12
Table 10: Preliminary uplink budget for 70 cm antenna
50
No Parameter Liner value
dB Remarks
1 Max satellite altitude h ( km) 850.00 2 Radial distance (km) 7221.00
3 Bit rate (bps) 1200.00 4 Bit error rate 1.00E-05 Assumed 5 Modulation method AFSK 6 Min elevation angle (deg) 10.00 7 Link frequency (MHz) 144.00 8 Ground station antenna gain (dB) 13.00
Ground Station Transmitter Power (W)
10020.00
9 Ground station antenna beamwidth (deg)
44.00 2 m antenna
9 Noise temperature at receiver T ( K) 80.00 10 Boltzmann constant μ (J/K) 1.38E-23
(C/N) req
11 Bandwidth B ( Hz) 2700.00 Ref 19 12 Eb/N 4.01E-03 Eq 6 13 Eb/N0 1.08E+01 Eq 8 14 (C/N) req 4.81E+00 6.82 Eq 7
(C/N) ach
15 Max distance d (km) 2.47E+03 Eq 18 16 Wave length (m) 2.08E+00 Eq 15 17 Max free space loss 4.51E-15 -143.45 Eq 12
18 Required link margin (dB) 10.00 Assumed 19 (C/N) ach 16.82 Eq 11 20 SC Noise Power N 2.98E-18 -175.26 Eq 14
21 GS EIRP 260.00 19+20
22 Minimum required SC antenna gain -274.98 Eq 12
Table 11: Preliminary uplink budget for 2 m antenna
51
CUTE-1 FM operation to find out the decoding ratio of IRV ground station The experiments were conducted during the handover pass with Tokyo (UT) - Kiruna
(IRV). First, during the link time in Tokyo, UT ground station sent the command to the
CUTE-I to start the FM downlink. During the handover from Tokyo to Kiruna, both
ground stations successfully received the FM telemetry (FM packets from CUTE-I) data
at each link time. As a result of this collaborative operation continuous status data was
obtained for more than 15 minutes. The interval time (time between LOS at Tokyo (UT)
and AOS at Kiruna (IRV)) between the each link time was only 3 minutes (theoretically)
but the interval time obtained from the experiment was about 8 minutes (as shown in
figure 32). This is because of its difficulty in data decoding in low elevation angle.
Figure 32: Plot of time stamps of decoded packet at each ground station
Note: 1-Orange dots: Tokyo (UT) 2-Blue dots: Kiruna (IRV)
Packet decoding rate for CUTE-1 cube satellite The interval time for packet output for CUTE-1 was 4 seconds
76(packets) / 158 (packets) = 48.25%
1 2
52
XI-IV FM operation to find overall data download ratio Handover experiments were carried out for the passes
1. Tokyo (UT) –Kiruna (IRV)
2. Kiruna (IRV) – California Polytechnic State University (CalPoly)
During the link time the respective ground stations uplink the commands to achieve the
downlink data and more than 60 Kbytes of data (68% of the total picture data stored in
the CUTE-1) were downloaded using 3 ground stations. The status data (three times for
each pass) and all the picture data from ROM 2, 3, 4 and 5 (data from ROM 1 was not
able to download during the experiment) were downloaded. Figure 33 shows the amount
of data obtained during the experiment. During the handover passes of Tokyo (UT) –
Kiruna (IRV) all the offset data sets were completely downloaded from ROM 2 and
ROM 5 and the handover passes of Kiruna (IRV) - CalPoly the data sets of ROM 4 were
completely downloaded.
Figure 33: Comparison of downloaded data at each pass.
Local Time (@Kiruna) [hour]
53
Figure 34: The integration of obtained data at each operation time.
Figure 35: The ratio of obtained data at each ground station
Figure 33 shows the comparison of the download data by each ground station. Figure 34
shows the cumulative value of downloaded data from each ground station. And figure 35
shows the total percentage of data downloaded by each ground station.
Local Time (@ Kiruna) [hour]
54
Packet decoding rate for XI-IV cube satellite 438(packets) / 1364(packets) = 32.1%
(In case of uplink success rate to be 90%, 438 / (1364 X 0.9) = 35.7%)
Interference monitoring Frequency scanning in VHF and UHF amateur radio bands were carried out once in every
hour for few days to track or listen to any kind of electromagnetic interference or radio
traffic.
Only the thermal noise can be hear when receivers are used at high sensitivity mode. But
it was not able to hear any kind of electromagnetic interference or radio traffic in normal
conditions.
Testing of the SWR for the antenna systems SWR was measured by using SWR meters and the reading was below 2 for both VHF
and UHF antenna systems
55
CHAPTER 5
DISCUSSION AND FUTURE WORK
At present the IRV ground station is fully functional in VHF and UHF amateur radio
bands. Due to the location of the IRV ground station, it is clear that it has a significant
advantage over other student ground stations. As IRV doesn’t have its own satellite, at
present generally only the beacon of the passing satellites can be record. On a joint
experiment with Tokyo University and California Polytechnic State University (CalPoly),
the uplink and downlink capabilities were tested and verified.
From the experiments it is found that the IRV ground station has a high data downloading
capacity for polar satellites (twice as university of Tokyo). Also it is found that the IRV
ground station has a data decoding rate around 40% (48.25 % CUTE-1 and 32.1% for the
XI-IV). Electromagnetic interferences due to external sources are negligible in amateur
radio bands and this is mainly due to the remote location of the IRV ground station. Also
it is observed that downlink is possible for low elevation angles such as 5 degrees and
this is mainly due to the obstacle free surroundings. The preliminary link calculation
shows that IRV ground station can receive the telemetry of a satellite which has a
minimum EIRP of -19 dB in 70 cm or -28 dB in 2m band. Also it can upload
telecommond to a satellite which has an antenna with a minimum gain of -267 dB in 70
cm band or - 275 dB in 2 m band. The antennas uses in the ground station are older than
15 years and due to this it is logical to believe that the performance are less than rated
values. Also it is observed that there is some oxidization in the radiator elements and
change of properties in the insulation materials and this will also affect the performance
of the antennas. Although the IRV ground station has high overall data download rate
(for polar satellites) compare to Tokyo University or CalPloy (since IRV has more
passes), the data downloading rate for a single pass is less than compare to Tokyo
university ground station. This is due to the poor performance of the antenna system.
Therefore it is recommended to replace the old antennas with high gain (more than 20
dB) new ones. It is expected that the replacement of the antennas will improve not only
the data downloading ratios but also the data decoding ratios too. Although it is
56
convenient to use the software TNC, the software TNC shows poor performance compare
to hardware TNC. Therefore it is recommend to use a hardware TNC as a backup system
specially for important experiments.
Since the IRV ground station is fully operation in VHF/UHF amateur radio bands, now it
is important to develop a satellite. It is almost impossible to carry out detail and long term
experiments without having its own satellite in orbit. At present there is a dish antenna
and a “S” band down converter available in the ground station. Therefore it is possible to
expand the ground station capabilities to S band in a short period of time. The GMS
software is still under testing phase and therefore there may be still bugs in the software.
These bugs can be effect in long term operations.
Because of high data downloading capability IRV ground station can play a very
important role in Ground Station Network (GENSO).
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CHAPTER 6
CONCLUSION
From the experiments it is found that the IRV ground station has high data downloading
capacity for polar satellites (twice as university of Tokyo). Also it’s found that the IRV
ground station has a data decoding rate around 40% (48.25 % CUTE-1 and 32.1% for the
XI-IV). Electromagnetic interferences due to external sources in amateur radio bands are
negligible. Also it is observed that downlink is possible for low elevation angles such as 5
degrees. The preliminary link calculations shows that IRV ground station can receive the
telemetry of a satellite which has a minimum EIRP of -19 dB in 70 cm or -28 dB in 2m
band. Also it can uplink telecommand to a satellite which has an antenna with a minimum
gain of -267 dB in 70 cm band or – 275 dB in 2 m band.
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CHAPTER 7
REFERENCE
1. Antenna toolkit, Joe Carr, Second Edition, Newnes Publications, 2001.
2. Ground segment and Earth station handbook, Bruce R. Elbert, Artch House,
Boston London.
3. Satellite Platform Design, Peter Berlin, fourth edition, Department of Space
Science, Lulea University of Techknology, Sweden, 2005.
4. Satellite Communications, T Pratt, C. Bostian, J. Allnutt, Second edition, John
Wiley & Sons Inc, NJ.
5. Space Mission Analysis and Design, J.R. Wertz and W.J. Larson, Third Edition,
Microcosm Press California, CA.
6. Spacecraft System Engineering, P. Fortescue, J. Stark, G. Swinerd, Third Edition,
John Wiley & Sons Ltd, England, 2003.
7. Antennas and Transmission lines, J.A. Kuecken, First edition, MJF Enterprises,
USA, 1996.
8. Radio Communication Handbook, Mike Dennison, Chris Lorek, 8th Edition,
Radio Society of Grate Britain, 2005.
9. Handbook for radio communication, Mark J Wilson, 84th edition, ARRL-the
national association for amateur radio, USA.
10. Development of a GS package suited for Spacecraft operation control and
optimization for satellite flyby over the ground station, Raj Gaurav Mishra,
Master thesis, Department of Informatics VII- Robotics and Telematics, Julius
Maximilian University of Wuerzburg, Germany, 25 December 2006
11. Priya Fernando, A.B.A.T Wickramanayake, Y.Oda: Importance of IRV, Kiruna
Ground Station in the Ground Station network; poster presentation at 1st
Hellenic-European Student Space Science and Technology Symposium, Patras ,
Greece, 9-11 October 2006.
12. Proceedings, The 1st International Workshop on Ground Station Network,
University Space Engineering Consortium, July 18th -20th 2006, Tokyo, Japan
59
13. Proceedings, The Global Educational Ground Station Network Workshop, at
ESA/ESTEC, Netherlands, 28-29 September 2006.
Web sites
14. http://www.amsat.org, 2007-05-25
15. University of Tokyo cubesat project,
http://www.space.t.u-tokyo.ac.jp/cubesat/main-e.html, 2007-05-26
16. California Polytechnic State University satellite project,
http://polysat.calpoly.edu/earthstation/, 2007-05-26
17. NORAD Two-Line Element Sets, http://celestrak.com/NORAD/elements/,
2007-05-26
18. GENSO, http://www.genso.org/latest-news/welcome-to-genso.html, 25-05-2007
19. Amateur wavelet modulation, http://www.falvotech.com/content/ideas/awm/,
25-05-2007.
20. http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/polclas.html, 25-5-2007
60
APPENDIX 1: Detail specification of hardware
ICOM IC-910H Specifications
General
• Frequency coverage (USA version): o Rx,Tx: 144.000-148.000 MHz o Rx: 136.000-174.000 MHz (guaranteed range 144.000-148.000 MHz) o Rx, Tx: 430.000-450.000 MHz o Rx, TX: 1240.000-1300.000 MHz {optional}
• Mode: SSB, CW, FM, FM-N (FM-N is not available on 1200 MHz band) • Frequency stability: ±3 ppm (-10°C to +60°C) • Frequency resolution: 1 Hz SSB/CW, 1-- Hz FM • Number of memory channels:328 (39 regular, 1 call, 6 scan edge for each band
plus 10 satellite) • Operating temperature range: -10°C to +60°C; +14°F to +140°F • Power supply requirement: 13.8 V DC ±15% (negative ground) • Current drain (at 13.8 V DC)
o Transmit high: 23.0 A low: 7.0 A
o Receive max. audio: 2.5 A stand-by: 2.0 A
• Dimensions: o 9 1/2(W) X 3 11/16(H) X 9 13/32(D) inches. o 241(W) X 94(H) X 239(D) mm
• Weight (approx.): 4.5 kg; 10 lb • Antenna connector
o VHF: SO-239 (50 ohm) o UHF: Type-N (50 ohm)
Transmitter
• Output power (continuously adjustable) o 144 MHz band: 5.0-100 Watts o 440 MHz band: 5.0-75 Watts o 1200 MHz band: 1.0-10 Watts {optional}
• Modulation system o SSB: Balanced modulation o FM: Variable reactance modulation
• Spurious emission
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o 144, 440 MHz band: Less than -60 dB o 1200 MHz band: Less than -50 dB {optional}
• Carrier suppression: More than 40 dB • Unwanted sideband: More than 40 dB • Microphone connector: 8-pin connector (600 ohms)
Receiver
o VHF SSB, CW: Single conversion superheterodyne FM: Double conversion superheterodyne
o UHF SSB, CW: Double conversion superheterodyne FM: Triple conversion superheterodyne
• Sensitivity o SSB, CW: 0.11 µV (at 10 dB S/N) o FM: 0.18 µV (at 12 dB SINAD)
• Squelch sensitivity o SSB, CW: 1.00 µV (at threshold) o FM: 0.18 µV (at threshold)
• Selectivity o SSB, CW: More than 2.8 kHz/-6dB; Less than 4.2 kHz/-60 dB o FM: More than 15.0 kHz/-6dB; Less than 30 kHz/-60 dB o FM-N: More than 6.0 kHz/-6dB; Less than 18 kHz/-60 dB
• Spurious rejection ratio: more than 60 dB • Audio output power (at 13.8 V DC): More than 2.0 W at 10% distortion with an 8
ohm load • RIT variable range
o SSB, CW: More than 1.0 kHz o FM: More than 5.0 kHz
• External speaker connector: 2-conductor 3.5 mm (1/8 inch) 8 ohm connector X 2 (for main and sub bands)
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Audio Noise Reduction Filter
63
Cable specifications
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65
66
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APPENDIX 2: Glossary
1. SSB - Single Side Band
2. RTTY - Radioteletype
3. CW - Carrier Wave
4. SSTV - Slow-Scan Television
5. PLL - Phase-Locked Loop
6. HF - High Frequency
7. VHF - Very High Frequency
8. UHF - Ultra High Frequency
9. TNC - Terminal Node Controller
10. AOS - Acquisition Of Signal
11. LOS - Los Of Signal
12. GMS - Ground station Management Software
13. TLE - Two Line Element
14. GS - Ground Station
15. IRV - institutionen för rymdvetenskap ( Department of Space Science)
16. RF - Radio Frequency
17. DC - Direct current
18. SWR -Standing wave ratio
19. ERP - Effective Radiate Power
20. VSWR - Voltage Standing Wave Ratio
21. SC - Spacecraft
22. EIRP - Equivalent isotropic radiated power
