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1. Character Name 1 Packet ID and processor ID 2 4 Orbit number 5 Approximate latitude 6 7 X side temperature 8 9 Y side temperature 10 11 Z side temperature 12 13 Checksum Table 2 7 Photovoltaic temperature packet fields Payload packet On each side of T sat 1 eight thin wire probes are exposed to the environment and are continously monitored to verify their degradation break no break during time in space The purpose of the test is to measure how long these wires survive in the Low Earth Orbit environment in particular related to the effect of atomic oxygen This is part of the experimental payload and is referred to as the material payload in this document The status of four wires per side is available in the beacon payload packet taking up 6 nibbles fig 2 9 M1 M6 A bit value of 0 in these nibbles means wire interrupted The issue of the test of an electromechanical device microrelais is available in char acter n 12 The structure of the packet is shown in figure 2 9 Refer to table 2 8 for decoding SU EPH OOOO 00 00 00 14 Sync PID orbit position Mi M2 M3 M4 M5 M6 Relais Chk Figure 2 9 Beacon payload packet GST Operative Manual 17 50 SSL SSL 100320_DI en CHAPTER 2 SPACE SEGMENT Character Name 1 Packet ID and processor ID 2 4 Orbit number 5 Approximative latitude 6 11 Material payload 12 Relais payload 13 14 Checksum
2. Table 2 8 Payload packet fields Complete packet A longer packet called Complete packet merges the information of the four shorter beacon packet discussed in the previous sections The data rate for the Complete packet is 100 WPM Field verification of communication reliability with packets of different length is one issue of interest for the TJsat 1 mission The structure of the packet is shown in figure 2 10 Refer to table 2 9 for decoding E L ee Sync orbit position T LiPo T Lilon V LiPo V LiPo 12 14 16 18 20 21 22 23 TCOMA T COMB TOBC T PVI TPV2 TPV6 Pelia Relais Figure 2 10 Beacon complete packet SSL 18 50 GST Operative Manual CHAPTER 2 SPACE SEGMENT SSL 100320_DI en Character Name 1 2 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 29 30 31 32 Packet ID and processor ID Orbit number Approximate latitude Lithium Polymer battery temperature Lithium Ion battery temperature Lithium Polymer battery voltage level Lithium Ion battery voltage level Alinco temperature Beacon temperature OBC temperature X side temperature Y side temperature Z side temperature Material payload Relais payload Checksum Table 2 9 Complete packet fields 2 3 6 Alinco Morse Packet Architecture See section 2 3 5 2 3 7 Alinco FSK Packet Architecture The AM FSK modulation is used to send a single packet of telemetry The data is
3. Scuola universitaria professionale Dipartimento della Svizzera italiana Tecnologie Innovative SSL SUPSI SpaceLab Tlsat 1 Ground Segment Team Operative Manual SUPSI SpaceLab 20 03 2010 Doc SSL 100320_ DI en Revisions Rev Date Author Description 0 20 03 2010 IBo First version 1 12 05 2010 IBo PCe Reviewed draft 1 1 11 06 2010 IBo PCe Production launch time version Date of printing July 11 2010 Contents 1 Introduction 2 Space Segment 2 1 An Overview of TIsat 1 000 2 2 COMM Subsystems Overview aoaaa a 2 2 1 Mission Sequence sos ein a ir a a E a a E a a a 2 2 2 Post Separation Operation a 2 2 3 Nominal RF Operating Scheme 2 2 4 Operating sequences LL 2 29 BEACON e Rol a tn A APS nni 2 2 6 gt Transceiver i i hee Oe A a a 223 Downlink e di iu i iste DA ALS ae amp Be ek x 2 3 1 Beacon CW Type of Modulation 2 2 2 3 2 Alinco Audio Morse Type of Modulation 2 3 3 Alinco Audio FSK Type of Modulation 2 2 3 4 Alinco Audio PSK Type of Modulation 2 3 5 Beacon Packet Architecture 200 2 3 6 Alinco Morse Packet Architecture 2 3 7 Alinco FSK Packet Architecture 2 3 8 Alinco PSK Packet Architecture 2 2 3 9 Beacon Packet Coding Details 2 3 10 Alinco Morse Coding Details
4. Nmin_1200Hz 1003 1200 6 2 3 4 Alinco Audio PSK Type of Modulation A tone of 1400Hz is the basis for the PSK modulation One period of the tone T 10 714 us represents one bit of data At the occurrence of each data bit of value 1 the phase of the tone is reversed shifted by 180 otherwise no phase shift is introduced fig 2 5 This is actually Differential Phase Shift Keying modulation DPSK data i 01001 0 i 0 NRZ PSK Figure 2 5 The PSK Modulation DPSK With this modulation TIsat 1 acheives a bit rate BR 1400 bit s PSK is used to download the complete telemetry of TIsat 1 2 3 5 Beacon Packet Architecture The Beacon of TIsat 1 sends a set of instantaneous parameter values using Morse code In order to make data packets as short as possible the encoding scheme of table 2 4 for every nibble of data was chosen The 16 shortest Morse characters were mapped to the 16 hexadecimal values 0x0 0xF possible with 4 bits i e a nibble For Tlsat 1 this is referred to as Morse short form Packets The beacon sends six different packets of data n Packet Name Data Rate Comment WPM 1 Callsign 16 Contains HB9DE in plain Morse no Short form encoding 2 Battery status 16 3 Subsystems status 16 4 Photovoltaic temperature 16 5 Payload 16 6 Complete 100 Collects all the above information The term nibble is larg
5. System Status Encoding System Status is bit mapped into three bytes of the Payload and System Status Packet ID 4 pag 25 This data structure is mainly legacy from ground debug time facilities and is of use for the T sat 1 mission team only This is an undocumented feature Bit Name Description 0 Debug state if l debug mode is disabled 1 Alinco ON OFF if T Alinco is ON 2 Alinco error if 1 Alinco not responding 3 Modem transmit if 1 the firmware modem is configured to transmit 4 Modem receive if 1 the firmware modem is configured to re ceive 5 Modem Morse mode if l the transmitter firmware modem is con figured for Morse 6 Modem melody mode if 1 the transmitter firmware modem is con figured in special tone melody mode 7 reserved 8 A reserved 9 Beacon ON OFF if 1 the beacon is ON 10 PC state if l ready 0 not configured 11 15 not used should always be 0 16 RTC error RTC failure to send acknowledge on the I2C bus 17 Eclipse sensor error Stored Eclipse value is unreadable failure to get acknowledge bit on the memory I2C bus or unrecoverable data error 18 Dawn detection Transition eclipse to sunlight detected 19 Sunset detection Transition sunlight to eclipse detected 20 Orbit number error Stored number of orbits is unreadable failure to get acknowledge bit on the memory I2C bus or unrecoverable data error 21 12C b
6. 1 fig 2 3 and is injected to the microphone input of the transceiver Aj 40 Morse Figure 2 3 The Morse modulation The symbols dot dit and dash dah are coded with a short long sound preceded and followed by silence Silences have different durations depending on their position inter symbol inter character of the same word inter word The duration for symbols and silences in the scheme adopted for T Isat 1 is reported in table 2 1 1 2 5 scheme Object Duration Dot dit base unit Dash dah 3 dots Inter symbol silence 1 dot Inter character silence 2 dots Inter words silence 5 dots Table 2 1 Morse symbol duration The Morse data rate is expressed in Words Per Minute WPM where the reference word is PARIS Table 2 2 shows the enconding for the standard word P A R I S 2 2 2 2 5 Table 2 2 Morse encoding of standard word PARIS The duration of a dot in seconds can be computed as follows The word PARIS contains 10 dots 4 dashes 9 inter symbol silences 4 inter character silences and 1 inter word silence which is equivalent to 10 1 4 3 9 1 4 2 1 5 44 dots 2 1 SSL 12 50 GST Operative Manual CHAPTER 2 SPACE SEGMENT SSL 100320_DI en Defining this value as dots per word dpw one can compute the time per dot as in equation 2 2 TimePer Dot 2 2 imePer Dot W P
7. 30 Voltage of the Li Ion battery Y Li Po 8 x 30 Temperature of the Li Po battery V Lithium Po 8 x 30 Voltage of the Li Po battery CSI 8 Checksum 1 CS2 8 Checksum 2 CS3 8 Checksum 3 1043 Total bit Table 2 13 The PSK battery packet fields TLithium Ion battery Lilon and Lithium Polymer LiPo GST Operative Manual 23 50 SSL SSL 100320_DI en CHAPTER 2 SPACE SEGMENT Photovoltaic Modules Packet ID 3 This packet carries temperature values of the backside of the 6 PV modules of T sat 1 The values are recorded during the past 150 min ca 1 5 orbits up to transmission time Every 10 minutes a new dataset with the 6 temperatures is taken Accordingly 15 datasets are carried in this packet Figure 2 16 shows the structure of this packet while table 2 14 explains its contents For the naming of the sides of T sat 1 see fig 2 1 An orbit profile in this case is the collection of 15 datasets with 6 temperature values each sync header orbit profile checksum ai E T 1 Eclipse Sunlight Reboot 9 9 9 9 9 9 4 5 6 7 8 9 7 8 9 Figure 2 16 PSK PV modules packet Name Size bit Description Sync Header 35 See table 2 11 Eclipse pointer 8 Identifies the first data set taken after orbital sunset Sunlight pointer 8 Identifies the first data set taken after orbital dawn Reboot counter 8 Number of unexpected reboots of the system from the beginn
8. 5 Operating Cycles The two microcontrollers are programmed to be functionally identical so they behave the same way during each one s timeslot 2 2 5 Beacon The beacon transmitter is tuned to the RF frequency of 437 305MHz The output of the transmitter is switched on and off to achieve information transport This procedure is commonly referred to as CW Continuous Wave or OOK On Off Keying modulation 2 2 6 Transceiver The transceiver used on Tlsat 1 is a FM device Its carrier frequency is set to 145 980MHz according to the IARU coordinated frequency for the spacecraft and is modulated by audio tones injected via the microphone jack The term modulation used in the following always refers to audio types of modulation All types of modulation for the transceiver have been implemented in software and are part of the experimental payload for T sat 1 The audio tones are generated by the OBC During eclipse the batteries cannot be recharged therefore the power consumption shall be limited GST Operative Manual 11 50 SSL SSL 100320_DI en CHAPTER 2 SPACE SEGMENT 2 3 Downlink 2 3 1 Beacon CW Type of Modulation The transmission method is based on Morse encoding The data rates are the same as for the FM transceiver i e 16 WPM at slow rate and 100 WPM at fast rate 2 3 2 Alinco Audio Morse Type of Modulation A 880Hz tone of changing duration interleaved with silence is synthesized by the OBC of TIsat
9. GST Operative Manual 25 50 SSL SSL 100320_DI en CHAPTER 2 SPACE SEGMENT Name Size bit Description Sync Header 35 See table 2 11 System status 24 Status of OBC and subsystems Reboot counter 8 Number of unexpected reboots from the be ginning of the mission Orbit time 8 Orbit period minutes Relais test 8 Test result for the micro relais payload Material 1 8 Material payload X side Material 2 8 Material payload Y side Material 3 8 Material payload Z side Material 4 8 Material payload X side Material 5 8 Material payload Y side Material 6 8 Material payload Z side Beacon SWR meter 8 Antenna match information for the beacon PV 9 poll 8 Bit mapped information for temperature above or below 0 C for each side Eclipse counter 8 Eclipse sunlight transition sampling shiftregister RF monitor E 16 RF power RF monitor A 16 RF power detected while the transceiver is operating RF monitor B 16 RF power detected while the beacon is oper ating Current Li Ion 8 Current consumption from Lithium Ion bat tery Current Li Po 8 Current consumption from Lithium Polymer battery CS1 8 Checksum 1 CS2 8 Checksum 2 CS3 8 Checksum 3 243 Total bit Table 2 15 The PSK payload and system status packet fields SSL 26 50 GST Operative Manual CHAPTER 2 SPACE SEGMENT SSL 100320_DI en The Golay 12 24 EDAC scheme All PSK packets are provided
10. with redundant data to allow for error detection and correction EDAC The adopted Golay 12 24 EDAC scheme allows detection of up to 4 faulty bits and correction of up to 3 bits on 12 bit dataframes In presence of 5 and 6 errors the algorithm is thrashed In the basic version of the algorithm given 12 bits of data 12 check bits are calculated Unfortunately 12 bits is not a multiple of 8 so it is not possible to use entire bytes for the computation of Golay without a padding strategy The firmware of TJsat 1 takes clusters of three bytes and divides the resulting 24 bits in two words of 12 bits each The first word takes the first byte and the most significant 4 bits of the second whereas the second word takes the 4 least significant bits of the second bytes concatenated with the third byte Twelve check bits are calculated for each of these 12 bit datawords ending up with clusters of 3 data bytes and 3 check bytes for a grand total of 24 24 48bits Figure 2 18 shows how these 48bit clusters are concatenated to build the PSK infor mation packet three bytes of data followed by three bytes two 12 bit groups of check bits Figure 2 18 A PSK packet with the Golay 12 24 EDAC data grey shaded SWe say simply 4 errors GST Operative Manual 27 50 SSL SSL 100320_DI en CHAPTER 2 SPACE SEGMENT 2 3 9 Beacon Packet Coding Details As one of the transmission modes of T sat 1 Morse was chosen because it is eas
11. 2 3 11 Alinco FSK Coding Details 2 3 12 Alinco PSK Coding Details 2 4 Uplink 3 TIsat Demodulator User s Manual 3 1 Basic Concepts 3 1 1 Download 3 1 2 Soft and Hardware Requirements 3 1 3 Workspace 3 1 4 Logs and Feedback 3 2 Installation Ovo USASe ena a ara SSL 100320_DI en CONTENTS Acronyms and Terms AGC Automatic Gain Control CCR Capture and Compare Registers DoL Days of Life in orbit mission duration ECC Error Correcting Code EOC End Of Charge related to batteries EOD End Of Discharge related to batteries EPS Electric Power Supply OBC On Board Computer OPR Orbit PRofile related to datasets in telemetry GS Ground Station PV Photovoltaic RFPC RF Power Checker RX Receive or Receiver TX Transmit or Transmitter TU Timing Unit CBD CPU Boot Delay the time between boot of the CPUs as assigned by the TU WPM Words per Minute the Morse transmission rate measure SSL 4 50 GST Operative Manual Chapter 1 Introduction TIsat 1 is the first staff and student made satellite of SUPSI SpaceLab For communication TJsat 1 relies on amateur radio frequencies which were coordi nated with the International Amateur Radio Union IARU This document describes 1 the radio communication system 2 the modulation methods 3 the communication frame architecture and 4 the frame details of TIsat 1 This information will enable dec
12. 38 C SSL 32 50 GST Operative Manual CHAPTER 2 SPACE SEGMENT SSL 100320_DI en Voltages Batteries voltages are represented by a single short format Morse character Me MorseChar MC Morse characters encoding 4 bits for the voltage value table 2 4 Example MC o dit dah sequence B Morse character 1100 Nibble table 2 4 Voltage METZ V Resulting voltage Voltage 1210222 3 9 V Voltage values are in the range 2 7 V 4 2 V GST Operative Manual 33 50 SSL SSL 100320_DI en CHAPTER 2 SPACE SEGMENT Payload Data Material Payload Refer to page 17 for introductory information on Material Pay load and to figure 2 9 for the packet structure The encoding of the Morse characters 6 to 11 each representing the status of four wires is shown in table 2 16 2 Material Bonding Wire Bonding Wire Bonding Wire Bonding Wire Bonding Wire Bonding Wire Bonding Wire Bonding Wire Bonding Wire Bonding Wire Bonding Wire DynaCable Bonding Wire Bonding Wire Bonding Wire Bonding Wire Bonding Wire Bonding Wire Bonding Wire Bonding Wire Bonding Wire Bonding Wire Bonding Wire Bonding Wire Packet Field Side 6 X 10 Y 11 Z SorFNMWOrFNMWIOrFNMNWIOrFNMNWOFrFNMN WOOF DY WwW Table 2 16 Materials payload details refer to fig 2 9 Microrelais Payload The team of TJsat 1 wanted to v
13. 69 187 0xBB 22 UU Checksum for Beacon Packets except Complete and Payload 1 Concatenate amp the received characters as shown in figure 2 20 2 Decode each character in a 4 bits value according to table 2 4 3 Left pad character 1 with zeros 4 Each couple or padded character is a byte 8 bits value The right most couple is the checksum computed on the satellite and included in the packet 5 Add all the bytes including the checksum byte modulo 256 equation 2 6 6 Verification if the result is 0 the checksum may be correct else it is wrong and the packet has to be considered corrupted IE EJE SIA EJA Ti A IJE Ri iox01i 0x00 i 0x4 i 0x50 i 0x52 0x1 0x08 is ae ie se ee Figure 2 20 Beacon packets except payload and complete example for checksum computation 0 amp 1 E amp E E amp S A amp E A amp T A amp I 234 222 0101 0000 0x04 0250 0252 0251 24810 248 mod 256 248 CheckSumByte 256 248 8 0208 22 ER SSL 36 50 GST Operative Manual CHAPTER 2 SPACE SEGMENT SSL 100320_DI en 2 3 10 Alinco Morse Coding Details The Alinco Morse Coding is the very same as the coding for the Beacon Please refer to section 2 3 9 2 3 11 Alinco FSK Coding Details The FSK modulation is plain ASCII not encoded GST Operative Manual 37 50 SSL SSL 100320_DI en CHAPTER 2 SPACE SEGMENT 2 3 12 Alinco PSK Coding Details PSK Packets
14. M dpw The Audio Morse type of modulation for T sat 1 runs at 16 WPM at slow rate and 100 WPM at fast rate Dot time for these rates is summarized in table 2 3 Data Rate WPM Dot time ms 16 85 2 100 13 6 Table 2 3 Dot time Morse modulation with the FM transceiver has modest throughput compared to the other modulation schemes 2 3 3 Alinco Audio FSK Type of Modulation The two logic symbols 0 and 1 are mapped to the audio tones 1200Hz and 600Hz The amplitude of the two tones is different and is tuned to favour the decoding process The digital raw data is Differential Manchester encoded prior to modulation The chosen encoding scheme fig 2 4 calls for a change at the beginning of each bit cell regardeless of the data value and further Data Value Center of Bit Cell Y No change 0 Change occurs data 0 1 0 0 1 1 Manchester AM FSK Figure 2 4 The FSK modulation with Manchester data enconding With this modulation TIsat 1 acheives a bit rate BR 100 bit s The minimum and maximum number of uninterrupted full tone periods can be cal culated as follows 1 1 Nmin ser tone 2 3 BR 2 1 Nmax BR Ftone 2 Nmin 2 4 5Documented as Biphase Mark Code in WikiPedia GST Operative Manual 13 50 SSL SSL 100320_DI en CHAPTER 2 SPACE SEGMENT Nmin numerical values 1 1 Nmin_600Hz 700 2 600 3 1 1
15. Refer to table 2 5 for decoding fs EE Sync PID orbit position T LiPo T Lilon VLiPo V Lilon Chk Figure 2 6 Beacon battery status packet GST Operative Manual 15 50 SSL SSL 100320_DI en CHAPTER 2 SPACE SEGMENT Character Name 1 Packet ID and processor ID 2 4 Orbit number 5 Approximate latitude 6 7 Lithium Polymer Temperature 8 9 Lithium Ion Temperature 10 Lithium Polymer Voltage 11 Lithium Ion Voltage 12 13 Checksum Table 2 5 Battery status packet fields Subsystems status packet Figure 2 7 and table 2 6 summarize the structure of the packet and the information of each field FAL eb ede Pee del Sync PID orbit position TCOMA TCOMB T OBC Chk Figure 2 7 Beacon Subsystems status packet Character Name 1 Packet ID and processor ID 2 4 Orbit number 5 Approximate latitude 6 7 Alinco temperature 8 9 Beacon temperature 10 11 OBC temperature 12 13 Checksum Table 2 6 Subsystems status packet fields Photovoltaic temperature packet Each of the 6 photovoltaic modules of TJsat 1 is monitored by a thermometer The temperature of the sides X Y and Z are available in this packet The structure of the packet is shown in figure 2 8 Refer to table 2 7 for decoding SSL 16 50 GST Operative Manual CHAPTER 2 SPACE SEGMENT SSL 100320_DI en selce Chk Sync PID orbit position TPVI TPV2 T PV6 Figure 2 8 Beacon Photovoltaic temperatures packet
16. aracter 1100 Nibble table 2 4 Position 22 5 MC I a 22 5 1210 270 Resulting position from the terminator GST Operative Manual 31 50 SSL SSL 100320_DI en CHAPTER 2 SPACE SEGMENT Temperatures All temperatures are encoded with two Morse characters chosen from the most con venient ones shortest dit dah sequences thus saving energy Temperature decoding is a two step process MC MO MorseCharl MorseChar0 MCI MCO Morse characters encoding the 3 bits of the temperature value Ta ble 2 4 is used for values 0 to 7 Example 1 Derive intermediate value MC1 MCO dit dah sequence N D Will be out of E I T N S A H D 0011 0111 Nibbles table 2 4 MSB is always zero 00 011 111 Intermediate Value Concatenate the 3 least significant bits of both charac ters and pad with zero Consider MCi as bit vector MCi 3 downto 0 and the sign amp as concatenation sign The intermediate value is 00 amp MC1 2 downto 0 amp MCO 2 downto 0 2 Calculate real temperature Temperature Intermediate Value 64 150 oc _ MC1 8 MCO 64 150 do 7 100 Where MC is the nibble value of the original Morse characters For the example 3119 64 150 Te t C emperature 100 310 8 710 64 150 og o 100 18 34 C Temperature values are in the range 2 C
17. cification SSL 8 50 GST Operative Manual CHAPTER 2 SPACE SEGMENT SSL 100320_DI en 2 2 4 Operating sequences COMM operating sequences are tied to the Operating Modes and Operating Cycles of the spacecraft The spacecraft Operating Modes TIsat 1 is programmed to periodically execute three basic operations during its nom inal life 1 perform housekeeping measurements and procedures and payload tests 2 transmit data to the Ground Stations 3 receive commands The firmware of the OBC is able to self configure the satellite depending on which operation has to be executed A fixed timeslot is allotted to each operation when the slot times out the current operation is terminated and the next is started The software and hardware configuration related to each operation is called Operating Mode There are five Operating Modes n Operating Mode Timeslot s Notes 1 Housekeeping 15 2 Transmission with FM radio 25 TX_FM mode 3 Transmission with beacon 25 TX_ Beacon mode 4 Reception 20 RX mode 5 Sleep 25 Houskeeping mode the CPU basically reads the sensors and stores the results in memory This operating mode takes 15 seconds No radio transmission is activated during this time When the housekeeping time expires T sat 1 enters one of two transmission modes unless energy saving is necessary in which case the satellite enters Sleep mode TX FM mode this mode
18. data treatment policy guarantees that data are not transmitted nor accessed nor utilized outside of the forum section 3 1 2 Soft and Hardware Requirements TIsat Demodulator is currently available only for Windows systems it has been tested with Windows XP SP 2 or 3 Windows Vista and Windows 7 It requires the Microsoft NET Framework version 2 0 or higher The minimum hardware configuration is rather modest and requires 1 Pentium II 1 GHz or equivalent 2 512 MB RAM 3 sound card with 16 bit 44100 samples 4 internet connection 43 SSL 100320_DI en CHAPTER 3 TISAT DEMODULATOR USER S MANUAL 3 1 3 Workspace The workspace is a user location a directory where Tlsat Demodulator works The contents of this location is generated and modified directly by TIsat Demodulator and should not be changed in any other way The structure of a workspace consists in a folder named TIsatLog containing the log files see next section for details and an XML configuration file Create a Workspace A workspace can be created either during installation see section 3 2 or during normal operation mode by selecting New Workspace from menu File In both cases the creation dialogue is the same One has to choose the location where the workspace will be created and insert the name of the workspace Following the confirmation a folder named as the workspace is created at the chosen location and will contain the XML configuration file with t
19. ed to send the full telemetry and the orbit profiles i e data collected and stored during the whole orbit Four PSK packets have been foreseen Each of them contains one or more complete profile with a selection of different parameters The four PSK packets are transmitted sequentially and transmission is repeated over and over during the dedicated time slice of TIsat 1 Integrity of the data can be checked and some correction can be applied at the re ceiving end thank to a Golay 12 24 error detection and correction EDAC scheme implemented on TIsat 1 Decoding of the PSK packets can be achieved even disregarding the EDAC scheme In the next sections the PSK packets will therefore be presented first ignoring the EDAC check bits An explanation of how to deal with and take advantage of the EDAC bits will be given in section 2 3 8 sync header orbit profile checksum f T T 1 T a Figure 2 12 Structure of PSK packets The header is followed by the orbit profiles depending on packet ID SSL 20 50 GST Operative Manual CHAPTER 2 SPACE SEGMENT SSL 100320_DI en Sync and Packet Header Each PSK packet starts with a sequence of ones 11 bits called Sync followed by what we call the header 3 bytes see figure 2 13 The PSK packet carries from 200 to 400 bytes fig 2 12 i 1 i 2 3 i bytes Approx Packet ID Orbit number P rie pia i 8 bit 12 bit i 4 bit Figure 2 13 Sync Header of PSK packet
20. ely used to define different quantities of bits For this document a nibble is 4 bits Two concatenated nibbles generate a byte 8 bits SSL 14 50 GST Operative Manual CHAPTER 2 SPACE SEGMENT SSL 100320_DI en Nibble Value Character Morse Code Length dots 0x0 E 1 0x1 I 3 0x2 T 3 0x3 N 5 0x4 S 5 0x5 A 5 0x6 H 7 Ox7 D T 0x8 R 7 0x9 M 7 OxA K 9 0xB U 7 OxC B 9 0xD En jc gt eens 9 OxE F 9 OxF L 9 Table 2 4 Morse short format encoding for TIsat 1 The beacon is thought to be easily heard and understood by anyone with knowledge of the Morse code Any standard Morse decoding software can be used to automatically put the dit dah into text Decoding can be acheived even by hand following the rules listed in the next sections SUPSI SpaceLab provides software to automatically gather check save and decode data from Tlsat 1 Battery status packet The battery status packet shows the actual temperature and voltage of the two bat teries of Tlsat 1 a Lithium Polimer LiPo 1400 mAh 4V nominal 3 6V and a Lithium Ion Lilon 2400 mAh 4V nominal 3 6 V The structure of the packet is shown in figure 2 6 Each square numbered 1 12 is one of Short form Morse charactes encoding a 4 bit value see table 2 4 The first box Sync on the left is the synchronization symbol a non standard Morse symbol
21. erify if a small electrome chanical device a microrelais would survive the high stress of the launch and the extreme environment conditions of LEO Thus TJsat 1 carries a microrelais which will periodically be activated by the processors while monitoring the contact position If the relay is working correctly the 12 Morse character of the payload packet fig 2 9 will be K see table 2 4 for the corresponding binary encoding Any other character identifies a test failure LEO Low Earth Orbit SSL 34 50 GST Operative Manual CHAPTER 2 SPACE SEGMENT SSL 100320_DI en Checksum An eight bit checksum is appended to each data packet to allow some verification of data correctness It is calculated as Vi CheckSumByte 256 O byte mod 256 2 5 where the index 7 indicates all data bytes contained in the packet The bytes for calculation are formed either concatenating two Morse characters nib bles according to table 2 4 or left padding a single nibble with four zeros At the receiving end the sum can be recalculated using the received data If the computed checksum matches the one received from the satellite the data are most probably correct Not all possible errors can be detected with this method Notice that by definition an error in the checksum does not automatically invalidate the packet received it is only an information value To calculate the checksum two different procedures depending on
22. exposed PCB 0 2mm 35um Cu soldermask protected PCB 0 8mm 35um Cu soldermask protected PCB 0 2mm 35um Cu Au coated exposed PCB 0 8mm 35um Cu Au coated exposed Bonding Wire 30um Au exposed Bonding Wire 30um Au exposed Bonding Wire 30um Au exposed Bonding Wire 30um Au exposed PCB 0 2mm 35um Cu soldermask protected PCB 0 8mm 35um Cu soldermask protected PCB 0 2mm 35um Cu Au coated exposed PCB 0 8mm 35um Cu Au coated exposed Bonding Wire 30um Au exposed Bonding Wire 30um Au exposed Field Side 6 X Y oF NWP ODNORrFNWHTDNOrFRNW KH ODN Continued on next page GST Operative Manual 39 50 SSL SSL 100320_DI en CHAPTER 2 SPACE SEGMENT Continued from previous page Y ce Material Bonding Wire 30um Au exposed DynaCable PCB 0 2mm 35um Cu soldermask protected PCB 0 8mm 35um Cu soldermask protected PCB 0 2mm 35um Cu Au coated exposed PCB 0 8mm 35um Cu Au coated exposed Bonding Wire 30um Au exposed Bonding Wire 30um Au exposed Bonding Wire 30um Au exposed Bonding Wire 30um Au exposed PCB 0 2mm 35um Cu soldermask protected PCB 0 8mm 35um Cu soldermask protected PCB 0 2mm 35um Cu Au coated exposed PCB 0 8mm 35um Cu Au coated exposed Bonding Wire 30um Au exposed Bonding Wire 30um Au exposed Bonding Wire 30um Au exposed Bonding Wire 30um Au exposed PCB 0 2mm 35um Cu soldermask protected PCB 0 8m
23. he Create Workspace button TIsat Demodulator 1 2b ES R1 SSL 48 50 GST Operative Manual CHAPTER 3 TISAT DEMODULATOR USER S MANUAL SSL 100320_DI en Configuration step 4 confirmation At the final step of the wizard the previously inserted data are summarized If some thing must be corrected one can press the Back button as usual Notice that when going backward through the wizard the data are already set so it is not necessary to retype them TIsat Demodulator 1 0b sat 2k 4 GST Operative Manual 49 50 SSL SSL 100320_DI en CHAPTER 3 TISAT DEMODULATOR USER S MANUAL 3 3 Usage TIsat Demodulator has been designed to be very easy to use A print screen of the application is shown in figure 3 1 The red numbers represent the 4 steps to be executed to successfully receive demodulate and decode data These steps are 1 In the control area select the right audio peripheral the desired demodulation format see chapter 2 and press Start sampling to start the demodulation Press Stop to stop the process 2 The raw data area continuously displays the received data The visualization can be single characters for Morse and AM FSK and couple of hexadecimal numbers for PSK binary telemetry 3 The signal acquired by the sound card is continuously drawn in the graphic area This demonstrated useful in the process of tuning the radio input level 4 Each time a packet has been ide
24. he first data set taken after orbital dawn Reboot counter 8 Number of unexpected reboots of the system from the beginning of the mission Y OBCI 8 x 30 Temperature of OBC PCB sensor Y OBC2 8 x 30 Temperature of CPU1 MSP internal sensor Y EPS1 8 x 30 Temperature of the EPS TU subsystem Y EPS2 8 x 30 Temperature of the EPS BM subsystem 9 COMM 8 x 30 Temperature of the transceiver board CS1 8 Checksum 1 CS2 8 Checksum 2 CS3 8 Checksum 3 1283 Total bit Table 2 12 The PSK subsystems packet fields SSL 22 50 GST Operative Manual CHAPTER 2 SPACE SEGMENT SSL 100320_DI en Battery Packet ID 2 This packet is dedicated to the two batteries of Tlsat 1 Each orbit profile holds 30 datasets taken one every 5 minutes during the most recent 150 min up to transmission time Each dataset holds temperatures and voltages as in figure 2 15 sync header orbit profile checksum e f T 1 Eclipse Sunlight Reboot 9 Vv 9 Vv ou uo o 4 5 6 7 8 9 10 Figure 2 15 PSK battery packet Name Size bit Description Sync Header 35 See table 2 11 Eclipse pointer 8 Identifies the first data set taken after orbital sunset Sunlight pointer 8 Identifies the first data set taken after orbital dawn Reboot counter 8 Number of unexpected reboots of the system from the beginning of the mission Y Li Ion 8 x 30 Temperature of the Li Ion battery V Li Ion 8 x
25. he same name as the workspace and the folder for the log files Open a Workspace A workspace can be opened either during the installation see section 3 2 or during the normal operation mode by selecting Open Workspace from menu File In both cases the opening dialogue is the same One has to browse to the location where the desired workspace is located open the folder named as the workspace and select the XML configuration file of the workspace By confirming the opening the software will load the workspace starting from that configuration file 3 1 4 Logs and Feedback Logfiles are located into the TIsatLog folder inside the workspace The logs are grouped by day with a folder for each day named with yyyymmdd e g for the 15 July 2010 the name will be 20100715 The logfiles will be placed in these folders Logfiles are created for each reception and are named with a date and hour string predeced by the modulation type selected using the format MODULATION_yyyymmdd_hhmmss Example The 4 July 2010 at 14 20 59 a PSK reception starts The logfile will be named PSK_20100704_142059 If it was a Morse reception it would be named MORSE_20100704_142059 In case of an AM FSK reception AMFSK_20100704_142059 Two logfiles are written for each reception 1 the packets file and 2 the raw file The first contains only the data that have been recognized as packets decoded for a particular modulation it is not ensured that packets are correc
26. hin 20 seconds the mode is terminated otherwise the satellite keeps in RX mode until a End of RX command is received or the processor timeslot max 5 minutes expires The RX mode is the only mandatory mode for each cycle its duration is at least 20s every 40s The spacecraft Operating Cycles A sequence of three operating modes that matches the basic operations of the satel lite is called a Operating Cycle Each Operating Cycle takes one minute to execute Figure 2 2 Operating modes bubbles and cycles closed paths of TIsat 1 Note fig 2 2 that any closed path following the oriented edges of the graph represents one possible Operating Cycle and takes 1 minute to execute 3Beacon Packets are described in section 2 3 5 SSL 10 50 GST Operative Manual CHAPTER 2 SPACE SEGMENT SSL 100320_DI en The scheduling and execution sequence of the operating modes depends on specific real time constraints Decisions are based on energy availability sunlight conditions temperature estimated position along the orbit etc Depending on the situation there can be cycles without TX state The Processor Timeslot For redundancy purposes the OBC of TIsat 1 is built with two independent micro controllers relaying each other periodically in control of the spacecraft The time allotted to each processor is called Processor Timeslot and for TIsat 1 it is set to 5 minutes During the timeslot the processor executes
27. ing of the mission Y PV1 8x 15 Temperature X side V PV2 8 x 15 Temperature Y side Y PV3 8 x 15 Temperature Z side Y PV4 8 x 15 Temperature X side V PV5 8x 15 Temperature Y side V PV6 8x 15 Temperature Z side CS1 8 Checksum 1 CS2 8 Checksum 2 CS3 8 Checksum 3 803 Total bit Table 2 14 The PV modules packet fields SSL 24 50 GST Operative Manual CHAPTER 2 SPACE SEGMENT SSL 100320_DI en Payload and System Status Packet ID 4 This packet carries information about the actual system status 3 bytes and payload status 18 bytes as well as an orbit profile of the battery currents Each orbit profile holds 30 datasets with two battery current values Each dataset is taken once every 5 minutes during the most recent 150 min ca 1 5 orbits up to transmission time Figure 2 17 shows the structure of this packet while table 2 15 explains its contents sync header N Reboot Orbit Relais Material Material Material Material Material Material Beacon PV amp System Status counter time test 1 2 3 4 5 6 rosmeter poll 4 5 6 7 8 9 10 11 12 13 14 15 16 17 orbit profile checksum csi CS2 CS3 Figure 2 17 PSK payload and system status packet The RF monitor parameter is picked up by a dedicated antenna circuit integrated on the PV modules outside the metal structure of TIsat 1 It gives information about the spacecraft s outer RF environment
28. is entered during even numbered orbits and lasts 25 seconds The satellite uses the FM radio going through its modulations schemes and packets four operating cycles with PSK and one with AM FSK packets The same packet is repeated so many times as needed to fill the 25 seconds of the TX mode After that the RX mode is activated TX Beacon mode this mode is entered during odd numbered orbits and lasts 25 seconds The satellite uses the beacon CW to send the specific packets at two different data rates Slow rate the transmission scheme is periodic in five steps 1 transmission of the callsign 2 Beacon short packet type 1 GST Operative Manual 9 50 SSL SSL 100320_DI en CHAPTER 2 SPACE SEGMENT 3 Beacon short packet type 2 4 Beacon short packet type 3 5 Beacon short packet type 4 The packets are repeated to fill the 25 seconds of the mode timeslot Fast rate the Beacon Complete packet described in section 2 3 5 is repeated over and over during the 25 seconds of the mode timeslot After that the Rx mode is activated Sleep mode in this mode no activity occurs for 25 seconds This is the power saving mode It is activated either in eclipse in case of emergency and over equatorial latitudes where the satellite has the maximum exposition of the solar panels RX mode the FM transceiver is turned on in receive mode and the satellite waits for commands from the Ground Stations If no command is received wit
29. m 35um Cu soldermask protected PCB 0 2mm 35um Cu Au coated exposed PCB 0 8mm 35um Cu Au coated exposed Bonding Wire 30um Au exposed Bonding Wire 30um Au exposed Bonding Wire 30um Au exposed Bonding Wire 30um Au exposed Field Side 10 Y 11 Z OrFRFNWKHTEDNOFNWHTEDNORN WKH ODN OF Table 2 18 Materials payload details Byte n 9 of the PSK payload packet fig 2 17 reports about the issue of the relay test The device is switched on and off several times by each processor while observing correct contact travel If the relay is confirmed to work correctly the byte will read OxAA Any other result is to be considered a failure of the relay Checksums In addition to EDAC pag 27 three bytes of checksum are used in each PSK packet to allow checking its correctness The three bytes are calculated as follows Assume there are n bytes in a PSK packet Checksum 1 is computed with all the bytes of the packet preceding the CS1 byte with following equation n 1 CheckSum 256 gt byte mod 256 2 10 i 0 SSL 40 50 GST Operative Manual CHAPTER 2 SPACE SEGMENT SSL 100320_DI en Checksum 2 is the xor function of all the bytes preceding the CS2 byte including the CS1 byte CheckSuma byte O byte D byte O byte _1 CS1 2 11 Checksum 3 is computed xor ing each byte of the PSK packet with its position index in the packet and all the result
30. ntified it is inserted into the packet list Double click on a packet list entry shows a pop up window with the decoded parameters of the packet Take care that the log file for the demodulation session is created when clicking on the Start sampling button and is closed when clicking on the Stop button EE TIsat Demodulator 1 0b workspace d 10 xj Eile Edit Help Sampled Audio Packet History Packet counter S packet type 2 received 11 03 2010 15 25 50 S packet type 2 received 11 03 2010 15 26 29 S packet type 2 received 11 03 2010 15 26 42 Amplitude O Audio Devices List HD Audio rear input y Demodulation Format Selection H 0p 00 000 Morse 1 200 24 4 4 000 1 000 24 7 25 7 23 5 24 0 25 0 24 5 ES M AMFS 4 A O 0 1 0 20 0 1 60 x O 1 200 24 4 4 000 1 000 24 7 25 7 23 5 24 0 25 0 24 5 3 art sampin Stop 0 1 0 20 0 1 60 4 23 4 4 000 1 200 24 4 000 1 000 24 7 25 7 23 5 24 Current Workspace workspace SUPSI Space Lab Connected 9 Figure 3 1 TIsat Demodulator operating SSL 50 50 GST Operative Manual
31. oding of T sat 1 s signals even without the specific software that SUPSI SpaceLab has prepared for the mission Further a short installation and user guide for the demodulation and decoding software provided by SUPSI SpaceLab is given SSL 100320_DI en CHAPTER 1 INTRODUCTION SSL 6 50 GST Operative Manual Chapter 2 Space Segment 2 1 An Overview of TIsat 1 Figure 2 1 shows the structure of TJsat 1 along with the naming convention for the sides Four antennas are depicted TJsat 1 actually carries only two of the four antennas Figure 2 1 Tlsat 1 structure Emission efficiency was experimentally found to be better with only two antennas 7 SSL 100320_DI en CHAPTER 2 SPACE SEGMENT 2 2 COMM Subsystems Overview TIsat 1 carries two radio devices working in the UHF respectively in the VHF band A home grown beacon transmitter is dedicated to downlink short telemetry i e essential information and operates in UHF 437 305 MHz with CW modulation The beacon is also used as emergency radio and first communication device just after the launch The second device is a commercial FM transceiver Alinco used for up as well as for down link It is adapted to handle several audio tone modulation schemes providing an higher bit rate than the beacon This radio is used to transmit the full telemetry in the VHF band 145 980 MHz The two radios relay each other during T sat 1 s mission with a time slice l
32. ogic 2 2 1 Mission Sequence The four stage PSLV rocket is expected to cut off thrust of PS4 fourth stage at liftoff 1034 2s This time is called T6 TIsat 1 will separate from the Launch Vehicle LV at T6 135 4s Up to separation time the spacecraft is powered off 2 2 2 Post Separation Operation After separation i e the spacecraft leaves the XPOD complying with the CDS rev 11 TIsat 1 will 1 wait for at least 900s before deploying antennas While waiting T sat 1 will sample the internal temperature and will activate the deployment system only if the temperature is above 0 C but not later than 130 min after separation No communication will take place during this time 2 After antenna deployment for the next 900s short beacon transmission are allowed The Morse string tisat1 hb9de is transmitted 3 After 1800s 30 min nominal spacecraft operation is entered 2 2 3 Nominal RF Operating Scheme The two downlink devices Beacon and FM transceiver alternate each orbit During even orbits the beacon is used while the FM transceiver is used during the next odd orbit During the FM transceiver orbit a data packet transmission is repeated for 25 seconds each minute queuing 4 PSK packets with 1 FSK packet Find additional information on packet encoding and transmission in the next sections The beacon transmission rate is toggled from slow 16 WPM to fast rate 100 WPM every 32 orbits CubeSat Design Spe
33. represented in a single string of ASCII characters letters numbers spaces and points as in table 2 10 The resulting string should appear as in figure 2 11 Negative values are appended in the string without space beginning with their minus sign 23 4 4 000 1 200 24 4 4 000 1 000 24 7 25 7 23 5 24 0 25 0 24 5 32 1 0 8 24 0 3 0 20 0 1 6 Figure 2 11 Example of Alinco FSK data string GST Operative Manual 19 50 SSL SSL 100320_DI en CHAPTER 2 SPACE SEGMENT Position Description Unit Format 1 Lithium ion battery temperature C_ t xxx 2 Lithium ion battery voltage V X XXX 3 Lithium ion current A X XXX 4 Lithium polymer temperature oC t xxx 5 Lithium polymer voltage V X XXX 6 Lithium polymer current A xxxx 7 FM radio board temperature C xxx 8 CW radio board temperature C t xxx 9 EPS 1 board temperature oC t xxx 10 EPS 2 board temperature C xxx 11 OBC board temperature 1 C xxx 12 OBC board temperature 2 C xxx 13 PV generator side X temperature oC t xxx 14 PV generator side Y temperature C xxx 15 PV generator side Z temperature C xxx 16 PV generator side X temperature C xxx 17 PV generator side Y temperature oC t xxx 18 PV generator side Z temperature oC xxx Table 2 10 Alinco FSK Packet Architecture 2 3 8 Alinco PSK Packet Architecture For TIsat 1 the PSK modulation offers the highest bit rate PSK is therefore us
34. s Name Size bit Description Sync 11 To synchronize detection of the packets Eleven bit at 1 Packet ID 8 Identifier Orbit number 12 Total number of orbits completed at the time of transmission Approximate latitude 4 In 5 360 starting from the termi nator at orbit time 35 Total bit Table 2 11 Sync header fields of the PSK packets refer to fig 2 13 GST Operative Manual 21 50 SSL SSL 100320_DI en CHAPTER 2 SPACE SEGMENT Subsystems Packet ID 1 This packet carries information about the subsystems of TIsat 1 recorded during the past 150 min ca 1 5 orbits up to transmission time There are 30 data sets taken one every 5 minutes Each data set holds temperature values 1 for the OBC 2 values 2 for the EPS PCBs 2 values and 3 for the COMM PCB transceiver 1 value Figure 2 14 shows the structure of this packet while table 2 12 explains its contents The collection of the 30 datasets with 5 parameters each is called orbit profile OPR sync header orbit profile checksum Wa a Eclipse Sunlight Reboot 9 9 9 9 9 pointer pointer counter OBC1 OBC2 EPS1 EPS2 COMM 4 5 6 7 8 9 10 11 Figure 2 14 PSK subsystem packet ID 1 Name Size bit Description Sync Header 35 See table 2 11 Eclipse pointer 8 Identifies the first data set taken after orbital sunset Sunlight pointer 8 Identifies t
35. s to each other CheckSum3 byte 0 byte 01 S P byte BK byte 10 n 1 0 CS1 n CS2 9 n 1 2 12 GST Operative Manual 41 50 SSL SSL 100320_DI en CHAPTER 2 SPACE SEGMENT 2 4 Uplink The uplink channel is reserved for commands to control the behavior of Tlsat 1 DTMF encoding is used The description of the recognised commands will be available in due course SSL 42 50 GST Operative Manual Chapter 3 TIsat Demodulator User s Manual 3 1 Basic Concepts TIsat Demodulator is a piece of software intended to demodulate and decode data from Tlsat 1 Audio signals from a radio receiver are first digitized through the sound card of a personal computer and than analyzed by the demodulation decoding software according to the selected modulation and or encoding format The received data is collected and stored in logfiles while being displayed in user friendly window frames The logfiles can then be submitted to SUPSI SpaceLab through a HTTPS connection system embedded inside the demodulation software The following sections explain the fundamental concepts of the software Sections 3 2 and 3 3 are targeted on the utilization of the software and assume that users known the basic concepts 3 1 1 Download TIsat Demodulator can be downloaded only after registering to the SUPSI SpaceLab forum Registration is absolutely free and personal data are stored only in the forum SUPSI SpaceLab
36. sat Demodulator users shall unzip the installation packet and run setup exe An installation wizard will guide them trough the procedure Once the installation has been completed the user can start TIsat Demodulator for the first time This will invoke a configuration wizard with the following steps Configuration step 1 welcome TIsat Demodulator 1 2b CE 3 1 Press next SSL 46 50 GST Operative Manual CHAPTER 3 TISAT DEMODULATOR USER S MANUAL SSL 100320_ DI en Configuration step 2 identification data Users are invited to insert into the text fields the data to identify themselves Note that username password and e mail are mandatory other fields are optional To allow an automatic registration of the data received from Tlsat 1 username and password must be the same used to register to the forum of SUPSI SpaceLab Oth erwise the software will allow you to receive data but will not upload them auto matically TIsat Demodulator 1 2b E 4 GST Operative Manual 47 50 SSL SSL 100320_ DI en CHAPTER 3 TISAT DEMODULATOR USER S MANUAL Configuration step 3 first workspace This step is used to configure the workspace to be used when TIsat Demodulator is started for the first time Later it is always possible to create open and use other workspaces Users can choose e if a workspace already exists the Open Workspace button e if no workspace exists t
37. t by 3 Morse characters for the 3 nibbles of the counter The characters are chosen according to table 2 4 MC2 MC1 MCO MorseChar2 MorseChar0 MC2 MCO Morse characters encoding the nibbles of the 12 bit counter accord ing to table 2 4 Example Orbit number 72310 MC2 MCI MCO dit dah sequence T 5 N Alphanumeric characters 0010 1101 0011 Nibbles table 2 4 0010110100112 72310 l MC2 16 MC1 16 MCO Resulting orbit number With the 12 bit counter and an orbit period of 97 minutes TIsat 1 can count orbits for roughly 9 months before the counter overflows 97 4096 60 24 30 9 months SSL 30 50 GST Operative Manual CHAPTER 2 SPACE SEGMENT SSL 100320_DI en Approximate Latitude position This field is included in every packet It identifies the approximate position of TIsat 1 on its circular orbit in units of 22 5 0 393rad counting from the crossing of the terminator When TIsat 1 crosses the terminator going from eclipse to sunlight a 4 bit counter rbit y 97 minutes is reset The counter is then incremented every Tax 16 6 0 minutes In angular units per every counter unit this is _ 360 16 0 22 5 0 393rad Omo MorseChar MC Morse characters encoding 4 bits for the approximate position of the satellite table 2 4 Example MC WE dit dah sequence B Morse ch
38. ted The second contains all data received and demodulated by the software The packet files are identified by a character P while a character R appended to the name of the log files identifies raw data files For the previous example SSL 44 50 GST Operative Manual CHAPTER 3 TISAT DEMODULATOR USER S MANUAL SSL 100320_DI en e the log file of the packets received for the Morse modulation would be MORSE_20100704_142059_P log while e MORSE_20100704_142059_R 1log would be the name of the logfile with raw data Log files are readable with any text editor They are formatted in three sections Header Data Termination Header The header contains the information shown in table 3 1 Parameter Value Description Version String Version of the software that generated the file type of log RAW DATA LOG PACKET LOG type of log file username string modulation MORSE PSK_NRZ AMFSK type of demodulation format selected Start logging date time stamp of the creation of the file Table 3 1 Log files header Data Raw data are written as in the raw data area number 2 in figure 3 1 Packet data are collected with the time stamp of the reception and the content of the packet Termination Contains the termination time stamp of the logging session GST Operative Manual 45 50 SSL SSL 100320_DI en CHAPTER 3 TISAT DEMODULATOR USER S MANUAL 3 2 Installation To install Tl
39. the packet type are used Checksum for Beacon Payload and Complete Packets 1 Concatenate amp the received characters in couples except for characters 1 and 12 fig 2 19 2 Decode each character in a 4 bits value according to table 2 4 3 Left pad characters 1 and 12 with zeros 4 Each couple or padded character is a byte 8 bits value The right most couple is the checksum computed on the satellite and included in the packet 5 Add all the bytes including the checksum byte modulo 256 to calculate Vi GroundCheck O byte CheckSumByte mod 256 2 6 6 Verification if GroundCheck 0 the checksum may be correct else it is wrong and the packet has to be considered corrupted 0 Calculating GroundCheck for the data of figure 2 19 yields 581 187 mod 256 768 mod 256 0 showing a correct checksum Checking for GroundCheck 0 is the same as recalculating the CheckSumByte eq 2 5 at the receiving end and looking if it is equal or not to the checksum received from the spacecraft GST Operative Manual 35 50 SSL SSL 100320_DI en CHAPTER 2 SPACE SEGMENT inie Eje sim kiu Bis Fikiu ui 10x03 0x00 0x04 i 0x9 i 0xBC i OxDE i0x0A 0xBB gogog Figure 2 19 Payload packet example checksum computation 0 amp N E amp E E amp S M amp K U amp B B amp F 0 amp K L3 224 0003 0100 0204 029A OxBC 0xDE 0x0A 58110 581 mod 256 69 CheckSumByte 256
40. us error EC bus bridge general error PCA9554 not responding 22 23 not used should always be 0 The first two bytes system status are exposed in the upper part of the table while Table 2 17 Bit mapping of the system status for PSK packets the last byte sensor status is on the lower SSL 38 50 GST Operative Manual CHAPTER 2 SPACE SEGMENT SSL 100320_DI en PSK Packets Temperature Encoding All temperatures are represented with one byte The real temperature in C can be calculated with byte 256 40 2 7 Temperature PSK Packets Voltage Encoding All voltages are represented with one byte The real voltage in V can be calculated with byte 256 40 2 1000 ee Voltage PSK Packets Current Encoding All currents are represented with one byte The real value of the current in A can be calculated with byte 256 2 1000 2 Current PSK Packets Payload Encoding The encoding of the material payload packet fig 2 17 and table 2 15 is shown in table 2 18 Each bit is associated with a material probe Reading the value 1 means that the probe is broken Material PCB 0 2mm 35um Cu soldermask protected PCB 0 8mm 35um Cu soldermask protected PCB 0 2mm 35um Cu Au coated exposed PCB 0 8mm 35um Cu Au coated exposed Bonding Wire 30um Au exposed Bonding Wire 30um Au exposed Bonding Wire 30um Au exposed Bonding Wire 30um Au
41. y to implement easy to decode is relatively resistant to noise and it is energy efficient Each Morse character in the beacon packets stays for a binary nibble of data ta ble 2 4 The encoding system for each parameter is shown in this section The data fields in the beacon packets fig 2 6 through 2 10 are 1 packet and processor ID PID 2 number of orbit orbit 3 approximate latitude position 4 temperature 5 voltage 6 payload data SSL 28 50 GST Operative Manual CHAPTER 2 SPACE SEGMENT SSL 100320_DI en Packet and Processor ID PID This field is included in every packet It identifies both the packet type 2 3 5 and the processor issuing it actually working on board PRO ID2 ID1 IDO bit3 bit0 bit 3 PRO Processor Identification 0 MSP430 1 PIC18 bit 2 0 ID2 IDO packet type identification 001 battery status 010 subsystems status 011 photovoltaic temperature 100 payload 101 complete Example PIC18 sending the Photovoltaic Temperature packet 1 0 i 1 bit3 bit0 GST Operative Manual 29 50 SSL SSL 100320_DI en CHAPTER 2 SPACE SEGMENT Number of orbit 4orbit This field is included in every packet It identifies the age of the mission in terms of the orbit number The number is incremented by every eclipse to sunlight transition detected by Tlsat 1 Orbit counting is made with a 12 bit counter sen

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