SIST EN 301 926 V1.2.1:2003

Satellite Earth Stations and Systems (SES); Radio Frequency and Modulation Standard for Telemetry, Command and Ranging (TCR) of Geostationary Communications Satellites

This EN will cover ECSS E-50 level 3 document, in cooperation with ECSS. ETSI TC SES WG on ECSS, with the help of STF 165, will produce the part of the ECSS standards concerning the communications satellites, which are part of the commercial market. ECSS will produce the part of the ECSS standards concerning mainly Space Agencies programmes. Nevertheless, for synergy reasons a common standard can be envisaged when preparing the standard.

Satelitske zemeljske postaje in sistemi (SES) - Radiofrekvenčni in modulacijski standard za telemetrijo, vodenje in merjenje oddaljenosti (TCR) geostacionarnih komunikacijskih satelitov

General Information

• Status: Published
• Publication Date: 31-Mar-2003
• ICS: 33.070.40 - Satellite
• Technical Committee: RES - Radio equipment and systems
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Apr-2003
• Due Date: 01-Apr-2003
• Completion Date: 01-Apr-2003
• Mandate: M/237
• Ref Project: ETSI EN 301 926 V1.2.1 (2002-06) - Satellite Earth Stations and Systems (SES); Radio Frequency and Modulation Standard for Telemetry, Command and Ranging (TCR) of Geostationary Communications Satellites

Standards Content (Sample)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.HRVWDFLRQDUQLKSatellite Earth Stations and Systems (SES); Radio Frequency and Modulation Standard for Telemetry, Command and Ranging (TCR) of Geostationary Communications Satellites33.070.40SatelitSatelliteICS:Ta slovenski standard je istoveten z:EN 301 926 Version 1.2.1SIST EN 301 926 V1.2.1:2003en01-april-2003SIST EN 301 926 V1.2.1:2003SLOVENSKI
STANDARD
ETSI ETSI EN 301 926 V1.2.1 (2002-06) 2
Reference DEN/SES-000-ECSS-1 Keywords control, modulation, satellite, telemetry ETSI 650 Route des Lucioles F-06921 Sophia Antipolis Cedex - FRANCE
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Important notice Individual copies of the present document can be downloaded from: http://www.etsi.org The present document may be made available in more than one electronic version or in print. In any case of existing or perceived difference in contents between such versions, the reference version is the Portable Document Format (PDF). In case of dispute, the reference shall be the printing on ETSI printers of the PDF version kept on a specific network drive within ETSI Secretariat. Users of the present document should be aware that the document may be subject to revision or change of status. Information on the current status of this and other ETSI documents is available at http://portal.etsi.org/tb/status/status.asp If you find errors in the present document, send your comment to: [e-mail] Copyright Notification No part may be reproduced except as authorized by written permission. The copyright and the foregoing restriction extend to reproduction in all media.
© European Telecommunications Standards Institute 2002. All rights reserved.
DECTTM, PLUGTESTSTM and UMTSTM are Trade Marks of ETSI registered for the benefit of its Members. TIPHONTM and the TIPHON logo are Trade Marks currently being registered by ETSI for the benefit of its Members. 3GPPTM is a Trade Mark of ETSI registered for the benefit of its Members and of the 3GPP Organizational Partners. SIST EN 301 926 V1.2.1:2003

ETSI ETSI EN 301 926 V1.2.1 (2002-06) 3
Contents Intellectual Property Rights.5 Foreword.5 1 Scope.6 2 References.6 3 Definitions and abbreviations.7 3.1 Definitions.7 3.2 Abbreviations.8 4 Applicability.9 5 Modulation requirements.10 5.1 General.10 5.2 Standard modulation.11 5.2.1 Modulating waveforms.11 5.2.2 PCM waveforms and symbol rates.12 5.2.3 Use of subcarriers.13 5.2.4 Choice of subcarrier frequencies.13 5.2.5 Uplink carrier deviation (Frequency Modulation).14 5.2.6 Downlink PM modulation index.14 5.2.7 PM sense of modulation.14 5.3 Spread spectrum modulation.14 5.3.1 General.14 5.3.2 Chip shaping.15 5.4 Coherency properties.16 5.4.1 FEC channel coding.16 6 Requirements on transmitted signals.16 6.1 Frequency stability requirements.16 6.1.1 Uplink.16 6.1.2 Downlink.16 6.2 Turnaround frequency ratio.16 6.3 Polarization.17 6.4 Phase noise.17 7 Link acquisition requirements.17 Annex A (informative): Operational configuration.18 A.1 Configuration 1: on board dual mode receiver and on board dual mode transmitter.19 A.2 Configuration 2: on board dual mode receiver and standard transmitter.20 A.3 Configuration 3: on board dual mode receiver, standard transmitter and dedicated RG SS transmitter.21 Annex B (informative): Hybrid Ranging process description.23 B.1 Presentation.23 B.2 Distance ambiguity resolution.24 B.3 Calibration.25 Annex C (informative): Modulator imperfections.26 C.1 Phase imbalance.26 C.2 BPSK phase imbalance.26 C.3 QPSK phase imbalance.26 SIST EN 301 926 V1.2.1:2003

ETSI ETSI EN 301 926 V1.2.1 (2002-06) 4
C.4 Amplitude imbalance.27 C.5 Data asymmetry.27 C.6 Data bit jitter.27 C.7 PN code asymmetry.27 C.8 PN code chip jitter.27 C.9 Chip transition time.28 C.10 I/Q data bit skew.28 C.11 I/Q PN code chip skew.28 Annex D (informative): SRRC chip filtering.29 Annex E (normative): PN code allocation, assignment and generation.31 E.1 PN code allocation.31 E.2 PN code assignment.31 E.3 PN code generation.31 E.3.1 Telecommand uplink or in-phase channel (Mode MTC2).31 E.3.2 Ranging uplink or quadrature channel (Mode MTC2).32 E.4 Telemetry Downlink.32 E.4.1 Coherent ranging mode (Mode MTM2).32 E.4.2 Non coherent mode (Mode MTM3).33 E.5 PN code libraries.34 Annex F (informative): Performance computations.38 Annex G (informative): FEC coding example.39 Annex H (informative): Bandwidth considerations and assumptions.40 Annex I (informative): Void.41 Annex J (informative): Modulation implementation.42 Annex K (informative): Bibliography.43 History.44
ETSI ETSI EN 301 926 V1.2.1 (2002-06) 5
Intellectual Property Rights IPRs essential or potentially essential to the present document may have been declared to ETSI. The information pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web server (http://webapp.etsi.org/IPR/home.asp). Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become, essential to the present document. Foreword This European Standard (Telecommunications series) has been produced by ETSI Technical Committee Satellite Earth Stations and Systems (SES). The contents of the present document are subject to continuing work within TC-SES and may change following formal TC-SES approval. Should TC-SES modify the contents of the present document it will then be republished by ETSI with an identifying change of release date and an increase in version number as follows: Version 1.m.n Where: - the third digit (n) is incremented when editorial only changes have been incorporated in the specification; - the second digit (m) is incremented for all other types of changes, i.e. technical enhancements, corrections, updates, etc.
National transposition dates Date of adoption of this EN: 14 June 2002 Date of latest announcement of this EN (doa): 30 September 2002 Date of latest publication of new National Standard or endorsement of this EN (dop/e):
31 March 2003 Date of withdrawal of any conflicting National Standard (dow): 31 March 2003
ETSI ETSI EN 301 926 V1.2.1 (2002-06) 6
1 Scope The present document applies to Telemetry, Command and Ranging (TCR) systems operating typically in the following bands: • 5 850 MHz; 6 725 MHz uplink; 3 400 MHz; 4 200 MHz downlink; • 12 750 MHz; 14 800 MHz and 17 300 MHz; 18 100 MHz uplink; 10 700 MHz; 12 750 MHz downlink; for Geostationary Communications Satellites. The present document sets out the minimum performance requirements and technical characteristics of the ground/satellite Radio Frequency (RF) interface partially based on Spread Spectrum Multiple Access (SSMA). With the growing number of satellites, the co-location constraints and the maximization of bandwidth for Communications Missions, and interference has motivated the elaboration of the present document for geostationary satellites based on Spread Spectrum techniques. The present document addresses the following applications: • Telemetry; • Command (Telecommand); • Ranging. Currently, no RF and Modulation standard exists for the TCR of geostationary communication satellites. The aim of the present document is to respond to such requirements. There are consequently similarities with existing agency standards, such as those listed in annex I, although some specifics have been introduced to respond to the requirement of multiple access for collocated geostationary communication satellites. 2 References The following documents contain provisions which, through reference in this text, constitute provisions of the present document. • References are either specific (identified by date of publication and/or edition number or version number) or non-specific. • For a specific reference, subsequent revisions do not apply. • For a non-specific reference, the latest version applies. [1] ETSI TR 101 956: "Satellite Earth Stations and Systems (SES); Technical analysis of Spread Spectrum Solutions for Telemetry Command and Ranging (TCR) of Geostationary Communications Satellites". SIST EN 301 926 V1.2.1:2003

ETSI ETSI EN 301 926 V1.2.1 (2002-06) 7
3 Definitions and abbreviations 3.1 Definitions For the purposes of the present document, the following terms and definitions apply: binary channel: binary communications channel (BPSK has 1 channel, QPSK has 2 channels) Spread Spectrum Multiple Access (SSMA)(== Code Division Multiple Access (CDMA)): modulation of a carrier by a code sequence, with association of a code to each user data rate: total number of uncoded data bits per second after packet and frame encoding NOTE: See figures 1 and 2. This is the Data Rate used in Link Budgets in [1]. symbol rate: rate of binary elements, considered on a single wire, after FEC coding NOTE: See figures 1 and 2. channel symbol rate: rate of binary elements, considered on a single wire, after FEC coding and channel allocation NOTE: See figure 2. This applies only to multi-channel modulations, thus to spread spectrum QPSK modes and not to standard PM/FM modes. Co-located Equivalent Capacity (CEC): number of collocated satellites that can be controlled with a perfect power balanced link between the ground and the satellite PACKET ENCODING (BLOCK CODE, INTERLEAVE ETC)FECCODING(EG CONV)WAVEFORMFORMATTING(EG NRZ-L)FM or PMMODULATIONRNGTMRF CARRIERRANGING TONESBPSKMODULATIONSUBCARRIERDATA SOURCEDATA RATESYMBOL RATESCOPE OF THE PRESENT DOCUMENTOPTIONAL Figure 1: Functional stages of transmit chain for standard modulation SIST EN 301 926 V1.2.1:2003

ETSI ETSI EN 301 926 V1.2.1 (2002-06) 8
PACKET ENCODING (BLOCK CODE, INTERLEAVE ETC)FECCODING(EG CONV)WAVEFORMFORMATTING(EG NRZ-L)OQPSKRF CARRIERALLOCATIONOF SYMBOLSTO CHANNELSDATA SOURCEDATA RATESYMBOL RATESCOPE OF THE PRESENT DOCUMENTI CH. BPSKMODULATIONQ CH. BPSKMODULATION+I CHANNEL PN CODEQ CHANNEL PN CODECHANNEL SYMBOL RATEOPTIONAL Figure 2: Functional stages of transmission chain for spread spectrum modulation 3.2 Abbreviations For the purposes of the present document, the following abbreviations apply: BPSK Binary Phase Shift Keying CDMA Code Division Multiple Access CEC Co-located Equivalent Capacity COM COMmunication channel CW Continuous Wave DSSS Direct Sequence Spread Spectrum DRSS Data Relay Satellite System (ESA) DRTS Data Relay and Tracking System (NASDA) ECSS European Co-operation for Space Standardization ESA European Space Agency FEC Forward Error Correction FM Frequency Modulation GTO Geostationary Transfer Orbit HPA High Power Amplifier LEOP Launch and Early Orbit Phase MTC1 TeleCommand Mode 1 MTC2 TeleCommand Mode 2 MTM1 TeleMetry Mode 1 MTM2 TeleMetry Mode 2 MTM3 TeleMetry Mode 3 NASA National Aeronautics and Space Administration (USA) NASDA National Astronautics and Space Development Administration (Japan) NRZ-L Non Return to Zero-Level NRZ-M Non Return to Zero-Mark OQPSK Offset Quaternary Phase Shift Keying PCM Pulse Coded Modulation PDF Probability Density Function PM Phase Modulation PN Pseudo Noise SIST EN 301 926 V1.2.1:2003

ETSI ETSI EN 301 926 V1.2.1 (2002-06) 9
PSD Power Spectral Density QPSK Quaternary Phase Shift Keying RF Radio Frequency RG RanGing SP-L Split Phase-Level (alias Bi-Φ -Level or Manchester encoded) SRRC Square Root Raised Cosine SS Spread Spectrum SSMA Spread Spectrum Multiple Access STD STanDard (for standard modulation) TC TeleCommand TCR Telemetry, Command and Ranging TDRSS Tracking and Data Relay Satellite System (NASA) TM TeleMetry TTC/TT&C Telemetry Tracking and Command (== Telemetry, Command and Ranging, TCR) UQPSK Unbalanced Quaternary Phase Shift Keying w.r.t with respect to 4 Applicability The present document applies to the typical TCR scenario shown in figure 3. The scenario comprises k satellites, which may be co-located on the same orbital position. Each satellite also goes through other mission phases like LEOP, drift and possibly emergency mode. These satellites may be controlled/monitored by N different TCR Ground Stations. The TCR links defined in the present document have to coexist with the Communication ground terminals and associated links also shown in figure 3. The present document defines the modulation on the TCR links. Modulation formats are described in clause 5 and the associated mission phases are described in annex A. COMMS TRAFIC1NTCRGROUNDTERMINALSSPACE SEGMENT:GTO, DRIFT ORCO-LOCATED SATELLITES1N’TCRGROUNDTERMINALSCOMMS TRAFICTC AND RANGINGTM AND RANGINGGROUND SEGMENTGROUND SEGMENTCOMMSTERMINALSCOMMSTERMINALSSatellite 1Satellite 2Satellite N Figure 3: Typical applicable scenario SIST EN 301 926 V1.2.1:2003

ETSI ETSI EN 301 926 V1.2.1 (2002-06) 10 5 Modulation requirements 5.1 General The generic system functional block diagram is shown in figure 4. Modulation modes and configurations are shown in table 1. TC DATACONDITIONINGSTANDARDMODE TC TxDSSSMODE TxSTD MODETC RxDSSS MODETC RxSTD MODETM TxDSSS MODETM TxRANGINGSUB SYSTEMSTANDARDMODE TC RxDSSSMODE RxTM DATACONDITIONINGTCTMTMTMTCTCGROUND SEGMENTSPACE SEGMENTPN code to RG tone processingRG toneRG PN code Figure 4: Generic system functional block diagram Table 1: Modulation modes and potential configurations
All standard mode All spread mode Hybrid mode Uplink MTC1: PCM/BPSK/FM MTC2: PCM/SRRC-UQPSK MTC2: PCM/SRRC-UQPSK Downlink (with ranging (see note): requires uplink present) MTM1: PCM/BPSK/PM MTM2: PCM/SRRC-OQPSK (PN code clock/epoch sync to uplink clock/epoch) MTM1: PCM/BPSK/PM Downlink (without ranging: can operate without uplink present)) MTM1: PCM/BPSK/PM MTM3: PCM/SRRC-OQPSK (PN code clock/epoch independent of uplink clock/epoch) MTM1: PCM/BPSK/PM NOTE: Further definition of ranging signals is given in following clauses.
In order to retain backward compatibility with existing ground networks and to allow simple operation during LEOP, in addition to the new Spread Spectrum modes, the existing "standard" FM/PM modulation modes are retained. It is envisaged that telecommand and telemetry modulation formats shall be independently configurable, allowing for example the following configuration possibilities (see also annex A for implementations and TR 101 956 [1]): •
all standard mode (as has existed in previous systems) using tone ranging on FM uplink (MTC1) and PM (MTM1) downlink; •
all spread mode (Direct Sequence Spread Spectrum: DSSS) using PN spreading code regenerative ranging on suppressed carrier up-and down-links (MTC2 and MTM2); •
hybrid mode using PN spreading code ranging on suppressed carrier DSSS uplink (MTC2), and tone ranging on PM downlink (MTM1). SIST EN 301 926 V1.2.1:2003

ETSI ETSI EN 301 926 V1.2.1 (2002-06) 11 In addition, on the spread spectrum (DSSS) mode downlink, there are 2 PN code sets defined, for coherent and non-coherent modes (modes MTM2 and MTM3 respectively). The physical partitioning of the functions may not exactly follow that shown in the system functional block diagram. The modulation configuration of the various modes is described in the rest of clause 5. Possible allocation of modes to mission phases is defined in annex A. 5.2 Standard modulation The Standard mode modulation formats shall be Frequency Modulation (FM) on Telecommand uplink and Phase Modulation (PM) on Telemetry downlink. The standard modes shall be known as MTC1 and MTM1 respectively. 5.2.1 Modulating waveforms The following modulating waveforms are permitted in standard modes: • Telemetry (mode MTM1): a sine wave sub carrier, itself BPSK modulated by PCM data; • Telecommand (mode MTC1): a sine wave subcarrier, itself BPSK modulated by PCM data; • Ranging (mode MTC1 + MTM1): an unmodulated sinewave subcarrier or combination of a number of such subcarriers. SIST EN 301 926 V1.2.1:2003

ETSI ETSI EN 301 926 V1.2.1 (2002-06) 12 5.2.2 PCM waveforms and symbol rates The PCM waveform formatting is defined in figure 5:
NRZ-L level A signifies symbol "1"
level B signifies symbol "0" SP-L level A during the first half-symbol followed by
level B during the second half-symbol signifies symbol "1"
level B during the first half-symbol followed by
level A during the second half-symbol signifies symbol "0" NRZ-M level change from A to B or B to A signifies symbol "1"
no change in level signifies symbol "0"
Figure 5: PCM waveforms formatting PCM data signals shall be limited to the waveforms and symbol rates given in table 2. Table 2: PCM waveforms and rates Function Symbol rate (symbols/s) PCM waveform Special requirements Telecommand (Mode MTC1) Between 8 sym/s up to 4 000 sym/s (see note) NRZ-L NRZ-M
Telemetry (Mode MTM1) Between 64 sym/s up to 20 ksym/s (see note) NRZ-L NRZ-M SP-L
NOTE: Coherency between symbols and sub-carrier is required.
ETSI ETSI EN 301 926 V1.2.1 (2002-06) 13 5.2.3 Use of subcarriers The subcarriers and modulating waveforms that shall be used are listed in table 3. Table 3: Subcarriers used with FM Or PM Rf carriers Function Subcarrier (kHz) Modulation waveform Subcarrier waveform Telecommand (Mode MTC1)
8 or 16 NRZ-L NRZ-M Sine Telemetry (Mode MTM1) 0,1 to 1 000 NRZ-L NRZ-M SP-L Sine Ranging (Mode MTM1 + MTC1) 0,1 to 100 None (CW Tone) Sine
5.2.4 Choice of subcarrier frequencies For telecommand transmission using a subcarrier, only two subcarrier frequencies are permitted. The subcarrier frequency shall be 8 kHz for all telecommand rates up to 2 000 sym/s. A 16 kHz subcarrier shall be used only in cases where the 4 000 sym/s symbol rate is needed or when required by the operator. The choice of the ranging and telemetry subcarrier frequencies shall take into account the requirements of: • carrier acquisition by the ground receivers; • compatibility between ranging and telemetry; • occupied bandwidth. Modulation of subcarriers used for telemetry and telecommand shall be BPSK (for ranging the subcarriers are unmodulated tones).
The following requirements shall be met for TC and TM subcarriers: • for NRZ-L and NRZ-M signal waveforms, the subcarrier frequency shall be a multiple (integer) of the symbol rate from 4 to 1 024; •
for SP-L signal waveforms, the subcarrier frequency shall be an even integer multiple of the symbol rate from 4 to 1 024; •
at each transition in the PCM formatted waveform, the subcarrier shall be reversed in phase; •
the transitions in the PCM formatted waveform shall coincide with a subcarrier zero crossing to within ±2,5 % of a subcarrier period; •
at all times, for more than 25 % of a subcarrier period after a phase reversal, the phase of the modulated subcarrier shall be within ±5° of that of a perfect BPSK signal; • for NRZ-L and SP-L waveforms, the beginning of the symbol intervals shall coincide with a positive-going subcarrier zero crossing for symbols "1" and with a negative-going zero crossing for symbols "0"; • for NRZ-M waveforms, the beginning of the symbol intervals shall coincide with a subcarrier zero crossing. SIST EN 301 926 V1.2.1:2003

ETSI ETSI EN 301 926 V1.2.1 (2002-06) 14 5.2.5 Uplink carrier deviation (Frequency Modulation) The FM deviation (modulation depth) is stated in table 4. Table 4: FM uplink frequency deviation Function Deviation (kHz) Telecommand (PCM/BPSK/FM) (Mode MTC1) Up to ±400 kHz Ranging Earth-to-space (FM) (Mode MTC1) (total deviation of all simultaneous major and minor tones) Up to ±400 kHz
5.2.6 Downlink PM modulation index Minima and maxima of the modulation index are stated in table 5. Table 5: PM modulation index Function Min.
(radians peak) Max.
(radians peak) Telemetry (PCM/BPSK/PM) (Mode MTM1) 0,1 1,5 Ranging space-to-Earth (PM) (Mode MTM1) 0,01 1,5
5.2.7 PM sense of modulation A positive-going video signal (modulated TM subcarrier and/or ranging) shall result in an advance of the phase of the downlink Radio Frequency carrier. 5.3 Spread spectrum modulation 5.3.1 General The spread modulation formats shall be: •
Telecommand Uplink: Square Root Raised Cosine filtered Unbalanced QPSK (SRRC-UQPSK); •
Telemetry Downlink: SRRC filtered Offset QPSK (SRRC-OQPSK). The spread modulation modes shall be as follows: •
Mode MTC2: spread spectrum telecommand uplink; •
Mode MTM2: spread spectrum telemetry downlink, coherent mode (long PN code); •
Mode MTM3: spread spectrum telemetry downlink, non-coherent mode (short PN code). The Spread Spectrum modulation characteristics shall be as defined in table 6. The modulation modes listed shall be available for communications between the Spacecraft and the Earth Terminal for a range of data rates. Symbol rates referred to in the present document include the channel coding overhead whenever channel coding is applied. The Symbol rate shall be selected depending on requirements, link budget and multiple access capabilities. Modulator imperfections are defined in annex C. SIST EN 301 926 V1.2.1:2003

ETSI ETSI EN 301 926 V1.2.1 (2002-06) 15 Table 6: Spread spectrum link modulation modes
Telecommand link, Mode MTC2 Coherent telemetry link, Mode MTM2 Non-coherent telemetry link, Mode MTM3 Symbol Rate 4 000/2n n=0,1.9 2n n=6.14 2n n=6.14 Channel Symbol rate on I channel (sym/s) =Symbol Rate =Symbol Rate (Same symbols on both channels) =Symbol Rate (Same symbols on both channels) Channel Symbol rate on Q channel (sym/s) PN code only =I channel symbol rate (Same symbols on both channels) =I channel symbol rate (Same symbols on both channels) Data format NRZ-L
NRZ-M NRZ-L
NRZ-M NRZ-L NRZ-M PN code family I channel Gold code Truncated m-sequence Gold code PN Code length I channel 210-1 (210-1) × 256 211-1 Code I epoch reference None Received Q code of MTC2 None
PN code family Q channel Truncated m-sequence Truncated m-sequence
Gold code PN Code length Q channel (210-1) × 256 (210-1) × 256 211-1 Code Q epoch reference I code x + 1/2 chips (x > 20 000) Delay w.r.t I ch of MTM2 1/2 chip delay w.r.t I of non-coherent mode return link Spreading code rate (Mc/s) 1 Mchip/s or 3 Mchip/s Identical to Received code 1 Mchip/s or 3 Mchip/s Modulation SRRC-UQPSK SRRC-OQPSK SRRC-OQPSK I/Q power ratio 10:1 1:1 1:1 Ranging service possible Yes Yes No
The Telecommand uplink signal in mode MTC2 shall be a spread spectrum SRRC-UQPSK modulated signal with the data and a short PN code on the I Channel and a long PN code on the Q channel. It has Square Root Raised Cosine (SRRC) chip shaping. The coherent mode telemetry downlink signal in mode MTM2 shall be a spread spectrum SRRC-OQPSK modulated signal with data on the Q channel and on the I channel. MTM2 supports ranging by transmission of a long PN code on the downlink I channel synchronized to the code received on the mode MTC2 uplink Q channel. A delayed version of this code is transmitted on the downlink Q channel. Mode MTM3 shall be a spread spectrum SRRC-OQPSK modulated signal with the data on the Q channel and on the I channel. MTM3 does not support ranging. A short (Gold) PN code is transmitted on the I channel and a half chip delayed Gold code is transmitted on the Q channel. For all spread PN coded transmissions, the data shall be modulo-2 added asynchronously to the PN code and any pulse shaping (i.e. SRRC) performed before being applied to the carrier modulator. 5.3.2 Chip shaping SRRC Square Root Raised Cosine pulse or chip shaping shall be applied, in order to achieve bandwidth restriction of the transmitted spread spectrum signal. SRRC filtering is defined in terms of a roll off factor α which has a value between 0 and 1, with the RF bandwidth of the spread spectrum signal given by (1 + α)Rc, where Rc is the chip rate.
For the purposes of the present document α = 0,5 shall be used, giving an RF bandwidth of 1,5 Rc. SIST EN 301 926 V1.2.1:2003

ETSI ETSI EN 301 926 V1.2.1 (2002-06) 16 5.4 Coherency properties In mode MTM1 and MTC1, coherency between symbol rate and sub-carrier is required. In non-coherent spread mode (MTM3), all of the clocks/carriers shall be derived from references local to the spacecraft and independent of the uplink: downlink RF carrier, TM data clock, PN chip clock and PN Epoch shall be local to the spacecraft. In coherent spread mode (MTM2), the downlink PN code Epoch and chip clock shall be synchronized to the uplink Q channel PN code. However, other downlink clocks/carriers may be local to the spacecraft and independent of the uplink: downlink RF carrier and TM data shall be local to the spacecraft. 5.4.1 FEC channel coding In order to achieve all requirements for the present document (see [1], annex B), following the analysis documented in [1], it has been concluded that a minimum FEC coding gain of up to 5 dB may be required in spread spectrum modes on both Telecommand and Telemetry links. Selection of FEC code type is outside the scope of the present document. An example of a coding scheme that can achieve such gain is documented in annex G. 6 Requirements on transmitted signals 6.1 Frequency stability requirements 6.1.1 Uplink In mode MTC2 (spread spectrum), the on-board receiver shall tolerate: •
A frequency shift due to Doppler effect of 1,4 ppm (for RF carrier, chip rate and data rate); •
A ratio FrequencyrateDoppler of 1,2 × 10-9 Hz (for RF carrier, chip rate and data rate). In mode MTC1 (FM), the on-board receiver shall tolerate: •
A frequency shift due to Doppler effect of 22 ppm (for RF carrier, subcarrier and data rate); •
A ratio FrequencyrateDoppler of 1,7 × 10-6 Hz (for RF carrier, subcarrier and data rate). The ground contribution to those deviations shall be negligible. 6.1.2 Downlink The Doppler values to take into account for the downlink shall be identical to uplink. The stability of the on-board generated RF frequency (for modes MTM1 or MTM2) shall be better than 5 ppm (end of life). The stability of the on-board generated downlink chip rate (for mode MTM3) shall be better than 5 ppm (end of life). 6.2 Turnaround frequency ratio No turnaround frequency ratio is required between the up and down RF links, since there shall be no coherency between uplink and downlink carriers. SIST EN 301 926 V1.2.1:2003

ETSI ETSI EN 301 926 V1.2.1 (2002-06) 17 6.3 Polarization Polarization is operator and mission phase dependent, and its definition is beyond the scope of the present document. 6.4 Phase noise The single-sided (2 L(f)) phase noise measured on a unmodulated carrier between 10 Hz and 100 kHz around the carrier shall be less than: Table 7 Frequency w.r.t. the carrier (Hz) Phase Noise power density (dBc/Hz) 10 -35 100 -63 1 000 -63 10 000 -72 100 000 -105
7 Link acquisition requirements The acquisition time of the uplink signal shall be less than 3 s, with a success probability greater than 99 %. For the downlink, the acquisition time of the downlink signal shall be less than 10 s, with a success probability greater than 99 %. In Modes MTC2, MTM2 and MTM3, the maximum Doppler that can be acquired without precompensation is specified in clause 6. For mission phases where Doppler is greater than this amount, either Standard Mode (MTC1/MTM1) shall be used, or Doppler precompensation shall be used to reduce the uncertainty below that specified in clause 6. In Mode MTM2, a long (truncated m-sequence) PN code is used, of length 256 × 1 023 chips. In order for the Ground demodulator to acquire this code, epoch estimation is required. This estimation shall be within ±1 000 chips, as used on Agency Data Relay Systems. SIST EN 301 926 V1.2.1:2003

ETSI ETSI EN 301 926 V1.2.1 (2002-06) 18 Annex A (informative): Operational configuration Communications satellites face different radio-frequency environments, depending on mission phase. There are 4 main different mission phases to consider: LEOP phase, drift orbit, nominal on station phase and emergency on station phase. Depending of the on-board implementation of the standard, spread spectrum or standard modulation can be used for uplink or downlink. The aim of this annex is to describe the operational configuration of three different possible implementations of the present document. These three configurations are: •
Configuration 1: on board dual mode receiver and on board dual mode transmitter; •
Configuration 2: on board dual mode receiver and standard transmitter; •
Configuration 3: on board dual mode receiver, standard transmitter and dedicated RG SS transmitter. A typical frequency plan is shown in figure A.1.
36 MHz channels with center frequency separation of 40,00 MHz UPLINK : (13,7 GHz to 14,5 GHz) Vertical polarisation KE2S KE4S KE6S KE10S KE12S K2S K4S K10S K20S K22S TC frequency bandwidth f1, f1', f2 DOWNLINK : (11,4 GHz to 12,2 GHz) Vertical polarisation 11,4 GHz 11,7 GHz KE2S KE4S KE6S KE10S KE12S K2S K4S K10S K20S K22S TM SS modulation TM STD modulation frequency bandwidth frequency bandwidth f2, f'2 f1
Figure A.1: Typical TCR frequency plan (Ku-Band) This frequency plan defines various TCR frequencies, but depending of the implementation, some of the frequencies are not used. It has been assumed for the analysis of SS modes (see [1]) that any TC-echo effect on the TM signal is negligible. Uplink: • f2 is the SS frequency; • f1 and f1' are in the same bandwidth as f2. Downlink: • f1 is the SS frequency; • f2 and f2' are the STD modulation frequencies, in a different bandwidth than the SS bandwidth. For each configuration below, the modulation mode (MTC1, MTC2, MTM1, MTM2, MTM3) refers to the definition given in clause 5. SIST EN 301 926 V1.2.1:2003

ETSI ETSI EN 301 926 V1.2.1 (2002-06) 19 A.1 Configuration 1: on board dual mode receiver and on board dual mode transmitter On board the satellite, a dual mode receiver shall be used, enabling the demodulation of either spread spectrum or standard modulation signal (both demodulations are done in parallel but only one is successful, depending of the modulation of the uplink signal). Dual mode transmitters (or two different transmitters, one for STD and one for SS modulation) are used for the downlink. The receiver and the transmitter simultaneously use spread spectrum in Spread Spectrum mode, and simultaneously use standard modulation in Standard Mode.
TM omni (+Z) TM omni
(-Z) TC TC TM RG RG TC omni (+Z) TC omni
(-Z) TWTA s P/L
3 dB Rx coupler 3 dB Tx coupler RHCP RHCP LHCP LHCP RHCP RHCP LHCP LHCP
dual mode command receiver TM RG RG from P/L path global horn Coaxial links Waveguide links SS Tx f1 code 1 SS Tx f1 code 2 STD Tx f2 STD Tx f2' data handling (CDMU) TM
dual mode command receiver standard F1 SS F2 standard F1' SS F2 2 additional CW beacons can also be added to provide CW signal for Ground station tracking
LHCP
Figure A.2: Configuration 1 typical TCR/RF architecture The associated on-board TCR/RF architecture is shown in figure A.2. The different operational configurations and the associated bandwidth are described in table A.1. Table A.1: Configuration 1 frequency and modulation assignment
Beginning of the LEOP
LEOP, apogee phase (low Doppler, possibility of jamming with Geo satellites) Drift orbit (low Doppler, possibility of jamming with Geo satellites) On station nominal On station emergency TC STD (MTC1), F1 or F'1
SS (MTC2), F2 SS (MTC2), F2 SS (MTC2), F2 STD (MTC1), F1 or F'1 TM STD (MTM1), f2 or/and f'2 SS (MTM2 or 3), f1 SS (MTM2 or 3), f1 SS (MTM2 or 3), f1 STD (MTM1), f2 or/and f'2 RG Same as TC/TM (see note 1) Same as TC/TM (see note 2) Same as TC/TM (see note 2) Same as TC/TM (see note 2) Same as TC/TM (see note 1) NOTE 1: TC and RG can be done simultaneously, depending of RF link budget margin and compatibility between RG tones and TC sub-carrier. NOTE 2: TC and RG can be done simultaneously.
ETSI ETSI EN 301 926 V1.2.1 (2002-06) 20 Note that for the emergency: • it may be necessary to command sequentially each satellite of a fleet of collocated satellites using the same bandwidth; • it may be necessary to foresee for the downlink an additional bandwidth ("emergency bandwidth"), distinct from the nominal TM bandwidth. A.2 Configuration 2: on board dual mode receiver and standard transmitter On board the satellite, a dual mode receiver shall be used, enabling the demodulation of either spread spectrum or standard modulation signal (both demodulations are done in parallel but only one is successful, depending of the modulation of the uplink signal). Standard transmitters are used for the downlink, whatever the mission phase of the satellites. A specific process (see annex B) enables the transformation of a PN code into a RG tone, so that for certain mission phases, SS modulation can be used for the uplink (including RG) while STD modulation is used for the downlink.
TM omni (+Z) TM omni
(-Z) TC TC TM RG RG TC omni (+Z) TC omni
(-Z) TWTA s P/L
3 dB Rx coupler 3 dB Tx coupler RHCP RHCP LHCP LHCP RHCP RHCP LHCP LHCP
dual mode command receiver TM RG RG from P/L path global horn Coaxial links Waveguide links STD Tx f2 STD Tx f2' data handling (CDMU) TM
dual mode command receiver standard F1 SS F2 standard F1' SS F2
Figure A.3: Configuration 2 typical TCR/RF architecture The associated on-board TCR/RF architecture is presented in figure A.3. The different operational configurations and the associated bandwidth are described in table A.2. SIST EN 301 926 V1.2.1:2003

ETSI ETSI EN 301 926 V1.2.1 (2002-06) 21 Table A.2: Configuration 2 frequency and modulation assignment
Beginning of the LEOP
LEOP, apogee phase (low Doppler, possibility of jamming with Geo satellites) Drift orbit (low Doppler, possibility of jamming with Geo satellites) On station nominal On station emergency TC STD (MTC1), F1 or F'1 SS (MTC2), F2 SS (MTC2), F2 SS (MTC2), F2 SS (MTC2), F2 TM STD (MTM1), f2 or/and f'2 STD (MTM1), f2 or/and f'2 STD (MTM1), f2 or/and f'2 STD (MTM1), f2 or/and f'2 STD (MTM1), f2 or/and f'2 RG Same as TC/TM (see note 1) Same as TC/TM (hybrid RG) (see note 2) Same as TC/TM (hybrid RG) (see note 2) Same as TC/TM (hybrid RG) (see note 2) Same as TC/TM (hybrid RG) (see note 2) NOTE 1: TC and RG can be done simultaneously, depending of RF link budget margin and compatibility between RG tones and TC sub-carrier. NOTE 2: TC and RG can be done simultaneously.
Note that for the emergency: • it may be necessary to command sequentially each satellite of a fleet of collocated satellites using the same bandwidth; • no additional bandwidth ("emergency bandwidth") is required for the emergency downlink. A.3 Configuration 3: on board dual mode receiver, standard transmitter and dedicated RG SS transmitter On board the satellite, a dual mode receiver shall be used, enabling the demodulation of either spread spectrum or standard modulation signal (both demodulations are done in parallel but only one is successful, depending of the modulation of the uplink signal). Standard transmitters are used for the downlink TM, whatever the mission phase of the satellites. Concerning the RG, a dedicated SS transmitter is used each time SS RG is used for the uplink.
TM omni (+Z) TM omni
(-Z) TC TC TM RG RG TC omni (+Z) TC omni
(-Z) TWTA s P/L
3 dB Rx couple3 dB Tx coupleRHCP RHCP LHCP LHCP RHCP RHCP LHCP LHCP
dual commareceivTM RG RG from P/L patglobahorn Coaxial Waveguide SS RG Tx f1 code 1 SS RG Tx f1 code 2 STD TM Tx f2 STD TM Tx f2' data handling (CDMU) TM
dual commareceivstandard F1 SS F2 standard F1' SS F2
Figure A.4: Configuration 3 typical TCR/RF architecture The associated on-board TCR/RF architecture is presented in figure A.4. SIST EN 301 926 V1.2.1:2003

ETSI ETSI EN 301 926 V1.2.1 (2002-06) 22 The different operational configurations and the associated bandwidth are described in table A.3. Table A.3: Configuration 3 frequency and modulation assignment
Beginning of the LEOP
LEOP, apogee phase (low Doppler, possibility of jamming with Geo satellites) Drift orbit (low Doppler, possibility of jamming with Geo satellites) On station nominal On station emergency TC STD (MTC1), F1 or F'1 SS (MTC2), F2 SS (MTC2), F2 SS (MTC2), F2 SS (MTC2), F2 TM STD (MTM1), f2 or/and f'2 STD (MTM1), f2 or/and f'2 STD (MTM1), f2 or/and f'2 STD (MTM1), f2 or/and f'2 STD (MTM1), f2 or/and f'2 RG Same as TC/TM (see note 1) SS up F2, SS
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