Télémesure-Télécommande [Mode de compatibilité].pdf

Pr. A. Addaim
Telemetry, Tracking Command Subsystem
 Introduction to TM, TC and Tracking
 Communication Protocol concept
Communication Protocol concept
 CCSDS Protocol Presentation
 CCSDS Recommandation : TELECOMMAND
Packet
Packet
 CCSDS Recommandation : TELEMETRY
P k
Packet

Pr. A. Addaim
UIR/SAE
Different flight altitude of a TT&C system

Pr. A. Addaim
UIR/SAE Telemetry, Tracking Command Subsystem
Introduction to TM, TC and Tracking
 Telemetry, Tracking Command Subsystem functions allow dialog between
the satellite and the ground stations using the following functions:
Telemetry = TM
T l d TC
Telecommand = TC
Measure of distance = TR
 The TELEMETRY allows the knowledge of the satellite state (platform and
g (p
payload). It transmits the thermal, electric and mechanical parameters
 The TELECOMMAND allows the modification of the satellite state.
 The TRACKING allows the knowledge of the position of the satellite in space.
It can be carried out by measurement of travel time (information of radial
distance satellite/station), by Doppler measurement, or angular measurement
.

Pr. A. Addaim
TM/TC link
 The TM/TC link consists of the transmission of Telecommand from Earth to the
satellite including instructions intended to be carried out on board the satellite and the
transmission of the telemetry from the satellite to Earth including data information
transmission of the telemetry from the satellite to Earth including data information
about the health of the satellite.
The TM/TC link must be established very reliably during all phases of the life of a
satellite e can globall disting ish fo r phases
satellite; we can globally distinguish four phases:
 Launch phase, which corresponds to the period from injection by the launcher
until the final position of the satellite is reached;
 Station-Keeping phase, which corresponds to the nominal operating phase of
the satellite;
 Safe mode phase, which corresponds to a failure or detection of operating
conditions considered dangerously out of the normal range;
 Deactivation or deorbitation phase, during which the satellite is sent into a so-
called Graveyard orbit.
.

Pr. A. Addaim
The TM, TC and Tracking System
 It consists of two fundamental segments
 Segment Ground
 Space segment
 Space segment
 The ground segment uses the national networks of ground stations deployed
worldwide
 The space segment included the whole Embedded equipments in direct interface
 The space segment included the whole Embedded equipments in direct interface
with the ground stations
 On board satellite, we find:
 Antennas of emission/receiving
 Receiving transmitter or transponder
 Decoder of Telecommand
 E d f T l t
 Encoder of Telemetry

Pr. A. Addaim
 For the LEO or MEO satellites in orbit, the following frequencies can be used
(service of space operations):
The frequencies for TM, TC and Tracking
(service of space operations):
SPACE > EARTHdownlink
 137-138 MHZ
 137 138 MHZ
 272-273 MHZ
 401-402 MHZ
 1525-1535 MHZ
5 5 535
 2200-2290 MHz
EARTH > SPACE uplink
p
 148-149 MHZ
 449.75-450.25 MHZ
 1427-1429 MHZ
 1427-1429 MHZ
 2015-2110 MHZ
 For the telecommunications satellites in the GEO orbit
 For the telecommunications satellites in the GEO orbit
 Frequency = bands of service (4/6 Ghz or 12/14 Ghz for example)

Pr. A. Addaim
 The antennas of the satellite are characterized by a quasi-isotrope radiation
The antennas characteristics
y q p
in order to cover the various attitudes taken by the satellite with respect to the
Ground station :
 Launching and orbital phases
 Losses of attitude
 Critical Situations in the event of faults
 The antennas of the ground stations are characterized by a very high gain
 The antennas of the ground stations are characterized by a very high gain
(very directive). They are able to automaticaly track the satellite during the fastest
passages, i.e. in the vicinity of the ground station zenith.
 The used Polarization (station ground)
 The used Polarization (station ground)
 TELECOMMAND: circular polarization
 TELEMETRY: circular polarization
 On the ground station, we use a combiner of polarization in order to increase the
level of the received signal.

Pr. A. Addaim
 Geostationary satellites: position in orbit must be maintained in a window of 0.1
wide in latitude and longitude;
Tracking satellite by ground stations
wide, in latitude and longitude;
An offset of approximately 60 km along and across the plane of orbit.
 TRACKING can be done in different ways:
 BY MEASUREMENT OF DISTANCES: measurement of propagation time
(round trip) of the radio wave emitted by the ground station.
(round trip) of the radio wave emitted by the ground station.
 BY DOPPLER MEASUREMENT: the transponder on board must be
capable of re-transmitting the telemetry carrier in coherence of frequency with
the telecommand carrier transmitted by the ground station (Coherent
the telecommand carrier transmitted by the ground station. (Coherent
transponder).
 BY ANGULAR MEASUREMENT: from the directivity characteristics of the
tracking network stations.
 BY INTERFEROMETRY: this process is used to locate the probes distant
from a network of earth stations as distant as possible from each other (very
o a et o o ea t stat o s as d sta t as poss b e o eac ot e ( e y
wide base interferometry) likewise that previously, it is also a method of
angular localization.

Pr. A. Addaim
DISTANCE Measurement
Principle
Principle
1. Emission on the ground of several tons (pure sinusoid) with FM modulation
2. Satellite retransmission of received tones
3 Cl bi it i l th d i i t
3. Clear ambiguity progressively on the ground using minor tones
4. Fine measurement on the ground of the delay time between the major tone
emitted and the major tone received.
D: outward distance = return distance
C: 3.108 m / s
TM: measured delay time
TB: delay time on board
TS: ground delay time
 
TS
TD
TM
C
D 


2
 PRECISION ON THE DISTANCE MEASUREMENT
Precision of an elementary measurement
Precision of an elementary measurement
 SYSTEMATIC ERROR: If TB = TS = 100 ns precision +/- 30 m on the
distance

Pr. A. Addaim
DISTANCE MEASUREMENT METHODS
1. ANGULAR MEASUREMENT
 Used for stationary geostationary satellites
y g y
 Too expensive for LEO or MEO satellites
2. DISTANCE MEASUREMENT
 Used for stationary geostationary satellites
 Delicate for LEO or MEO satellites
3. DOPPLER MEASUREMENT
 Used for LEO or MEO satellites : f = 400MHz Doppler of 10KHz
 Not suitable for geostationary satellites
 Not suitable for geostationary satellites

Pr. A. Addaim
 Telecommand decoder functions (ground-to-space Link): :
Telecommand decoder/Telemetry encoder
 Receive the demodulated RF signal from communication susbsyetm
 Ensure bit synchronization
 Ensure frame synchronization
 Ensure frame decoding and validation
 validation and distribution of Telecommands towards the on-board computer
 Encrypted Telecommands
 Encrypted Telecommands
 Encrypted telecommands can be used for make the uplink safer
 Authentication of the encrypted message
 The basic telecommand decoder is kept and additional circuits are
 The basic telecommand decoder is kept and additional circuits are
introduced to ensure encryption and authentication functions of the
message received (depending on the mission)
 Telemetry Encoder functions (space-to-ground Link):
 Telemetry data acquisition in platform subsystems and payloads.
 Data compression (preprocessing) and coding;
 Formatting and transmission of the stream bit to the Communication
subsystem.

Pr. A. Addaim
Classification of telemetry data
Housekeeping
ouse eep g
 Monitoring the health status of the satellite, and the operating mode.
 Temperatures
 Voltages and currents
 Voltages and currents
 Operating state
 Redundancy status
 Deployment of mechanism
 Deployment of mechanism
Attitude
 Sun sensor
 Earth horizon sensor
 Star sensor
 Gyroscopes
 A l t
 Accelerometers
Payload : it varies by mission
 Technological data,
g ,
 Scientific data from an instrument, etc.

Pr. A. Addaim

Pr. A. Addaim
Protocoles de communication entre le bord et le sol
 L'objet ici est de décrire les principes, les
formats numériques et protocoles associés, utilisés
q p ,
dans la transmission des données entre le bord et
le sol.
 Ces formats numériques font l'objet de
q j
recommandations du comité international CCSDS
(CCSDS : Consultative Committee for Space Data
( p
Systems) et de standards établis par les deux
principales agences spatiales : la NASA et l'ESA.
p p g p

Pr. A. Addaim
Les
Les principes
principes de
de transmission
transmission de
de la
la TM
TM
Les
Les principes
principes de
de transmission
transmission de
de la
la TM
TM
Types de télémesures susceptibles d'être utilisés sont
é t ié
répertoriées:
 suivant le délai entre l'acquisition à bord et la transmission
 suivant le délai entre l acquisition à bord et la transmission
au sol, on distingue :
 les TM temps réel,
 les TM enregistrées (transmises en temps différé lors
des périodes de isibilité)
des périodes de visibilité)

Pr. A. Addaim
Le standard CCSDS

Pr. A. Addaim
Trois structures de données principales : le paquet (TC packet), la trame (frame)
et le message (CL TU).
La hiérarchie des structures de données en TC par paquets

Pr. A. Addaim
F t d t CCSDS (TC TM)
Format du paquet CCSDS (TC ou TM)

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