Page 1 SATELLITE TO SATELLITE TRACKING...

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All rights reserv ed © 2005, Alcatel Alenia Space

GOCE Workshop

SATELLITE TO SATELLITE TRACKINGSATELLITE TO SATELLITE TRACKINGINSTRUMENTINSTRUMENT

A. Zin, S. Landenna

A. Conti

DESIGN

PERFORMANCE

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HERITAGE

SSTI instrument is based on the LAGRANGE receiver architecture

LAGRANGE receiver development started in 1998 with Alcatel Alenia Space Italia S.p.A.internal funds

The product is developed, manufactured and tested by the Navigation Department inMilan plant

LAGRANGE X-prototype developed in 1999 with ASI contribution for demonstrative flighton SAC-C satellite

LAGRANGE fully space compatible design completed end 2001

LAGRANGE is onboard the following satellites:n RADARSAT-2 (2 FM’s)

n COSMO SKYMED constellation: 3 satellites (1 EQM + 6 FM’s)

n OCEANSAT (1 EM + 1 FM tailored for Radio Occultation application)

n Soyuz (1 FM)

LAGRANGE was onboard Soyuz mission 10S in April 2005 in the frame of ENEIDEmission

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DESIGN 1/3

Receiver Type: Integrated GPS receiver for

spaceborne applications

Channels: 12 dual-frequency channels

Frequency Band: GPS L1: 1575.42 MHz

GPS L2: 1227.6 MHz

Observables: L1CA, L1P(Y) & L2P(Y) Code

L1CA & L2P Carrier phase

Instantaneous Doppler

Time (Bias, Bias Rate)

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DESIGN 2/3

Receiver Unit: RF/IF Module

Synch Module

AGGA 2 Module

Processor Module

Power Supply Module

+ Motherboard

RYMSA

GPS L1/L2 Antenna

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DESIGN 3/3

DUAL BAND

GPS ANTENNA

DIPLEXER

L1 Band

L2 Band

RF

CA

BL

E

LNA

A/D

LNA

A/D

OCXO5 MHz

L1 BandPLL

L2 BandPLL

SMPLCLK

RF/IF Board

TH TH

TH TH

EMI

FILTERON / OFF

DC/DC

CONVERTERSECTION

+3.3V

+5V

-5V

+12V

-12V

POWER BUS

ON/OFF (R)

ON/OFF (N)

TRMN

ASMN

J01

RSMNDC/DC Relay Sensing

+5V Analog Monitor

Thermistor

RSMN

J02DC/DC Board

AGGA2# 1

AGGA2# 2

AGGA2

# 3

NA

V(0

:3)

DSP21020

PROGRAM

MEMORY

DATA

MEMORY

1553

I/F

AGGA2 Board

1553I/F (N)

J03

1553I/F (R)

CPUCLK

DSP Board

HOUSEKEEPING

ACQUISITION

PPS

SYNCH

J04

J06

J07J08

J09

PPS

PPS

WDEN / DIS

WD E/D (R)

WD E/D (N)

HPC

HPC

HPC

HPC

PWR

PWR

PPS (N)

PPS (R)

HPC

HPC

HPC

HPC

J05

M_EPOCH

1553

1553

WD E/D Relay Sensing

SYNC Board

Receiver Processor Unit

+5V

+12V

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MAIN FUNCTIONALITY

Pseudorange measurements (Code Phase)

n C/A Code, for GPS L1

n P(Y) Code, for GPS L1 & L2

Integrated Doppler measurements (Carrier Phase)

n L1 and L2 Carrier Phase

Signal and Noise measurements

n Signal to Noise Ratio C/No in dB/Hz units evaluated at the tracking loop input

Real-Time Orbit Determination, determined using GPS C/A signalobservations and navigation messages (PVT solution through SPS andNavigation Kalman Filter)

Time measurements, determined from the GPS system

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ELECTRICAL INTERFACES

POWER LINES:

n N° 1 Unregulated Primary Power Supply Interface (connected to Satellite Power Bus)

TELECOMMANDS:

n N° 8 High Power ON/OFF Command (HPC) (Nom + Red for Receiver ON, Nom + Red

for Receiver OFF, Nom + Red for Watch Dog Enabling, Nom + Red for Watch Dog

disabling)

TELEMETRY:

n N° 2 MIL-STD-1553B I/F (Nominal + Redundant)

n N° 1 Temperature Sensing Monitor I/F (TSMN) (Thermistor on the DC/DC Board)

n N° 1 Analog Single Ended Monitor (ASMN) (5V Secondary Voltage Monitor)

n N° 2 Relay Sensing Monitor (RSMN) (Unit ON/OFF and Watch-Dog EN/DIS Relays)

SYNCHRONISATION:

n N° 2 External Synchronization Pulse Per Second (PPS) (Nominal and Redundant)

RF INTERFACE:

n N° 1 RF Input (from Antenna)

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PHYSICAL BUDGETS

Mechanical Dimensions

n 250 mm x 200 mm x 190 mm (LxHxW) including mounting feet

n 29.32 mm x 212.1 mm x 225.5 including Diplexer & LNA Cables

Mass:

n Receiver Unit : ~ 5.35 Kg

n Antenna: ~ 490 g

n Cable to antenna: ~ 225 g

Power Consumption:

n ~ 29.3 W (steady state)

n ~ 32.1 W (OCXO warm-up)

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SSTI PERFORMANCE

SSTI Characteristics

n Tight requirements in order to comply with system specifications

n Performance Requirements on three large areas:

!Real-Time Navigation (PVT)

!Raw Measurements (errors, acquisition/tracking thresholds, biases…)

!Robustness

n Temperature Sensors on-board placed on sensitive points of the RF board inorder to allow calibration of Rx-specific biases (IFB)

n Precise Modeling/Testing of errors (Multipath, antenna CoP etc.)

n Peculiar measurement sampling procedure (sample after PPS in input),typical of timing receivers

n Freely drifting Rx time scale, Rx bias bound between ± 10 ms

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SSTI PERFORMANCE

SSTI Performance Test Setup:

Navigation A ntenna

Port

Occ ul ta tion Antenna

Ports

I/O Data Interface

1553-B

Com mands & Da ta

Output D ata

Output Da ta

Com mands & Da ta

PC – GOCE RX

PC – GOCE RX

GSS Sim WS

TE - PC

GOCE RX

Power Supply

Single/Mult i-channel

Simulator

Antenna RF Cables (or simulation)

Optional link (for autom ated tes ts)

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SSTI PERFORMANCE

RT Navigation Testing

n Tested under Selective Availability ON and OFF (major source of RTnavigation error)

n Output tested in different reference frames (ECI J2000, ECI TOD,ECEF)

n Orbital GOCE scenario, usually having a duration of 12 hours

!Period of time representative of GPS orbital period

!GOCE orbit modeled using a 70x70 gravity field model, GPS 8x8

!Drag-free simulation (DFAC compensation), no SRP

!Force model and reference frame basically limited by Spirentimplementation.

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SSTI PERFORMANCE

RT Navigation Scheme

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SSTI PERFORMANCE

Real Time Navigation Requirements:

RT Navigation Results (S/A on):

Results with S/A off (current GPS status) - much better:

NKF Position J2000.0 (3D - 3s): ~ 30.35 m

NKF Velocity J2000.0 (3D - 3s): ~ 0.12 m/s

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SSTI PERFORMANCE

Navigation Results (example)

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SSTI PERFORMANCE

Visibility to GPS (example)

Direction Of Arrival Density Plot

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SSTI PERFORMANCE

Acquisition-Tracking thresholds & Measurements accuracy:

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SSTI PERFORMANCE

n A dedicated test campaign has been carried out to check robustness against

ionospheric scintillation activity

n Ad-hoc test set-up (Test Equipment, SSTI firmware modifications)

n GISM (Global Ionospheric Scintillation Model) simulator by IEEA has been used to

generate the scintillation time series in terms of amplitude and phase errors

n Amplitude fades injected at RF level using a programmable RF attenuator

n Phase errors injected at DSP level in the SSTI (pre-correlators carrier rotation)

n Orbital scenario in the RF simulator, scintillation error applied repeatedly during a pass.

n S4 values from 0 (no effect) up to 0.8. GISM version has S4 & sigma_phi linked

n Analyses in terms of loss of lock on carrier phase in post-processing

SSTI Sensitivity to Ionospheric Scintillation

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SSTI PERFORMANCE

Ionospheric Scintillation Test Setup

Navigation Antenna

Port

Occ ulta tion Antenna

Ports

I/O Data Interface

1553-B

Comm ands & Da ta

Output D ata

Output Da ta

Comm ands & Da ta

PC – GOCE RX

PC – GOCE RX

GSS Sim WS

TE - PC

GOCE RX

Power Supply

Single/Mult i-channel

Simulator

Antenna RF Cables (or simulat ion)

Optional link

(for automated tes ts )

Attenuation P rofi le

Programmable

Attenuator(PA13)

Test Setup

Phase error injection

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SSTI PERFORMANCE

Example of amplitude and phase errors applied:

Characterization in terms of loss of

lock sensitivity to S4 parameter

Scintillation Time Series

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SSTI PERFORMANCE

Example of Results

S4 = 0.6: OK!

S4 = 0.76: Not OK!

SUMMARY:

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SSTI precursor: ENEIDE

n LAGRANGE receiver installed inside the Soyuz

Orbital Module

n GNSS antenna installed outside the Soyuz vehicle

n Laptop installed inside the Orbital Module and

connected with LAGRANGE Receiver via MIL-

BUS1553 data cable

n The Crew MMI provides commanding and

monitoring functions

n All the data acquired by LAGRANGE Receiver

handled by the Laptop Software and stored on the

PCMCIA Hard-Drive

SSTI-Like experience on ENEIDE experiment (May 2005):

different target application (combined

GPS/EGNOS/WAAS tracking from space) but same

technological base of SSTI

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ENEIDE experiment antenna

LAGRANGE

receiver

T. Col. Vittori

ENEIDE

Experiment

Conductor

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All the analyses conducted on the flight data allow to

say that the ENEIDE experiment was carried out

successfully.

ENEIDE proved to be a benchmark for the validation of the AAS-I

receivers of LAGRANGE class, like GOCE SSTI. The different

environmental conditions in which the receiver operated (Sun-pointing

attitude, orbital attitude, peculiar antenna pointing constraints etc.) made

the experiment an important laboratory for different applications like

attitude analysis, atmospheric sounding, space weather, real-time

navigation and control.

Reference:

A. Zin, S. Landenna, A. Conti, L. Marradi, M. S. Di Raimondo, “ENEIDE: an Experiment of a Space-borne, L1/L2

Integrated GPS/WAAS/EGNOS Receiver”, European Navigation Conference 2006, (ENC 2006), May 08-10 2006,

Manchester, UK.

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GOCE SSTI: FACTS

State-of-art GPS space receiver technologyState-of-art GPS space receiver technology

Advanced performanceAdvanced performance

Twelve LAGRANGE flight models built (two SSTI Twelve LAGRANGE flight models built (two SSTI FMsFMs))

Fully qualified for space applications for severalFully qualified for space applications for several

satellitessatellites

Flight provenFlight proven

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Thanks for your attention !Thanks for your attention !

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