OPS Forum Autotrack 01.09.2006

OPS-G Forum

September 1th, 2006

M. Lanucara, OPS-GSY

M. Lanucara, OPS-GSYOPS-G Forum 1/9/2006 Slide 2Upgrade of ESTRACK Autotrack system

Introduction.Fundamentals of monopulse autotrack.Architecture of the present autotrack system in ESTRACK.System guidelines for the new autotrack concept.Future architecture of the autotrack system.Comparison between new and present architecture.Deployment plan.Completed/outstanding tasks.Conclusions.


Introduction


Autotrack is the capability of an antenna to stay pointed in direction of a moving satellite, only based upon the reception of the on-board transmitted downlink signal, unmodulated or modulated with telemetry according to a remnant or suppressed carrier modulation scheme.Autotrack does not require pointing predictions (apart from initial acquisition). Many implementations are possible, “monopulse” autotrack widely used due to good tracking performances.


a) Correct pointing during LEOP or critical phases: ensuring correct pointing to the satellite, if the predicted pointing elements are highly degraded, wrong or simply not available.

b) Provision of antenna angles: measuring the satellite position in the plane of sky, providing time-tagged antenna angles for orbit determination purposes.

c) Telecommunications link improvement: improving the end-to-end telecommunications link by minimising the ground station tracking error, during any mission phase.


a) Correct pointing during LEOP or critical phases: fulfilled in S-Band by the 15m antennas, harming conditions originated from:

Transitions between coherent and non coherent transponder operations.High Doppler dynamics.High signal-to-noise (SNR) ratio dynamics.


b) Provision of antenna angles: fulfilled in S-Band by the 15m antennas, measurement affected by errors:

Systematic errors in the pointing.Jitter in the measurement due to incorrect raw data sub sampling.

c) Telecommunications link improvement: not strongly required for the S-Band routine support due to the good program track performances of the 15m antennas. Envisat/ERS2 use the S-Band downlink for autotrack in order to improve the X-Band downlink.


To replace obsolete elements of the present system.To increase the robustness of the autotrack function during critical phases.To consolidate the existing functionality at higher frequency (use of X-Band or Ka-Band).To extend the existing functionality to new scenarios (deep space missions).To ensure proper maintainability of the system in the future years.


Show the new architecture for the ESTRACK autotrack system.Applicability is straightforward for the 15m antennas.Reference to the present system is made in the presentation, focusing on the “less obsolete” autotrack systems deployed in ESTRACK, i.e. Kourou, Perth and Redu.Applicability of the concept to the 35m antennas is addressed.


Fundamentals of monopulse autotrack


Purpose of the monopulse system:

detect signals proportional to the tracking error components (el and xel).

Transform the error signals into Azimuth (az) and Elevation (el) errors, to be used within the servo control loop.

Reference: M. Gaudim, Design and Performance of the Monopulse Pointing System of the DSN 34-Meter Beam-Waveguide antennas, TMO Progress report 42-138, August 15, 1999


Practical implementation:Primary detection in the feed: pointing misalignment → high order modes, whose energy is extracted in the tracking mode coupler.Magnitude of the extracted signal proportional to the off-pointing (θF).Full orientation (θF and φF) resolved by detecting the same high order mode at different orientations or by using distinct high order modes.

θF

φF z

y

x


Reference: VIL4 - FATR2 meeting February 2004 - Ka band, presentation by Telecom LAB Italia

Phase Amplitude


The demodulation of the misalignment information is made in the tracking receiver, using the sum signal as reference.Coordinate transformation is required to pass from the feed to the az-el coordinate system.Loop is closed in the servo system.

( ) ( )( ) ( )

( ) ( )ccFFccFF

cFcF

cc

tPtP

tPt

tPt

φωφγθφωφγθ

φφωγθ

φω

+−+

=++=∆

+=Σ

sinsin2coscos2

cos2

cos2

Misalignment information available at the output of a hybrid network as modulation of the difference signal in a phase quadrature scheme.

For a simple sinusoidal signal:


Reference: M. Gaudim, Design and Performance of the Monopulse Pointing System of the DSN 34-Meter Beam-Waveguide antennas, TMO Progress report 42-138, August 15, 1999


Differential phase and gain errors along the sum and difference downlink paths alter the misalignment information.Differential gain errors can be easily eliminated at installation.Differential phase errors cannot be eliminated, the differential delay between the sum and the difference downlink paths has to be minimised, the residual phase error over frequency must be compensated via calibration tables.


Two possible demodulation modes: Cross-correlation and PLL.In PLL the remnant carrier of the sum signal is reconstructed by using a phase-locked loop, prior to correlation with the difference signal. PLL mode allows tracking in lower signal-to-noise scenarios than cross-correlation mode.Cross-correlation mode is insensitive to carrier acquisition and tracking issues.


Architecture of the present system


Template for present system

SERVO POWER AZIMUTH

δXEL,δELTRK enbl

SCU

All switches and LNAs

LHC Mode

coupler

S/X-BAND FEED

OMT RHC

TE01 TM01

DPLX1 DPLX2

SDC TDC

Hybrid

RHC LHC

LHC Mode

coupler OMT RHC

TE210° TE2145°

DPLX1 DPLX2

XLNA3

XDC

Hybrid

RHC LHC

M&C/AGC

TRRX

δXEL,δELTRK enbl

Pol. Select

FILTER

SLNA3

FILTER

Σ1

Σ2

∆

X

Y

X

Y

ADLS

ADLS

SMC

Pol. Select

δXEL,δELTRK enbl

δXEL,δELTRK enbl

ACU

Program track/

M&C

SERVO POWER ELEVATION

DRIVE SYSTEM AZIMUTH

DRIVE SYSTEM ELEVATION

S8

S7S13

S14

S15

S9

FEC FECFEC

FEC (via SMC)

FEC (via SMC)

FEC (via SMC)

FEC (via SMC)

FEC

Program track/Servo M&C

Front-end Equipment on M&C

interface

STC

MER

AER

APEX

SLNA1

SLNA2

S5

Phase shifter

Phase shifter

Phase shifter

XLNA1

XLNA2

S6

Phase shifter

Phase shifter

Phase shifter


Autotrack system is complex.The full system is located in the antenna (in AER and in the apex cabin).There are many different types of receivers in ESTRACK (supplied along the years by BTM, MBB, SMP), based on either analogue (KIR-1, MSP, VIL-1, VIL-2) or digital (PER, KRU, RED) technology.There are several single points of failure for the autotrack function (e.g. all down conversion and amplification elements of the tracking channel, as well as the tracking receiver) .


All non-RF signals are transmitted over dedicated analogue or digital interfaces.Main phase and amplitude calibration

Conducted by the front-end Integrator after major upgrades.Requires the use of an external calibration tower.Phase calibration values are stored in the front-end controller.Effectiveness of the present procedure is doubtful in X-Band, the procedure itself is under revision for such a band.

• Spot checks conducted before mission support, at specific frequencies of interest.


System Guidelines for the new architecture


Scope of the system guidelines:Implementing the high-level objectives of the autotrack function.Incorporating new available tools related to the autotrack function in one homogeneous system.Maximising the use of existing infrastructure elements.Minimising risks linked to the introduction of a new architecture.


1. Full compatibility with the present system, from a functional and performance point of view.

2. Introduction of combined autotrack mode, in addition to the present “direct autotrack”, for telecommunication link improvement.

3. Introduction of conical scan as tracking mode, for validation prior to use for 35 meters antennas.

4. Improvement and automation of the phase calibration function.5. Improvement of the accuracy of the antenna angles tracking

products.


6. Increase of reliability of the autotrack function by adding redundancy for units that are presently single points of failures.

7. Increase of robustness of the autotrack system against planned or unplanned changes of the operational mode of the transponder affecting the frequency of the downlink signal.

8. Use of autotrack for high Doppler rate and low SNR scenarios.9. Maximum re-use of proven infrastructure elements.10. Mitigation of risks related to the operational phase-in of the new

concept.


Future architecture of the autotrack system


1. Introduction of the new concept in addition to the existing tracking system in operational stations in order to fulfil continuity.

2. Extensive comparative tests.3. First deployment proposed for Maspalomas station in conjunction

with the planned station upgrade.4. Progressive phase-out of the existing system.


FEC

Program track and ACU M&C Autotrack/ Link message (LAN) Antenna position (LAN)

Switches and LNAs

SDC TDC

XDC

M&C/AGC

TRRX

δXEL,δELTRK enbl

Pol. Select

Σ1

Σ2

∆

X

Y

X

Y

ADLS

ADLS

SMC

Pol. selection (digital)

δXEL,δELTRK enbl

M&C/Cross-pol Setting (LAN)

Autotrack/Link message

(LAN)

FEC

FEC

FEC

Front-end Equipment on M&C

interface

STC

S-Band X Channel

S-Band Y Channel

S-Band ∆ Channel

X-Band X Channel

X-Band Y Channel

X-Band ∆ Channel

SERVO SYSTEM

ADLS

ADLS

LDC1 X XY Y∆ ∆

LDC2 ∆ ∆Y YX X

ADLS

IFMS1Cross-pol

X settingY ∆


(LAN)

IFMS2Cross-pol

∆ settingY X


(LAN)

XY

XY

SDC

XDC

SDC ∆

XDC ∆

MCM STC, MMI

LAN infrastructureTracking VLAN

MER

AER

APEX

IFMS1IFMS2MCM

FECA/B

IFMS MMI MCM MMI FEC MMI

IFMS MMIMCM MMIFEC MMI

Parts of the existing autotrack system not subject to upgrade/modification

Parts of the existing ground station equipment re-used for the new autotrack system

Parts to be added/upgraded for the new autotrack system

LAN infrastructureStation VLAN

LAN infrastructureEngineering VLAN Tracking VLAN

Engineering VLAN Station VLAN Tracking VLAN physical port

MCM

X Σ1 Y Σ2

ACU2ACU1

δXEL,δEL (ana)TRK enbl (ana)

Program track and ACU M&C(LAN)

Antenna position(LAN)

Autotrack/link message (LAN

Ch1Ch2

Ch1Ch2

Ch1Ch2

Ch1Ch2

Ch1Ch2

Ch1Ch2

SMC

SMC

FECIFMS


Template for new architecture (functional)

Feed

X

∆

IF sampling

FFT for

PLL

Doppler pred.

Σ/∆

delay equal.

X/Y

crossing

D/L chain and

switch network

Monopulse corr.

Σ1 PLL

Σ1 IF filter

Σ2 PLL

Σ2 IF filter

∆ IF filter

Post corr. filter

Y

Conv. to antenna coordin.

Conv. to AZ/EL errors

Direct auto track

Σ

∆

SMC

Sum selection switch

Amplitude/phase calibr.

Comb. auto track

Program track

Antenna velocity ctrl loop

Encoders position

TRRX i/f handling

Tracking/link i/f handling

SNR, AGC, phase lock loop, sum selection

information

Sum selection

Link (SNR, AGC, PLL)

Tracking errors

Program track data

Antenna

PLL/cross-correlation tracking mode switch

IFMS

ACU

FEC i/f handling

Antenna position

Program track

δEL, δXEL metric transf.

__t(·)

__t(·)

ACU redund. management

F-E pol crossing

FEC

TRRX i/f handling

Extended Calibr.

Conical Scan

ACU i/f handling

Autotrack/link message

F-E Switch

handling

TRRX i/f handling

Tracking info.

Visual.


Existing tracking system in antenna is kept as fall-back for validation phase.Existing IFMSs are used as tracking receivers.Existing L-Band telemetry down converters are used for tracking.Sum and difference signals are transmitted cross-site.New Switch M&C unit (SMC) is developed.Servo Control Unit is deleted, cold redundancy is established for the Antenna Control Unit (ACU) hardware.


Interfaces moved/built over local area network:Autotrack/link message, used for transmission of tracking errors and other information (UDP).

Interface SMC → IFMS, used for front-end polarisation switch selection (TCP/IP).

Interface ACU → FEC, used for transporting the real-time antenna positions (UDP).

existing traffic FEC ↔ ACU, used for program track and servo M&C (TCP/IP).


Local man machine interfaces (MMI) for the IFMS and the MCM are installed in AER.Combined autotrack is introduced.Extended calibration functions are introduced as part of FEC andACU → automatic phase calibration during a satellite pass. Phase (and amplitude) calibration tables are stored on the IFMS.Conical scan is introduced as part of the FEC. Detailed requirements still TBD, all required interfaces are in place.


In Combined autotrack the program track data are used as baseline information for tracking. Tracking error signals from tracking receiver correct for slowlyvarying offsets between predicted and actual trajectory (e.g. deformations due to temperature, systematic pointing errors, small errors in predicts). Combined autotrack mode requires the integration of the tracking error signals over time.Suitable for improving autotrack robustness and telecommunications link in routine passes.


Conical scan is an autotrack technique widely used in the NASA Deep Space Network (DSN).Scan pattern is superimposed on the program track trajectory, while retrieving time-tagged link and antenna position information. Processing of such information allows estimating the tracking error and the tracking error variance.Conical scan autotrack requires only link data (level and signalto noise ratio) as feedback information.


Present autotrack mode is migrated in the new architecture, new tracking modes are added.Analogue autotrack not available in the new concept. Risk mitigation: the antenna control unit is made redundant.In case of autotrack on a dedicated beacon, the redundancy of the telemetry function is degraded.

HighCompatibility between present and new architecture.

RemarksFulfilmentGuideline


Implemented in the FEC, automatic calibration during a pass will be possible.Existing problems concerning the use of calibration tower at X-Band are not completely removed, presently under investigation.

HighExtension of the phase/amplitude calibration function.

Implemented in the ACU/FEC.FullCombined autotrack and conical scan.



Reduction of jitter component expected due to higher raw sampling rate, prior to filtering and sub-sampling.Reduction of systematic point error expected via use of the extended calibration function.Quantitative improvement requirements should be formulated.

HighImprovement of antenna angles accuracy.



Two redundant tracking chains allow diversifying the autotrack configuration.

HighRobustness against planned/ unplanned changes of the transponder operational mode.

Tracking L-Band down converter and the tracking receiver are hot redundant, the antenna control unit is cold redundant.

HighIncrease of redundancy for the autotrack function.



In PLL mode, all IFMS existing capabilities are used.In cross-correlation mode, use of small pre-correlation bandwidths (minimum is 50 kHz today, it will be 5 kHz on IFMS ATRK) will be possible in combination with Doppler presteering.

HighUse of autotrack for high Doppler rate and low SNR scenarios



The present system can be left available until the new architecture is fully validated.

FullMitigation of risks for operational phase-in.

New tracking receiver is integrated in the IFMS. Signal interfaces are moved to LAN over the available LAN infrastructure, wherever feasible/convenient.

FullRe-use of existing infrastructure elements.



KPOL

RHC/LHC

SPOL S-Band feed

OMT LHC/RHC DPLX1

DPLX2

SDC

SLNA1

SLNA2

RHC/LHC

LHC/RHC DPLX1DPLX2

XDC

XLNA1

XLNA2

ADLS

LDC1

LDC2Y

X

Y

X

Y

X

Y

X IFMS2 Link message

LDC3Y

X


IFMS1 Link message

IFMS3 Link message

FEC

Program track and ACU M&C

Link message Antenna position

SERVO SYSTEM

ACU2

ACU1


Antenna position

Link message

LHC/RHC XPOL X-Band

feed OMT RHC/LHC DPLX1

DPLX2

XDC

XLNA1

XLNA2

LHC/RHC

OMT RHC/LHC

KDC

KLNA1

KLNA2

ADLS

Y

X

Y

X

Ka-Bandfeed

Mode coupler

KLNA3RHC LHC ∆

LDC1YX IFMS1

Autotrack/Link message∆

LDC2YX IFMS2


LDC3YX IFMS3



FEC


Autotrack/Link message Antenna position

SERVO SYSTEM

ACU2

ACU1


Antenna position


NEW NORCIA

CEBREROS

Parts of the existing ground station equipment re-used for the new autotrack system

Parts to be added/upgraded for the new autotrack system

Tracking VLAN Station VLAN Tracking VLAN physical port

Switch control

FECFEC

FEC

MCM

STC

STC

STC

MCM

STC

STC

STC

FECFEC

FEC

FEC IFMS

MCM MCM

Front-end devices

Front-end devices

FEC

STC

STC

XPOL X-Band feed

OMT

Switch Control


New NorciaA monopulse system cannot be installed for S/X-Band unless of major refurbishment of the feed system (no tracking coupler).Conical Scan is a possible option for both bands.The time-tagged link information required by Conical Scan is embedded in the same autotrack/link message introduced for the 15m antennas.


CebrerosThe ground station is prepared for a monopulse system in Ka-Band.Conical Scan is an alternative option in Ka-Band, and is the unique choice in X-Band.


Comparison between new and present architectures


The new concept has a wider applicability than the present one, autotrack function is extended to deep space scenarios.New tracking modes and functions are possible, like Conical Scan and the extended phase calibration.The reliability of the autotrack function increases.The ground station configuration can be diversified during critical phases.Improvement of antenna angles quality is expected.The architecture is easily extendable to the 35m antennas.Re-use of existing infrastructure elements ensures full maintainability in the future years.


Complexity of local operations will increase due to the distributed character of the new architecture.The procedure for phase and amplitude calibration will require adaptation in respect the one applicable today. Need for increasing the number of calibration curves is expected (this isthe case also for the present system, in X-Band).


Deployment plan


Deployment in Maspalomas in July/August 2007, new system is introduced as back-up of the existing one.Existing tracking receiver is replaced with a conventional COTS unit.Practical comparison between new architecture and existing system is possible during true satellite operations.Replacement of the conventional tracking receiver is justified by obsolescence of the present unit.Other stations belonging to ESTRACK (15m and 35m) are upgraded taking into account the planned station utilisation.


ESTRACK terminal(*)Acronym KIR-1 KRU-1 MSP-1 PER-1 RED-1 CEB-1 NNO-1 DS3

Downlink band(s) S/X S/X S/X S/X S X/Ka S/X X(/Ka)

Proposed architecture

Short/medium term (until 2009)

Modernised present system

Modernised present system

New architecture:Conical scan for S/X-Band

Long term TBD TBD TBD

Missions (to be launched or still flying after mid 2007)ERS2XMMCLUENVINTMEXROSVEX

SOHOULY

METOP1ISS-ATV

HPMSG3LISA

METOP2GAIAMSG4

ExoMarsBC

METOP3

(*) Only 15m and 35m antennas are shown, and related supported missions.

Full new architecture

New architecture:Monopulse for Ka-BandConical scan for X/Ka-

Band

TBD once the supported downlink bands are

selected




ID Start Finish

7 Fri 28/07/0 Fri 29/06/08 Mon 04/12/ Fri 15/12/9 Fri 28/07/ Tue 13/02/10 Fri 01/09/ Thu 31/05/11 Mon 01/01/ Fri 29/06/12 Mon 16/04/0 Fri 29/06/013 Mon 16/04/ Fri 29/06/14 Mon 05/02/0 Fri 30/03/015 Mon 05/02/ Fri 30/03/16 Mon 01/01/0 Thu 31/05/017 Mon 01/01/ Thu 31/05/18 Mon 19/06/0 Fri 25/05/019 Mon 19/06/ Tue 13/02/20 Mon 26/03/ Fri 06/04/21 Mon 21/05/ Fri 25/05/22 Mon 22/01/0 Fri 15/06/023 Mon 22/01/ Fri 02/03/24 Mon 26/03/ Fri 06/04/25 Mon 07/05/ Fri 15/06/26 Mon 02/04/0 Fri 31/08/027 Mon 02/04/ Fri 06/04/28 Mon 04/06/ Fri 15/06/29 Mon 02/07/ Fri 31/08/30 Mon 02/07/ Fri 20/07/31 Mon 16/07/ Fri 03/08/32 Mon 16/07/ Fri 03/08/33 Mon 16/07/ Fri 03/08/

Front end04/12 Feed exchange

28/07 COTS tracking recevier01/09 SMC development

01/01 Front-end upgrade design and procurementLAN infrastructure

16/04 LAN upgrade designACU

05/02 ACU modification designFEC

01/01 FEC (conical scan, auto calibr, angle OCC i/f and post pIFMS TRK

19/06 IFMS ATRK development26/03 MSP IFMS upgrade to RRD

21/05 IFMS ATRK GDSP upgrade (preparation)STC

22/01 STC standard tailoring - IFMS ATRK26/03 STC upgrade to RRD

07/05 STC standard tailoring - FECOn-site activities

02/04 ACU upgrade04/06 Antenna A/C upgrade

02/07 Front-end upgrade - on site activities02/07 MSP LAN upgrade

16/07 MSP FEC upgrade16/07 MSP IFMS upgrade16/07 MSP STC upgrade

Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May2006 2007 2008


Completed /outstanding tasks


Study project for IFMS tracking receiver: a prototype has been developed and installed in VIL-4 IFMS. Definition of a system concept for the new autotrack system architecture, presented at EUTF on January 2006.Tracking tests using the IFMS prototype tracking receiver with Smart-1 (KaTE), Integral, ERS-2 and Envisat: the possibility to transmit tracking errors over the LAN has been demonstrated.Analysis and tests about transmission of sum and difference signals cross-site.


Start of all hardware subsystems development/procurementIFMS development started 19th of June 2006, completion expected 13th February 2007 (SAR).SMC development will start 1st week of September, completion expected end of May 2007.COTS tracking receiver, technical specification was sent to potential suppliers end of July 2006.

Definition of all ICDs for new/modified interfaces.


Definition of an implementation plan for the Maspalomas upgrade.Completion of X-Band autotrack verification tests in Perth.Definition of technical specifications for new autotrack-related FEC and ACU functions and start of related development.STC standard and operational tailoring.LAN upgrade design.Deployment in Maspalomas.Deployment in ESTRACK according to an agreed deployment plan.


The new architecture for the ESTRACK autotrack system can be flexibly tailored to several operational scenarios, like critical LEOP activities or routine support to Near Earth/Deep Space missions.Maximum re-use is made of proven infrastructure elements, which ensures maintainability in the long term, and operational reliability.Attention is given to the risks associated to the operational phase-in of the new system, and to the identification of the related mitigation measures.

Technology

OPS Forum Autotrack 01.09.2006