SpaceOps 2006 Conference

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• SpaceOps 2006 Conference

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SpaceOps 2006

• ESA Station Tracking Network (ESTRACK) Augmented
  by the Second Deep Space Antenna at
  Cebreros/Spain
• R.A. Plemel
• SED Systems, a division of Calian Ltd,
• Saskatoon, Canada
• M. Warhaut and R. Martin
• ESA/ESOC, Darmstadt, Germany 

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Introduction

• This paper describes the subsystem developments
  used in the 35m DSAs that have recently been
  added to the ESTRACK network
• The core ESA Ground Station Tracking Network
  (ESTRACK) comprises
• General purpose 15m S/X-Band ground stations
• DSA1 deep space ground station
• 35m S/X-band
• New Norcia, Western Australia
• Entered service in June 2003
• DSA2 deep space ground station
• 35m X/Ka-band
• Cebreros, Spain
• entered service November 2005
• Assets of other agencies can be added to form the
  augmented ESTRACK or cooperative ESTRACK

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ESA Tracking Station Network (ESTRACK)
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ESA Antennas
DSA1 (New Norcia, Western Australia)
DSA2 (Cebreros, Spain)
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Operational Scenarios for the ESA Deep Space
Antennas
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RF Design Criteria for the ESA 35m Deep Space
Antennas
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Optical Design

• Tradeoff studies resulted in a decision to use EL
  over AZ turning head, beam waveguide (BWG)
  optical design.

DSA1 New Norcia
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Optical Design
DSA2 Cebreros
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Optical Design

• Both antennas use the same main and subreflector
  shapes
• BWG design was optimized separately for DSA1 and
  DSA2.
• Frequency selective dichroic plates were
  developed
• DSA1 reflects S-band, and passes X-band.
• DSA2 reflects X-band and passes Ka-band signals.
• Measurements of G/T, EIRP, and Tsys show that RF
  performance requirements were achieved.

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DSA1 Feeds and BWG Mirrors before AER Shroud
Installed
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Upper BWG Mirror Installation
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Dichroic Plate M6 in its Shipping Crate
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Inside AER Shroud (DSA2)
AER Ceiling
Fiberglass manwalk upper level
Kapton/AI tape
Fiberglass ladders
Fiberglass manwalk lower level
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RF System Design
Block Diagram of DSA2 RF Subsystem
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Feed Developed for DSA1 and DSA2

• X-band feed
• Low insertion loss (? 0.13 dB in Rx band)
• High power operation (20 kW) without burst noise
• Consists of corrugated horn, mode launcher,
  motorized polarizer, and orthomode transducer
  (OMT), diplexers.
• Polarizer is used to change the polarization
  routed to each of the two downlink chains
• Diplexers provide isolation between the uplink
  and downlink signals to allow simultaneous
  transmit and receive operation.

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X-band Feed During FAT
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Feed Developed for DSA1 and DSA2

• S-band feed
• similar architecture and manufacturing techniques
• operates with 20 kW HPA
• KaRx-band feed
• scaled down version of the X-band feed, except it
  is receive-only (no diplexers)
• includes a tracking coupler to allow future
  addition of monopulse tracking system

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Ka-band Rx-band feed used in DSA2
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LNAs

• S, X, and Ka-band cryogenic LNA subsystems were
  developed for use in ESAs ground station
  network.
• The cryogenic LNA subsystem consists of
• Vacuum dewar assembly
• spurious rejection filter
• injection coupler for test signals
• high electron mobility transistor (HEMT)
  amplifier.
• Cooled to 15 K
• Second stage post amplifier at ambient
  temperature.
• 2-stage Helium closed-cycle refrigerators
• Monitor and control system

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LNAs
Ka-band LNA Dewars Bottom View
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Frequency Converters

• Upconverters and downconverters used in DSA1 and
  DSA2 were developed for use in ESAs ground
  station network.
• The designs pay particular attention to phase
  noise and phase stability.

Frequency Converters Used in DSA1 and DSA2
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Downconverters
Ka-band Downconverter Front Panel
X-band Downconverter
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Power Amplifiers
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Antenna Mechanical Structure
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Main Reflector

• Shaped paraboloid
• Back-structure is a truss constructed from steel
  pipes.
• Supports the quadrapod mount for the
  subreflector.
• Reflector and supporting structure are
  counterbalanced about the elevation axis by
  ballast cantilevers.
• 300 high-accuracy panels.

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DSA1 Main Reflector Lift
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DSA2 Main Reflector Surface Accuracy Map
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Subreflector

• Shaped hyperboloid, 4.2 m in diameter
• Subreflector positioning system, automatically
  positions the subreflector to within 0.1 mm of
  its optimum position as the antenna elevation
  changes.

Installation of Subreflector and Struts (DSA2)
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Azimuth Structure

• Three story steel structure
• Supports the elevation axis on two fixed bearings
• Houses the drive motors, gearboxes, encoders, BWG
  mirrors
• Azimuth motion two gearboxes each fitted with
  two servo motors.
• Elevation motion four gearboxes with one servo
  motor each, engaging toothed gear segments on the
  ballast cantilevers

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Azimuth Part
Cebreros Installation June 2004
Azimuth Bearing
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Antenna Building

• The antenna building is a ten-sided reinforced
  concrete structure with a conical roof that
  supports the azimuth bearing
• Designed to deflect lt 1 mdeg under worst-case
  operational wind and thermal conditions.

FEA model for DSA2 Antenna Foundation and Tower
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View of AER and Maser Room
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Ancillary Facility Systems

• AC power distribution
• short break power from main and diesel
  generator
• no-break power from UPS
• Air conditioning
• main air conditioning system controls temperature
  and humidity in the AER
• separate systems regulate the temperature of RF
  equipment and maser room to within ?1?C
• De-ionized chilled water system for 20 kW HPAs
• NDI chilled water system for waveguide
  components, feeds, LNA cryogenic compressors, and
  main air conditioning system.

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AER Air-conditioning Subsystem
Supply to AER
MC
Air handler 2
Air handler 1
Fresh air inlet
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De-ionized Chilled Water Subsystem
NDI Chillers DSA2
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Servo System

• Consists of
• antenna control unit (ACU). Manages the servo
  system
• safety interlock system
• servo amplifiers
• drive motors
• optical encoders
• subreflector control system.
• Servo system implements pointing compensation
  models
• atmospheric refraction
• systematic pointing error due to residual
  alignment errors
• thermal deformation of the main and subreflector
  (DSA2 only).
• 250 temperature sensors, located on the structure
  are used to calculate this correction.
• tilt meters located at the elevation axis
  compensate for tilt of the tower and azimuth
  structure, due to thermal gradients or steady
  wind.

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Pointing Calibration System

• For DSA2, a PCS was developed and integrated with
  the servo system.
• performs PE measurements
• calculates SPEM coefficients from the PE
  measurements
• calculates real-time thermal deformation
  correction
• Residual pointing error in both X and Ka-band is
  less than 4 mdeg (3-sigma) under low wind
  conditions.
• Can degrade by up to 2 mdeg under worst-case wind
  and thermal conditions.

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DSA2 Ka-band Residual PE
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Monitor and Control Subsystem

• DSA1 and DSA2 antennas are operated remotely from
  ESOCs operations centre in Darmstadt, Germany.
• Key elements of the MC system are
• Front End Controller (FEC-NT) Developed by ESA
  for the ESOC ground station network
• Station Local Area Network (LAN)
• RF and servo equipment interface to the FEC
• Connects the FEC to the Main Equipment Room (MER)
  (an operations building adjacent to the antenna
  building) to permit remote control from
  Darmstadt.

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Conclusion

• DSA1 and DSA2 are fully integrated into the
  ESTRACK network
• They are used on a routine basis for ESAs most
  important missions
• The performance achieved validates the design
  approach and demonstrates that the equipment
  developments undertaken for these projects have
  been successful.
• The ability of each antenna to operate in several
  bands, and transmit and receive, allows great
  flexibility in planning future missions.
• Planning is underway for a third 35m DSA.
  Construction should begin in 2007

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