1 / 24

esa

1. Authors. Dennis R. AkinsSED Systems, a division of Calian Ltd., Saskatoon, Saskatchewan, S7N 3R1, CanadaRolf MartinESOC / ESA, Darmstadt, 64293, Germany. 2. Overview. In July of 1998, SED Systems of Saskatoon, Canada was awarded a contract by ESOC to supply the DSA1 TT

Audrey
Download Presentation

esa

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

    1. ESA / ESOC35-meter Deep Space Antenna Front-End Systems

    2. 1

    3. 2 Overview In July of 1998, SED Systems of Saskatoon, Canada was awarded a contract by ESOC to supply the DSA1 TT&C antenna system 35 m diameter Initial operation in S-band and X-band – downlink and uplink Upgradeable to Ka-band reception Installed at New Norcia, Western Australia Operational since November 2002 Currently Supports the European Mars Express and Rosetta Missions

    4. 3 DSA1 35 m S/X Deep Space Antenna

    5. 4 DSA2 SED is currently supplying a second 35 m front-end antenna system for ESOC Based on the DSA1 design Initial configuration: X-band downlink and uplink, and Ka-band downlink Upgradeable to Ka-band transmit Will be installed at Cebreros, Spain Scheduled for acceptance in July 2005 To be used for the European Venus Express spacecraft to be launched in November 2005 Remotely controlled from ESOC Mission Centre at Darmstadt, Germany

    6. 5 System Design Mission Requirements RF Design Optical Design Antenna Building Antenna Mechanical Structure Servo System

    7. 6 RF Requirements

    8. 7 Mechanical and Servo Requirements

    9. 8 RF Design – DSA2

    10. 9 Major RF Equipment Passive RF components Feeds Beam waveguide mirrors Frequency selective dichroic plates Cryogenic LNAs - redundant Downconverters - redundant Upconverters - redundant HPAs DSA1: 20 kW S-band and X-band KPAs 2 kW backup S-band and X-band KPAs DSA2: Primary: 20 kW X-band KPA Backup: 2 kW X-band KPA and 500 W X-band SSPA

    11. 10 Major RF Equipment Ranging calibration system – for medium and long loop back testing Test Subsystem (uplink power/frequency monitoring, noise temperature measurement) Monitor and control equipment and software

    12. 11 Optical Design

    13. 12 Beam Waveguide (BWG) Optical Design Consists of reflective mirrors Dichroic plates (frequency selective surfaces) DSA1: M6: S/X and future M4a: SX/Ka DSA2: M6: X/Ka and future M7a: KaRx/KaTx Permit the use of separate feeds optimized for each band Feeds Optimized independent of one another X-band feeds are water cooled to operate with 20 kW uplinks Are stationary, mounted in the antenna base near LNAs, HPAs and other RF equipment

    14. 13 Antenna Building Ten-sided reinforced concrete structure 14 m diameter, 5.4 m high ceiling Conical roof supports the azimuth bearing Provides an environmentally controlled room for feeds and RF equipment Foundation is a reinforced concrete ring beam on reinforced concrete piles The outer walls are clad with insulating panels to keep deflections due to differential thermal expansion to less than 1 mdeg

    15. 14 Antenna Building Ancillary systems are tightly integrated with the building Redundant air conditioners Non-deionized chilled water system for waveguide, feeds, helium compressors, and air-conditioners Deionized chilled water system for 20 kW HPAs Electrical power distribution (short break, no-break) Maser room Shroud to provide safety and RFI isolation from high power feeds in AER

    16. 15 Mechanical Subsystem The azimuth housing is mounted on the antenna building by means of a roller bearing and a fixed steel base ring Azimuth housing: Three story steel structure Two fixed bearings are mounted to the azimuth housing and define the elevation axis Supports the elevation portion on which the main reflector is mounted Elevation drive Four gear boxes and drive motors Gearboxes drive toothed gear segments on the two ballast cantilevers

    17. 16 Mechanical Subsystem

    18. 17 Main Reflector The main reflector is 35 meters in diameter DSA1 and DSA2 use identical surface shapes Over 300 high-accuracy panels made out of aluminum Panels attach to the reflector back-structure via adjustable studs The main reflector supporting structure A rigid truss constructed from steel pipes Supports the quadrapod for the subreflector Reflector and supporting structure are counterbalanced about the elevation axis by ballast cantilevers Precision alignment of the reflector surface uses a photogrammetry technique

    19. 18 Subreflector 4.2 m diameter shaped hyperboloid Cast and welded aluminum Subreflector positioner Adjusts subreflector position to compensate for gravity displacement and tilt of the subreflector as the elevation angle changes Improves antenna efficiency S-band: the effect is negligible X-band: up to 0.7 dB loss if positioner is not used Ka-band: up to 5 dB loss, if positioner is not used

    20. 19 Servo Design The servo system consists of: Antenna Control Unit (ACU). Interfaces to the Front End Controller (FEC) for receiving remotely generated program track data Safety interlock system Servo drive amplifiers Az and El axis drive motors and encoders Tiltmeters, used compensate for deflection of the azimuth part and tower due to wind pressure, thermal gradients, and/or foundation settling Pointing Calibration System (PCS) for DSA2

    21. 20 Servo Design The ACU implements compensation models, in conjunction with the PCS to reduce systematic pointing errors: Tower tilt Az and el encoder offset errors Gravity deformation of the main and subreflector Azimuth and elevation axis misalignment Collimation error between the RF beam and the optical axis Beam waveguide mirror and feed misalignment Polarization and frequency dependent beam squint Azimuth encoder gearing and toothing errors Thermal gradient deformation of main and subreflector Atmospheric refraction

    22. 21 Servo Design The PCS is designed and manufactured by SED Measures systematic pointing errors Uses a sensitive radiometer to measure system noise temperature Tracks radio stars to determine the pointing error Determines the systematic pointing error model (SPEM) for the antenna Uses many individual pointing error measurements Curvefit technique is used to determine the SPEM (pointing error as function of Az and El) Compensates for thermal gradient deformation/displacement of main and subreflector 250 temperature sensors are distributed over the main reflector back-structure and subreflector support struts PCS reads these every 60 seconds Calculates the correction for the servo system to apply

    23. 22 Conclusion The implementation of ESA’s 35 m Deep Space Network is well advanced DSA1 is in service at New Norcia for European Mars Express and Rosetta missions DSA2 is scheduled completion at Cebreros, Spain in mid 2005 Planned Ka/Rx Upgrade for DSA1 Planned Ka/Tx Upgrade for DSA2 DSA3 is in planning stages Lessons learned are being applied to achieve higher performance of successive antennas

More Related