MAXIM Data Systems

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MAXIM Data Systems

• Command Data HandlingSpace - Ground
  LinkGround System
• 19 August 1999

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MAXIM Data Systems Topics

• Data System Recommendations
• Options and Trades
• Spectrum Utilization
• Ground Antenna Capabilities
• Data System Drivers
• Data System Block Diagram
• Mass/Power Summary
• Operations Concept
• Link Margin Summary
• Cost Data
• Suggested Study Areas

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Recommendations for MAXIM

• Detector satellite will transmit science data
  using S-Band to Optics Spacecraft for combined
  transmission to ground stations
• Store data continuously dump daily for 12 min
  using DSN 34M using X-Band
• Total downlink data rate 300 Kbps
• Use 21 data compression
• Use S-band for Optics/Detector transmissions
• Use S-band for backup comm from DSN for both
  Optics Detector

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Options/Trades

• Detector spacecraft to transmit telemetry to
  Optics spacecraft for combined relay to ground
  station ( vs separate links)
• Less ground station time required
• Smaller antenna required for Detector Spacecraft
  much simpler communication system
• Optics spacecraft sends recorded data vs real
  time
• Ground costs significantly less
• Allows good availability on DSN 34M system

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Options/Trades

• DSN 34M recommended (vs 13M commercial)
• Allows hi-rate playback
• Reduces contact time
• Much lower cost
• Proven deep space operation
• 13 M commercial has unproven ranging capability
  at 40 million Km

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Spectrum Utilization

• X-band Space to Ground Link
• () Uplink and downlink frequency assignments
  available
• () More efficient than S-Band (approx 11.5 dB)
• () S/C hardware is available
• (-) Rain attenuation (approx 2 dB)
• S-band for Optics/Detector link
• ( ) More efficient than X-Band (omni/omni)
• () Existing hardware available with
  modifications of frequency Rx/Tx
• () Allows backup to ground if needed (UHF not
  readily available)
• S-Band to ground link (emergency)
• (0) Future allocation in DSN band may be
  questionable

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Ground Antenna Capabilities

• DSN 34M
• X-Band Rx/Tx
• G/T 52.4 dBi/K
• EIRP 103 dBw max(can go to 110 dBw)
• S-Band Rx/Tx
• G/T 42.1 dBi/K
• EIRP 98 dBw
• 13M commercial
• X-Band Rx/Tx (uplink and ranging need to be
  added)
• G/T 37 dBi/K
• EIRP 90 dBw
• S-Band Rx/Tx
• G/T 24.5 dBi/K
• EIRP 68 dBw

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MAXIM Data System Drivers

• Maximum Range 40 million KM
• Daily Data Volume 432 Mbits

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MAXIM Data Systems Block Diagram
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RF Communications Mass/ Power
Optics Spacecraft
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RF Communications Mass/ Power
Detector Spacecraft
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MAXIM Operations Concept Diagram
S-band command and telemetry _at_ 4 Kbps
X-band Command _at_ 2 Kbps/Telemetry_at_ 300 Kbps and
Ranging S-band Emergency Command _at_ 12
bps/Telemetry _at_ 100 bps
S-band Emergency Command _at_ 12 bps and telemetry _at_
100 bps
Commands
MAXIM MOC
DSN 34 M BWG (Stations at Canberra, Madrid,
Goldstone)
MAXIM Science
Telemetry (Housekeeping/Science)
MAXIM Science Data
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MAXIM Operations Concept

• Detector spacecraft will continuously transmit _at_
  S-Band to Optics spacecraft _at_ 4 Kbps (3 Kbps
  science, 1 Kbps housekeeping, uncompressed)
• Optics spacecraft will compress 21 all Detector
  data and 1 Kbps Optics housekeeping data
• Optics spacecraft will continuously record all
  compressed data for playback 1/day for 12 min _at_
  300 Kbps to DSN 34M _at_ X-Band through 1 of 2 HGA
  antennas
• Nominal commanding/ranging to Optics spacecraft
  will be done via
• X-Band through DSN 34M BWG
• Both Optics Detector will have S-Band low-rate
  command/telemetry through DSN 34M for emergency
  operations
• Commands throughput from MOC, telemetry FTPd
  from fileserver

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MAXIM Link Margin Summary
All links have 3 dB required performance
margins All links have rate 1/2 convolutional
encoding
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Cost

• Ground systems
• DSN 34M _at_ 1hr/day 365k/yr x 3 1.1M
• 13M commercial _at_ 8 hr/day 7M
• Optics Spacecraft
• X Band
• XPDRs(2) 2M
• HGA antennas(2) 2M
• S-band
• XCVR(4) 2.8M
• omni antennas(4) 300K
• CDH 2M

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Cost(contd)

• Detector Spacecraft
• S-band XCVR(2) 1.4M
• omni antennas(2) 150K

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Suggested Study Areas

• Use of new coding schemes (e.g. Turbo Codes)
• Modified frequency scheme for S-band XCVR

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Acronym List

• ACS - Attitude Control System
• ACU - Antenna Control Unit
• BC - Bus Controller
• BWG - Beam Wave Guide
• DSN - Deep Space Network
• FTP - File Transfer Protocol
• HGA - High Gain Antenna
• HSKP - housekeeping
• I/F - Interface
• MOC - Mission Operations Center
• RF - Radio Frequency
• SSR - Solid State Recorder
• XCVR - Transceiver
• XPDR - Transponder