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X-Ray Delta: Gratings Redux Mission

X-Ray Delta: Gratings Redux Mission. Communications Ron Vento Blake Lorenz 02-04 May 2012. Topics. Overview Block Diagram Configuration (Block) Driving Requirements and Assumptions L2 Orbit, Timeline and Attitude Data rates and Storage Selected Configuration and Rationale

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X-Ray Delta: Gratings Redux Mission

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  1. X-Ray Delta: Gratings Redux Mission Communications Ron Vento Blake Lorenz 02-04 May 2012

  2. Topics • Overview • Block Diagram Configuration (Block) • Driving Requirements and Assumptions • L2 Orbit, Timeline and Attitude • Data rates and Storage • Selected Configuration and Rationale • Functional Configuration • Signal Margin Summary • Cost/Mass/Power Summary • DSN Support • RF Communication Costs • Risks and Concerns • Backup

  3. Overview • Ka-Band for science and data dumps via DSN 34 meter • Data dumps at 10 Mbps • One 14 minute contact per day require to dump data. • Two back to back 6 hour peak events would require three days of 32 minute contacts to complete transmission within the 72 hour latency requirement. • S-Band TT&C via High Gain Antenna (HGA) to DSN 34 meter • 2 kbps command • 8 kbps telemetry • S-Band TT&C via Omni antenna to DSN 34 meter • 1 kbps command • 2 kbps telemetry • DSN Ranging for orbit determination • S-Band thru TDRSS for launch and LEO critical events • 1 kbps command • 1 kbps telemetry

  4. Functional Configuration decrypter S S/Ka-band Transponder Diplexer Hybrid S S-Band Omnis PA SWITCH K S decrypter S C&DH Diplexer PA S SWITCH S/Ka-band Transponder S Hybrid SWITCH ISOLATOR Ka-band TWTA SWITCH S / Ka HGA Triplexer K Ka-band TWTA

  5. Driving Requirements & Assumptions • Orbit parameters – Earth-Sun L2 orbit - ( 800,000 km Lissajous or Halo ) • Launchdate – June 2021 • LV– Falcon 9 • Mission Lifetime – 3 year / 5 year goal (expendables sized for 5 years) • Mission class –B • Disposal plans – at L2 1 m/sec delta-V at EOL recommended • Orbit determination via DSN ranging • Ranging required • One 60 minute period/day during transfer orbit • One 30 minute period/day when on orbit • Timing requirement of 100 ms at L2 • Stellar pointing • Latency: 72 hours for nominal data • This may be relaxed up to one week for Peak data • Telemetry BER: 10-6 • Nominal Instrument data rate 66 kbps • Peak science collection rates up to 6 hours at 651 kbps forbright object observations at random intervals (assume twice a month) • RF Comm - Observations continue during downlink

  6. L-2 Orbit L2 Earth-Sun angle: 7 to 34º Lunar Orbit L2 Transfer Trajectory E To Sun Courtesy - JWST 800,000 km amplitude L2 Orbit w/180 Day Orbit Earth L2 Distance:1.5x106 Max Range: 1.8x106 • L2 800,000 km semi-major axis halo orbit • 0% solar or lunar obscuration throughout 10 years • Essentially the same orbit as JWST

  7. X-ray Grating Mission Timeline

  8. X-ray Grating – Pitch, yaw, roll from L2

  9. Instrument Data Requirements • Storage Size Requirement 48 hours including 12 hours of peak rate and 36 hours of average rate (this is called 48-hour-peak-volume) + up to 1 day of missed passes (ie., an additional 24 hrs of avg data rate) ____________________________________________________________________________ = A TOTAL of 12 hours peak plus 60 hours of avg data ( 42Gbits ) ( 58Gbits with contingency & overhead) (Assumed 100% efficiency for this 72 hour storage sizing) • Downlink / Latency Requirement • Data collected at average rate must meet 72 hour latency requirement • Size to downlink 48-hour-peak-volume over period of 2 weeks above the avg. rate required for data latency of 72 hours • Allows for 2 bright source observations (peak) per month • 5 year Mission Data Composition Requirement • 98.3 % of time data collected at the low rate. • 1.7 % of the time data collected at peak data rate

  10. X-ray Delta Grating Data Rates

  11. Previous X-ray Grating Data Rates

  12. Data Rate and Storage Analysis

  13. Previous Data Rate and Storage Analysis

  14. Data Rate and Storage Analysis • Instrument (raw) data rate • Nominal: 66.1 kbps • Peak: 651.1 kbps • Instrument Housekeeping: Included in instrument data rates • Spacecraft Housekeeping: 4 kbps • Transmitted nominal daily volume: 8 Gbits • Data downlink rate: 10 Mbps • Additional peak data volume each month (2 - 6 Hr peak events): 38 Gbits • Data Storage: 58 Gbits for 60 hours nominal data plus 12 hours of peak data

  15. Selected Configuration & RationaleKa-Band • Ka-band used for data dumps • Two DSN S/Ka-Band transponders • Two 10Watt Ka-Band TWTAs • Data will be LDPC rate ½ encoded • (If rate 7/8 encoding is used a 15 Watt TWTA will be needed ) • QPSK modulation will be used for Ka-band (Residual carrier for S-band when ranging) • Gimbaled 0.33 M dual frequency high-gain antenna • On the Earth pointed axis • Transmit data rate of 10Mbps to DSN 34 meter • Multiple rates can be included if lower or higher rates needed • A 30 minute contact is required every day for ranging. • 14 minutes required to transmit data simultaneous with the 30 min ranging contact • 95% rain availability is assumed • Redundancy except for the antenna systems • Worst case back to back peak events could be transmitted with three daily 32 minute contacts (or 3.5 days of 30 minutes)

  16. Selected Configuration & RationaleS-Band • S/Ka-band communications using DSN 34 m • S-Band for TT&C • 5 watts RF using 5 watt power amplifiers via omnis or the HGA • Use Omni Antennas • 2 kbps telemetry • 1 kbps command • Use HGA • 8 kbps telemetry (rates up to 250 kbps are achievable) • 2 kbps command • Use TDRSS for launch and LEO critical events • 1 kbps command • 1 kbps telemetry • Ranging: One hour contact per day during transfer orbit and one 30 minute contact per day when on orbit, alternating between north and south locations

  17. Functional Configuration 1 kbps Tlm1 kbps Command (launch & LEO) TDRS Ka-band: 10 Mbps telemetry S-band: 8 kbps Tlm 2 kbps command,& Ranging 34M MOCC White Sands complex DSN Command Command Housekeeping Science & Hskpg

  18. Link Margin Summary

  19. Component Summary

  20. Previous Component Summary *This Transponder would be similar to one developed for JWST Separate S-band transponders and Ka-band transmitters that exist could be used but with additional weight of ~7 kg. NRE costs would have to be compared with the cost of separate units * *Antenna slew should be done in between passes normally, not during a pass.

  21. DSN Support • Launch and early orbit • Continuous tracking for the first 48 hours • DSN 34M/Transfer orbit • Two 30 minute contacts/day • 24 hour support before and after each mid course corrections (Two corrections planned) • 100 days to orbit • Orbit insertion • DSN 34M/ Mission orbit • One 30 minute contact /day • Two back to back 6 hour peak events would require three days of 32 minute contacts to complete transmission within the 72 hour latency requirementBack to back peak support is unlikely, and the peak data latency can by extended. • Pre-pass time: 45 minutes • Post-pass time: 15 minutes

  22. RF Communication Costs • Total mission costs for 3 years: $12.8 M Total mission costs for 5 years: $14.7 M (Excludes timing system and FTEs) • Launch and early orbit: $155 k • TDRSS costs: $55 k • 2 hours SSA support: $15.2 k • Documentation: $40 k • DSN 48 hours support: $100 k • DSN 34M/Transfer orbit: $602 k • 0ne hour contact/day: $345.3 k • 100 days to orbit • Two mid course corrections: $171 k • Orbit insertion: $85.6 k • DSN 34M/ Mission orbit: $2.78 M/3 years DSN 34M/ Mission orbit: $4.65 M/5 years • One 30 minute contact /day: $2.77M/3yr, $4.63M/5yr ($925 K/year) • 6 extra minutes/month : ~$10k/3yr, ~$17k/5yr • Spacecraft cost: $9.26 M

  23. Previous Total Costs • Total mission costs for 5 years: $15.2 M (Excludes timing system and FTEs • Launch and early orbit: $155 k • TDRSS costs: $55 k • 2 hours SSA support: $15 k • Documentation: $40 k • DSN 48 hours support: $100 k • DSN 34M/Transfer orbit: $588 k • 0ne hour contact/day: $331.5 k • 96 days to orbit • Two mid course corrections: $171 k • Orbit insertion: $85.6 k • DSN 34M/ Mission orbit: $4.67 M/5 years • One 30 minute contact /day: $4.55M ($910 K/year) • Spacecraft cost: $9.76 M

  24. Risks and / or Concerns • LDPC rate ½ implementation in the DSN is still expected well before 2021, but the project should keep verifying the schedule for this until it is actually implemented.

  25. . Back-up Slides Ka-band (HGA) to 34 meter (at 10 Mbps) S-band (HGA) to 34 meter S-band 34 meter to HGA S-band (omni) to 34 meter S-band 34 meter to omni TDRSS return link TDRSS forward link S / Ka band Antenna

  26. Ka-Band (HGA) to 34m BWG

  27. S-Band (HGA) to 34M BWG

  28. S-Band 34 M to S/C HGA

  29. S-Band 34 M to S/C Omni

  30. S-Band S/C Omni to 34 M

  31. S-Band S/C Omni to TDRSS

  32. S-Band TDRSS to S/C OMNI

  33. X-ray Grating Ka- / S-band Antenna

  34. Acronyms

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