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  1. X-ray Missions Delta:AXSIO Redux Communications Ron Vento Blake Lorenz 30 April – 1 May, 2012

  2. Topics • Overview • Change implications • Functional Configuration • Driving Requirements and Assumptions • Mission Orientation • Data Volume • Data rates & Storage • Selected Configuration and Rationale • Signal Margin Summary • Cost/Mass/Power Summary • X-ray AXSIO antenna parameters • Backup

  3. Overview • Ka-Band for science and data dumps via DSN 34 meter • Data dumps at 20 Mbps • One 20minute contact per day require to dump data. • Two peak views back to back could be downlinked in one 2.5 hour contact • Mission typical nominal plus peak data averages ~ 25 minutes downlink time • S-Band TT&C via HGA to DSN 34 meter • 2 kbps command • 8 kbps telemetry • S-Band TT&C via Omni to DSN 34 meter • 1 kbps command • 2 kbps telemetry • Ranging for orbit determination • S-Band thru TDRSS for launch and LEO critical events • 1 kbps command • 1 kbps telemetry

  4. Change implications Even though the data rates have increased, there would be no significant saving by having a larger or smaller diameter High Gain Antenna (for a lower or higher data rate).

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

  6. Functional Configuration 1 kbps tlm1 kbps Command (launch & LEO) TDRS Ka-band: 20 Mbps telemetry S-band: 8 kbps Tlm 2 kbps command,& Ranging 34M MOCC White Sands complex DSN Command Command Housekeeping Science & Hskpg

  7. Driving Requirements & Assumptions • Launch: ~ 15 June 2022 • Mission Life: 3 years design (size expendable for 5 years) • Mission Class: B • Nominal Orbit: L2 Lissajous • Stellar pointing • Orbit determination via DSN ranging • Ranging required • One 60 minute period/day during transfer orbit • One 30 minute period/day when on orbit • Absolute timing requirement of 100 ɥs at L2 (handled by Avionics with Atomic clock) • Latency: 72 hours for nominal data • Telemetry BER: 10-6 • Nominal Instrument data rate: 205 kbps • Peak science collection rates up to 12 hours at 3.085 Mbps forbright object observations at random intervals • (assume up to two 6 hour peak observation in a month)

  8. L-2 Orbit 800,000 km amplitude L-2 Orbit with 180 day period L-2 Earth-Sun angle: 7 to 34º Lunar Orbit L-2 Transfer Trajectory E Earth- L2 Distance: 1.5 x 106 km To Sun Courtesy - JWST Max Range: 1.8 x 106 km • L2 800,000 km semi-major axis halo orbit • 0% solar or lunar obscuration throughout 10 years • Essentially the same orbit as JWST

  9. Data Rate and Storage Analysis • Storage Size Requirement (from Project) 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 (Assumed 100% efficiency for this 72 hour storage sizing)

  10. Data Volume

  11. Data Storage Volume

  12. Data Storage Volume

  13. Selected Configuration & RationaleKa-Band • Ka-band used for data dumps • Two DSN S/Ka-Band transponders • Two 10 watt Ka-Band TWTAs • Data will be LDPC rate ½ encoded • QPSK modulation will be used for Ka-band (Residual carrier for S-band when ranging) • Gimbaled 0.5 M dual frequency high-gain antenna (On the Earth pointed axis) • Transmit data rate of 20Mbps 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. • 20 minutes required to transmit nominal data simultaneous with the 30 min ranging contact • Two 6 hour peak observations would require 2.5 hours extra time to downlink the data • 3 days for 70 minutes would downlink 12 hours peak data in 3 days • ~17 days for 30 minutes would downlink 12 hours peak data • 95% rain availability is assumed • Redundancy except for the antenna systems

  14. 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 omnis • 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 hemisphere locations • Avionics is implementing an atomic click to accommodate the strict timing requirement

  15. Link Margin Summary TDRSS guarantees support with a margin of >0 dB S-Band return links use residual carrier (worse case) for ranging.

  16. Component Summary

  17. X-ray AXSIO Ka- / S-band Antenna

  18. 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 • Twice a month a 2.0 hour contact (for peak rate data or contingency if needed) • Pre-pass time: 45 minutes • Post-pass time: 15 minutes

  19. Total Costs • Total mission costs for 3 years: $14.0 M Total mission costs for 5 years: $15.5 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: $2.77 M/3 years DSN 34M/ Mission orbit: $4.67 M/5 years • One 30 minute contact /day: $2.77M/3yr, $4.63M/5yr ($925 K/year) • Two 2 hour contacts/month: $204k/3yr, $340k/5yr ($68 k/year) • Spacecraft cost: $9.76 M

  20. . 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

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

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

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

  24. S-Band 34 M to S/C omni

  25. S-Band S/C omni to 34 M

  26. S-Band S/C omni to TDRSS

  27. S-Band TDRSS to S/C OMNI

  28. Acronyms