X-Ray Gratings Mission

1. X-Ray Gratings Mission Communications Ron Vento Blake Lorenz 19 – 23 March 2012

2. Topics • Overview • Functional Configuration • Driving Requirements and Assumptions • L2 Orbit, Timeline and Attitude • Data rates and Storage • Selected Configuration and Rationale • Functional Configurations • 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 20 Mbps • One 13 minute contact per day require to dump data. • Twice a month 31 minute contact required for addition of peak data • 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 • 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 • Mission class –B • Disposal plans – None Required at L2 ( small push to a stable orbit 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 • Latency: 72 hours for nominal data • Telemetry BER: 10-6 • Nominal Instrument data rate 131.1 kbps • Peak science collection rates up to 6 hours at 1,281 kbps forbright object observations at random intervals (assume twice a month) • Stellar pointing • 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 ( 84 Gbits ) ( 109 Gbits w/ continency ) (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 Grating Data Rates

11. Data Rate and Storage Analysis • Instrument data rate • Nominal: 131.1 kbps • Peak: 1281.1 kbps • Instrument Housekeeping: Included in instrument data rates • Spacecraft Housekeeping: 4 kbps • Nominal transmission rate:179 kbps • Instruments: 131.1 kbps • S/C bus housekeeping: 4 kbps • Contingency data: 30% • CCSDS overhead: 2% • Transmitted nominal daily volume: 15.5 Gbits • Data downlink rate: 20 Mbps • Additional peak data volume each month: 73.4 Gbits • 1281.1 kbps for 6hours twice a month • S/C bus housekeeping: 4 kbps • Contingency data: 30% • CCSDS overhead: 2% • Data Storage: 110 Gbits for 60 hours nominal data plus 12 hours of peak data

12. Data Rate and Storage Analysis

13. 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 0.5 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. • 13 minutes required to transmit data simultaneous with the 30 min ranging contact • 95% rain availability is assumed • Redundancy except for the antenna systems • Up to twice a month a 31 minute contact is required for the addition of the peak data

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 locations

15. 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

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

17. 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.

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 • Up to twice a month a 31 minute contact (for peak rate data) • Pre-pass time: 45 minutes • Post-pass time: 15 minutes

19. 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

20. Driving Requirements & Assumptions -2- • Nominal mission implements the Off Plane Grating Instrument Concept • Investigate impact of implementing alternate Grating Instrument (CAT grating) • Similar operating concept , similar interface parameters • Any changed interface parameters are lessened with the CAT instrument concept • Comparison of SC interface parameters will be provided at the MDL • No significant change to the RF Communication system

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

22. . Back-up Slides Ka-band (HGA) to 34 meter (at 20 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

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

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

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

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

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

28. S-Band S/C omni to TDRSS

29. S-Band TDRSS to S/C OMNI

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