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Frank Stocklin Ron Vento Bob Summers May 17 2002

Frank Stocklin Ron Vento Bob Summers May 17 2002. Micro-Arcsecond Imaging Mission, Pathfinder (MAXIM-PF). Data Systems. Data Systems Topics. Ops Concept Driving Requirements and Assumptions Selected Configuration and Rationale Signal Margin Summary Component Power/Mass/Cost Summary

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Frank Stocklin Ron Vento Bob Summers May 17 2002

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  1. Frank Stocklin Ron Vento Bob Summers May 17 2002 Micro-Arcsecond Imaging Mission, Pathfinder (MAXIM-PF) Data Systems

  2. Data SystemsTopics • Ops Concept • Driving Requirements and Assumptions • Selected Configuration and Rationale • Signal Margin Summary • Component Power/Mass/Cost Summary • Risk Assessment • LASER option • Backup LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  3. OPS CONCEPT • HUB to Free Flyers(FF) • UHF • Coherent for ranging/ 60 Kbps duplex data transfer • CDMA • simultaneous receive of 6 FF’s • Time share transmits to 6 FF’s • may also be able to simultaneous transmit to FF’s if necessary-needs some NRE • LASER reflector FF to HUB to determine relative position • HUB to Detector • S-Band • 34 kbps/5.5 Kbps using HGA’s w/omni backup • Simultaneous receive/transmit with HUB to FF • LASER reflector to determine relative position • Detector to Ground • X Band to DSN • 5 Mbps/5 Kbps • 15 minute dump/day LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  4. Data SystemsDriving Requirements & Assumptions • Launch Date: August 2015 • Mission Life: 4 years required/5 year goal • Nominal Orbit: L2 Location • Stellar pointing • One HUB S/C & 6 identical Free Flyers located in a spherical arc forming a radius of 100-500 m • 50 Kbps to/from • One Detector S/C located at 20 KKM from HUB • 34/5.5 Kbps to/from • Distance from HUB to FF’s must be determined • RF ranging will be course & LASER will be fine • Distance from HUB to Detector must be determined • RF ranging will be course & LASER will be fine • Formation flying • Maintained by continuous RF & LASER LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  5. Data SystemsDriving Requirements & Assumptions • No FF inter-communications • Data Latency: None • Telemetry BER =10-5 • Selective redundancy appropriate LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  6. Selected Configuration & RationaleFree Flyers • UHF selected because of ease of antenna design to minimize nulls • Transponder design from current transceiver design* • CDMA used to enable simultaneous communication with 6 FF’s • Ranging enabled by use of PN code • FF’s will compute range to HUB • 60 Kbps duplex link between HUB & FF’s • Baseline approach is to time share transmissions from HUB to FF’s • Possible to design for simultaneous transmissions-needs some NRE • Laser • Used for range and position of the HUB to FF’s * Prototype will fly on STS this summer LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  7. Selected Configuration & RationaleHUB • UHF/S-Band Transponders (2) • S-Band • 2 omnis • Fixed HGA (0.3 M) • 2 HPAs (10 watts) • Transmit/receive 34 kbps/5.5 kbps to/from detector (operational mode) • Transmit/receive 50 bps with detector (coarse ranging and emergency) • UHF • 2 omnis (or patches) • Transmit 60 kbps to each of 6 FFs (time shared - effective rate received at each FF is 10 kbps) LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  8. Selected Configuration & RationaleDetector • S-Band • 2 transponders • 2 omnis • Fixed HGA (0.3 M) • 2 HPA (10 watts) • Transmit/receive 5.5kbps/34 kbps to/from HUB (operational mode) • Transmit/receive 50 bps with HUB (coarse ranging and emergency) • X-Band • 2 Transponders • 2 omnis • 2 gimbaled HGAs (0.5 M) • Transmit/Receive 50 Kbps/5 kbps with DSN 34 M (using S/C HGA) • Transmit/Receive 50 bps/5 kbps with DSN 34 M (using S/C omni) • Ranging available LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  9. Data SystemsSelected Configuration & Rationale RF DETECTOR RF RF RF HUB RF Free Flyers(6) RF RF LASER HUB to DETECTOR LASER FF’s to HUB X Band 34M MOC DSN 34 M Command Science & Hskpg LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  10. Selected Configuration and RationalFunctional Free Flyer Block Diagram Multi Channel UHF transponder Diplexer Hybrid Omnis/ patches CMD/TLM C&DH LASER To HUB LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  11. Selected Configuration and RationalFunctional HUB Block Diagram Multi CH UHF/S Band Transponder(2) Diplexer Hybrid UHF Omnis/patches CMD/TLM 6 Channels from FF’s CDMA HUB to FF communications HPA (2) S-Band Omnis RF Switch Hybrid C&DH Diplexer 6 LASER Reflectors 0.3M S-Band Reflector LASER To Detector HUB to Detector communications LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  12. Selected Configuration and RationalFunctional Detector Block Diagram S Band Transponder(2) HPA (2) Diplexer S Band Omnis Hybrid CMD/TLM 0.3 M HGA RF Switch Detector to HUB communications RF Switch Hybrid X Band Transponder(2) C&DH Diplexer X-Band Omnis 0.5M X-Band Reflector 1 LASER Reflector Detector to Ground communications LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  13. Maxim_PF Signal Margins LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  14. Power/Mass/Cost SummaryFree Flyer LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  15. Mass/Cost/Power Summary HUB LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  16. Mass/Cost/Power Summary Detector *Includes gimbals, booms, deployment hardware LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  17. Data SystemsCost Summary FreeFlyer (6) $0.8 M HUB $4.5 M Detector $11 .7 M Ground station $2.4 M (4 years)** TOTAL $19.4 M* *Laser cost included in instruments ** Includes 1 hr pre/post pass time LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  18. LASER OPTION • Laser data link between the HUB and Detector • Eliminates two 0.3 M antennas • 4 kg and $2 M savings on both HUB and Detector. • RF transponders and HPAs still required for coarse ranging and emergency modes • Requires 1.9 kg,and 1.9 watts on both HUB and Detector • $1 M NRE and $0.5 M per flight unit • Net difference from RF • -2.1 kg, + 2 watts, -$0.5 M (Detector-Includes all NRE) • -2.1 kg, + 2 watts, -$1.5 M (HUB) ** Exact details are given in the backup charts LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  19. Data SystemsRisk Assessment • Some NRE to make current transceiver design to transponder • Multi channel receive for HUB is an evolving capability but is not a concern for the time frame of this mission • Simultaneous transmission of 2 independent signals (HUB to FF & Detector) is also doable but should be encouraged(funded) to make it happen • Simultaneous transmission of 6 signals (HUB to FF’s) is probably doable but needs to be funded & demonstrated • Basic design is low-medium risk LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  20. Back-Up Charts LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  21. UHF HUB/Freeflyer - Freeflyer/Hub50 kbps *** DOWNLINK MARGIN CALCULATION*** GSFC C.L.A.S.S. ANALYSIS #1 DATE & TIME: 5/14/ 2 14: 9:47 PERFORMED BY: R. VENTO LINKID: MAXIM FREQUENCY: 400.0 MHz RANGE: 0.5 km MODULATION: BPSK DATA RATE: 50.000 kbps CODING: RATE 1/2 CODED BER: 1.00E-05 OMNIS AT 300 DEG 1 MILLIWATT PARAMETER VALUE REMARKS --------------------------------------------------------------------------------------------- 01. USER SPACECRAFT TRANSMITTER POWER - dBW -30.00 0.0 WATTS 02. USER SPACECRAFT PASSIVE LOSS - dB 5.00 NOTE A 03. USER SPACECRAFT ANTENNA GAIN - dBi 0.00 NOTE A 04. USER SPACECRAFT POINTING LOSS - dB 0.00 NOTE A 05. USER SPACECRAFT EIRP - dBWi -35.00 06. POLARIZATION LOSS - dB 0.30 NOTE A 07. FREE SPACE LOSS - dB 78.46 NOTE B 08. ATMOSPHERIC LOSS - dB 0.00 NOTE A 09. RAIN ATTENUATION - dB 0.00 NOTE A 10. MULTIPATH LOSS - dB 0.00 NOTE A 11. GROUND STATION ANTENNA GAIN - dB 0.00 NOTE A 12. GROUND STATION PASSIVE LOSS - dB 5.00 NOTE A 13. GROUND STATION POINTING LOSS - dB 0.00 NOTE A 14. SYSTEM NOISE TEMPERATURE - dB-DEGREES-K 24.77 NOTE A 15. GROUND STATION G/T - dB/DEGREES-K -29.77 16. BOLTZMANN'S CONSTANT - dBW/(Hz*K) -228.60 CONSTANT 17. RECEIVED CARRIER TO NOISE DENSITY - dB/Hz 85.07 18. MODULATION LOSS - dB 0.00 NOTE A 19. DATA RATE - dB-bps 46.99 NOTE A 20. DIFFERENTIAL ENCODING/DECODING LOSS - dB 0.00 NOTE A 21. USER CONSTRAINT LOSS - dB 0.00 NOTE A 22. RECEIVED Eb/No - dB 38.08 23. IMPLEMENTATION LOSS - dB 3.00 NOTE A 24. REQUIRED Eb/No - dB 4.25 NOTE B 25. REQUIRED PERFORMANCE MARGIN - dB 0.00 NOTE A 26. MARGIN - dB 30.83 * MAXI04 * Minus 7.8 dB when supporting 6 Freeflyers simultaneously LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  22. X-band Downlink Detector to 34M BWG5 Mbps HGA *** DOWNLINK MARGIN CALCULATION*** GSFC C.L.A.S.S. ANALYSIS #1 DATE & TIME: 5/14/ 2 14:36:44 PERFORMED BY: R. VENTO LINKID: 11 FREQUENCY: 8475.0 MHz RANGE: 1800000.0 km MODULATION: BPSK DATA RATE: 5000.000 kbps CODING: TURBO BER: 1.00E-05 S/C 0.5 METER ANTENNA 99% AVAILABILITY PARAMETER VALUE REMARKS --------------------------------------------------------------------------------------------- 01. USER SPACECRAFT TRANSMITTER POWER - dBW 6.99 5.0 WATTS 02. USER SPACECRAFT PASSIVE LOSS - dB 3.00 NOTE A 03. USER SPACECRAFT ANTENNA GAIN - dBi 30.35 NOTE A 04. USER SPACECRAFT POINTING LOSS - dB 0.50 NOTE A 05. USER SPACECRAFT EIRP - dBWi 33.84 06. POLARIZATION LOSS - dB 0.50 NOTE A 07. FREE SPACE LOSS - dB 236.11 NOTE B 08. ATMOSPHERIC LOSS - dB 0.50 NOTE A 09. RAIN ATTENUATION - dB 1.00 NOTE A 10. MULTIPATH LOSS - dB 0.00 NOTE A 11. GROUND STATION ANTENNA GAIN - dB 68.20 NOTE A 12. GROUND STATION PASSIVE LOSS - dB 0.00 NOTE A 13. GROUND STATION POINTING LOSS - dB 0.00 NOTE A 14. SYSTEM NOISE TEMPERATURE - dB-DEGREES-K 20.79 NOTE A 15. GROUND STATION G/T - dB/DEGREES-K 47.41 16. BOLTZMANN'S CONSTANT - dBW/(Hz*K) -228.60 CONSTANT 17. RECEIVED CARRIER TO NOISE DENSITY - dB/Hz 71.74 18. MODULATION LOSS - dB 0.00 NOTE A 19. DATA RATE - dB-bps 66.99 NOTE A 20. DIFFERENTIAL ENCODING/DECODING LOSS - dB 0.00 NOTE A 21. USER CONSTRAINT LOSS - dB 0.00 NOTE A 22. RECEIVED Eb/No - dB 4.75 23. IMPLEMENTATION LOSS - dB 3.00 NOTE A 24. REQUIRED Eb/No - dB 1.00 NOTE A 25. REQUIRED PERFORMANCE MARGIN - dB 0.00 NOTE A 26. MARGIN - dB 0.75 MAXI06 NOTE A: PARAMETER VALUE FROM USER PROJECT - SUBJECT TO CHANGE NOTE B: FROM CLASS ANALYSIS IF COMPUTED LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  23. S-band Detector/Hub - Hub/Detector5.5 Kbps - 34 Kbps HGAs *** DOWNLINK MARGIN CALCULATION*** GSFC C.L.A.S.S. ANALYSIS #1 DATE & TIME: 5/14/ 2 12:17:48 PERFORMED BY: R. VENTO LINKID: MAXIM FREQUENCY: 2250.0 MHz RANGE: 20000.0 km MODULATION: BPSK DATA RATE: 34.000 kbps CODING:TURBO BER: 1.00E-05 S/C ANTENNAS ARE 0.3 METERS AT 300 DEG TURBO CODES PARAMETER VALUE REMARKS ----------------------------------------------------------------------------------------------------------- 01. USER SPACECRAFT TRANSMITTER POWER - dBW 6.99 5.0 WATTS 02. USER SPACECRAFT PASSIVE LOSS - dB 3.00 03. USER SPACECRAFT ANTENNA GAIN - dBi 14.51 04. USER SPACECRAFT POINTING LOSS - dB 0.00 05. USER SPACECRAFT EIRP - dBWi 18.50 06. POLARIZATION LOSS - dB 0.30 07. FREE SPACE LOSS - dB 185.51 08. ATMOSPHERIC LOSS - dB 0.00 09. RAIN ATTENUATION - dB 0.00 10. MULTIPATH LOSS - dB 0.00 11. GROUND STATION ANTENNA GAIN - dBi 14.51 0.3 M, EFF: 55.0% 12. GROUND STATION PASSIVE LOSS - dB 0.00 13. GROUND STATION POINTING LOSS - dB 0.00 14. SYSTEM NOISE TEMPERATURE - dB-DEGREES-K 24.77 15. GROUND STATION G/T - dB/DEGREES-K -10.26 16. BOLTZMANN'S CONSTANT - dBW/(Hz*K) -228.60 CONSTANT 17. RECEIVED CARRIER TO NOISE DENSITY - dB/Hz 51.04 18. MODULATION LOSS - dB 0.00 19. DATA RATE - dB-bps 45.31 20. DIFFERENTIAL ENCODING/DECODING LOSS - dB 0.00 21. USER CONSTRAINT LOSS - dB 0.00 22. RECEIVED Eb/No - dB 5.72 23. IMPLEMENTATION LOSS - dB 3.00 24. REQUIRED Eb/No - dB 1.00 25. REQUIRED PERFORMANCE MARGIN - dB 0.00 26. MARGIN - dB 1.72 MAXI02 LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  24. -X-Band DSN 34 M BWG to Detector5 Kbps HGA TABLE 0.5 S/C ANTENNA UPLINK DATE & TIME: 05/14/02 15: 1:25 MAXIM PF FREQUENCY - 7200.000 MHZ GROUND ANTENNA - - - 34 BWG POWER - 0.2000 K WATTS --------------------------------------------------------------------------- PARAMETERS UNITS VALUES ESTIMATED TOLERANCES (MAX RNG: (MIN RNG: DB 1805260. KM 1800000. KM 10.0 EL) 90.0 EL) FAV ADV --------------------------------------------------------------------------- EFFECTIVE RADIATED POWER DBM 120.0 120.0 1.0 -1.0 FREE SPACE DISPERSION LOSS DB -234.7 -234.7 0.0 0.0 ATMOSPHERIC LOSS DB -0.5 0.0 0.0 0.0 POLARIZATION LOSS DB -3.0 -3.0 0.0 0.0 SPACECRAFT ANTENNA GAIN DBI 28.5 28.5 0.0 0.0 SPACECRAFT PASSIVE LOSS DB -5.0 -5.0 0.5 -0.5 MAXIMUM TOTAL RECEIVED POWER DBM -94.7 -94.2 1.1 -1.1 SPACECRAFT ANTENNA NULL DEPTH DB 0.0 0.0 0.0 0.0 MINIMUM TOTAL RECEIVED POWER DBM -94.7 -94.2 1.1 -1.1 SYSTEM NOISE DENSITY DBM/HZ -171.6 -171.6 0.0 0.0 IF NOISE BANDWIDTH( 3000.000 KHZ) DB-HZ 64.8 64.8 0.0 0.0 IF NOISE POWER DBM -106.8 -106.8 0.0 0.0 IF SNR (MIN) DB 12.1 12.6 1.1 -1.1 --------------------------------------------------------------------------- CARRIER CHANNEL ------- ------- CARRIER/TOTAL POWER DB -2.9 -2.9 0.3 -0.3 RECEIVED CARRIER POWER DBM -97.6 -97.1 1.2 -1.2 CARRIER LOOP NOISE BW( 800. HZ) DB-HZ 29.0 29.0 0.0 0.0 NOISE POWER DBM -142.6 -142.6 0.0 0.0 CARRIER/NOISE DB 45.0 45.5 1.2 -1.2 REQUIRED CARRIER/NOISE DB 15.0 15.0 0.0 0.0 AVAILABLE CARRIER MARGIN DB 30.0 30.5 1.2 -1.2 REQUIRED PERFORMANCE MARGIN DB 3.0 3.0 0.0 0.0 NET MARGIN DB 27.0 27.5 1.2 -1.2 --------------------------------------------------------------------------- COMMAND CHANNEL (PCM/PSK/PM) ------- ------- ------------ COMMAND/TOTAL POWER(MI=1.10 RAD) DB -3.5 -3.5 0.3 -0.3 RECEIVED COMMAND POWER DBM -98.2 -97.7 1.2 -1.2 PREDETECTION (PSK) NOISE BW(80.000 KHZ) DB-HZ 49.0 49.0 0.0 0.0 PREDETECTION (PSK) NOISE POWER DB -122.6 -122.6 0.0 0.0 PREDETECTION (PSK) SNR DB 24.4 24.9 1.2 -1.2 COMMAND DATA RATE ( 5.000KBPS) DB-BPS 37.0 37.0 0.0 0.0 AVAILABLE ENERGY PER BIT/NOISE DENSITY DB 36.4 36.9 1.2 -1.2 DECODER DEGRADATION DB -2.0 -2.0 0.0 0.0 REQUIRED ENERGY PER BIT/NOISE DENSITY (BER=E-5) DB 10.5 10.5 0.0 0.0 AVAILABLE COMMAND MARGIN DB 23.9 24.4 1.2 -1.2 REQUIRED PERFORMANCE MARGIN DB 3.0 3.0 0.0 0.0 NET MARGIN DB 20.9 21.4 1.2 -1.2 --------------------------------------------------------------------------- LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  25. X-band Downlink Detector to 34M BWG5 Kbps OMNI Mode *** DOWNLINK MARGIN CALCULATION*** GSFC C.L.A.S.S. ANALYSIS #1 DATE & TIME: 5/15/ 2 10:39:22 PERFORMED BY: R. VENTO LINKID: 11 FREQUENCY: 8475.0 MHz RANGE: 1800000.0 km MODULATION: BPSK DATA RATE: 5.000 kbps CODING: TURBO BER: 1.00E-05 S/C 0.5 METER ANTENNA 99% AVAILABILITY PARAMETER VALUE REMARKS --------------------------------------------------------------------------------------------- 01. USER SPACECRAFT TRANSMITTER POWER - dBW 6.99 5.0 WATTS 02. USER SPACECRAFT PASSIVE LOSS - dB 3.00 NOTE A 03. USER SPACECRAFT ANTENNA GAIN - dBi 0.00 NOTE A 04. USER SPACECRAFT POINTING LOSS - dB 0.00 NOTE A 05. USER SPACECRAFT EIRP - dBWi 3.99 06. POLARIZATION LOSS - dB 0.50 NOTE A 07. FREE SPACE LOSS - dB 236.11 NOTE B 08. ATMOSPHERIC LOSS - dB 0.50 NOTE A 09. RAIN ATTENUATION - dB 1.00 NOTE A 10. MULTIPATH LOSS - dB 0.00 NOTE A 11. GROUND STATION ANTENNA GAIN - dB 68.20 NOTE A 12. GROUND STATION PASSIVE LOSS - dB 0.00 NOTE A 13. GROUND STATION POINTING LOSS - dB 0.00 NOTE A 14. SYSTEM NOISE TEMPERATURE - dB-DEGREES-K 20.79 NOTE A 15. GROUND STATION G/T - dB/DEGREES-K 47.41 16. BOLTZMANN'S CONSTANT - dBW/(Hz*K) -228.60 CONSTANT 17. RECEIVED CARRIER TO NOISE DENSITY - dB/Hz 41.89 18. MODULATION LOSS - dB 0.00 NOTE A 19. DATA RATE - dB-bps 36.99 NOTE A 20. DIFFERENTIAL ENCODING/DECODING LOSS - dB 0.00 NOTE A 21. USER CONSTRAINT LOSS - dB 0.00 NOTE A 22. RECEIVED Eb/No - dB 4.90 23. IMPLEMENTATION LOSS - dB 3.00 NOTE A 24. REQUIRED Eb/No - dB 1.00 NOTE A 25. REQUIRED PERFORMANCE MARGIN - dB 0.00 NOTE A 26. MARGIN - dB 0.90 MAXI12 NOTE A: PARAMETER VALUE FROM USER PROJECT - SUBJECT TO CHANGE NOTE B: FROM CLASS ANALYSIS IF COMPUTED LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  26. S-band Detector/Hub - Hub/Detector50 bits OMNIs *** DOWNLINK MARGIN CALCULATION*** GSFC C.L.A.S.S. ANALYSIS #1 DATE & TIME: 5/15/ 2 10:29:54 PERFORMED BY: R. VENTO LINKID: MAXIM PF FREQUENCY: 2250.0 MHz RANGE: 20000.0 km MODULATION: BPSK DATA RATE: 0.050 kbps CODING: TURBO BER: 1.00E-05 PARAMETER VALUE REMARKS --------------------------------------------------------------------------------------------- 01. USER SPACECRAFT TRANSMITTER POWER - dBW 10.00 10.0 WATTS 02. USER SPACECRAFT PASSIVE LOSS - dB 5.00 NOTE A 03. USER SPACECRAFT ANTENNA GAIN - dBi 0.00 NOTE A 04. USER SPACECRAFT POINTING LOSS - dB 0.00 NOTE A 05. USER SPACECRAFT EIRP - dBWi 5.00 06. POLARIZATION LOSS - dB 0.30 NOTE A 07. FREE SPACE LOSS - dB 185.51 NOTE B 08. ATMOSPHERIC LOSS - dB 0.00 NOTE A 09. RAIN ATTENUATION - dB 0.00 NOTE A 10. MULTIPATH LOSS - dB 0.00 NOTE A 11. GROUND STATION ANTENNA GAIN - dB 0.00 NOTE A 12. GROUND STATION PASSIVE LOSS - dB 2.00 NOTE A 13. GROUND STATION POINTING LOSS - dB 0.00 NOTE A 14. SYSTEM NOISE TEMPERATURE - dB-DEGREES-K 24.77 NOTE A 15. GROUND STATION G/T - dB/DEGREES-K -26.77 16. BOLTZMANN'S CONSTANT - dBW/(Hz*K) -228.60 CONSTANT 17. RECEIVED CARRIER TO NOISE DENSITY - dB/Hz 21.02 18. MODULATION LOSS - dB 0.00 NOTE A 19. DATA RATE - dB-bps 16.99 NOTE A 20. DIFFERENTIAL ENCODING/DECODING LOSS - dB 0.00 NOTE A 21. USER CONSTRAINT LOSS - dB 0.00 NOTE A 22. RECEIVED Eb/No - dB 4.03 23. IMPLEMENTATION LOSS - dB 3.00 NOTE A 24. REQUIRED Eb/No - dB 1.00 NOTE A 25. REQUIRED PERFORMANCE MARGIN - dB 0.00 NOTE A 26. MARGIN - dB 0.03 MAXI10 NOTE A: PARAMETER VALUE FROM USER PROJECT - SUBJECT TO CHANGE NOTE B: FROM CLASS ANALYSIS IF COMPUTED LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  27. HUB - DETECTOR LASER COMMUNICATIONS Concept: A low power laser communications link can exploit the precision alignment of the spacecraft to provide low rate data links with simple, low power, lightweight equipment. • Assumptions: • Operates only when both spacecraft are in operational attitude. • A low bandwidth RF link is used to control Hub and Detector spacecraft positioning into the operational attitude. • Approach: • Use low power “laser pointer” technology for the transmitters. • Use a different frequency from the beacon to avoid interference. • Simplify layout by using separate optics from beacon and star tracker. • Use simple modulation without forward error correction. • Requirements: • Operate at a range of 20,000 kilometers between spacecraft. • Communicate Forward data continuously from the Detector to the Hub at 5500 bps. • Communicate Return data from continuously from the Hub to the Detector at 34,000 bps. LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  28. Laser communications links • Transmitters: • 671 nm, 10 & 50 mW GaAs diode lasers. • 500 microradian beam divergence (simple lens). • Higher power version of 5 mW “laser pointer.” • Receivers: • 10 cm (4”) spacecraft telescope. • 3.5 dB Implementation Loss; 2.0 dB Pointing Loss. • Limited motion gimbal. LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  29. WEIGHT AND POWER ESTIMATE Using parametric model and engineering estimates: Note: 10 mW transmitter will require less power (< 100 mW). LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  30. COST & SCHEDULE ESTIMATE COST • Based on COTS laser technology; still requires a receiver. • Assumes that fundamental R&D is completed; designs exist. • NRE to adapt existing designs to specific spacecraft: ~$1M. • Recurring engineering for flight units: $0.2M to $0.5M. SCHEDULE ESTIMATE (FLIGHT EQUIPMENT) • NRE: ~ 6-12 months • Recurring Build & Test: ~ 6-12 months LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  31. SUMMARY • Simple, low power “laser pointer” transmitter still requires a receiver with a telescope. • Eliminating gimbals requires precise co-alignment, though • Gimbals, if needed, can be very limited motion. • Fixed geometry of spacecraft eliminates need for “look ahead.” Therefore • Sharing the telescope for both transmit and receive could be better: • Increased transmitter gain allows smaller telescope, or • Can use even lower power lasers, and • Would allow much higher data rates. • Little impact on mass and power. • Scalability very good (either alternative) through: • Changing transmitter power (first choice up to about 100 mW). • Use coding and/or better modulation (second choice). • Increasing receiver telescope aperture (last choice). LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

  32. SHARED TELESCOPE ALTERNATIVE EXAMPLE • Reduced shared aperture to 2.5 cm. • Decreased laser power to 2 mW and 10 mW. SCALABILITY LAI-Maxim-PF May 17.2002 Goddard Space Flight Center

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