Final Version Frank Stocklin Ron Vento Bob Summers May 17 2002 Data Systems Micro-Arcsecond Imaging...

Final Version

Frank StocklinRon Vento

Bob Summers

May 17 2002

Data Systems

Micro-Arcsecond Imaging Mission, Pathfinder (MAXIM-PF)

Data SystemsPage 2

LAI-Maxim-PF May 17.2002Goddard Space Flight Center

Final Version

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

Data SystemsPage 3


Final Version

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

Data SystemsPage 4


Final Version 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

Data SystemsDriving Requirements &

Assumptions

Data SystemsPage 5


Final Version No FF inter-communications

Data Latency: None Telemetry BER =10-5

Selective redundancy appropriate

Data SystemsDriving Requirements &

Assumptions

Data SystemsPage 6


Final Version

Selected Configuration & Rationale

Free 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

Data SystemsPage 7


Final Version

Selected Configuration & Rationale

HUB

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)

Data SystemsPage 8


Final Version

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

Data SystemsPage 9


Final Version

Data SystemsSelected Configuration &

Rationale

MOCDSN 34 M

Science & Hskpg

Command

HUB

34M

Free Flyers(6)

DETECTOR

LASER FF’s to HUB

RF

RFRF

RFRFRF

RF

LASER HUB to DETECTOR

X Band

Data SystemsPage 10


Final Version

Selected Configuration and Rational

Functional Free Flyer Block Diagram

C&

DH

LASER

CMD/TLM

Multi Channel UHF transponder HybridDiplexer Omnis/

patches

To HUB

Data SystemsPage 11


Final Version


Functional HUB Block Diagram

C&

DH

UHF Omnis/patche

s

0.3M S-Band

ReflectorLASER

Multi CH UHF/S BandTransponder(2)

CMD/TLM

Diplexer Hybrid

S-Band Omnis

Hybrid

HUB to FF communications

HUB to Detector communications

6 Channels from FF’s

CDMA

RF SwitchDiplexer

To Detecto

r

6 LASER

Reflectors

HPA(2)

Data SystemsPage 12


Final Version


Functional Detector Block Diagram

C&

DH

S Band Omnis

0.5M X-Band

Reflector

S BandTransponder(2)

CMD/TLM

Diplexer Hybrid

X-Band Omnis

Hybrid

Detector to HUB communications

Detector to Ground communications

RF SwitchDiplexer

1 LASER

Reflector

RF Switch

HPA(2)

X BandTransponder(2)

0.3 M

HGA

Data SystemsPage 13


Final Version

Maxim_PF Signal Margins

Mode Data Rate Margin (dB) Max Range

Antennas

UHF HUB/ Freeflyer Freeflyer/ HUB

60 kbps 22.3 Omnis at 1 milliwatt

S-band Hub to Detector

34 kbps 4.7 0.3 M HGA

X-Band Tlm Detector to 34 M

5 Mbps 0.7 0.5 M HGA

X-Band Uplink 34 M Detector

5 kbps 20.9 S/ C 0.5 HGA 34 M at 200 watts

S-Band Detector to HUB

5.5 kbps 9.6 0.3 M HGA

S-band Hub to Detector to HUB

50 bps 0.0 Omnis

X-Band Tlm Detector to 34 M

5 kbps 0.9 Omni

X-Band Uplink 34 M Detector

5 kbps 2.5 S/ C Omni 34 M at 2000 watts

Data SystemsPage 14


Final Version

Power/Mass/Cost SummaryFree Flyer

Component Power (Peak/ Average)

Mass Cost

UHF Omni Antenna (2)

----- 2 kg $ 100 k

UHF xpndr

10/ 10 watts 3.5 kg $ 500 k

Diplexer , hybrid , Misc

----- 2 kg $ 200 k

Laser I ncluded in instruments

TOTALS 10/ 10 watts 7.5 kg $800 k

Data SystemsPage 15


Final Version

Mass/Cost/Power Summary HUB

Component Power

Peak/ Average Mass Cost

S/ UHF-band Omni Antennas (4)

----- 4kg $200 k

S/ UHF-band Xpndr (2)

22 / 22watts 7 kg $1.0 M

S-Band HPA (2) 40/ 40 watts 8 kg $1.0 M

S-Band HGA (fi xed)

---- 4 kg $2.0 M

Diplexers ,Hybrids Miscellaneous

----- 6kg $ 300 k

Laser Reflectors (6) ----- TBD TBD

Laser I ncluded in instruments

Total 62/ 62 watts 29 kg $4.5 M

Data SystemsPage 16


Final Version

Mass/Cost/Power Summary Detector

*Includes gimbals, booms, deployment hardware

ComponentPower

(peak/Average)Mass Cost

S/X-band Omni Antennas (2 each)

4 kg $200K

X-Band xpndr (2) 42/25 watts 8 kg $1.0 M

S-Band xpndr (2) 22/22 watts 7 kg $1.0 M

S-Band HPA (2) 40/40 watts 8 kg $1.0 M

S-Band HGA (fixed) 4 kg $2.0 M

X-Band HGA (2)( gimbaled)

16/1 watts 24 kg * $6.0 M

Hybrids, diplexers, switches, misc

10 kg $500K

Laser reflectorIncluded in instruments

Total 120/88 watts 65 kg $11.7 M

Data SystemsPage 17


Final Version

Data SystemsCost Summary

FreeFlyer (6) $0.8 MHUB $4.5 MDetector $11 .7 MGround station $2.4 M (4 years)**

TOTAL $19.4 M*

*Laser cost included in instruments ** Includes 1 hr pre/post pass time

Data SystemsPage 18


Final Version

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

Data SystemsPage 19


Final Version

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

Data SystemsPage 20


Final Version

Back-Up Charts

Data SystemsPage 21


Final Version

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

Data SystemsPage 22


Final Version

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

Data SystemsPage 23


Final Version

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

Data SystemsPage 24


Final Version

-

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 ---------------------------------------------------------------------------

Data SystemsPage 25


Final Version *** 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

X-band Downlink Detector to 34M BWG5 Kbps OMNI Mode

Data SystemsPage 26


Final Version

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

Data SystemsPage 27


Final Version

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.

Data SystemsPage 28


Final Version

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.

Det-to-Hub Hub-to-DetPtransmit -20.0 -13.0 dBWTx Gain (net) 75.6 75.6 dBRange Loss -291.5 -291.5 dB

Data SystemsPage 29


Final Version

WEIGHT AND POWER ESTIMATE

Using parametric model and engineering estimates:

Mass (kg) Power (W)Telescope 0.17 0.4Solar Filter 0.10Gimbal 0.40 0.5Optics 0.20Laser Transmitter 0.10 0.2Sensor & Detector Assembly 0.20 0.2Support Electronics 0.20 0.2Mechanical & Cabling 0.20Power Conditioning 0.30 0.4

TOTAL (without margin) 1.87 1.88

Note: 10 mW transmitter will require less power (< 100 mW).

Data SystemsPage 30


Final Version

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

Data SystemsPage 31


Final Version

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).

Data SystemsPage 32


Final Version

SHARED TELESCOPE ALTERNATIVE

EXAMPLE Reduced shared aperture to 2.5 cm. Decreased laser power to 2 mW and 10 mW.

SCALABILITY

DATA RATE LASER POWER MOD’N & CODING APERTURE 5 kbps 1 mW Simple; No FEC 2.5 cm

500 kbps 100 mW “ “ 1 Mbps “ Coherent; FEC “

10 Mbps “ “ 5.0 cm

Det-to-Hub Hub-to-DetPtransmit -10.0 -20.0 dBWTx Gain (net) 101.9 95.9 dBRange Loss -291.5 -291.5 dBRx Gain (net) 99.1 93.1 dBPower(receive) -100.5 -122.5 dBWPower(required) -104.9 -126.6 dBWMargin 4.4 4.0 dB

Date post:	18-Jan-2016
Category:	Documents
Upload:	abner-powers
View:	218 times
Download:	0 times

Final Version Frank Stocklin Ron Vento Bob Summers May 17 2002 Data Systems Micro-Arcsecond Imaging...

Documents