# Presentation: 276662

## Frank Stocklin
Ron Vento
Bob Summers

May 17 2002

**Ron Vento**
**Bob Summers**
**May 17 2002**

**Data Systems**

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

## Data SystemsTopics

- Ops Concept
- Driving Requirements and Assumptions
- Selected Configuration and Rationale
- Signal Margin Summary
- Component Power/Mass/Cost Summary
- Risk Assessment
- LASER option
- Backup

##  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

## 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

- 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 Systems****Driving Requirements & Assumptions**

## No FF inter-communications
Data Latency: None
Telemetry BER =10-5
Selective redundancy appropriate

- Data Latency: None
- Telemetry BER =10-5
- Selective redundancy appropriate

**Data Systems****Driving Requirements & Assumptions**

## 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

## 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)

## Selected Configuration & RationaleDetector

**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 SystemsSelected Configuration & Rationale

**Data Systems****Selected Configuration & Rationale**

- MOC

- DSN 34 M

- Science & Hskpg

- Command

- HUB

- 34M

- Free Flyers(6)

- DETECTOR

- LASER FF’s to HUB

- RF

- RF

- RF

- RF

- RF

- RF

- RF

- LASER HUB to DETECTOR

- X Band

## Selected Configuration and RationalFunctional Free Flyer Block Diagram

- C&DH

** ****LASER**

- CMD/TLM

**Multi Channel UHF**
** ****transponder**

- Hybrid

- Diplexer

- Omnis/
- patches

- To HUB

## Selected Configuration and RationalFunctional HUB Block Diagram

- C&DH

- UHF Omnis/patches

- 0.3M S-Band Reflector

- LASER

**Multi CH UHF/S Band**
**Transponder(2)**

- CMD/TLM

- Diplexer

- Hybrid

- S-Band Omnis

- Hybrid

- HUB to FF communications

- HUB to Detector communications

- 6 Channels from FF’s CDMA

- RF
- Switch

- Diplexer

- To Detector

**6 LASER**
**Reflectors**

- HPA
- (2)

## Selected Configuration and RationalFunctional Detector Block Diagram

- C&DH

- S Band Omnis

- 0.5M X-Band Reflector

**S Band**
**Transponder(2)**

- CMD/TLM

- Diplexer

- Hybrid

- X-Band Omnis

- Hybrid

- Detector to HUB communications

- Detector to Ground communications

- RF
- Switch

- Diplexer

**1 LASER**
**Reflector**

- RF
- Switch

- HPA
- (2)

**X Band**
**Transponder(2)**

- 0.3 M
- HGA

## Maxim_PF Signal Margins 

** **

## Power/Mass/Cost SummaryFree Flyer

## Mass/Cost/Power Summary HUB

## Mass/Cost/Power Summary Detector

- *Includes gimbals, booms, deployment hardware

| Component | Power (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 reflector | Included in instruments |  |  |
| Total | 120/88 watts | 65 kg | $11.7 M |

## Data SystemsCost 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

## 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 SystemsRisk 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

**Back-Up Charts**

## UHF HUB/Freeflyer - Freeflyer/Hub50 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

## X-band Downlink Detector to 34M BWG5 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

## S-band Detector/Hub - Hub/Detector5.5 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

## -X-Band DSN 34 M BWG to Detector5 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
-       ---------------------------------------------------------------------------

## X-band Downlink Detector to 34M BWG5 Kbps  OMNI Mode

-       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 BWG****5 Kbps  OMNI Mode**

## S-band Detector/Hub - Hub/Detector50 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

## 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.**

## 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.**

## WEIGHT AND POWER ESTIMATE

**Using parametric model and engineering estimates:**

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

## 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**

## 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).**

## SHARED TELESCOPE ALTERNATIVE

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

**SCALABILITY**