MAXIM Data Systems

Command & Data HandlingSpace - Ground Link

Ground System19 August 1999

MAXIM Data Systems Topics

Data System Recommendations Options and Trades Spectrum Utilization Ground Antenna Capabilities Data System Drivers Data System Block Diagram Mass/Power Summary Operations Concept Link Margin Summary Cost Data Suggested Study Areas

Recommendations for MAXIM

Detector satellite will transmit science data using S-Band to Optics Spacecraft for combined transmission to ground stations

Store data continuously & dump daily for 12 min using DSN 34M using X-Band

Total downlink data rate: 300 Kbps Use 2:1 data compression Use S-band for Optics/Detector transmissions Use S-band for backup comm from DSN for both Optics & Detector

Options/Trades

Detector spacecraft to transmit telemetry to Optics spacecraft for combined relay to ground station ( vs separate links)

Less ground station time required Smaller antenna required for Detector Spacecraft & much simpler

communication system

Optics spacecraft sends recorded data vs real time Ground costs significantly less Allows good availability on DSN 34M system

Options/Trades

DSN 34M recommended (vs 13M commercial) Allows hi-rate playback Reduces contact time Much lower cost Proven deep space operation 13 M commercial has unproven ranging capability at 40 million Km

Spectrum Utilization

X-band Space to Ground Link (+) Uplink and downlink frequency assignments available (+) More efficient than S-Band (approx 11.5 dB) (+) S/C hardware is available (-) Rain attenuation (approx 2 dB)

S-band for Optics/Detector link (+ ) More efficient than X-Band (omni/omni) (+) Existing hardware available with modifications of frequency Rx/Tx (+) Allows backup to ground if needed (UHF not readily available)

S-Band to ground link (emergency) (0) Future allocation in DSN band may be questionable

Ground Antenna Capabilities

DSN 34M: X-Band Rx/Tx

G/T = 52.4 dBi/K EIRP = 103 dBw max(can go to 110 dBw)

S-Band Rx/Tx G/T = 42.1 dBi/K EIRP = 98 dBw

13M commercial: X-Band Rx/Tx (uplink and ranging need to be added)

G/T = 37 dBi/K EIRP = 90 dBw

S-Band Rx/Tx G/T = 24.5 dBi/K EIRP = 68 dBw

MAXIM Data System Drivers

Maximum Range: 40 million KM Daily Data Volume: 432 Mbits

MAXIM Data Systems Block Diagram

X-bandXponder

&P wr A m p

Com m ands a 2 K bps

C& DH

S /C 1553B B US

OpticsS -bandXCV R

A CSS S R

BC

Sw

itch

Dip

lexer

S-bandXCV R

P layback @ 300 K bps

X-band Cm d/Tlm& Ranging

34M P rim e70M B ackup

DS NS tations

Com m ands

Telem etry

Sate llite d is h

S -band E m ergencyCm d/Tlm

MaximMOC

MaximScienceHSKP

X-band1.5 m HGA s

Hybrid

Dip

lexerX

X

S -band Om niA ntennas

Tlm @ 100 bpsCmd @ 12 bps H

ybrid

Dip

lexer

X

X

S -band Om niA ntennas

To/From Detector

RF Communications Mass/ Power

X-band Transponder (2) 6 Kg Rx RxTx3 watt 32 wattsCont. for 1 hr/day

S-band XCVR &Diplexers (4)

14 Kg Rx RxTx10 watts 25 watts 1-2 hours/day

C&DH 4.5 Kg 30 watts

X-Band Antenna & ACU (2) 15 Kg 5 watts moving

S-Band OMNI (4) 2 Kg

Optics Spacecraft

RF Communications Mass/ Power

S-band XCVR &Diplexers (2)

7 Kg 25 watts continuous

S-Band OMNI (2) 1 Kg

Detector Spacecraft

DSN 34 M BWG(Stations at Canberra, Madrid, Goldstone)

MAXIMMOC

MAXIMScience Data

MAXIM Operations Concept Diagram

MAXIM Science

X-band Command @ 2 Kbps/Telemetry@ 300 Kbps and

Ranging

S-bandEmergency Command @ 12

bps/Telemetry @ 100 bps

S-band command and telemetry @ 4 Kbps

Telemetry (Housekeeping/Science)

Commands

S-band Emergency Command@ 12 bps and telemetry @ 100 bps

MAXIM Operations Concept

Detector spacecraft will continuously transmit @ S-Band to Optics spacecraft @ 4 Kbps (3 Kbps science, 1 Kbps housekeeping, uncompressed)

Optics spacecraft will compress 2:1 all Detector data and 1 Kbps Optics housekeeping data

Optics spacecraft will continuously record all compressed data for playback 1/day for 12 min @ 300 Kbps to DSN 34M @ X-Band through 1 of 2 HGA antennas

Nominal commanding/ranging to Optics spacecraft will be done via

X-Band through DSN 34M BWG Both Optics & Detector will have S-Band low-rate command/telemetry

through DSN 34M for emergency operations Commands throughput from MOC, telemetry FTP’d from fileserver

MAXIM Link Margin Summary

34 M BWG 13 M Commercial OMNI to Ground Spacecraft toSpacecraft

Downlink Rate 300 Kbps 7.5 Kbps 100 bits 4 Kbps

Uplink Rate 2 Kbps 2 Kbps 12 bits - - - - -

Contact Time 12 minutes 8 hours - - - - - - - - - -

Margin Downlink 3.5 dB 1.5 dB 0 dB 7.2 dB

Margin Uplink 2.5 dB 1.9 dB 0 dB - - - - -

Ranging Uplink 15.9 dB - - - - - - - - - - - - - - -

Ranging Downlink 21.0 dB - - - - - - - - - - - - - - -

All links have 3 dB required performance marginsAll links have rate 1/2 convolutional encoding

Cost

Ground systems:

DSN 34M @ 1hr/day = $365k/yr x 3= $1.1M

13M commercial @ 8 hr/day = $7M

Optics Spacecraft: X Band

XPDRs(2) =$2M HGA antennas(2)= $2M

S-band XCVR(4) = $2.8M omni antennas(4) = $300K

C&DH = $2M

Cost(cont’d)

Detector Spacecraft: S-band XCVR(2)= 1.4M omni antennas(2) = $150K

Suggested Study Areas

Use of new coding schemes (e.g. Turbo Codes) Modified frequency scheme for S-band XCVR

Acronym List

ACS - Attitude Control System ACU - Antenna Control Unit BC - Bus Controller BWG - Beam Wave Guide DSN - Deep Space Network FTP - File Transfer Protocol HGA - High Gain Antenna HSKP - housekeeping I/F - Interface MOC - Mission Operations Center RF - Radio Frequency SSR - Solid State Recorder XCVR - Transceiver XPDR - Transponder