Section Number - 1 NASA’s Goddard Space Flight Center Communication Systems Jason A. Soloff NASA/GSFC Code 567 August 16-17, 2005

Section Number - 1NASA’s Goddard Space Flight Center

Communication Systems

Jason A. Soloff

NASA/GSFC Code 567

August 16-17, 2005


Level 2431-SPEC-000008 LRO Electrical Systems Specification431-OPS-000042 LRO Mission Concept of Operations431-REQT-000004 LRO Mission Requirements Document431-SPEC-000091 General Thermal Systems Specification

Level 3431-REQT-000137 Communication System Requirements for the Lunar Reconnaissance Orbiter451-RFICD-LRO/LN Radio Frequency Interface Control Document (RFICD) Between the Lunar Reconnaissance Orbiter

(LRO) and the Lunar Network (LN)Derived (Level 4)

431-SPEC-000121 Performance Specification for the LRO S-Band Transceiver Subsystem431-SPEC-000138 Performance Specification for the LRO Ka-Band Modulator431-SPEC-000178 Performance Specification for the LRO Ka-Band Traveling Wave Tube Amplifier431-SPEC-000179 Performance Specification for the LRO High Gain Antenna System431-SPEC-TBD Performance Specification for the LRO Ka-Band Isolator431-SPEC-TBD Performance Specification for the LRO Omnidirectional Antennas431-SPEC-TBD Performance Specification for the LRO S-Band Hybrid431-SPEC-TBD Performance Specification for the LRO S-Band Isolator

Derived (ICD)431-ICD-TBD LRO High Gain Antenna ICD431-ICD-TBD LRO Omnidirectional Antenna Mechanical ICD431-ICD-TBD LRO S-Band Subsystem ICD431-ICD-TBD LRO Ka-Band Subsystem ICD

Derived (I&T Procedures & Plans)431-PLAN-TBD LRO S-Band Subsystem Integration & Test Procedure431-PLAN-TBD LRO Ka-Band Subsystem Integration & Test Procedure

Lunar Reconnaissance Orbiter (LRO)

Communication System Document List


Level 2 Req.431-REQT-000137

Communication System Requirements for the Lunar Reconnaissance Orbiter

Concept/Compliance

Paragraph Requirement

MRD-119

(TT&C)

MRD-123

(TLM D/L) CONOPS-9.2.2

CSR-3 The spacecraft shall include a S-Band transmit system capable of supporting S-Band telemetry in all flight conditions.

Provides S-Band downlink data capability for telemetry function

MRD-119 (TT&C)

MRD-121 (Radiometrics) MRD-123

(TLM D/L)

CSR-1 The spacecraft shall include a S-Band transmitter with an output frequency of 2091.3967 MHz +/- 2.5 MHz.

Frequency assignment per GSFC Spectrum Management office.

MRD-119

(TT&C)

MRD-121

(Radiometrics) MRD-122

(CMD U/L)

CSR-2 The spacecraft shall include a S-Band receiver with an operating frequency of 2271.2 MHz +/- 2.5 MHz


MRD-119

(TT&C)

MRD-121

(Radiometrics)

CSR-10 The spacecraft transponder shall support STDN compatible operation. STDN provides S-Band TT&C, including the capability for radiometric measurement.


Communication System Level 2 Flow Down KeyRequirements




Concept/Compliance


MRD-119

(TT&C)

MRD-123

(TLM D/L)

CONOPS-9.2.2

CSR-15 The spacecraft transponder shall support downlink subcarrier modulation of data at rates up to 273 kbps (791.7 Kilo-symbols/sec after FEC coding). Telemetry data shall be PSK modulated on a 1.7 (TBD) MHz subcarrier.

Provides S-Band downlink data capability for LRO nominal and unusual attitude telemetry data rates per CONOPS.

MRD-119

(TT&C)

MRD-123

(TLM D/L)

CONOPS-9.2.2

CSR-16 The spacecraft transponder shall support direct carrier modulation of data at rates up to 2.186 Mbps (5 Msps). Telemetry data shall be OQPSK modulated at baseband on the downlink carrier.

Provides S-Band downlink data capability for LRO telemetry data rates during high rate contingencies per CONOPS

MRD-119

(TT&C)

MRD-122

(Radiometrics)

CSR-11 The spacecraft transponder receiver shall receive and demodulate command uplink data at a rate of 4 kbps. Command data shall be PSK modulated on a 16 kHz subcarrier.

Provides S-Band uplink capability for TT&C function at LRO command data rates per CONOPS






Concept/Compliance


MRD-39

(Radiometric Tracking)

MRD-41

(Orbit Determination)

MRD-121

(Radiometric)

MRD-146

(Mission Planning)

CSR-18 The spacecraft transponder shall support radiometric measurement.

Radiometric measurement provides range and range-rate (Doppler) data to the FDF and LRO Flight Dynamics team.

MRD-119

(TT&C)

MRD-123

(TLM D/L)

CSR-5 The spacecraft shall include a S-Band transmit system with a radiated EIRP of not less than 34 dBm through the omnidirectional antennas.

Sufficient EIRP to meet LRO telemetry requirements during off-nominal flight as described in CONOPS

MRD-119

(TT&C)

MRD-123

(TLM D/L)

CSR-9 The S-Band transmit gain over of the combined omnidirectional antenna system shall not be less than 0 dBi over 90% (TBD) of the spherical radiation pattern, including losses due to the omnidirectional antenna hybrid.

Provides antenna visibility for TLM/CMD during off-nominal attitudes & spacecraft contingencies.

MRD-119

(TT&C)

MRD-123

(TLM D/L)

CSR-4 The spacecraft shall include a S-Band transmit system with a radiated EIRP of not less than 55 dBm through the high gain antenna.

Sufficient EIRP to meet LRO telemetry requirements during nominal flight as described in CONOPS






Concept/Compliance


MRD-119

(TT&C)

MRD-123

(TLM D/L)

MRD-124

(High Rate D/L)

CSR-25 The spacecraft downlink telemetry shall be FEC coded using concatenated CCSDS Reed-Solomon, interleave level 8, and rate ½ convolutional codes.

FEC coding provides necessary coding gain to ensure required link BER and link margin.

MRD-119

(TT&C)

MRD-121

(Radiometrics)

MRD-122

(Command Link)

CSR-31 Ground stations in the LRO Ground System shall provide an S-Band transmit EIRP of not less than 79 dBW.

Allocation to ground station in link budget.

MRD-119

(TT&C)

MRD-121

(Radiometrics)

MRD-123

(TLM D/L)

CSR-32 Ground stations in the LRO Ground System shall provide a station S-Band G/T of not less than 20.3 dB/K, including full lunar noise.







Concept/Compliance


MRD-124

(High Rate D/L)

CONOPS-9.2

CSR-33 The spacecraft shall include a transmitter with an output frequency of 25.650 GHz +/- 200 MHz.


MRD-124

(High Rate D/L)

CONOPS-9.2.1.3

CSR-34 The Ka-Band transmitter shall modulate a Ka-Band carrier using OQPSK, direct carrier modulation, at data rates up to 100 Mbps (229 Mega-symbols per second including all FEC encoding).

OQPSK is required to support LRO’s downlink data volume within the allocated spectrum.

MRD-124

(High Rate D/L)

CSR-35 The spacecraft shall include a Ka-Band transmit system with an EIRP of not less than 54 dBW.

Sufficient EIRP to meet LRO high rate telemetry requirements during nominal flight as described in CONOPS

MRD-124

(High Rate D/L)

CSR-40 The high speed science data shall be encoded using concatenated CCSDS Reed-Solomon, with interleave level 8, and rate ½ convolutional encoding.

FEC coding provides necessary coding gain to ensure required link BER and link margin.

MRD-124

(High Rate D/L)

CSR-49 Ground stations in the LRO Ground System shall have a Ka-Band receive G/T of not less than 45 dB/K in the presence of full lunar noise under clear sky conditions.





Lunar Reconnaissance Orbiter (LRO)Communication System Block Diagram

S-Band TT&C Subsystem

TT&C RX CLK/DATA

TT&C TX I CH CLK/DATA

2.5 Msymbols/secRS-422

4 KSpsRS-422

BRF / Diplexer

Omni B

OmniA

TX to HGA

50Ω

20dBCoupler

TX PA

TT&CTransponder

TT&C Omni / HGA RF SwitchDiscrete

3dB Hybrid

IN OUT

COUPISO IN

OUT

COUP

TT&C OmniTest Port

20dBCoupler

OUT

COUP

TT&C HGA

Test Port

IN

HGA

50Ω

50Ω

TT&C TX Q CH CLK/DATA

2.5 Msymbols/secRS-422

TT&C SerialTLM / CMD

RS-422

BRF / Diplexer

50Ω

6dBCoupler

TX

RX

RF from HGA & Omnis

RX

TX to Omni

TX

Isolator

IN

OUT

COUP


Lunar Reconnaissance Orbiter (LRO)Communication System Block Diagram

Ka-Band High Rate Downlink Subsystem

TWTA RF Control

HGA

TWTA WGWG115 Msymbols/sec

LVDSHigh RateModulator

HIGH RATE I CH CLK/DATA

HIGH RATE Q CH CLK/DATA

TWTAEPC

High VoltageTube Power

High Rate SerialTLM / CMD

RS-422

115 Msymbols/secLVDS

WG


Lunar Reconnaissance OrbiterCommunication System

Preliminary Verification Approach

• Communication System Analysis– S-Band frequency spectrum interference analysis– S-Band link budget calculation– Ka-Band link budget calculation– HGA RF field calculation and modeling– Omnidirectional antenna RF phasing analysis– Navigation signal accuracy analysis– Mini-RF interference analysis

• Flight Module Testing– Performed at vendor and as part of LRO I&T

• Comm System Verifications– RF compatibility test (RF Compat Lab, TURFTS)– Antenna radiation pattern measurement (GEMAC)– End-to-end communication link BER measurement– EMI/EMC compliance testing with Mini-RF


Lunar Reconnaissance OrbiterCommunication System Summary

• LRO Communication driving requirements are defined– COMM preliminary architecture developed in accordance with

defined driving requirements– COMM system functional allocation of requirements completed– COMM system component specifications in development– Interfaces being defined between the following elements at Level 3

• S-Band / C&DH interface• Ka-Band / C&DH interface• HGA / Mechanisms interface

– Driving requirements still in development• Information assurance based on no encryption requirement

The Comm Subsystem is ready for Preliminary Design

Documents

Section Number - 1 NASA’s Goddard Space Flight Center Communication Systems Jason A. Soloff NASA/GSFC Code 567 August 16-17, 2005